BR122022016938B1 - VIDEO ENCODER, VIDEO DECODER AND CORRESPONDING METHODS - Google Patents

Abstract

The present disclosure relates to methods and devices for encoding and decoding image or video signals. These include determining whether the current block size is greater than a minimum allowable quaternary tree leaf node size. If the current block size is not greater than the minimum allowable quaternary tree leaf node size, a multi-type tree split is applied to the current block. The minimum allowable quaternary tree leaf node size is not greater than a maximum allowable binary tree root node size, or the minimum allowable quaternary tree leaf node size is not greater than a maximum allowable ternary tree root node size.

Description

FIELD OF TECHNIQUE

[0001] Embodiments of the present application generally relate to the field of video coding and, more particularly, to coding unit division and partitioning.

FUNDAMENTALS

[0002] Video coding (video encoding and decoding) is used in a wide range of digital video applications, for example, digital broadcast TV, video transmission over the Internet and mobile networks, real-time conversation applications such as video chat, video conferencing, DVD and Blu-ray Discs, video content acquisition and editing systems, and security application camcorders.

[0003] Since the development of the block-based hybrid video coding approach in the H.261 standard in 1990, new video coding techniques and tools have been developed and have formed the basis for new video coding standards. Other video coding standards include MPEG-1 video, MPEG-2 video, ITU-T H.262/MPEG-2, ITU-T H.263, ITU-T H.264/MPEG-4 Part 10 Advanced Video Coding (AVC), ITU-T H.265/High Efficiency Video Coding (HEVC), ITU-T H.266/Versatile Video Coding (VVC), and extensions, e.g., scalability and/or three-dimensional (3D) extensions, of these standards. As video creation and use become increasingly ubiquitous, video traffic is a major burden on communication networks and data storage. Consequently, one of the goals of most video coding standards has been to achieve a bitrate reduction compared to their predecessors without sacrificing image quality. Even the latest High Efficiency Video Coding (HEVC) can compress video about twice as much as AVC without sacrificing quality; new techniques are needed to further compress video compared to HEVC.

[0004] The amount of video data required to represent even a relatively short video can be substantial, which can result in difficulties when the data must be streamed or otherwise communicated over a communications network with limited bandwidth capacity. Therefore, video data is typically compressed before being communicated over modern telecommunications networks. The size of a video can also be an issue when the video is stored on a storage device because memory resources may be limited. Video compression devices often use software and/or hardware at the source to encode the video data before transmission or storage, thereby decreasing the amount of data required to represent digital video images. The compressed data is then received at the destination by a video decompression device that decodes the video data. With limited network resources and increasing demands for higher video quality, improved compression and decompression techniques that improve the compression ratio with little or no sacrifice in image quality are desirable.

SUMMARY

[0005] Embodiments of the present application (or of the present disclosure) provide apparatus and methods for encoding and decoding according to the independent claims.

[0006] The foregoing and other objects are achieved by the subject matter of the independent claims. Other forms of implementation are evident from the dependent claims, the description and the figures.

[0007] According to a first aspect, the invention relates to a method for decoding video. The method is performed by a decoding device. The method comprises: determining whether the size of a current block is greater than a minimum allowed quaternary tree leaf node size; if the size of the current block is not greater than the minimum allowed quaternary tree leaf node size, applying multi-type tree splitting to the current block; wherein the minimum allowed quaternary tree leaf node size is not greater than a maximum allowed binary tree root node size or the minimum allowed quaternary tree leaf node size is not greater than a maximum allowed ternary tree root node size.

[0008] Wherein the current block may be obtained by splitting an image or a coding tree unit (CTU).

[0009] Where the method may comprise two cases: 1) treeType is equal to SINGLE_TREE or DUAL_TREE_LUMA; 2) treeType is equal to DUAL_TREE_CHROMA. For case 1), the current block is a luma block, and for case 2), the current block is a chroma block.

[0010] Wherein the maximum allowed binary tree root node size may be the maximum luma size in luma samples of a luma encoding root block that can be split using a binary tree split.

[0011] Wherein the maximum allowed ternary tree root node size may be a maximum luma size in luma samples of a luma encoding root block that can be split using a ternary tree split.

[0012] Wherein the minimum allowed quaternary tree leaf node size may be a minimum luma size in luma samples of a luma leaf block resulting from quaternary tree splitting.

[0013] This approach facilitates efficient splitting or signaling of splitting parameters for image/video blocks.

[0014] Furthermore, in a possible implementation form of the method according to the first aspect, the method further comprises the steps of determining whether the current block of an image is a boundary block. Wherein if the size of the current block is not greater than the minimum allowed quaternary tree leaf node size, applying multi-type tree splitting to the current block comprises: if the current block is a boundary block and the size of the current block is not greater than the minimum allowed quaternary tree leaf node size, applying binary splitting to the current block. It is noted that in this case, the minimum allowed quaternary tree leaf node size is not greater than the maximum allowed binary tree root node size. Therefore, if the current block size is not greater than the minimum allowed quaternary tree leaf node size, the current block size is not greater than the maximum allowed binary tree root node size, the above-mentioned application of multi-type tree split on the current block comprises applying binary split to the current block, if the current block is a boundary block and the current block size is not greater than the minimum allowed quaternary tree leaf node size.

[0015] Wherein the method may further comprise obtaining the reconstructed block from a block obtained directly or indirectly from applying binary division to the current block.

[0016] This provision of binary splitting may be particularly advantageous for blocks at the boundary of the image/video frame, e.g., for blocks that are cut by the boundary. Thus, in some implementations, it may be beneficial to apply this approach to the boundary blocks and not apply it to the remaining blocks. However, the present disclosure is not limited thereto, and as mentioned above, this approach of applying binary splitting may also be applied to non-boundary blocks and signaled efficiently.

[0017] In a possible form of implementation of the method according to the first aspect or the aforementioned embodiments, the minimum allowable quaternary tree leaf node size is not larger than a maximum allowable binary tree root node size, and the minimum allowable quaternary tree leaf node size is not larger than a maximum allowable ternary tree root node size.

[0018] In one possible form of implementation of the method according to the first aspect or the aforementioned embodiments, applying multi-type tree splitting to the current block may comprise applying ternary splitting to the current block, or applying binary splitting to the current block. However, the present disclosure is not limited thereby, and in general, multi-type tree splitting may also include more or other different types of splitting.

[0019] In a possible implementation form of the method according to the first aspect or the aforementioned embodiments, the method may further comprise determining the maximum allowable binary tree root node size based on the minimum allowable quaternary tree leaf node size. This facilitates efficient signaling/storage of the parameters. For example, the maximum allowable binary tree root node size may be assumed to be equal to the minimum allowable quaternary tree leaf node size. As a further example, the lower bound value of the maximum allowable binary tree root node size may be assumed to be equal to the minimum allowable quaternary tree leaf node size, and the minimum allowable quaternary tree leaf node size may be used to determine the validity of the maximum allowable binary tree root node size. However, the present disclosure is not limited thereby, and another relationship may be assumed to derive the maximum allowable binary tree root node size.

[0020] According to an exemplary embodiment, in addition to or alternatively to the first aspect or the aforementioned embodiments, the method may further comprise the steps of dividing an image into blocks, wherein the blocks comprise the current block. Applying binary split to the current block comprises applying binary split to the boundary block with a maximum boundary multi-type partition depth, wherein the maximum boundary multi-type partition depth is a sum of at least a maximum multi-type tree depth and a maximum multi-type tree depth offset, wherein the maximum multi-type tree depth is greater than 0. Furthermore, in some implementations, the maximum multi-type tree depth is greater than 0 when applying binary split to the boundary block.

[0021] In a possible implementation form of the method according to the first aspect or the aforementioned embodiments, it may further comprise dividing an image into blocks (the blocks comprising the current block). Applying multi-type tree splitting to the current block comprises applying multi-type tree splitting to the current block of the blocks with a final maximum multi-type tree depth, wherein the final maximum multi-type tree depth is a sum of at least a maximum multi-type tree depth and a maximum multi-type tree depth offset, wherein the maximum multi-type tree depth is greater than or equal to subtracting the Log2 value of the minimum allowed transform block size from the Log2 value of the minimum allowed quaternary tree leaf node size, or the maximum multi-type tree depth is greater than or equal to subtracting the Log2 value of the minimum allowed coding block size from the Log2 value of the minimum allowed quaternary tree leaf node size. This facilitates further splitting even for larger partitioning depths.

[0022] The current block may be a non-frontier block. The maximum multitype tree depth offset may be 0. The current block may alternatively or also be a frontier block, and the multitype tree split is a binary split. The multitype tree split may be or include a ternary split.

[0023] According to a second aspect, the invention relates to a method for encoding. The method is performed by an encoding device. The method comprises the steps of: determining whether the size of a current block is greater than a minimum allowed quaternary tree leaf node size; if the size of the current block is not greater than the minimum allowed quaternary tree leaf node size, applying multitype tree splitting to the current block; wherein the minimum allowed quaternary tree leaf node size is not greater than a maximum allowed binary tree root node size or the minimum allowed quaternary tree leaf node size is not greater than a maximum allowed ternary tree root node size.

[0024] The encoding method may apply any of the aforementioned rules and restrictions described in relation to the decoding method. Hence, the encoder side and the decoder side must share the bitstream. In particular, the encoding side generates the bitstream after encoding the partitions resulting from the partitioning described above, while the decoding side analyzes the bitstream and reconstructs the decoded partitions accordingly. The same applies to the embodiments related to the encoding device (encoder) and the decoding device (decoder) described below.

[0025] According to a third aspect, the invention relates to a decoding device, comprising circuitry configured to: determine whether the size of a current block is greater than a minimum allowable quaternary tree leaf node size; if the size of the current block is not greater than the minimum allowable quaternary tree leaf node size, apply multi-type tree splitting to the current block; wherein the minimum allowable quaternary tree leaf node size is not greater than a maximum allowable binary tree root node size or the minimum allowable quaternary tree leaf node size is not greater than a maximum allowable ternary tree root node size. It is noted that the determination of whether the size of a current block is greater than a minimum allowable quaternary tree leaf node size may be performed based on signaling in the bitstream at the decoding side.

[0026] Also according to a fourth aspect, the invention relates to a coding device comprising circuitry configured to: determine whether the size of a current block is greater than a minimum allowed quaternary tree leaf node size; if the size of the current block is not greater than the minimum allowed quaternary tree leaf node size, apply multi-type tree splitting to the current block; wherein the minimum allowed quaternary tree leaf node size is not greater than a maximum allowed binary tree root node size or the minimum allowed quaternary tree leaf node size is not greater than a maximum allowed ternary tree root node size.

[0027] The method according to the first aspect of the invention can be carried out by the apparatus or device according to the third aspect of the invention. Further features and implementation forms of the method according to the third aspect of the invention correspond to the features and implementation forms of the apparatus according to the first aspect of the invention.

[0028] The method according to the second aspect of the invention can be carried out by the apparatus or device according to the fourth aspect of the invention. Further features and implementation forms of the method according to the fourth aspect of the invention correspond to the features and implementation forms of the apparatus according to the second aspect of the invention.

[0029] According to a fifth aspect, the invention relates to an apparatus for decoding a video stream that includes a processor and a memory. The memory is storing instructions that cause the processor to perform the method according to the first aspect.

[0030] According to a sixth aspect, the invention relates to an apparatus for encoding a video stream including a processor and a memory. The memory is storing instructions that cause the processor to perform the method according to the second aspect.

[0031] According to a seventh aspect, there is proposed a computer-readable storage medium having instructions stored therein that, when executed, cause one or more configured processors to encode video data. The instructions cause the one or more processors to perform a method according to the first or second aspect, or any possible embodiment of the first or second aspect.

[0032] According to an eighth aspect, the invention relates to a computer program comprising program code for performing the method according to the first or second aspect or any possible embodiment of the first or second aspect when executed on a computer.

[0033] According to a ninth aspect, a non-transitory computer-readable storage medium is provided that stores programming for execution by processing circuitry, wherein the programming, when executed by the processing circuitry, configures the processing circuitry to perform any of the above-mentioned methods.

[0034] For purposes of clarity, any of the embodiments disclosed herein may be combined with any one or more of the other embodiments to create a new embodiment within the scope of the present disclosure.

[0035] Details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description, drawings, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In the following embodiments of the invention are described in further detail with reference to the accompanying figures and drawings, in which:

[0037] Figure 1A is a block diagram showing an example of a video encoding system configured to implement embodiments of the invention;

[0038] Figure 1B is a block diagram showing another example of a video encoding system configured to implement embodiments of the invention;

[0039] Figure 2 is a block diagram showing an example of a video encoder configured to implement embodiments of the invention;

[0040] Figure 3 is a block diagram showing an example structure of a video decoder configured to implement embodiments of the invention;

[0041] Figure 4 is a block diagram illustrating an example of an encoding apparatus or a decoding apparatus;

[0042] Figure 5 is a block diagram illustrating another example of an encoding apparatus or a decoding apparatus;

[0043] Figure 6 is an illustrative diagram of an example of block partitioning using a quaternary tree-binary tree (QTBT) structure;

[0044] Figure 7 is an illustrative diagram of an example tree structure corresponding to block partitioning using the QTBT structure of Figure 6;

[0045] Figure 8 is an illustrative diagram of an example of horizontal ternary tree partition types; and

[0046] Figure 9 is an illustrative diagram of an example of vertical ternary tree partition types.

[0047] Figures 10 A-F show different modes of splitting CU into VVC.

[0048] Figure 11A shows a forced QT partition of CTU (128x128) of HD (1920x1080) lower boundary.

[0049] Figure 11B shows a forced BT partition of CTU (128x128) of HD (1920x1080) lower boundary according to an embodiment of the disclosure.

[0050] Figure 12 shows an example of a boundary definition.

[0051] Figure 13A shows an example of a corner case forced QTBT partition in accordance with an embodiment of the disclosure.

[0052] Figure 13B shows an example of a forced QTBT partition for a block located in a corner in accordance with an embodiment of the disclosure.

[0053] Figure 14 shows an embodiment of a boundary definition.

[0054] Figure 15 is a block diagram showing an example of a video encoder configured to implement embodiments of the invention;

[0055] Figure 16 is a block diagram showing an example structure of a video decoder configured to implement embodiments of the invention;

[0056] Figure 17 is a block diagram showing an example structure of a content delivery system 3100 that performs a content delivery service.

[0057] Figure 18 is a block diagram showing a structure of an example of a terminal device.

DETAILED DESCRIPTION OF THE MODALITIES

[0058] In the following description, reference is made to the accompanying figures, which are part of the disclosure, and which show, by way of illustration, specific aspects of embodiments of the invention or specific aspects in which embodiments of the present invention may be used. It is understood that embodiments of the invention may be used in other aspects and comprise structural or logical changes not represented in the figures. The following detailed description, therefore, should not be taken in a limiting sense, and the scope of the present invention is defined by the accompanying claims.

[0059] For example, it is understood that a disclosure in connection with a described method may also be true of a corresponding device or system configured to perform the method, and vice versa. For example, if one or a plurality of specific method steps are described, a corresponding device may include one or a plurality of units, e.g., functional units, for performing the described method step or plurality of steps (e.g., a unit performing the one or plurality of steps, or a plurality of units each performing one or more of the plurality of steps), even if such one or more units are not explicitly described or illustrated in the figures. On the other hand, for example, if a specific apparatus is described based on one or a plurality of units, e.g., functional units, a corresponding method may include a step for performing the functionality of the one or plurality of units (e.g., a step performing the functionality of the one or plurality of units, or a plurality of steps each performing the functionality of one or more of the plurality of units), even if such one or plurality of steps are not explicitly described or illustrated in the figures. Furthermore, it is understood that the features of the various exemplary embodiments and/or aspects described herein may be combined with each other, unless specifically indicated otherwise.

[0060] Video coding typically relates to the processing of a sequence of images, which form the video or video sequence. Instead of the term "image", the term "frame" or "picture" may be used synonymously in the field of video coding. Video coding as used in the present application (or present disclosure) indicates either video encoding or video decoding. Video encoding is performed on the source side, typically comprising processing (e.g., by compression) the original video images to reduce the amount of data required to represent the video images (for more efficient storage and/or transmission). Video decoding is performed on the destination side and typically comprises the inverse processing compared to the encoder to reconstruct the video images. Embodiments that refer to "coding" video images (or images in general, as will be explained later) should be understood as relating to either "encoding" or "decoding" for video sequence. The combination of the encoding part and the decoding part is also referred to as CODEC (Coding and Decoding).

[0061] In the case of lossless video coding, the original video images can be reconstructed, i.e., the reconstructed video images have the same quality as the original video images (assuming no transmission loss or other data loss during storage or transmission). In the case of lossy video coding, additional compression, e.g., by quantization, is performed to reduce the amount of data representing the video images, which cannot be completely reconstructed at the decoder, i.e., the quality of the reconstructed video images is lower or worse compared to the quality of the original video images.

[0062] Several video coding standards since H.261 belong to the group of "hybrid lossy video codecs" (i.e., they combine spatial and temporal prediction in the sample domain and 2D transform coding to apply quantization in the transform domain). Each picture of a video sequence is typically partitioned into a set of non-overlapping blocks, and coding is typically performed at a block level. In other words, in the encoder, video is typically processed, i.e., encoded, at the block (video block) level, for example, using spatial prediction (intra-frame) and temporal prediction (inter-frame) to generate a prediction block, subtracting the prediction block from the current block (currently processed/to-be-processed block) to obtain a residual block, transforming the residual block, and quantizing the residual block in the transform domain to reduce the amount of data to be transmitted (compression). Meanwhile, in the decoder, the inverse processing compared to the encoder is partially applied to the encoded or compressed block to reconstruct the current block for representation. Furthermore, the encoder duplicates the decoder's processing loop so that both will generate identical predictions (e.g., intra- and inter-predictions) and/or reconstructions for processing, i.e., encoding, subsequent blocks.

[0063] As used herein, the term "block" may be a portion of a picture or frame. For convenience of description, embodiments of the invention are described herein with reference to High Efficiency Video Coding (HEVC) or Versatile Video Coding (VVC) reference software developed by the Joint Collaboration Team on Video Coding (JCT-VC) of the Video Coding Experts Group (VCEG) of ITU-T and Moving Picture Experts Group (MPEG) of ISO/IEC. One of ordinary skill in the art will understand that embodiments of the invention are not limited to HEVC or VVC. Reference may be made to a CU (coding units), PU (prediction units), and TU (transform units). In HEVC, a CTU (coding tree unit) is divided into CUs using a quaternary tree structure referred to as a coding tree. The decision to encode an image region using inter- (temporal) or intra- (spatial) image prediction is made at the CU level. Each CU can be divided into one, two, or four PUs depending on the PU division type. Within a PU, the same prediction process is applied, and relevant information is transmitted to the decoder based on the PU. After obtaining the residual block by applying the prediction process based on the PU division type, a CU can be partitioned into transform units (TUs) according to another quaternary tree structure similar to the coding tree for the CU. In the most recent development of video compression technology, the quaternary tree and binary tree (QTBT) partitioning framework is used to partition a coding block. In the QTBT block structure, a CU can be either square or rectangular in shape. For example, a coding tree unit (CTU) is first partitioned using a quaternary tree structure. The leaf nodes of a quaternary tree are further partitioned using a binary tree structure. Binary tree leaf nodes are called coding units (CUs), and this segmentation is used for prediction and transform processing without any additional partitioning. This means that the CU, PU, and TU have the same block size in the QTBT coding block structure. In parallel, multiple partitioning, such as Ternary Tree (TT) partitioning, has also been proposed for use in conjunction with the QTBT block structure. The term "device" can also be "apparatus," "decoder," or "encoder."

[0064] The following embodiments of an encoder 20, a decoder 30, and a coding system 10 are described based on Figures 1-3.

[0065] Figure 1A is a conceptual or schematic block diagram illustrating an example coding system 10, e.g., a video coding system 10, that may utilize techniques of the present application (present disclosure). The encoder 20 (e.g., video encoder 20) and the decoder 30 (e.g., video decoder 30) of the video coding system 10 represent examples of devices that may be configured to perform techniques according to various examples described in the present application. As shown in Figure 1A, the coding system 10 comprises a source device 12 configured to provide encoded data 13, e.g., an encoded image 13, e.g., to a destination device 14 for decoding the encoded data 13.

[0066] The source device 12 comprises an encoder 20, and may additionally, i.e. optionally, comprise an image source 16, a pre-processing unit 18, e.g., an image pre-processing unit 18, and a communication interface or communication unit 22.

[0067] The image source 16 may comprise or be any type of image capture device, e.g., a generating device for capturing a real-world image and/or any type of an image or commentary (for encoding screen content, some on-screen text is also considered a part of an image or image to be encoded), e.g., a computer graphics processor for generating a computer-animated image, or any type of device for obtaining and/or providing a real-world image, a computer-animated image (e.g., a screen content, a virtual reality (VR) image), and/or any combination thereof (e.g., an augmented reality (AR) image). The image source may be any type of memory or storage that stores any of the aforementioned images.

[0068] A (digital) image is or may be considered as a two-dimensional array or array of samples with intensity values. A sample in the array may also be referred to as a pixel (short for picture element) or a pel. The number of samples in the horizontal and vertical direction (or axis) of the array or image defines the size and/or resolution of the image. For color representation, typically three color components are employed, i.e., the image may be represented by or include three sample arrays. In RBG format or color space, an image comprises a corresponding red, green, and blue sample array. However, in video coding, each pixel is typically represented in a luminance/chrominance format or color space, e.g., YCbCr, which comprises a luminance component denoted by Y (sometimes also L is used alternatively) and two chrominance components denoted by Cb and Cr. The luminance (or luma for short) component, Y, represents the brightness or gray-level intensity (e.g., as in a grayscale image), while the two chrominance (or chroma for short) components, Cb and Cr, represent the chromaticity or color information components. Consequently, a YCbCr format image comprises one luminance sample array of luminance sample values (Y), and two chrominance sample arrays of chrominance values (Cb and Cr). RGB format images can be converted or transformed to YCbCr format and vice versa; this process is also known as color transformation or conversion. If an image is monochromatic, the image may comprise only one luminance sample array.

[0069] The image source 16 (e.g., video source 16) may be, for example, a camera for capturing an image, a memory, for example, an image memory, comprising or storing a previously captured or generated image, and/or any type of interface (internal or external) for obtaining or receiving an image. The camera may be, for example, a local or integrated camera that is integrated into the source device; the memory may be a local or integrated memory, for example, integrated into the source device. The interface may be, for example, an external interface for receiving an image from an external video source, for example, an external image capture device such as a camera, an external memory, or an external image generation device, for example, an external graphics processor, computer, or server. The interface may be any type of interface, for example, a wired or wireless interface, an optical interface, according to any proprietary or standardized interface protocol. The interface for obtaining the image data 17 may be the same interface or a part of the communication interface 22.

[0070] To distinguish from the pre-processing unit 18 and the processing performed by the pre-processing unit 18, the image or image data 17 (e.g., video data 16) may also be referred to as the raw image or raw image data 17.

[0071] The preprocessing unit 18 is configured to receive the (raw) image data 17 and to perform preprocessing on the image data 17 to obtain a preprocessed image 19 or preprocessed image data 19. Preprocessing performed by the preprocessing unit 18 may, for example, comprise cropping, color format conversion (e.g., from RGB to YCbCr), color correction, or noise elimination. It may be understood that the preprocessing unit 18 may be an optional component.

[0072] The encoder 20 (e.g., video encoder 20) is configured to receive the preprocessed image data 19 and output encoded image data 21 (further details will be described below, e.g., based on Figure 2 or Figure 4).

[0073] The communication interface 22 of the source device 12 may be configured to receive the encoded image data 21 and to transmit the encoded image data 21 (or any other further processed version thereof) over the communication channel 13 to another device, e.g., the destination device 14 or any other device, for storage or direct reconstruction.

[0074] The communication interface 22 of the source device 12 may be configured to receive the encoded image data 21 and to transmit it to another device, for example, the destination device 14 or any other device, for direct storage or reconstruction, or to process the encoded image data 21 respectively before storing the encoded data 13 and/or transmitting the encoded data 13 to another device, for example, the destination device 14 or any other device for decoding or storage.

[0075] The target device 14 comprises a decoder 30 (e.g., a video decoder 30) and may additionally, i.e., optionally, comprise a communication interface or communication unit 28, a post-processing unit 32, and a display device 34.

[0076] The communication interface 28 of the destination device 14 is configured to receive the encoded image data 21 (or any further processed version thereof), e.g., directly from the source device 12 or from any other source, e.g., a storage device, e.g., an encoded image data storage device, and provide the encoded image data 21 to the decoder 30.

[0077] The communication interface 28 of the destination device 14 is configured to receive the encoded image data 21 or the encoded data 13, for example, directly from the source device 12 or from any other source, for example, a storage device, for example, an encoded image data storage device.

[0078] The communication interface 22 and the communication interface 28 may be configured to transmit or receive the encoded image data 21 or encoded data 13 via a direct communication link between the source device 12 and the destination device 14, e.g., a direct wired or wireless connection, or via any type of network, e.g., a wired or wireless network or any combination thereof, or any type of private and public network, or any type of combination thereof.

[0079] The communication interface 22 may be, for example, configured to package the encoded image data 21 in an appropriate format, e.g., packets, and/or process the encoded image data using any type of transmission encoding or processing for transmission over a communication link or communication network.

[0080] The communication interface 28, forming the counterpart of the communication interface 22, may be, for example, configured to unpack the encoded data 13 to obtain the encoded image data 21.

[0081] The communication interface 28, forming the counterpart of the communication interface 22, may be, for example, configured to receive the transmitted data and process the transmission data using any type of corresponding transmission decoding or processing and/or unpacking to obtain the encoded image data 21.

[0082] Both communication interface 22 and communication interface 28 may be configured as unidirectional communication interfaces as indicated by the arrow for encoded image data 13 in Figure 1A pointing from source device 12 to destination device 14, or bidirectional communication interfaces, and may be configured, for example, to send and receive messages, for example, to establish a connection, to confirm and exchange any other information related to the communication link and/or data transmission, for example, transmission of encoded image data.

[0083] The decoder 30 is configured to receive the encoded image data 21 and provide decoded image data 31 or a decoded image 31 (further details will be described below, e.g., based on Figure 3 or Figure 5).

[0084] The post-processor 32 of the target device 14 is configured to post-process the decoded image data 31 (also called reconstructed image data), e.g., the decoded image 31, to obtain post-processed image data 33, e.g., a post-processed image 33. The post-processing performed by the post-processing unit 32 may comprise, e.g., color format conversion (e.g., from YCbCr to RGB), color correction, cropping or resampling, or any other processing, e.g., to prepare the decoded image data 31 for presentation, e.g., by the display device 34.

[0085] The display device 34 of the target device 14 is configured to receive the post-processed image data 33 to display the image, e.g., to a user or viewer. The display device 34 may be or comprise any type of display for representing the reconstructed image, e.g., an integrated or external display or monitor. Displays may, for example, comprise liquid crystal displays (LCD), organic light-emitting diode (OLED) displays, plasma displays, projectors, microLED displays, liquid crystal on silicon (LCoS), digital light processing (DLP), or any other type of display.

[0086] Although Figure 1A depicts the source device 12 and the destination device 14 as separate devices, embodiments of devices may also comprise both or both functionality of the source device 12 or corresponding functionality and the destination device 14 or corresponding functionality. In such embodiments, the source device 12 or corresponding functionality and the destination device 14 or corresponding functionality may be implemented using the same hardware and/or software or by separate hardware and/or software, or any combination thereof.

[0087] As will be apparent to the skilled person based on the description, the existence and (exact) division of functionalities of the different units or functionalities within the source device 12 and/or the target device 14 as shown in Figure 1A may vary depending on the actual device and application.

[0088] Encoder 20 (e.g., a video encoder 20) and decoder 30 (e.g., a video decoder 30) may each be implemented as any of a variety of suitable circuitry, such as one or more microprocessors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), discrete logic, hardware, or any combinations thereof. If the techniques are implemented partially in software, a device may store instructions for the software on a suitable non-transitory computer-readable storage medium and may execute the instructions in hardware using one or more processors to perform the techniques of this disclosure. Any of the foregoing (including hardware, software, a combination of hardware and software, etc.) may be considered to be one or more processors. Each of the video encoder 20 and video decoder 30 may be included in one or more encoders or decoders, any of which may be integrated as part of a combined encoder/decoder (CODEC) in a respective device.

[0089] Encoder 20 may be implemented via processing circuitry 46 to incorporate the various modules as discussed with respect to encoder 20 of Figure 2 and/or any other encoder system or subsystem described herein. Decoder 30 may be implemented via processing circuitry 46 to incorporate the various modules as discussed with respect to decoder 30 of Figure 3 and/or any other decoder system or subsystem described herein. The processing circuitry may be configured to perform the various operations as discussed later. As shown in Figure 5, if the techniques are implemented partially in software, a device may store instructions for the software on a suitable non-transitory computer-readable storage medium and may execute the instructions in hardware using one or more processors to perform the techniques of this disclosure. Either of the video encoder 20 and the video decoder 30 may be integrated as part of a combined encoder/decoder (CODEC) in a single device, for example, as shown in Figure 1B.

[0090] The source device 12 may be referred to as a video encoding device or a video encoding apparatus. The destination device 14 may be referred to as a video decoding device or a video decoding apparatus. The source device 12 and the destination device 14 may be examples of video encoding devices or video encoding apparatus.

[0091] The source device 12 and the destination device 14 may comprise any of a wide range of devices, including any type of handheld or stationary devices, for example, notebook or laptop computers, mobile phones, smartphones, tablets or tablet computers, cameras, desktop computers, set top boxes, televisions, display devices, digital media players, video game consoles, video streaming devices (such as content service servers or content delivery servers), broadcast receiver device, broadcast transmitter device, or the like, and may not use or use any type of operating system.

[0092] In some cases, the source device 12 and the destination device 14 may be equipped for wireless communication. Thus, the source device 12 and the destination device 14 may be wireless communication devices.

[0093] In some instances, the video encoding system 10 illustrated in Figure 1A is merely an example, and the techniques of the present application may apply to video encoding embodiments (e.g., video encoding or video decoding) that do not necessarily include any data communication between the encoding and decoding devices. In other examples, data is retrieved from local memory, streamed over a network, or the like. A video encoding device may encode and store data in memory, and/or a video decoding device may retrieve and decode data from memory. In some examples, encoding and decoding are performed by devices that do not communicate with each other, but simply encode data into memory and/or retrieve and decode data from memory.

[0094] For convenience of description, embodiments of the invention are described herein, for example, by reference to High Efficiency Video Coding (HEVC) or Versatile Video Coding (VVC) reference software, the next-generation video coding standard developed by the Joint Collaboration Team on Video Coding (JCT-VC) of the ITU-T Video Coding Experts Group (VCEG) and ISO/IEC Moving Picture Experts Group (MPEG). One of ordinary skill in the art will understand that embodiments of the invention are not limited to HEVC or VVC. It should be understood that, for each of the examples described above with reference to video encoder 20, video decoder 30 may be configured to perform a reciprocal process. With respect to signaling syntax elements, video decoder 30 may be configured to receive and parse such syntax element and decode the associated video data accordingly. In some examples, video encoder 20 may entropy encode one or more syntax elements in the encoded video bitstream. In such examples, video decoder 30 may analyze such syntax element and decode the associated video data accordingly.

[0095] Figure 1B is an illustrative diagram of another example video coding system 40 including encoder 20 of Figure 2 and/or decoder 30 of Figure 3 according to an exemplary embodiment. System 40 may implement techniques according to various examples described herein. In the illustrated implementation, video coding system 40 may include image generation device(s) 41, video encoder 100, video decoder 30 (and/or a video encoder implemented via logic circuitry 47 of processing unit(s) 46), an antenna 42, one or more processors 43, one or more memory stores 44, and/or a display device 45.

[0096] As illustrated, imaging device(s) 41, antenna 42, processing unit(s) 46, logic circuitry 47, video encoder 20, video decoder 30, processor(s) 43, memory store(s) 44, and/or display device 45 may be capable of communicating with one another. As discussed, although illustrated with both video encoder 20 and video decoder 30, video coding system 40 may include only video encoder 20 or only video decoder 30 in various examples.

[0097] As shown, in some examples, video encoding system 40 may include antenna 42. Antenna 42 may be configured to transmit or receive an encoded bitstream of video data, for example. Further, in some examples, video encoding system 40 may include display device 45. Display device 45 may be configured to present video data. As shown, in some examples, logic circuitry 47 may be implemented by processing unit(s) 46. Processing unit(s) 46 may include application-specific integrated circuit (ASIC) logic, graphics processor(s), general-purpose processor(s), or the like. Video encoding system 40 may also include optional processor(s) 43, which may similarly include application-specific integrated circuit (ASIC) logic, graphics processor(s), general-purpose processor(s), or the like. In some examples, logic circuitry 47 may be implemented via hardware, dedicated video encoding hardware, or the like, and processor(s) 43 may implement general-purpose software, operating systems, or the like. Furthermore, memory repository(ies) 44 may be any type of memory, such as volatile memory (e.g., Static Random Access Memory (SRAM), Dynamic Random Access Memory (DRAM), etc.) or non-volatile memory (e.g., flash memory, etc.), and so on. In a non-limiting example, memory repository(ies) 44 may be implemented via cache memory. In some examples, logic circuitry 47 may access memory repository(ies) 44 (for implementing a picture buffer, for example). In other examples, logic circuitry 47 and/or processing unit(s) 46 may include in-memory repositories (e.g., cache or the like) for implementing an image buffer or the like.

[0098] In some examples, video encoder 100 implemented via logic circuitry may include a picture buffer (e.g., either via processing unit(s) 46 or memory repository(ies) 44) and a graphics processing unit (e.g., via processing unit(s) 46). The graphics processing unit may be communicatively coupled to the picture buffer. The graphics processing unit may include video encoder 100 as implemented via logic circuitry 47 to incorporate the various modules as discussed in connection with Figure 2 and/or any other encoder system or subsystem described herein. Logic circuitry may be configured to perform the various operations as discussed herein.

[0099] Video decoder 30 may be implemented in a similar manner as implemented via logic circuitry 47 to incorporate the various modules as discussed with respect to decoder 30 of Figure 3 and/or any other decoder system or subsystem described herein. In some examples, video decoder 30 may be implemented via logic circuitry that may include a picture buffer (e.g., via either processing unit(s) 420 or memory store(s) 44) and a graphics processing unit (e.g., via processing unit(s) 46). The graphics processing unit may be communicatively coupled to the picture buffer. The graphics processing unit may include video decoder 30 as implemented via logic circuitry 47 to incorporate the various modules as discussed with respect to Figure 3 and/or any other decoder system or subsystem described herein.

[0100] In some examples, antenna 42 of video coding system 40 may be configured to receive an encoded bitstream of video data. As discussed, the encoded bitstream may include data, indicators, index values, mode selection data, or the like associated with encoding a video frame as discussed herein, such as data associated with the coding partition (e.g., transform coefficients or quantized transform coefficients, optional indicators (as discussed), and/or data defining the coding partition). Video coding system 40 may also include video decoder 30 coupled to antenna 42 and configured to decode the encoded bitstream. Display device 45 configured to present video frames.

[0101] Figure 2 shows a schematic/conceptual block diagram of an example video encoder 20 that is configured to implement the techniques of the present application. In the example of Figure 2, the video encoder 20 comprises a residual calculation unit 204, a transform processing unit 206, a quantization unit 208, an inverse quantization unit 210, and inverse transform processing unit 212, a reconstruction unit 214, a buffer 216, a loop filter unit 220, a decoded picture buffer (DPB) 230, a prediction processing unit 260, and an entropy coding unit 270. The prediction processing unit 260 may include an inter prediction unit 244, an intra prediction unit 254, and a mode selection unit 262. The inter prediction unit 244 may include a motion estimation unit and a motion compensation unit (not shown). A video encoder 20 as shown in Figure 2 may also be referred to as a hybrid video encoder or a video encoder according to a hybrid video codec.

[0102] For example, the residual calculation unit 204, the transform processing unit 206, the quantization unit 208, the prediction processing unit 260, and the entropy coding unit 270 form a forward signal path of the encoder 20, while, for example, the inverse quantization unit 210, the inverse transform processing unit 212, the reconstruction unit 214, the buffer 216, the filter loop 220, the decoded picture buffer (DPB) 230, and the prediction processing unit 260 form a regression signal path of the encoder, wherein the regression signal path of the encoder corresponds to the signal path of the decoder (see decoder 30 in Figure 3).

[0103] The inverse quantization unit 210, the inverse transform processing unit 212, the reconstruction unit 214, the loop filter 220, the decoded picture buffer (DPB) 230, the inter prediction unit 244, and the intra prediction unit 254 are also referred to form the "embedded decoder" of the video encoder 20. The encoder 20 is configured to receive, for example, by the input 202, a picture 201 or a block 203 of the picture 201, e.g., picture of a sequence of pictures forming a video or video sequence. The picture block 203 may also be referred to as the current picture block or the picture block to be coded, and the picture 201 as the current picture or the picture to be coded (in particular in video coding to distinguish the current picture from other pictures, e.g., previously coded and/or decoded pictures of the same video sequence, i.e., the video sequence that also comprises the current picture).

[0104] A (digital) image is or can be considered as a two-dimensional array or matrix of samples with intensity values. A sample in the array can also be referred to as a pixel (short for picture element) or pel. The number of samples in the horizontal and vertical direction (or axis) of the array or image defines the size and/or resolution of the image. For color representation, typically three color components are employed, i.e., the image can be represented or include three sample arrangements. In RBG format or color space, an image comprises a corresponding red, green, and blue sample arrangement. However, in video coding, each pixel is typically represented in a luminance and chrominance format or color space, for example, YCbCr, which comprises a luminance component denoted by Y (sometimes also L is used alternatively) and two chrominance components denoted by Cb and Cr. The luminance (or luma for short) component, Y, represents the brightness or gray-level intensity (e.g., as in a grayscale image), while the two chrominance (or chroma for short) components, Cb and Cr, represent the chromaticity or color information components. Consequently, a YCbCr format image comprises one luminance sample array of luminance sample values (Y), and two chrominance sample arrays of chrominance values (Cb and Cr). RGB format images can be converted or transformed to YCbCr format and vice versa; this process is also known as color transformation or conversion. If an image is monochromatic, the image may comprise only one luminance sample array. Accordingly, an image may be, for example, an array of luma samples in monochrome format, or an array of luma samples and two corresponding arrays of chroma samples in 4:2:0, 4:2:2, and 4:4:4 color format.

PARTITIONING

[0105] Embodiments of the encoder 20 may comprise a partitioning unit (not depicted in Figure 2) configured to partition the picture 201 into a plurality of (typically non-overlapping) picture blocks 203. These blocks may also be referred to as root blocks, macroblocks (H.264/AVC), or coding tree blocks (CTB) or coding tree units (CTU) (H.265/HEVC and VVC). The partitioning unit may be configured to use the same block size for all pictures of a video sequence and the corresponding grid defining the block size, or to change the block size between pictures or subsets or groups of pictures, and partition each picture into the corresponding blocks.

[0106] In other embodiments, the video encoder may be configured to directly receive a block 203 of the picture 201, e.g., one, several, or all of the blocks that form the picture 201. The picture block 203 may also be referred to as the current picture block or the picture block to be encoded. In one example, the prediction processing unit 260 of the video encoder 20 may be configured to perform any combination of the partitioning techniques described above.

[0107] Like image 201, block 203 once again is or may be considered as a two-dimensional array or matrix of samples with intensity values (sample values), albeit of lower dimension than image 201. In other words, block 203 may comprise, for example, one sample array (e.g., one luma array in the case of a monochrome image 201), or three sample arrays (e.g., one luma and two chroma arrays in the case of a color image 201), or any other number and/or type of arrays depending on the color format applied. The number of samples in the horizontal and vertical direction (or axis) of block 203 defines the size of block 203. Accordingly, a block may, for example, be an MxN array of samples (M column by N row), or an MxN array of transform coefficients.

[0108] The encoder 20 as shown in Figure 2 is configured to encode the image 201 block by block, for example, the encoding and prediction are performed per block 203.

[0109] Embodiments of the video encoder 20 as shown in Figure 2 may be further configured to partition and/or encode the image using slices (also referred to as video slices), wherein an image may be partitioned or encoded using one or more slices (typically non-overlapping), and each slice may comprise one or more blocks (e.g., CTUs) or one or more groups of blocks (e.g., tiles (H.265/HEVC and VVC) or bricks (VVC)).

[0110] Embodiments of the video encoder 20 as shown in Figure 2 may be further configured to partition and/or encode the image using slice/tile groups (also referred to as video tile groups) and/or tiles (also referred to as video tiles), wherein an image may be partitioned or encoded using one or more slice/tile groups (typically non-overlapping), and each slice/tile group may comprise, for example, one or more blocks (e.g., CTUs) or one or more tiles, wherein each tile, for example, may be rectangular in shape and may comprise one or more blocks (e.g., CTUs), for example, full or fractional blocks.

RESIDUAL CALCULATION

[0111] The residual calculation unit 204 is configured to calculate a residual block 205 based on the image block 203 and a prediction block 265 (further details about the prediction block 265 are provided later), for example, by subtracting sample values of the prediction block 265 from the sample values of the image block 203, sample by sample (pixel by pixel) to obtain the residual block 205 in the sample domain.

TRANSFORMED

[0112] The transform processing unit 206 is configured to apply a transform, e.g., a discrete cosine transform (DCT) or discrete sine transform (DST), to the sample values of the residual block 205 to obtain transform coefficients 207 in a transform domain. The transform coefficients 207 may also be referred to as transform residual coefficients and represent the residual block 205 in the transform domain.

[0113] The transform processing unit 206 may be configured to apply integer approximations of DCT/DST, such as the transforms specified for HEVC/H.265. Compared to an orthogonal DCT transform, such integer approximations are typically scaled by a certain factor. In order to preserve the norm of the residual block that is processed by the forward and inverse transforms, additional scaling factors are applied as part of the transform process. The scaling factors are typically chosen based on certain constraints such as scaling factors being a power of two for shift operation, bit depth of the transform coefficients, tradeoff between accuracy and implementation costs, etc. Specific scaling factors are, for example, specified for the inverse transform, e.g., by inverse transform processing unit 212, in a decoder 30 (and the corresponding inverse transform, e.g., by inverse transform processing unit 212 in an encoder 20), and corresponding scaling factors for the forward transform, e.g., by transform processing unit 206, in an encoder 20 may be specified accordingly.

[0114] Embodiments of video encoder 20 (relative to transform processing unit 206) may be configured to output transform parameters, e.g., a transform type or transforms, e.g., directly or encoded or compressed via entropy coding unit 270, so that, e.g., video decoder 30 may receive and use the transform parameters for decoding.

QUANTIZATION

[0115] The quantization unit 208 is configured to quantize the transform coefficients 207 to obtain quantized transform coefficients 209, for example, by applying scalar quantization or vector quantization. The quantized transform coefficients 209 may also be referred to as quantized residual coefficients 209. The quantization process may reduce the bit depth associated with some or all of the transform coefficients 207. For example, an n-bit transform coefficient may be rounded down to an m-bit transform coefficient during quantization, where n is greater than m. The degree of quantization may be modified by adjusting a quantization parameter (QP). For example, for scalar quantization, different scales may be applied to achieve finer or coarser quantization. Smaller quantization step sizes correspond to finer quantization, while larger quantization step sizes correspond to coarser quantization. The applicable quantization step size may be indicated by a quantization parameter (QP). The quantization parameter may, for example, be an index to a predefined set of applicable quantization step sizes. For example, small quantization parameters may correspond to fine quantization (small quantization step sizes), and large quantization parameters may correspond to coarse quantization (large quantization step sizes), or vice versa. Quantization may include division by a quantization step size, and corresponding dequantization or inverse quantization, e.g., inverse quantization 210, may include multiplication by the quantization step size. Embodiments of some standards, e.g., HEVC, may be configured to use a quantization parameter to determine the quantization step size. In general, the quantization step size can be calculated based on a quantization parameter using a fixed-point approximation of an equation including division. Additional scaling factors can be introduced for quantization and dequantization to restore the residual block norm, which could be modified due to the scaling used in the fixed-point approximation of the equation for the quantization step size and quantization parameter. In an example implementation, inverse transform scaling and dequantization could be combined. Alternatively, custom quantization tables can be used and signaled from an encoder to a decoder, for example, in a bitstream. Quantization is a lossy operation, where the loss increases with increasing quantization step sizes.

[0116] Embodiments of video encoder 20 (relative to quantization unit 208) may be configured to output quantization parameters (QP), e.g., directly or encoded via entropy coding unit 270, so that, e.g., video decoder 30 may receive and apply the quantization parameters for decoding.

[0117] The inverse quantization unit 210 is configured to apply the inverse quantization of the quantization unit 208 to the quantized coefficients to obtain dequantized coefficients 211, for example, by applying the inverse of the quantization scheme applied by the quantization unit 208 based on or using the same quantization step size as the quantization unit 208. The dequantized coefficients 211 may also be referred to as dequantized residual coefficients 211 and correspond—although typically not identical to the transform coefficients due to quantization loss—to the transform coefficients 207.

[0118] The inverse transform processing unit 212 is configured to apply the inverse transform of the transform applied by the transform processing unit 206, e.g., an inverse discrete cosine transform (DCT) or inverse discrete sine transform (DST), to obtain an inverse transform block 213 in the sample domain. The inverse transform block 213 may also be referred to as the inverse transform dequantized block 213 or the inverse transform residual block 213.

[0119] The reconstruction unit 214 (e.g., adder 214) is configured to add the inverse transform block 213 (i.e., reconstructed residual block 213) to the prediction block 265 to obtain a reconstructed block 215 in the sample domain, for example, by adding the sample values of the reconstructed residual block 213 and the sample values of the prediction block 265.

[0120] Optionally, the buffer unit 216 (or "buffer" 216 for short), e.g., a line buffer 216, is configured to buffer or store the reconstructed block 215 and the respective sample values, e.g., for intra prediction. In other embodiments, the encoder may be configured to use unfiltered reconstructed blocks and/or the respective sample values stored in the buffer unit 216 for any type of estimation and/or prediction, e.g., intra prediction.

[0121] Embodiments of encoder 20 may be configured such that, for example, buffer unit 216 is not only used to store the reconstructed blocks 215 for intra prediction 254, but also for loop filter unit 220 (not shown in Figure 2), and/or such that, for example, buffer unit 216 and decoded picture buffer unit 230 form a buffer. Other embodiments may be configured to use filtered blocks 221 and/or blocks or samples from decoded picture buffer 230 (both not shown in Figure 2) as input or basis for intra prediction 254.

[0122] The loop filter unit 220 (or "loop filter" 220 for short) is configured to filter the reconstructed block 215 to obtain a filtered block 221, for example, to smooth pixel transitions, or otherwise improve video quality. The loop filter unit 220 is intended to represent one or more loop filters such as a deblocking filter, a sample-adaptive offset (SAO) filter, or other filters, for example, a bilateral filter or an adaptive loop filter (ALF), or sharpening or smoothing filters, or collaborative filters. Although the loop filter unit 220 is shown in Figure 2 as being an in-loop filter, in other embodiments, the loop filter unit 220 may be implemented as a post-loop filter. The filtered block 221 may also be referred to as the filtered reconstructed block 221. The decoded picture buffer 230 may store the reconstructed coding blocks after the filter loop unit 220 performs the filtering operations on the reconstructed coding blocks.

[0123] The loop filter unit 220 (or "loop filter" 220 for short) is configured to filter the reconstructed block 215 to obtain a filtered block 221 or, in general, to filter reconstructed samples to obtain filtered sample values. The loop filter unit is, for example, configured to smooth pixel transitions or otherwise enhance video quality. The loop filter unit 220 may comprise one or more loop filters, such as a deblocking filter, an adaptive sample shift (SAO) filter, or one or more other filters, for example, an adaptive loop filter (ALF), a noise suppression filter (NSF), or any combination thereof. In one example, the loop filter unit 220 may comprise a deblocking filter, an SAO filter, and an ALF filter. The order of the filtering process may be deblocking, SAO, and ALF filter. In another example, a process called luma mapping with chroma scaling (LMCS) (i.e., the adaptive in-loop reshaper) is added. This process is performed before deblocking. In another example, the deblocking filter process can also be applied to internal subblock edges, e.g., affine subblock edges, ATMVP subblock edges, subblock transform (SBT) edges, and intra-subpartition (ISP) edges. Although the loop filter unit 220 is shown in Figure 2 as an in-loop filter, in other embodiments, the loop filter unit 220 can be implemented as a post-loop filter. The filtered block 221 can also be referred to as the filtered reconstructed block 221.

[0124] Embodiments of video encoder 20 (relative to loop filter unit 220) may be configured to output loop filter parameters (such as SAO filter parameters or ALF filter parameters or LMCS parameters), for example, directly or encoded via entropy coding unit 270, so that, for example, a decoder 30 may receive and apply the same loop filter parameters or respective loop filters for decoding.

[0125] Embodiments of encoder 20 (relative to filter loop unit 220) may be configured to output filter loop parameters (such as sample-adaptive offset information), e.g., directly or entropy-encoded via entropy coding unit 270 or any other entropy coding unit, so that, e.g., a decoder 30 may receive and apply the same filter loop parameters for decoding.

[0126] The decoded picture buffer (DPB) 230 may be a reference picture memory that stores reference picture data for use in encoding video data by video encoder 20. The DPB 230 may be formed by any of a variety of memory devices, such as dynamic random access memory (DRAM), including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. The DPB 230 and the buffer 216 may be provided by the same memory device or separate memory devices. In some example, the decoded picture buffer (DPB) 230 is configured to store the filtered block 221. The decoded picture buffer 230 may be further configured to store other previously filtered blocks, e.g., previously reconstructed and filtered blocks 221, of the same current picture or of different pictures, e.g., previously reconstructed pictures, and may provide complete previously decoded, i.e., reconstructed pictures (and corresponding reference blocks and samples) and/or a partially reconstructed current picture (and corresponding reference blocks and samples), e.g., for inter-prediction. In some example, if reconstructed block 215 is reconstructed but without in-loop filtering, decoded picture buffer (DPB) 230 is configured to store one or more unfiltered reconstructed blocks 215, or in general unfiltered reconstructed samples, e.g., if reconstructed block 215 is not filtered by loop filter unit 220, or any other further processed version of the reconstructed blocks or samples.

[0127] The prediction processing unit 260, also referred to as the block prediction processing unit 260, is configured to receive or obtain the block 203 (current block 203 of the current picture 201) and reconstructed image data, e.g., reference samples of the same (current) picture from the buffer 216 and/or reference image data 231 from one or a plurality of clearly decoded pictures from the decoded picture buffer 230, and to process such data for prediction, i.e., to provide a prediction block 265, which may be an inter-mode predicted block 245 or an intra-mode predicted block 255.

[0128] The mode selection unit 262 may be configured to select a prediction mode (e.g., an intra- or inter-prediction mode) and/or a corresponding prediction block 245 or 255 to be used as prediction block 265 for the calculation of the residual block 205 and for the reconstruction of the reconstructed block 215.

[0129] Embodiments of the mode selection unit 262 may be configured to select the prediction mode (e.g., from those supported by the prediction processing unit 260) that provides the best matching, or in other words, the minimum residual (minimum residual means best compression for transmission or storage), or a minimum signaling overhead (minimum signaling overhead means best compression for transmission or storage), or that considers or balances both. The mode selection unit 262 may be configured to determine the prediction mode based on rate distortion optimization (RDO), i.e., select the prediction mode that provides a minimum rate distortion optimization or whose associated rate distortion at least meets a prediction mode selection criterion.

[0130] Next, prediction processing (e.g., by prediction processing unit 260) and mode selection (e.g., by mode selection unit 262) performed by an exemplary encoder 20 will be explained in more detail.

[0131] In addition to or alternatively to the aforementioned embodiments, in other embodiments according to Figure 15, the mode selection unit 260 comprises partitioning unit 262, inter prediction unit 244, and intra prediction unit 254, and is configured to receive or obtain original image data, e.g., an original block 203 (current block 203 of the current image 17), and reconstructed image data, e.g., filtered and/or unfiltered reconstructed samples or blocks from the same (current) image and/or from one or a plurality of previously decoded images, e.g., from the decoded image buffer 230 or other buffers (e.g., row buffer, not shown). The reconstructed image data is used as reference image data for prediction, e.g., inter prediction or intra prediction, to obtain a prediction block 265 or predictor 265.

[0132] The mode selection unit 260 may be configured to determine or select a partitioning for a current block prediction mode (including no partitioning) and a prediction mode (e.g., an intra- or inter-prediction mode), and generate a corresponding prediction block 265, which is used for the calculation of the residual block 205 and for the reconstruction of the reconstructed block 215.

[0133] Embodiments of mode selection unit 260 may be configured to select the partitioning and prediction mode (e.g., from those supported by or available to mode selection unit 260) that provide the best matching, or in other words the minimum residual (minimum residual means best compression for transmission or storage), or a minimum signaling overhead (minimum signaling overhead means best compression for transmission or storage), or that considers or balances both. Mode selection unit 260 may be configured to determine the partitioning and prediction mode based on rate distortion optimization (RDO), i.e., select the prediction mode that provides a minimum rate distortion. Terms such as "best," "minimum," "optimal," etc. in this context do not necessarily relate to a "best," "minimum," "optimal," etc. general, but may also refer to the fulfillment of a termination or selection criterion such as a value exceeding or falling below a threshold or other constraints potentially leading to "suboptimal selection" but reducing complexity and processing time.

[0134] In other words, the partitioning unit 262 may be configured to partition a picture of a video sequence into a sequence of coding tree units (CTUs), and the CTU 203 may be further partitioned into smaller block partitions or sub-blocks (which again form blocks), for example, iteratively using quaternary tree (QT) partitioning, binary tree (BT) partitioning, or triple tree (TT) partitioning, or any combination thereof, and to perform, for example, prediction for each of the block partitions or sub-blocks, wherein the mode selection comprises selecting the tree structure of the partitioned block 203, and the prediction modes are applied to each of the block partitions or sub-blocks.

[0135] Next, the partitioning (e.g., by partitioning unit 260) and prediction processing (by inter prediction unit 244 and intra prediction unit 254) performed by an exemplary video encoder 20 will be explained in further detail. Partitioning

[0136] The partitioning unit 262 may be configured to partition a picture of a video sequence into a sequence of coding tree units (CTUs), and the partitioning unit 262 may partition (or divide) a coding tree unit (CTU) 203 into smaller partitions, e.g., smaller square or rectangular sized blocks. For a picture that has three sample arrangements, a CTU consists of an N x N block of luma samples along with two corresponding blocks of chroma samples. The maximum allowable luma block size in a CTU is specified as 128 x 128 in the evolving versatile video coding (VVC), but may be specified as something other than 128 x 128 in the future, e.g., 256 x 256. The CTUs of a picture may be clustered as groups of slices/tiles, tiles, or bricks. A tile covers a rectangular region of an image, and a tile can be divided into one or more bricks. A brick consists of multiple CTU lines within a tile. A tile that is not partitioned into multiple bricks can be referred to as a brick. However, a brick is a true subset of a tile and is not referred to as a tile. There are two tile group modes supported in VVC: raster-scan tile group mode and rectangular slice mode. In raster-scan tile group mode, a tile group contains a sequence of raster-scan tiles from an image. In rectangular slice mode, a slice contains a number of image bricks that collectively form a rectangular region of the image. The bricks within a rectangular slice are in the slice's brick raster scan order. These smaller blocks (also called sub-blocks) can be partitioned into even smaller partitions. This also refers to tree partitioning or hierarchical tree partitioning, where a root block, e.g., at tree level 0 (hierarchy level 0, depth 0), can be recursively partitioned, e.g., into two or more blocks of a next-lower tree level, e.g., nodes at tree level 1 (hierarchy level 1, depth 1), where these blocks can be further partitioned into two or more blocks of a next-lower level, e.g., tree level 2 (hierarchy level 2, depth 2), etc., until the partitioning is terminated, e.g., because a termination criterion is met, e.g., a maximum tree depth or minimum block size is reached. Blocks that are not further partitioned are also referred to as leaf blocks or leaf nodes of the tree. A tree that uses partitioning into two partitions is referred to as a binary tree (BT), a tree that uses partitioning into three partitions is referred to as a ternary tree (TT), and a tree that uses partitioning into four partitions is referred to as a quaternary tree (QT).

[0137] For example, a coding tree unit (CTU) may be or comprise a CTB of luma samples, two corresponding CTBs of chroma samples of an image that has three sample arrangements, or a CTB of samples of a monochrome image or an image that is coded using three separate color planes and syntax structures used to encode the samples. Correspondingly, a coding tree block (CTB) may be an NxN block of samples for some value of N such that dividing a component into CTBs is a partitioning. A coding unit (CU) may be or comprise a coding block of luma samples, two corresponding coding blocks of chroma samples of an image that has three sample arrangements, or a coding block of samples of a monochrome image or an image that is coded using three separate color planes and syntax structures used to encode the samples. Correspondingly, a coding block (CB) can be an MxN block of samples for some values of M and N so that dividing a CTB into coding blocks is a partitioning.

[0138] In embodiments, for example, according to HEVC, a coding tree unit (CTU) may be divided into CUs using a quaternary tree structure denoted as coding tree. The decision of whether or not to encode a picture area using inter-picture (temporal) or intra-picture (spatial) prediction is made at the leaf CU level. Each leaf CU may be divided into one, two, or four PUs according to the PU division type. Within a PU, the same prediction process is applied, and relevant information is transmitted to the decoder based on the PU. After obtaining the residual block by applying the prediction process based on the PU division type, a leaf CU may be partitioned into transform units (TUs) according to another quaternary tree structure similar to the coding tree for the CU.

[0139] In embodiments, for example, according to the latest video coding standard currently under development, which is referred to as Versatile Video Coding (VVC), a nested quaternary tree combined with multi-type tree using binary and ternary splits segmentation structure, for example, is used to partition a coding tree unit. In the coding tree structure within a coding tree unit, a CU may have either a square or rectangular shape. For example, the coding tree unit (CTU) is first partitioned by a quaternary tree. Then, the leaf nodes of the quaternary tree may be further partitioned by a multi-type tree structure. There are four split types in the multi-type tree structure, vertical binary split (SPLIT_BT_VER), horizontal binary split (SPLIT_BT_HOR), vertical ternary split (SPLIT_TT_VER), and horizontal ternary split (SPLIT_TT_HOR). The leaf nodes of a multitype tree are called coding units (CUs), and unless the CU is too large for the maximum transform length, this segmentation is used for prediction and transform processing without any additional partitioning. This means that, in most cases, the CU, PU, and TU have the same block size in a quaternary tree with a nested multitype tree coding block structure. The exception occurs when the maximum supported transform length is smaller than the width or height of the CU's color component. VVC develops a unique signaling mechanism for partition split information in a quaternary tree with a nested multitype tree coding tree structure. In the signaling mechanism, a coding tree unit (CTU) is treated as the root of a quaternary tree and is first partitioned by a quaternary tree structure. Each leaf node of the quaternary tree (when large enough to allow it) is then further partitioned by a multitype tree structure. In the multi-type tree structure, a first flag (mtt_split_cu_flag) is flagged to indicate whether the node is further split; when a node is further split, a second flag (mtt_split_cu_vertical_flag) is flagged to indicate the split direction, and then a third flag (mtt_split_cu_binary_flag) is flagged to indicate whether the split is binary or ternary. Based on the values of mtt_split_cu_vertical_flag and mtt_split_cu_binary_flag, the multi-type tree splitting mode (MttSplitMode) of a CU can be derived by a decoder based on a predefined rule or a table. It should be noted that for a given design, e.g., a 64 x 64 Luma block and a 32 x 32 Chroma thread design in VVC hardware decoders, TT division is prohibited when the width or height of a luma encoding block is greater than 64, as shown in Figure 6. TT division is also prohibited when either the width or height of a chroma encoding block is greater than 32. The thread design will divide an image into Virtual Thread Data Units (VPDUs), which are defined as non-overlapping units in an image. In hardware decoders, successive VPDUs are processed by multiple thread stages simultaneously. The VPDU size is roughly proportional to the buffer size in most thread stages, so it is important to keep the VPDU size small. In most hardware decoders, the VPDU size can be adjusted within the maximum transform block size (TB). However, in VVC, ternary tree (TT) and binary tree (BT) partitioning can lead to increased VPDU sizes.

[0140] Furthermore, it should be noted that when a portion of a tree node block exceeds the bottom or right border of the image, the tree node block is forced to be split until all samples of the entire encoded CU are located within the image borders.

[0141] As an example, the Intra Subpartitions (ISP) tool can divide intra-predicted luma blocks vertically or horizontally into 2 or 4 subpartitions depending on the block size.

[0142] In one example, the mode selection unit 260 of the video encoder 20 may be configured to perform any combination of the partitioning techniques described herein. As described above, the encoder 20 is configured to determine or select the best or an optimal prediction mode from a set of (predetermined) prediction modes. The set of prediction modes may comprise, for example, intra-prediction modes and/or inter-prediction modes.

[0143] The set of intra prediction modes may comprise 35 different intra prediction modes, e.g., non-directional modes such as DC (or average) mode and planar mode, or directional modes, e.g., as defined in H.265, or may comprise 67 different intra prediction modes, e.g., non-directional modes such as DC (or average) mode and planar mode, or directional modes, e.g., as defined for VVC. As an example, several conventional wide-angle intra prediction modes are adaptively replaced by wide-angle intra prediction modes for the non-square blocks, e.g., as defined in VVC. As a further example, to avoid splitting operations for DC prediction, only the longest side is used to compute the average for non-square blocks. And, the planar mode intra prediction results may be further modified by a position-dependent intra prediction (PDPC) combination method.

[0144] The intra prediction unit 254 is configured to use reconstructed samples from neighboring blocks of the same current image to generate an intra prediction block 265 according to an intra prediction mode of the set of intra prediction modes.

[0145] The intra prediction unit 254 (or in general the mode selection unit 260) is further configured to output intra prediction parameters (or in general information indicative of the intra prediction mode selected for the block) to the entropy coding unit 270 in the form of syntax elements 266 for inclusion in the encoded image data 21, so that, for example, the video decoder 30 can receive and use the prediction parameters for decoding.

[0146] The set of (or possible) inter prediction modes depends on the available reference pictures (i.e., at least partially decoded previous pictures, e.g., stored in DBP 230) and other inter prediction parameters, e.g., whether the entire reference picture or only a part, e.g., a search window area around the current block area, of the reference picture is used to search for a best-matching reference block, and/or e.g., whether pixel interpolation is applied, e.g., half/semi pel, quarter pel, and/or 1/16 pel interpolation, or not.

[0147] In addition to the above prediction modes, skip mode, direct mode and/or other inter prediction mode can be applied.

[0148] For example, Extended Fusion Prediction, the fusion candidate list of this mode is constructed by including the following five types of candidates in order: Spatial MVP of spatially neighboring CUs, Temporal MVP of colocated CUs, History-based MVP of a FIFO table, Pairwise average MVP, and Zero MVs. And a decoder lateral motion vector refinement (DMVR) based on bilateral pairing can be applied to increase the accuracy of the MVs of the fusion mode. Fusion mode with MVD (MMVD), which comes from the fusion mode with motion vector differences. An MMVD flag is signaled just after sending a skip flag and a fusion flag to specify whether the MMVD mode is used for a CU. And a CU-level adaptive motion vector resolution (AMVR) scheme can be applied. AMVR allows the MVD of the CU to be encoded in different precision. Depending on the prediction mode for the current CU, the MVDs of the current CU can be adaptively selected. When a CU is encoded in fusion mode, the combined inter/intra prediction (CIIP) mode can be applied to the current CU. The weighted average of the inter and intra prediction signals is performed to obtain the CIIP prediction. In affine motion-compensated prediction, the affine motion field of the block is described by motion information from two control points (4 parameters) or three control point motion vectors (6 parameters). Sub-block-based temporal motion vector prediction (SbTMVP), which is similar to temporal motion vector prediction (TMVP) in HEVC, predicts the motion vectors of sub-CUs within the current CU. Bidirectional optical flow (BDOF), formerly referred to as BIO, is a simpler version that requires much less computation, especially in terms of the number of multiplications and the size of the multiplier. Triangular partition mode: In this mode, a CU is divided equally into two triangular partitions using either diagonal or antidiagonal partitioning. Furthermore, the dual prediction mode is extended beyond simple averaging to allow for the weighted average of the two prediction signals.

[0149] In addition to the above prediction modes, skip mode and/or direct mode can be applied.

[0150] The prediction processing unit 260 may further be configured to partition the block 203 into smaller block partitions or sub-blocks, e.g., iteratively using quaternary tree partitioning (QT), binary partitioning (BT), or ternary tree partitioning (TT), or any combination thereof, and to perform, e.g., prediction for each of the block partitions or sub-blocks, wherein the mode selection comprises selecting the tree structure of the partitioned block 203 and the prediction modes applied to each of the block partitions or sub-blocks.

[0151] The inter prediction unit 244 may include motion estimation unit (ME) (not shown in Figure 2) and motion compensation unit (MC) (not shown in Figure 2). The motion estimation unit is configured to receive or obtain the image block 203 (current image block 203 of the current image 201) and a decoded image 231, or at least one or a plurality of previously reconstructed blocks, e.g., reconstructed blocks from one or a plurality of other/different previously decoded images 231, for motion estimation. For example, a video sequence may comprise the current image and the previously decoded images 231, or in other words, the current image and the previously decoded images 231 may be part of or form a sequence of images forming a video sequence.

[0152] The encoder 20 may, for example, be configured to select a reference block from a plurality of reference blocks of the same or different pictures of the plurality of other pictures and provide a reference picture (or reference picture index, ...) and/or an offset (spatial deviation) between the position (x, y coordinates) of the reference block and the position of the current block as inter prediction parameters for the motion estimation unit (not shown in Figure 2). This offset is also called a motion vector (MV).

[0153] The motion compensation unit is configured to obtain, e.g., receive, an inter prediction parameter and to perform inter prediction based on or using the inter prediction parameter to obtain an inter prediction block 265. Motion compensation, performed by the motion compensation unit, may involve obtaining or generating the prediction block based on the motion/block vector determined by motion estimation, possibly performing interpolations to subpixel accuracy. Interpolation filtering may generate additional pixel samples from known pixel samples, thereby potentially increasing the number of candidate prediction blocks that can be used to encode an image block. Upon receiving the motion vector for the PU of the current image block, the motion compensation unit may locate the prediction block to which the motion vector points in one of the reference image lists.

[0154] The intra prediction unit 254 is configured to obtain, e.g., receive, the image block 203 (current image block) and one or a plurality of previously reconstructed blocks, e.g., by recording neighboring constructed blocks of the same image for intra estimation. The encoder 20 may, e.g., be configured to select an intra prediction mode from a plurality of (predetermined) intra prediction modes.

[0155] Embodiments of encoder 20 may be configured to select the intra prediction mode based on an optimization criterion, e.g., minimum residual (e.g., the intra prediction mode providing the prediction block 255 most similar to the current image block 203) or minimum rate distortion.

[0156] The intra prediction unit 254 is further configured to determine based on the intra prediction parameter, e.g., the selected intra prediction mode, the intra prediction block 255. In any case, after selecting an intra prediction mode for a block, the intra prediction unit 254 is also configured to provide intra prediction parameter, i.e., information indicative of the selected intra prediction mode for the block, to the entropy coding unit 270. In one example, the intra prediction unit 254 may be configured to perform any combination of the intra prediction techniques described below.

[0157] The entropy coding unit 270 is configured to apply an algorithm or scheme entropy coding scheme (e.g., a variable length coding scheme (VLC), a context-adaptive VLC scheme (CALVC), an arithmetic coding scheme, a context-adaptive binary arithmetic coding (CABAC), syntax-based context-adaptive binary arithmetic coding (SBAC), probability interval partitioning entropy coding (PIPE), or another entropy coding methodology or technique) to the quantized residual coefficients 209, inter-prediction parameters, intra-prediction parameter, and/or loop filter parameters, individually or jointly (or not) to obtain encoded image data 21 that may be output by the output 272, for example, in the form of an encoded bitstream 21. The encoded bitstream 21 may be transmitted to the video decoder 30 or archived for later transmission or retrieval by the video decoder 30. The entropy coding unit 270 may be further configured to entropy encode the other syntax elements for the current video slice being encoded.

[0158] Other structural variations of the video encoder 20 may be used to encode the video stream. For example, a non-transform-based encoder 20 may quantize the residual signal directly without the transform processing unit 206 for certain blocks or frames. In another implementation, an encoder 20 may have the quantization unit 208 and the inverse quantization unit 210 combined into a single unit.

[0159] Figure 3 shows an example video decoder 30 that is configured to implement the techniques of the present application. The video decoder 30 is configured to receive encoded image data (e.g., encoded bitstream) 21, e.g., encoded by encoder 100, to obtain a decoded image 131. During the decoding process, the video decoder 30 receives video data, e.g., an encoded video bitstream representing image blocks of an encoded video slice and associated syntax elements, from the video encoder 100.

[0160] In the example of Figure 3, the decoder 30 comprises an entropy decoding unit 304, an inverse quantization unit 310, an inverse transform processing unit 312, a reconstruction unit 314 (e.g., an adder 314), a buffer 316, a loop filter 320, a decoded picture buffer 330, and a prediction processing unit 360. The prediction processing unit 360 may include an inter prediction unit 344, an intra prediction unit 354, and a mode selection unit 362. The video decoder 30 may, in some examples, perform a generally reciprocal mode decoding pass to the encoding pass described with respect to the video encoder 100 of Figure 2.

[0161] As explained with respect to encoder 20, inverse quantization unit 210, inverse transform processing unit 212, reconstruction unit 214, filter loop 220, decoded picture buffer (DPB) 230, inter prediction unit 344, and intra prediction unit 354 are also referred to as forming the "embedded decoder" of video encoder 20. Accordingly, inverse quantization unit 310 may be identical in function to inverse quantization unit 110, inverse transform processing unit 312 may be identical in function to inverse transform processing unit 212, reconstruction unit 314 may be identical in function to reconstruction unit 214, filter loop 320 may be identical in function to filter loop 220, and decoded picture buffer 330 may be identical in function to in function of the decoded picture buffer 230. Therefore, the explanations given for the respective units and functions of the video encoder 20 apply correspondingly to the respective units and functions of the video decoder 30.

[0162] The entropy decoding unit 304 is configured to perform entropy decoding on the encoded image data 21 to obtain, for example, quantized coefficients 309 and/or decoded coding parameters (not shown in Figure 3), for example, any or all of the (decoded) inter prediction parameters, intra prediction parameter, loop filter parameters, and/or other syntax elements. The entropy decoding unit 304 is further configured to forward inter prediction parameters, intra prediction parameter, and/or other syntax elements to the prediction processing unit 360. The video decoder 30 may receive the syntax elements at the video slice level and/or video block level.

[0163] The entropy decoding unit 304 is configured to analyze the bit stream 21 (or in general encoded image data 21) and perform, e.g., entropy decoding on the encoded image data 21 to obtain, e.g., quantized coefficients 309 and/or decoded coding parameters (not shown in Figure 3), e.g., any or all inter prediction parameters (e.g., reference image index and motion vector), intra prediction parameter (e.g., intra prediction mode or index), transform parameters, quantization parameters, loop filter parameters, and/or other syntax elements. The entropy decoding unit 304 may be configured to apply the decoding algorithms or schemes corresponding to the coding schemes as described with respect to the entropy coding unit 270 of the encoder 20. The entropy decoding unit 304 may be further configured to provide inter-prediction parameters, intra-prediction parameters, and/or other syntax elements to the mode application unit 360 and other parameters to other units of the decoder 30. The video decoder 30 may receive the syntax elements at the video slice level and/or video block level. In addition to or as an alternative to the slices and their respective syntax elements, tile groups and/or tiles and their respective syntax elements may be received and/or used.

[0164] The inverse quantization unit 310 may be identical in function to the inverse quantization unit 110, the inverse transform processing unit 312 may be identical in function to the inverse transform processing unit 112, the reconstruction unit 314 may be identical in function to the reconstruction unit 114, the buffer 316 may be identical in function to the buffer 116, the filter loop 320 may be identical in function to the filter loop 120, and the decoded picture buffer 330 may be identical in function to the decoded picture buffer 130.

[0165] Embodiments of the decoder 30 may comprise a partitioning unit (not depicted in Figure 3). In one example, the prediction processing unit 360 of the video decoder 30 may be configured to perform any combination of the partitioning techniques described above.

[0166] The prediction processing unit 360 may comprise an inter prediction unit 344 and an intra prediction unit 354, wherein the inter prediction unit 344 may resemble the inter prediction unit 144 in function, and the intra prediction unit 354 may resemble the intra prediction unit 154 in function. The prediction processing unit 360 is typically configured to perform the block prediction and/or obtain the prediction block 365 from the encoded data 21 and to receive or obtain (explicitly or implicitly) the prediction-related parameters and/or the information about the selected prediction mode, for example, from the entropy decoding unit 304.

[0167] When the video slice is encoded as an intra (I) mode encoded slice, the intra prediction unit 354 of the prediction processing unit 360 is configured to generate the prediction block 365 for a picture block of the current video slice based on a signaled intra prediction mode and data from previously decoded blocks of the current frame or picture. When the video frame is encoded as an inter (i.e., B or P) mode encoded slice, the inter prediction unit 344 (e.g., motion compensation unit) of the prediction processing unit 360 is configured to produce prediction blocks 365 for a video block of the current video slice based on the motion vectors and other syntax elements received from the entropy decoding unit 304. For inter prediction, the prediction blocks may be produced from one of the reference pictures within one of the reference picture lists. The video decoder 30 may construct the reference frame lists, List 0 and List 1, using standard construction techniques based on reference pictures stored in the DPB 330.

[0168] The prediction processing unit 360 is configured to determine prediction information for a video block of the current video slice by analyzing motion vectors and other syntax elements, and uses the prediction information to produce prediction blocks for the current video block being decoded. For example, the prediction processing unit 360 uses some of the received syntax elements to determine a prediction mode (e.g., intra- or inter-prediction) used to encode the video blocks of the video slice, an inter-prediction slice type (e.g., B-slice, P-slice, or GPB-slice), construction information for one or more of the reference picture lists for the slice, motion vectors for each inter-mode encoded video block of the slice, inter-prediction status for each encoded video block of the slice, and other information for decoding the video blocks in the current video slice.

[0169] The inverse quantization unit 310 is configured to inversely quantize, i.e., dequantize, the quantized transform coefficients provided in the bitstream and decoded by the entropy decoding unit 304. The inverse quantization process may include using a quantization parameter calculated by video encoder 100 for each video block in the video slice to determine a degree of quantization and, likewise, a degree of inverse quantization that should be applied.

[0170] The inverse quantization unit 310 may be configured to receive quantization parameters (QP) (or in general information related to inverse quantization) and quantized coefficients from the encoded image data 21 (e.g., by analysis and/or decoding, e.g., by entropy decoding unit 304) and to apply based on the quantization parameters an inverse quantization on the decoded quantized coefficients 309 to obtain dequantized coefficients 311, which may also be referred to as transform coefficients 311.

[0171] The inverse transform processing unit 312 is configured to apply an inverse transform, e.g., an inverse DCT, an inverse integer transform, or a conceptually similar inverse transform process, to the transform coefficients in order to produce residual blocks in the pixel domain.

[0172] The inverse transform processing unit 312 may be configured to receive dequantized coefficients 311, also referred to as transform coefficients 311, and to apply a transform to the dequantized coefficients 311 in order to obtain reconstructed residual blocks 213 in the sample domain. The reconstructed residual blocks 213 may also be referred to as transform blocks 313. The transform may be an inverse transform, e.g., an inverse DCT, an inverse DST, an inverse integer transform, or a conceptually similar inverse transform process. The inverse transform processing unit 312 may be further configured to receive transform parameters or corresponding information from the encoded image data 21 (e.g., by parsing and/or decoding, e.g., by entropy decoding unit 304) to determine the transform to be applied to the dequantized coefficients 311.

[0173] The reconstruction unit 314 (e.g., adder 314) is configured to add the inverse transform block 313 (i.e., reconstructed residual block 313) to the prediction block 365 to obtain a reconstructed block 315 in the sample domain, for example, by adding the sample values of the reconstructed residual block 313 and the sample values of the prediction block 365.

[0174] The loop filter unit 320 (in the encoding circuit or after the encoding circuit) is configured to filter the reconstructed block 315 to obtain a filtered block 321, for example, to smooth pixel transitions, or otherwise improve video quality. The loop filter unit 320 may comprise one or more loop filters, such as a deblocking filter, a sample adaptive offset (SAO) filter, or one or more other filters, for example, an adaptive loop filter (ALF), a noise suppression filter (NSF), or any combination thereof. In one example, the loop filter unit 220 may comprise a deblocking filter, an SAO filter, and an ALF filter. The order of the filtering process may be deblocking, SAO, and ALF filter. In another example, a process called luma mapping with chroma scaling (LMCS) (namely, the adaptive in-loop reshaper) is added. This process is performed before deblocking. In another example, the deblocking filter process can also be applied to internal subblock edges, e.g., affine subblock edges, ATMVP subblock edges, subblock transform (SBT) edges, and intra-subpartition (ISP) edges. Although the loop filter unit 320 is shown in Figure 3 as an in-loop filter, in other configurations, the loop filter unit 320 can be implemented as a post-loop filter.

[0175] The decoded video blocks 321 in a given frame or image are then stored in the decoded image buffer 330, which stores reference images used for subsequent motion compensation.

[0176] The decoded video blocks 321 of a picture are then stored in the decoded picture buffer 330, which stores the decoded pictures 331 as reference pictures for subsequent motion compensation for other pictures and/or for output with respect to display.

[0177] The decoder 30 is configured to output the decoded image 331, for example, via the output 332, for presentation or display to a user.

[0178] Other variations of the video decoder 30 may be used to decode the compressed bitstream. For example, the decoder 30 may produce the output video stream without the loop filtering unit 320. For example, a non-transform based decoder 30 may inversely quantize the residual signal directly without the inverse transform processing unit 312 for certain blocks or frames. In another implementation, the video decoder 30 may have the inverse quantization unit 310 and the inverse transform processing unit 312 combined into a single unit.

[0179] In addition to or alternatively to the aforementioned embodiments, in other embodiments according to Figure 16, the inter prediction unit 344 may be identical to the inter prediction unit 244 (in particular to the motion compensation unit) and the intra prediction unit 354 may be identical to the inter prediction unit 254 in function, and performs splitting or partitioning and prediction decisions based on the partitioning and/or prediction parameters or respective information received from the encoded image data 21 (e.g., by parsing and/or decoding, e.g., by entropy decoding unit 304). The mode application unit 360 may be configured to perform prediction (intra or inter prediction) per block based on reconstructed images, on blocks or on respective samples (filtered or unfiltered) to obtain the prediction block 365.

[0180] When the video slice is coded as an intra (I) mode coded slice, the intra prediction unit 354 of the mode application unit 360 is configured to generate the prediction block 365 for a picture block of the current video slice based on a signaled intra prediction mode and previously decoded block data of the current picture. When the video picture is coded as an inter (i.e., B or P) mode coded slice, the inter prediction unit 344 (e.g., motion compensation unit) of the mode application unit 360 is configured to produce prediction blocks 365 for a video block of the current video slice based on the motion vectors and other syntax elements received from the entropy decoding unit 304. For inter prediction, the prediction blocks may be produced from one of the reference pictures within one of the reference picture lists. The video decoder 30 may construct the lists of reference frames, List 0 and List 1, using standard construction techniques based on reference pictures stored in the DPB 330. The same or similar may be applied to or by embodiments using tile groups (e.g., video tile groups) and/or tiles (e.g., video tiles) in addition to or alternatively to slices (e.g., video slices), for example, a video may be encoded using I, P, or B tile groups and/or tiles.

[0181] The 360-mode application unit is configured to determine prediction information for a video block of the current video slice by analyzing motion vectors or related information and other syntax elements, and uses the prediction information to produce prediction blocks for the current video block being decoded. For example, the 360-mode application unit uses some of the received syntax elements to determine a prediction mode (e.g., intra- or inter-prediction) used to encode the video blocks of the video slice, an inter-prediction slice type (e.g., B-slice, P-slice, or GPB-slice), construction information for one or more of the reference picture lists for the slice, motion vectors for each inter-mode encoded video block of the slice, inter-prediction status for each encoded video block of the slice, and other information for decoding the video blocks in the current video slice. The same or similar may be applied to or by embodiments using tile groups (e.g., video tile groups) and/or tiles (e.g., video tiles) in addition to or alternatively to slices (e.g., video slices), for example, a video may be encoded using I, P, or B tile groups and/or tiles.

[0182] Embodiments of the video decoder 30, as shown in Figure 3, may be configured to partition and/or decode the picture using slices (also referred to as video slices), wherein a picture may be partitioned or decoded using one or more slices (typically non-overlapping), and each slice may comprise one or more blocks (e.g., CTUs) or one or more groups of blocks (e.g., tiles (H.265/HEVC and VVC) or bricks (VVC)).

[0183] Embodiments of the video decoder 30 as shown in Figure 3 may be configured to partition and/or decode the picture using slice/tile groups (also referred to as video tile groups) and/or tiles (also referred to as video tiles), wherein a picture may be partitioned into or decoded using one or more slice/tile groups (typically non-overlapping), and each slice/tile group may comprise, for example, one or more blocks (e.g., CTUs) or one or more tiles, wherein each tile, for example, may be rectangular in shape and may comprise one or more blocks (e.g., CTUs), for example, full or fractional blocks.

[0184] Other variations of the video decoder 30 may be used to decode the encoded image data 21. For example, the decoder 30 may produce the output video stream without the loop filtering unit 320. For example, a non-transform based decoder 30 may inversely quantize the residual signal directly without the inverse transform processing unit 312 for certain blocks or frames. In another implementation, the video decoder 30 may have the inverse quantization unit 310 and the inverse transform processing unit 312 combined into a single unit.

[0185] It should be understood that, in encoder 20 and decoder 30, a processing result from a current step may be further processed and then sent to the next step. For example, after interpolation filtering, motion vector derivation, or loop filtering, an additional operation, such as Clip or Shift, may be performed on the processing result of the interpolation filtering, motion vector derivation, or loop filtering.

[0186] Figure 4 is a schematic diagram of a video encoding device 400 according to an embodiment of the disclosure. The video encoding device 400 is suitable for implementing the disclosed embodiments as described herein. In one embodiment, the video encoding device 400 may be a decoder, such as the video decoder 30 of Figure 1A, or an encoder such as the video encoder 20 of Figure 1A. In one embodiment, the video encoding device 400 may be one or more components of the video decoder 30 of Figure 1A or the video encoder 20 of Figure 1A as described above.

[0187] The video encoding device 400 comprises ingress ports 410 and receiver (Rx) units 420 for receiving data; a processor, logic unit, or central processing unit (CPU) 430 for processing the data; transmitter (Tx) units 440 and egress ports 450 for transmitting the data; and a memory 460 for storing the data. The video encoding device 400 may also comprise optical-to-electrical (OE) components and electrical-to-optical (EO) components coupled to the ingress ports 410, the receiver units 420, the transmitter units 440, and the egress ports 450 for egressing or ingressing optical or electrical signals.

[0188] Processor 430 is implemented by hardware and software. Processor 430 may be implemented as one or more CPU chips, cores (e.g., as a multi-core processor), FPGAs, ASICs, and DSPs. Processor 430 is in communication with ingress ports 410, receiver units 420, transmitter units 440, egress ports 450, and memory 460. Processor 430 comprises an encoding module 470. Encoding module 470 implements the disclosed embodiments described above. For example, encoding module 470 implements, processes, prepares, or provides the various encoding operations. The inclusion of encoding module 470, therefore, provides a substantial enhancement to the functionality of video encoding device 400 and effects a transformation of video encoding device 400 to a different state. Alternatively, the encoding module 470 is implemented as instructions stored in memory 460 and executed by the processor 430.

[0189] Memory 460 comprises one or more disks, tape drives, and solid-state drives and may be used as an overflow data storage device, to store programs when such programs are selected for execution, and to store instructions and data that are read during program execution. Memory 460 may be volatile and/or non-volatile and may be read-only memory (ROM), random-access memory (RAM), ternary content-addressable memory (TCAM), and/or static random-access memory (SRAM).

[0190] Figure 5 is a simplified block diagram of an apparatus 500 that may be used as one of or both the source device 310 and the destination device 320 of Figure 1 according to an exemplary embodiment. The apparatus 500 may implement techniques of the present application described above. The apparatus 500 may be in the form of a computing system including multiple computing devices, or in the form of a single computing device, e.g., a mobile phone, a tablet computer, a laptop computer, a notebook computer, a desktop computer, and the like.

[0191] A processor 502 in apparatus 500 may be a central processing unit. Alternatively, processor 502 may be any other type of device, or multiple devices, having the capability to manipulate or process information now existing or later developed. Although the disclosed implementations may be practiced with a single processor, as shown, for example, processor 502, advantages in speed and efficiency may be achieved by using more than one processor.

[0192] A memory 504 in the apparatus 500 may be a read-only memory (ROM) device or a random access memory (RAM) device in one implementation. Any other suitable type of storage device may be used as the memory 504. The memory 504 may include code and data 506 that are accessed by the processor 502 using a bus 512. The memory 504 may additionally include an operating system 508 and application programs 510, the application programs 510 including at least one program that enables the processor 502 to perform the methods described herein. For example, the application programs 510 may include applications 1 through N, which additionally include a video encoding application that performs the methods described herein. The apparatus 500 may also include additional memory in the form of secondary storage 514, which may, for example, be a memory card used with a mobile computing device. Because video communication sessions may contain a significant amount of information, it may be stored in whole or in part in secondary storage 514 and loaded into memory 504 as needed for processing. The apparatus 500 may also include one or more output devices, such as a display 518. The display 518 may be, in one example, a touch-sensitive display that combines a display with a touch-sensitive element operable to sense touch inputs. The display 518 may be coupled to the processor 502 via the bus 512.

[0193] Apparatus 500 may also include one or more output devices, such as a display 518. Display 518 may be, in one example, a touch-sensitive display that combines a display with a touch-sensitive element that is operable to sense touch inputs. Display 518 may be coupled to processor 502 via bus 512. Other output devices that allow a user to program or otherwise use apparatus 500 may be provided in addition to or as an alternative to display 518. When the output device is or includes a display, the display may be implemented in a variety of ways, including by a liquid crystal display (LCD), a cathode ray tube (CRT) display, a plasma display, or a light-emitting diode (LED) display, such as an organic LED display (OLED).

[0194] The apparatus 500 may also include or be in communication with an image sensing device 520, e.g., a camera, or any other image sensing device 520 now existing or later developed that can sense an image such as the image of a user operating the apparatus 500. The image sensing device 520 may be positioned so that it is directed toward the user operating the apparatus 500. In one example, the position and optical axis of the image sensing device 520 may be configured so that the field of view includes an area that is directly adjacent to the display 518 and from which the display 518 is visible.

[0195] The apparatus 500 may also include or be in communication with a sound sensing device 522, e.g., a microphone, or any other sound sensing device now existing or later developed that can sense sounds near the apparatus 500. The sound sensing device 522 may be positioned so that it is directed toward the user operating the apparatus 500 and may be configured to receive sounds, e.g., speech or other utterances, made by the user while the user operates the apparatus 500.

[0196] Although Figure 5 depicts the processor 502 and memory 504 of the apparatus 500 as being integrated into a single unit, other configurations may be utilized. The operations of the processor 502 may be distributed across multiple machines (each machine having one or more of the processors) that may be coupled directly or via a local area or other network. The memory 504 may be distributed across multiple machines such as a network-based memory or memory on multiple machines that perform the operations of the apparatus 500. Although depicted here as a single bus, the bus 512 of the apparatus 500 may be composed of multiple buses. Furthermore, the secondary storage 514 may be directly coupled to the other components of the apparatus 500 or may be accessed via a network and may comprise a single integrated unit such as a memory card or multiple units such as multiple memory cards. The apparatus 500 may thus be implemented in a wide variety of configurations.

[0197] Next Generation Video Coding (NGVC) removes the separation of the concepts of CU, PU, and TU, and supports more flexibility for CU partition formats. A CU size corresponds to a coding node size and can be square or non-square (e.g., rectangular) in shape.

[0198] In J. An et al., "Block partitioning structure for next generation video coding", International Telecommunication Union, COM16-C966, September 2015 (hereinafter, "VCEG COM16-C966 proposal"), quaternary tree-binary tree (QTBT) partitioning techniques were proposed for the future video coding standard beyond HEVC. Simulations showed that the proposed QTBT structure is more efficient than the quaternary tree structure used in HEVC. In HEVC, inter-prediction for small blocks is restricted to reduce motion compensation memory access, and inter-prediction is not supported for 4 x 4 blocks. In JEM's QTBT, these restrictions are removed.

[0199] In QTBT, a CU can be either square or rectangular in shape. As shown in Figure 6, a coding tree unit (CTU) is first partitioned by a quaternary tree structure. The leaf nodes of the quaternary tree can be further partitioned by a binary tree structure. There are two types of splitting, symmetric horizontal splitting and symmetric vertical splitting, in binary tree splitting. In each case, a node is split by splitting the node in half, either horizontally or vertically. The leaf nodes of the binary tree are called coding units (CUs), and this segmentation is used for prediction and transform processing without any further partitioning. This means that CU, PU, and TU have the same block size in the QTBT coding block structure. A CU sometimes consists of coding blocks (CBs) of different color components, e.g., a CU contains one luma CB and two chroma CBs in the case of P and B slices of 4:2:0 chroma format, and sometimes consists of a CB of a single component, e.g., a CU contains only one luma CB or only two chroma CBs in the case of I slices.

[0200] The following parameters are defined for the QTBT partitioning scheme.- CTU Size: the root node size of a quaternary tree, the same concept as in HEVC- MinQTSize: the minimum allowed quaternary tree leaf node size- MaxBTSize: the maximum allowed binary tree root node size- MaxBTDepth: the maximum allowed binary tree depth- MinBTSize: the minimum allowed binary tree leaf node size

[0201] In an example of the QTBT partitioning structure, when the quaternary tree node has a size equal to or less than MinQTSize, no additional quaternary tree is considered. It will not be further split by the binary tree since its size (MinQTSize) exceeds MaxBTSize. Otherwise, the quaternary tree leaf node could be further partitioned by the binary tree. Therefore, the quaternary tree leaf node is also the root node of the binary tree and has the binary tree depth as 0 (zero). When the binary tree depth reaches MaxBTDepth (i.e., 4), no additional splits are considered. When the binary tree node has a width equal to MinBTSize (i.e., 4), no additional horizontal splits are considered. Similarly, when the binary tree node has a height equal to MinBTSize, no additional vertical splits are considered. The leaf nodes of the binary tree are further processed by prediction and transform processing without any additional partitioning. In JEM, the maximum CTU size is 256 x 256 luma samples. Binary tree leaf nodes (CUs) can be further processed (e.g., by performing a prediction process and a transform process) without any additional partitioning.

[0202] Figure 6 illustrates an example of a block 30 (e.g., a CTB) partitioned using QTBT partitioning techniques. As shown in Figure 6, using QTBT partitioning techniques, each of the blocks is split symmetrically through the center of each block. Figure 7 illustrates the tree structure corresponding to the block partitioning of Figure 6. Solid lines in Figure 7 indicate quaternary tree splitting and dashed lines indicate binary tree splitting. In one example, at each split (i.e., non-leaf) node of the binary tree, a syntax element (e.g., a flag) is flagged to indicate the type of split performed (e.g., horizontal or vertical), where 0 indicates horizontal splitting and 1 indicates vertical splitting. For quaternary tree splitting, there is no need to indicate the type of splitting, since quaternary tree splitting always splits a block horizontally and vertically into 4 subblocks of equal size.

[0203] As shown in Figure 7, at node 50, block 30 (corresponding to root 50) is split into the four blocks 31, 32, 33, and 34, shown in Figure 6, using QT partitioning. Block 34 is not further split and is therefore a leaf node. At node 52, block 31 is further split into two blocks using BT partitioning. As shown in Figure 7, node 52 is marked with a 1, indicating vertical split. Thus, the split at node 52 results in block 37 and the block including both blocks 35 and 36. Blocks 35 and 36 are created by a further vertical split at node 54. At node 56, block 32 is further split into two blocks 38 and 39 using BT partitioning.

[0204] At node 58, block 33 is split into 4 equal-sized blocks using QT partitioning. Blocks 43 and 44 are created from this QT partition and are not further split. At node 60, the top-left block is first split using vertical binary tree splitting, resulting in block 40 and a right-hand vertical block. The right-hand vertical block is then split using horizontal binary tree splitting into blocks 41 and 42. The bottom-right block created from the quaternary tree split at node 58, is split at node 62 using horizontal binary tree splitting into blocks 45 and 46. As shown in Figure 7, node 62 is marked with a 0, indicating horizontal splitting.

[0205] In addition to QTBT, a block partitioning structure called multi-type tree (MTT) is proposed to replace BT in QTBT-based CU structures, which means that a CTU can be divided by QT partitioning firstly to obtain a block of the CTU, and then the block can be divided by MTT partitioning secondly.

[0206] The MTT partitioning structure is still a recursive tree structure. In MTT, multiple different partition structures (e.g., two or more) are used. For example, according to MTT techniques, two or more different partition structures may be used for each respective non-leaf node of a tree structure, at each depth of the tree structure. The depth of a node in a tree structure may refer to the length of the traversal (e.g., the number of splits) from the node to the root of the tree structure.

[0207] In MTT, there are two partition types, BT partitioning and ternary tree (TT) partitioning. The partition type can be selected from BT partitioning and TT partitioning. The TT partition structure differs from the QT or BT structures in that the TT partition structure does not split a block at the center. The central region of the block remains together in the same subblock. Unlike QT, which produces four blocks, or binary tree, which produces two blocks, splitting according to a TT partition structure produces three blocks. Exemplary partition types according to the TT partition structure include symmetric partition types (both horizontal and vertical) as well as asymmetric partition types (both horizontal and vertical). Furthermore, symmetric partition types according to the TT partition structure can be irregular/non-uniform or regular/uniform. Asymmetric partition types according to the TT partition structure are irregular/non-uniform. In an example, a TT partition structure may include at least one of the following partition types: regular/uniform horizontal symmetric ternary tree, regular/uniform vertical symmetric ternary tree, irregular/non-uniform horizontal symmetric ternary tree, irregular/non-uniform vertical symmetric ternary tree, irregular/non-uniform horizontal asymmetric ternary tree, or irregular/non-uniform vertical asymmetric ternary tree partition types.

[0208] In general, an irregular/non-uniform symmetric ternary tree partition type is a partition type that is symmetric about a block centerline, but where at least one of the three resulting blocks is not the same size as the other two. A preferred example is where the side blocks are 1/4 the size of the block, and the center block is 1/2 the size of the block. A regular/uniform symmetric ternary tree partition type is a partition type that is symmetric about a block centerline, and the resulting blocks are all the same size. Such a partition is possible if the block height or width, depending on a vertical or horizontal partition, is a multiple of 3. An irregular/non-uniform asymmetric ternary tree partition type is a partition type that is not symmetric about a block centerline, and where at least one of the resulting blocks is not the same size as the other two.

[0209] Figure 8 is a conceptual diagram illustrating optional example horizontal ternary tree partition types. Figure 9 is a conceptual diagram illustrating optional examples of vertical ternary tree partition types. In both Figure 8 and Figure 9, h represents the block height in luma or chroma samples, and w represents the block width in luma or chroma samples. Note that the respective centerline of a block does not represent the block boundary (i.e., ternary tree partitions do not split a block along the centerline). Instead, the centerline \ is used to represent whether or not a particular partition type is symmetric or asymmetric about the original block centerline. The centerline is also along the direction of the split.

[0210] As shown in Figure 8, block 71 is partitioned with a regular/uniform horizontal symmetric partition type. The regular/uniform horizontal symmetric partition type produces upper and lower halves that are symmetric about the centerline of block 71. The regular/uniform horizontal symmetric partition type produces three equally sized sub-blocks, each with a height of h/3 and a width of w. The regular/uniform horizontal symmetric partition type is possible when the height of block 71 is evenly divisible by 3.

[0211] Block 73 is partitioned with an irregular/non-uniform horizontal symmetric partition type. The irregular/non-uniform horizontal symmetric partition type produces top and bottom halves that are symmetric about the centerline of block 73. The irregular/non-uniform horizontal symmetric partition type produces two blocks of equal size (e.g., top and bottom blocks with a height of h/4), and a center block of a different size (e.g., a center block with a height of h/2). In one example, under the irregular/non-uniform horizontal symmetric partition type, the area of the center block is equal to the combined areas of the top and bottom blocks. In some examples, the irregular/non-uniform horizontal symmetric partition type may be preferred for blocks with a height that is a power of 2 (e.g., 2, 4, 8, 16, 32, etc.).

[0212] Block 75 is partitioned with an irregular/non-uniform horizontal asymmetric partition type. The irregular/non-uniform horizontal asymmetric partition type does not produce a symmetric top and bottom half about the centerline of block 75 (i.e., the top and bottom halves are asymmetric). In the example of Figure 8, the irregular/non-uniform horizontal asymmetric partition type produces a top block with a height of h/4, a center block with a height of 3h/8, and a bottom block with a height of 3h/8. Of course, other asymmetric arrangements may be used.

[0213] As shown in Figure 9, block 81 is partitioned with a regular/uniform vertical symmetric partition type. The regular/uniform vertical symmetric partition type produces left and right halves that are symmetric about the centerline of block 81. The regular/uniform vertical symmetric partition type produces three equally sized sub-blocks, each with a width of w/3 and a height of h. The regular/uniform vertical symmetric partition type is possible when the width of block 81 is evenly divisible by 3.

[0214] Block 83 is partitioned with an irregular/non-uniform vertical symmetric partition type. The irregular/non-uniform vertical symmetric partition type produces left and right halves symmetric about the centerline of block 83. The irregular/non-uniform vertical symmetric partition type produces left and right halves symmetric about the centerline of block 83. The irregular/non-uniform vertical symmetric partition type produces two blocks of equal size (e.g., left and right blocks with a width of w/4), and a center block of a different size (e.g., a center block with a width of w/2). In one example, under the irregular/non-uniform vertical symmetric partition type, the area of the center block is equal to the combined areas of the left and right blocks. In some examples, the irregular/non-uniform vertical symmetric partition type may be preferred for blocks having a width that is a power of 2 (e.g., 2, 4, 8, 16, 32, etc.).

[0215] Block 85 is partitioned with an irregular/non-uniform vertical asymmetric partition type. The irregular/non-uniform vertical asymmetric partition type does not produce a left and right half that is symmetric about the centerline of block 85 (i.e., the left and right halves are asymmetric). In the example of Figure 9, the irregular/non-uniform vertical asymmetric partition type produces a left block with a width of w/4, a center block with a width of 3w/8, and a right block with a width of 3w/8. Of course, other asymmetric arrangements may be used.

[0216] In addition to (or alternatively to) the parameters for QTBT defined above, the following parameters are defined for the MTT partitioning scheme. - MaxBTSize: the maximum allowed binary tree root node size - MinBtSize: the minimum allowed binary tree root node size - MaxMttDepth: the maximum multitype tree depth - MaxMttDepth Offset: the maximum multitype tree depth offset - MaxTtSize: the maximum allowed ternary tree root node size - MinTtSize: the minimum allowed ternary tree root node size - MinCbSize: the minimum allowed coding block size

[0217] Embodiments of the disclosure may be implemented by a video encoder or a video decoder, such as video encoder 20 of Figure 2 or video decoder 30 of Figure 3, according to an embodiment of the present application. One or more structural elements of video encoder 20 or video decoder 30, including partition unit, may be configured to perform the techniques of embodiments of the disclosure.

[0218] In embodiments of the disclosure: In JVET-K1001-v4, log2_ctu_size_minus2, log2_min_qt_size_intra_slices_minus2, and log2_min_qt_size_inter_slices_minus2 are flagged in SPS (as syntax elements).

[0219] The parameter log2_ctu_size_minus2 plus 2 specifies the luma coding tree block size of each CTU. In particular:CtbLog2SizeY = log2_ctu_size_minus2 + 2 (7 - 5)CtbSizeY = 1 << CtbLog2SizeY (7 - 6)

[0220] In other words, CtbLog2SizeY specifies the log2 value of the CTU size CtbSizeY, corresponding to the coding tree block (CTB) size for luma (Y).

[0221] Other settings are provided as follows:MinCbLog2SizeY = 2 (7-7)MinCbSizeY = 1 << MinCbLog2SizeY (7-8)MinTbSizeY = 4 (7-9)MaxTbSizeY = 64 (7-10)

[0222] The log2_min_qt_size_intra_slices_minus2 plus 2 parameter specifies the minimum luma size of a leaf block resulting from quaternary tree division of a CTU into slices with slice_type equal to 2 (I), that is, intra slices. The Log2_min_qt_size_intra_slices_minus2 value must be in the range 0 to CtbLog2SizeY - 2, inclusive. MinQtLog2SizeIntraY = log2_min_qt_size_intra_slices_minus2 + 2 (722)

[0223] The log2_min_qt_size_inter_slices_minus2 plus 2 parameter specifies the minimum luma size of a leaf block resulting from quaternary tree division of a CTU into slices with slice_type equal to 0 (B) or 1 (P), that is, inter slices. The Log2_min_qt_size_inter_slices_minus2 value must be in the range 0 to CtbLog2SizeY - 2, inclusive. MinQtLog2SizeInterY = log2_min_qt_size_inter_slices_minus2 + 2 (723)

[0224] MinQtSizeY is set to (7-30), which means the minimum allowed quaternary tree split size in luma sample. If the coding block size is less than or equal to MinQtSizeY, quaternary tree split is not allowed. Other settings are provided as follows: MinQtLog2SizeY = (slice_type == I) ? MinQtLog2SizeIntraY : MinQtLog2SizeInterY (7-25) MaxBtLog2SizeY = CtbLog2SizeY - log2_diff_ctu_max_bt_size (7-26) MinBtLog2SizeY = MinCbLog2SizeY (7-27) MaxTtLog2SizeY = (slice_type == I) ? 5:6 (7-28)MinTtLog2SizeY = MinCbLog2SizeY (7-29)MinQtSizeY = 1 << MinQtLog2SizeY (7-30)MaxBtSizeY = 1 << MaxBtLog2SizeY (7-31)MinBtSizeY = 1 << MinBtLog2SizeY (7-32)MaxTtSizeY = 1 << MaxTtLog2SizeY (7-33)MinTtSizeY = 1 << MinTtLog2SizeY (7-34)MaxMttDepth = (slice_type = = I)?max_mtt_hierarchy_depth_intra_slices:max_mtt_hierarchy_depth_inter_slices (7-35)

[0225] The max_mtt_hierarchy_depth_intra_slices and max_mtt_hierarchy_depth_inter_slices parameters denote the maximum hierarchy depth for MTT-type slicing for intra and inter slices, respectively.

[0226] Based on the semantics of delog2_min_qt_size_intra_slices_minus2 and log2_min_qt_size_inter_slices_minus2, the ranges of delog2_min_qt_size_intra_slices_minus2 and log2_min_qt_size_tLoges_minus2 are from 0 to CtbLog2SizeY - 2

[0227] Here, the CtbLog2SizeY is defined in the semantics of log2_ctu_size_minus2, which means that the log2 value of the luma coding tree block size of each CTU, the CtbLog2SizeY in VTM2.0 is equal to 7.

[0228] Based on (7-22) and (7-23), the range of MinQtLog2SizeIntraY and MinQtLog2SizeInterY is from 2 to CtbLog2SizeY.

[0229] Based on (7- 25), the range of MinQtLog2SizeY is from 2 to CtbLog2SizeY.

[0230] Based on (7 - 30), the range of MinQtSizeY, in JVET-K1001- v4, is from (1<< 2) to (1<< CtbLog2SizeY), in VTM2.0 the range is from (1 < <2) to (1<< 7), which is equal to from 4 to 128.

[0231] In JVET-K1001-v4, log2_diff_ctu_max_bt_size is conditionally flagged in the Slice header.

[0232] The log2_diff_ctu_max_bt_size parameter specifies the difference between the luma CTB size and the maximum luma size (width or height) of a coding block that can be divided using binary division. The Log2_diff_ctu_max_bt_size value must be in the range 0 to CtbLog2SizeY - MinCbLog2SizeY, inclusive.

[0233] When log2_diff_ctu_max_bt_size is not present, the value Log2_diff_ctu_max_bt_size is inferred to be equal to 2.

[0234] The MinCbLog2SizeY is set to (7-7), which means the minimum allowed coding block size.

[0235] Based on the semantics of log2_diff_ctu_max_bt_size, the range of log2_diff_ctu_max_bt_size is from 0 to CtbLog2SizeY - MinCbLog2SizeY.

[0236] Based on (7-26), the range of MaxBtLog2SizeY is from CtbLog2SizeY to MinCbLog2SizeY

[0237] Based on (7-31), the range of MaxBtSizeY is from (1<< CtbLog2SizeY) to (1<< MinCbLog2SizeY).

[0238] Based on (7-7), the range of MaxBtSizeY, in JVET-K1001-v4, is from (1<< CtbLog2SizeY) to (1<< 2), as in VTM2.0 CtbLog2SizeY is equal to 7, the range of MaxBtSizeY in VTM2.0 is equal to 128 to 4.

[0239] Therefore, MinQtSizeY has the range from 4 to (1<< CtbLog2SizeY), in VTM2.0 from 4 to 128, MaxBtSizeY has the range from (1<< CtbLog2SizeY) to 4, in VTM2.0 from 128 to 4.

[0240] Consequently, there is a possibility that MinQtSizeY is greater than MaxBtSizeY.

[0241] Furthermore, based on the current boundary treatment in VVC 2.0, only QT and BT partitioning is allowed for blocks located on the boundary (TT not allowed, non-splitting not allowed).

[0242] If the current coding block is located on the boundary, and the current coding block size cbSizeY satisfies the condition: MinQtSizeY > cbSizeY > MaxBtSizeY, there is no QT nor BT split possible for the current coding block. Therefore, there is no partition mode available for the current block.

MODALITY 1

[0243] The solution (embodiments of the invention) of the above-mentioned problems, including the boundary box problem, are described below in more detail.

[0244] According to an embodiment, to solve the mentioned problem, the lower bound of MaxBtSizeY should be limited to MinQtSizeY, to ensure that MaxBtSizeY is not smaller than MinQtSizeY. In particular, the lower bound of MaxBtSizeY may be equal to MinQtSizeY, so the range of MaxBtSizeY should be from (1<< CtbLog2SizeY) to (1<< MinQtLog2SizeY), so the range of MaxBtLog2SizeY should be from CtbLog2SizeY to MinQtLog2SizeY, so the range of log2_diff_ctu_max_bt_size should be from 0 to CtbLog2SizeY - MinQtLog2SizeY. Thus the information of MinQtSizeY can be used to determine the validity of MaxBtSizeY. In other words, MaxBtSizeY can be determined based on information from MinQtSizeY.

[0245] The corresponding change in the draft (video standard) text is in the semantics of log2_diff_ctu_max_bt_size as follows: log2_diff_ctu_max_bt_size specifies the difference between the luma CTB size and the maximum luma size (width or height) of a coding block that can be divided using binary division. The Log2_diff_ctu_max_bt_size value must be in the range 0 to CtbLog2SizeY - MinQtLog2SizeY, inclusive.

[0246] The corresponding encoding method implemented by an encoding device (decoder or encoder) may be as follows: determining whether the current block of an image is a boundary block; determining whether the current block size is greater than a minimum allowed quaternary tree leaf node size; if the current block is a boundary block and the current block size is not greater than the minimum allowed quaternary tree leaf node size, applying binary split to the current block; wherein the minimum allowed quaternary tree leaf node size (MinQtSizeY) is not greater than a maximum allowed binary tree root node size (MaxBtSizeY).

[0247] Wherein applying binary split to the current block may comprise applying forced binary split to the current block.

[0248] In this document, coding corresponds to the coding of image, video or moving image.

[0249] Being a boundary block means that the image/frame boundary intersects the block, or in other words, that the block is on the image/frame boundary. In the above embodiment, binary split is applied to the current block if the current block is a boundary block (condition 1) and its size is not greater than the minimum allowed quaternary tree leaf node size (condition 2). It is noted that in some embodiments, ternary split or another split may be used instead of binary split. Furthermore, in some embodiments, binary split may be applied under condition 2 independently of condition 1. In other words, condition 1 does not need to be evaluated. If the current block size is indeed greater than the minimum allowed quaternary tree leaf node size (i.e., condition 2 is not met), quaternary tree split may be applied.

[0250] It is noted that there are embodiments in which binary splitting is used only for the boundary blocks (condition 1). For non-boundary blocks, quaternary tree splitting may be the only splitting used. Applying binary (or ternary) splitting at the image/frame boundary provides a possibly more efficient splitting advantage, e.g., horizontal binary/ternary partitions at the horizontal boundary and vertical binary/ternary partitions at the vertical boundary.

[0251] Another corresponding encoding method implemented by an encoding device (decoder or encoder) may be as follows: determining whether the size of a boundary block is greater than a minimum allowed quaternary tree leaf node size. If the boundary block size is not greater than the minimum allowed quaternary tree leaf node size, the minimum allowed quaternary tree leaf node size is not greater than a maximum allowed binary tree root node size (e.g., by standard specification), and binary splitting is applied to the boundary block.

[0252] Optionally, the boundary block may not comprise a corner block. In other words, the corner block that is cut by both the vertical and horizontal boundaries of the image/frame is not considered a boundary block for the purpose of the above-mentioned condition 1.

MODALITY 2

[0253] Other embodiments of the disclosure (combinable with the embodiments mentioned above) are described below.

[0254] In JVET-K1001-v4, max_mtt_hierarchy_depth_inter_slices and max_mtt_hierarchy_depth_intra_slices is flagged in SPS. In other words, max_mtt_hierarchy_depth_inter_slices and max_mtt_hierarchy_depth_intra_slices are syntax elements, meaning that their value is included in the bitstream including also the encoded image or video.

[0255] In particular, max_mtt_hierarchy_depth_inter_slices specifies the maximum hierarchy depth for coding units resulting from multi-type tree splitting of a quaternary tree leaf into slices with slice_type equal to 0 (B) or 1 (P). The value of max_mtt_hierarchy_depth_inter_slices must be in the range 0 to CtbLog2SizeY - MinTbLog2SizeY, inclusive.

[0256] max_mtt_hierarchy_depth_intra_slices specifies the maximum hierarchy depth for coding units resulting from multi-type tree splitting of a quaternary tree leaf into slices with slice_type equal to 2 (I). The value of max_mtt_hierarchy_depth_intra_slices shall be in the range 0 to CtbLog2SizeY - MinTbLog2SizeY, inclusive.

[0257] MinTbSizeY is defined in (7-9), which is fixed as 4, therefore, MinTbLog2SizeY = log2 MinTbSizeY which is fixed as 2.

[0258] MaxMttDepth is set, which means the maximum allowed depth of Multi-type tree partition. If the current Multi-type tree partition depth is greater than or equal to MaxMttDepth, Multi-type tree partition is not allowed (enforced).

[0259] Based on the semantics of max_mtt_hierarchy_depth_inter_slices and max_mtt_hierarchy_depth_intra_slices, the range of max_mtt_hierarchy_depth_inter_slices and max_mtt_hierarchy_depth_intra_slices is 0 to CtbLog2SlogSlize2 - MintraSlices.

[0260] Based on (7-35), the range of MaxMttDepth is 0 to CtbLog2SizeY - MinTbLog2SizeY. Since in VTM2.0 CtbLog2SizeY is equal to 7, the range of MaxMttDepth is 0 to 5.

[0261] Therefore, MaxMttDepth has the range from 0 to CtbLog2SizeY - MinTbLog2SizeY, in VTM2.0 from 0 to 5

[0262] Based on the current boundary treatment in VVC 2.0, only QT and BT partitioning is allowed for a block located on the boundary (TT not allowed, non-splitting not allowed).

[0263] If the first problem mentioned above is solved (MaxBtSizeY >= MinQtSizeY), then the following condition will still be fulfilled: cbSizeY <= MinQtSizeY MaxMttDepth = 0

[0264] There are not enough levels of BT partitions (generally any MTT, including TT) for boundary treatment.

[0265] For example, MinQtSizeY is equal to 16, MinTbSizeY is equal to 4, MaxMttDepth is 0.

[0266] If a boundary block with cbSizeY = 16, and the parent partition is QT, and this block is still located on the boundary, no further partition can be performed, because the Mttdepth of the current block is reached MaxMttDepth.

[0267] Solution (an Embodiment of the Invention) of this boundary box problem: To solve the mentioned problem, the lower bound of MaxMttDepth should be bounded to 1 (in other words, it cannot take the value of zero), to ensure that after QT partitioning, there are enough levels of multi-type tree partition for boundary box. Or, further, the lower bound of MaxMttDepth should be bounded to (MinQtLog2SizeY - MinTbLog2SizeY), to ensure that after QT partitioning, there are enough levels of multi-type tree partitions for both boundary and non-boundary box.

[0268] The corresponding change in the draft (default) text is in the semantics of max_mtt_hierarchy_depth_inter_slices and max_mtt_hierarchy_depth_intra_slices as follows: max_mtt_hierarchy_depth_inter_slices specifies the maximum hierarchy depth for coding units resulting from multi-type tree splitting of a quaternary tree leaf into slices with slice_type equal to 0 (B) or 1 (P). The value of max_mtt_hierarchy_depth_inter_slices will be in the range 1 to CtbLog2SizeY - MinTbLog2SizeY, inclusive. max_mtt_hierarchy_depth_intra_slices specifies the maximum hierarchy depth for coding units resulting from multi-type tree splitting of a quaternary tree leaf into slices with slice_type equal to 2 (I). The value of max_mtt_hierarchy_depth_intra_slices must be in the range 1 to CtbLog2SizeY - MinTbLog2SizeY, inclusive. or, max_mtt_hierarchy_depth_inter_slices specifies the maximum hierarchy depth for coding units resulting from multitype tree splitting of a quaternary tree leaf into slices with slice_type equal to 0 (B) or 1 (P). The value of max_mtt_hierarchy_depth_inter_slices must be in the range MinQtLog2SizeY - MinTbLog2SizeY to CtbLog2SizeY - MinTbLog2SizeY, inclusive. max_mtt_hierarchy_depth_intra_slices specifies the maximum hierarchy depth for coding units resulting from multitype tree splitting of a quaternary tree leaf into slices with slice_type equal to 2 (I). The value of max_mtt_hierarchy_depth_intra_slices must be in the range MinQtLog2SizeY - MinTbLog2SizeY to CtbLog2SizeY - MinTbLog2SizeY, inclusive.

[0269] The corresponding encoding method implemented by an encoding device (decoder or encoder) may be as follows:

[0270] Splitting an image into blocks, wherein the blocks comprise a boundary block; Applying binary split to the boundary block with a maximum boundary multi-type partition depth, wherein the maximum boundary multi-type partition depth is a sum of at least a maximum multi-type tree depth and a maximum multi-type tree depth offset, wherein the maximum multi-type tree depth is greater than 0. This embodiment may be combined with EMBODIMENT 1 or may be applied without EMBODIMENT 1.

[0271] Optionally, the maximum multitype tree depth is greater than 0 when applying binary split to the boundary block.

[0272] Optionally, the boundary block may not comprise a corner block.

MODALITY 3

[0273] In other embodiments of the disclosure:

[0274] In JVET-K1001-v4, If MinQtSizeY > MaxBtSizeY and MinQtSizeY > MaxTtSizeY.

[0275] If cbSize = MinQtsizeY, the partition cannot reach MinCbSizeY (MinTbSizeY and MinCbsizeY are fixed and equal to 4), because there is no possible partition mode available.

[0276] Solution of this non-boundary box or boundary box problem: To solve the mentioned problem, the lower bound of MaxBtSizeY should be bounded to MinQtSizeY, to ensure that MaxBtSizeY is not less than MinQtSizeY. Or, the lower bound of MaxTtSizeY should be bounded to MinQtSizeY, to ensure that MaxTtSizeY is not less than MinQtSizeY.

[0277] The corresponding change in the draft text is in the semantics of log2_diff_ctu_max_bt_size specifies the difference between the luma CTB size and the maximum luma size (width or height) of a coding block that can be divided using binary division. The Log2_diff_ctu_max_bt_size value must be in the range 0 to CtbLog2SizeY - MinQtLog2SizeY, inclusive.

[0278] And/or, log2_min_qt_size_intra_slices_minus2 plus 2 specifies the minimum luma size of a leaf block resulting from quaternary tree splitting of a CTU into slices with slice_type equal to 2 (I). The Log2_min_qt_size_intra_slices_minus2 value must be in the range 0 to MaxTtLog2SizeY - 2, inclusive. log2_min_qt_size_inter_slices_minus2 plus 2 specifies the minimum luma size of a leaf block resulting from quaternary tree splitting of a CTU into slices with slice_type equal to 0 (B) or 1 (P). The Log2_min_qt_size_inter_slices_minus2 value must be in the range 0 to MaxTtLog2SizeY - 2, inclusive.

[0279] The corresponding encoding method implemented by an encoding device (decoder or encoder) may be as follows:

[0280] Determine whether the size of a current block is greater than a minimum allowed quaternary tree leaf node size;

[0281] If the current block size is not greater than the minimum allowed quaternary tree leaf node size, apply multi-type tree splitting to the current block;

[0282] Wherein the minimum allowed quaternary tree leaf node size is not greater than a maximum allowed binary tree root node size or the minimum allowed quaternary tree leaf node size is not greater than a maximum allowed ternary tree root node size.

[0283] Optionally, the minimum allowed quaternary tree leaf node size is no greater than a maximum allowed binary tree root node size, and the minimum allowed quaternary tree leaf node size is no greater than a maximum allowed ternary tree root node size.

[0284] Optionally, applying multi-type tree splitting to the current block comprises applying ternary splitting to the current block, or applying binary splitting to the current block.

[0285] Optionally, the boundary block may not comprise the corner block.

MODALITY 4

[0286] In other embodiments of the disclosure: If MaxBtSizeY >= MinQtSizeY, MinQtSizeY > MinTbLog2SizeY, and MaxMttDepth <(MinQtLog2SizeY - MinTbLog2SizeY), If cbSize = MinQtsizeY, the partition cannot reach MinCbSizeY because there are not enough levels of tree partition of multiple types that are allowed.

[0287] The solution of this non-boundary box or boundary box problem: To solve the mentioned problem, the lower bound of MaxMttDepth should be limited to (MinQtLog2SizeY- MinTbLog2SizeY), to ensure that after QT partition, there are enough levels of multi-type tree partition for both boundary box and non-boundary box.

[0288] The corresponding change in the draft text is in the semantics of max_mtt_hierarchy_depth_inter_slices and max_mtt_hierarchy_depth_intra_slices as follows: max_mtt_hierarchy_depth_inter_slices specifies the maximum hierarchy depth for coding units resulting from multi-type tree splitting of a quaternary tree leaf into slices with slice_type equal to 0 (B) or 1 (P). The value of max_mtt_hierarchy_depth_inter_slices will be in the range MinQtLog2SizeY - MinTbLog2SizeY to CtbLog2SizeY - MinTbLog2SizeY, inclusive. max_mtt_hierarchy_depth_intra_slices specifies the maximum hierarchy depth for coding units resulting from multi-type tree splitting of a quaternary tree leaf into slices with slice_type equal to 2 (I). The value of max_mtt_hierarchy_depth_intra_slices will be in the range MinQtLog2SizeY - MinTbLog2SizeY to CtbLog2SizeY - MinTbLog2SizeY, inclusive.

[0289] The corresponding encoding method implemented by an encoding device (decoder or encoder) may be as follows: Dividing an image into blocks; Applying multi-type tree splitting to a block of the blocks with a final maximum multi-type tree depth, wherein the final maximum multi-type tree depth is a sum of at least a maximum multi-type tree depth and a maximum multi-type tree depth offset, wherein the maximum multi-type tree depth is greater than or equal to the minimum allowable transform block size Log2 value subtraction from the minimum allowable quaternary tree leaf node size Log2 value, or the maximum multi-type tree depth is greater than or equal to the minimum allowable coding block size Log2 value subtraction from the minimum allowable quaternary tree leaf node size Log2 value.

[0290] Optionally, the block is a non-boundary block.

[0291] Optionally, the maximum multitype tree depth offset is 0.

[0292] Optionally, the block is a boundary block and the multi-type tree split is binary split.

[0293] Optionally, the multi-type tree split is (or includes) ternary split.

[0294] Optionally, the boundary block may not comprise a corner block.

[0295] Embodiments 1-4 may be applied at the encoder side to partition the picture/frame into coding units and to encode the coding units. Embodiments 1-4 may be applied at the decoder side to provide partitions of the picture/frame, i.e., coding units, and to decode the coding units accordingly (e.g., parse the coding units correctly from the stream and decode them).

[0296] According to some embodiments, a set-top box is provided, comprising one or more processors; and a non-transitory computer-readable storage medium coupled to the processors and storing programming for execution by the processors, wherein the programming, when executed by the processors, configures the set-top box to perform any of the methods described above with reference to embodiments 1-4.

[0297] Furthermore, an encoder is provided, comprising one or more processors; and a non-transitory computer-readable storage medium coupled to the processors and storing programming for execution by the processors, wherein the programming, when executed by the processors, configures the encoder to perform any of the methods described above with reference to embodiments 1-4.

ADDITIONAL MODALITIES RELATED TO BORDER PARTITIONING

[0298] In VVC, a multiple-type (binary/ternary/quaternary) tree segmentation structure (BT/TT/QT or binary tree/ternary tree/quaternary tree) should replace, or may replace, the concept of multiple partition unit types, i.e., it removes the separation of the concepts of CU, PU, and TU except as needed for CUs that have a size too large for the maximum transform length, and supports more flexibility for CU partition formats. [J]

[0299] Figures 10A-F illustrate, by way of example, the partitioning modes currently used in VTM. Figure 10A shows an unpartitioned (splitless) block, Figure 10Bb shows quaternary or quaternary tree (QT) partitioning, Figure 10C shows horizontal binary or binary tree (BT) partitioning, Figure 10D shows vertical binary or binary tree (BT) partitioning, Figure 10E shows horizontal ternary or ternary tree (TT) partitioning, and Figure 10F shows vertical ternary or ternary tree (TT) partitioning of a block such as a CU or CTU. Embodiments may be configured to implement the partitioning modes as shown in Figures 10A-10F.

[0300] In embodiments, the following parameters may be defined and specified by sequence parameter set (SPS) syntax elements for the BT/TT/QT coding tree scheme: CTU Size: the root node size of a quaternary tree MinQTSize: the minimum allowed quaternary tree leaf node size MaxBTTSize: the maximum allowed binary and ternary tree root node size MaxBTTDepth: the maximum allowed binary and ternary tree depth, and MinBTTSize: the minimum allowed binary and ternary tree leaf node size

[0301] In other embodiments, the minimum quaternary tree leaf node size parameter MinQTSize may also be comprised in other headers or sets, e.g., the slice header (SH) or image parameter set (PPS).

[0302] In the HEVC standard, coding tree units (CTU) or coding units (CU), which are located at slice/picture boundaries, will be forcibly split using quaternary tree (QT) until the bottom right sample of the leaf node is located within the slice/picture boundary. The forced QT partition or partitioning does not need to be signaled in the bitstream because both the encoder and the decoder, e.g., video encoder 20 and video decoder 30, know when to apply forced QT. The purpose of the forced partition is to make the CTU/CU boundary possible by video encoder 20/video decoder 30.

[0303] International patent publication number WO 2016/090568 discloses a QTBT (quaternary tree plus binary tree) structure, and also in VTM 1.0, the boundary CTU/CU forced partitioning process is inherited from HEVC. This means that the CTU/CU located at the frame boundary is forcibly partitioned by a quaternary tree (QT) structure without considering rate distortion (RD) optimization until the entire current CU is within the picture boundary. These forced partitions are not signaled in the bitstream.

[0304] Figure 11A shows an example of a forced partition for a forced QT-partitioned high definition (HD) (1920x1080 pixels) (128x128) lower boundary CTU. In Figure 11, the HD image is or is 1920x1080 pixels and the CTU is or is 128x128 pixels.

[0305] In SubCE2 (Image boundary treatment) of CE1 (Partitioning) at the San Diego meeting (04.2018) [JVET-J1021, 15 tests were proposed for image boundary treatment using BT, TT, or ABT (Asymmetric BT). In JVET-K0280 and JVET-K0376, for example, the boundary is defined as shown in Figure 12. Figure 12 shows the edges of an image by dot-dash lines and areas of boundary boxes in straight lines, namely, a bottom boundary box, a corner boundary box, and a right boundary box. A lower boundary can be partitioned by horizontal forced BT or forced QT, a right boundary can be partitioned by vertical forced BT or forced QT, and a corner box can only be partitioned by forced QT, where the decision to use either forced BT or forced QT partitioning is based on a rate-distortion optimization criterion and is signaled in the bitstream. Forced partitioning means that the block must be partitioned; for example, forced partitioning is applied to boundary blocks that cannot be coded using "no-splitting," as shown in Figure 10A.

[0306] If forced QT splitting is used in a forced frontier partitioning, the MinQTSize partitioning constraint is ignored. For example, in Figure 13A, if the MinQTSize is flagged as 32 in the SPS, to match the frontier with a forced QT method, a QT split to an 8x8 block size would be required, which ignores the constraint of MinQTSize being 32.

[0307] According to embodiments of the disclosure, if forced QT is used for image boundary partitioning, the forced QT split obeys, e.g., does not ignore, a split constraint as signaled, e.g., in an SPS. If an additional forced split is required, only forced BT is used, which in combination may also be referred to as forced QTBT. In embodiments of the disclosure, e.g., the MinQTSize partition constraint is considered for forced QT partitioning at image boundaries, and no additional signaling for forced BT partitioning is required. Embodiments also allow harmonizing partitioning for normal (non-boundary) blocks and boundary blocks. For example, in conventional solutions, two “MinQTSize” parameters are required, one for normal block partitioning and one for boundary block partitioning. Modalities require only a common "MinQTSize" parameter for both normal block and boundary block partitioning, which can be flexibly set between the encoder and decoder, for example, by flagging a "MinQTSize" parameter. Furthermore, Modalities require fewer partitions than, for example, forced QT.

[0308] Solutions for bottom bounding box and right bounding box

[0309] In the bottom and right boundary case, if the block size is larger than MinQTSize, then the partition mode for image boundary partitioning can be selected between forced BT partitioning and forced QT partitioning, e.g., based on RDO (rate distortion optimization). Otherwise (i.e., if the block size is equal to or smaller than MinQTSize), only forced BT partitioning is used for image boundary partitioning, more specifically, forced horizontal BT is used for a bottom boundary respectively for a boundary block located at the bottom boundary of an image, and forced vertical BT is used for a right boundary respectively for a boundary block located at the right boundary of an image.

[0310] Enforced BT partitioning may comprise recursively partitioning the current block by a horizontal enforced boundary partitioning until a subpartition of the current block is located at the bottom boundary of the image, and recursively partitioning the subpartition by a vertical enforced boundary partitioning until a leaf node is located entirely at the right boundary of the image. Alternatively, enforced BT partitioning may comprise recursively partitioning the current block by a vertical enforced boundary partitioning until a subpartition of the current block is located at the bottom boundary, and recursively partitioning the subpartition by a horizontal enforced boundary partitioning until a leaf node is located entirely at the right boundary. MinQTSize may also be applied to control the partitioning of a non-boundary block.

[0311] For example, in the case shown in Figure 11A, if the MinQTSize is, or is limited to, 32, although the size of a rectangular (non-square) block of height or width 8 samples is required to match the image boundary, forced BT partitioning will be used to partition the block located at the 32x32 boundary. The BT partitions may be further partitioned using forced BT partitioning of the same type, e.g., in case forced vertical BT partitioning has been applied, only further forced vertical BT partitioning will be applied, and in case forced horizontal BT partitioning has been applied, only forced horizontal BT partitioning will be applied. Forced clipping into BT portions is continued until the leaf node is entirely within the image.

[0312] Figure 11B shows an exemplary partitioning of a lower frontier CTU with a sample size of 128x128 according to an embodiment of the invention. The lower frontier CTU, which forms a root block or root node of a partitioning tree, is partitioned into smaller partitions, e.g., smaller square or rectangular blocks. These smaller partitions or blocks can be further partitioned into even smaller partitions or blocks. In Figure 11B, the CTU is first quaternary tree partitioned into four square blocks 710, 720, 730, and 740, each with a sample size of 64x64. Of these blocks, blocks 710 and 720 are again lower frontier blocks, while blocks 730 and 740 are out-of-picture (are respectively located outside the picture) and are not processed.

[0313] Block 710 is further partitioned using quaternary tree partitioning into four square blocks 750, 760, 770, and 780, each having a sample size of 32x32. Blocks 750 and 760 are located within the image, while blocks 770 and 780 again form lower boundary blocks. Since the size of block 770 is not larger than MinQTSize, which is for example 32, recursive horizontal forced binary partitioning is applied to block 770 until a leaf node is entirely within or located entirely within the image, for example, until at leaf node block 772, a rectangular non-square block having 32x16 samples is within the image (after one horizontal binary partitioning), or at leaf node block 774, a rectangular non-square block located at the lower border of the image and having 32x8 samples is within the image (after two horizontal binary partitionings). The same applies to block 780.

[0314] Embodiments of the disclosure allow for harmonizing partitioning for normal blocks located completely within the image and partitioning for boundary blocks. Boundary blocks are blocks that are neither completely within the image nor completely outside the image. In other words, boundary blocks are blocks that comprise a portion that is located within the image and a portion that is located outside the image. Furthermore, embodiments of the disclosure allow for reduced flagging since forced BT partitioning at or below MinQTSize does not need to be flagged.

[0315] Corner box solutions

[0316] In corner boxing, some approaches only allow a forced QT split, which also ignores the MinQTSize constraint. Embodiments of the present invention provide two solutions for corner boxing. A corner boxing occurs when the currently processed block is in the corner of the image. This is the case if the current block is crossed by or is adjacent to two image boundaries (vertical and horizontal).

[0317] Solution 1:

[0318] The corner box is considered as a bottom boundary box or a right boundary box. Figure 14 shows one embodiment of a boundary definition. Figure 14 shows the boundaries of an image by dot-dash lines and areas of boundary boxes in straight lines. As shown, the corner box is defined as a bottom boundary box. Thus, the solution is the same as described for the bottom boundary box and right boundary box above. In other words, first a horizontal partitioning is applied (as described for the bottom boundary box) until the blocks or partitions are entirely within the image (in the vertical direction), and then a vertical partitioning is applied (as described for the right boundary box) until the leaf nodes are entirely within the image (in the horizontal direction). A boundary box can also be a block boundary.

[0319] Solution 2:

[0320] The definition of the boundary boxes is still kept as is. If forced QT is constrained by MinQTSize (current block size equal or smaller than MinQTSize), use horizontal forced BT to match the bottom boundary, when the bottom boundary matches, use vertical forced BT to match the right boundary.

[0321] For example, in Figure 13A, which shows an embodiment of a forced QTBT for a block located in a corner of an image, if MinQTSize is, or is limited to, 32 for the corner box forced QTBT partition, another BT partition will be used after the 32x32 block partition until the forced partition is finished.

[0322] Figure 13B shows additional details of an exemplary partitioning of a boundary CTU at or in a corner of an image according to an embodiment of the invention, wherein the CTU has a sample size of 128x128. The CTU is first quaternary tree partitioned into four square blocks, each having a sample size of 64x64. Of these blocks, only the top left block 910 is a boundary block, while the other three are located outside (entirely outside) the image and are not processed further. Block 910 is further partitioned using quaternary tree partitioning into four square blocks 920, 930, 940, and 950, each having a sample size of 32x32. Block 920 is located inside the image, while blocks 930, 940, and 950 again form boundary blocks. Since the size of these blocks 930, 940 and 950 is not greater than MinQTSize, which is 32, forced binary partitioning is applied to blocks 930, 940 and 950.

[0323] Block 930 is located on a right-hand boundary and is partitioned using recursive vertical forced binary partitioning until a leaf node is within the image, e.g., block 932 located on the right-hand boundary of the image (hereinafter two vertical binary partitionings).

[0324] Block 940 is located at a lower boundary and is partitioned using recursive horizontal forced binary partitioning until a leaf node is within the image, e.g., block 942 located at the right boundary of the image (hereinafter two horizontal binary partitionings).

[0325] Block 950 is located at a corner boundary and is partitioned using first recursive horizontal forced binary partitioning until a subpartition or block, here block 952, is located at a lower boundary of the image (hereinafter two horizontal binary partitionings) and then recursive partitioning of the subpartition by a vertical forced boundary partitioning until a leaf node or block, e.g., block 954, is located at the right boundary of the image (hereinafter two vertical binary partitionings), or respectively, until a leaf node is located within the image.

[0326] The above approaches may be applied to both decoding and encoding. For decoding, MinQTSize may be received via an SPS. For encoding, MinQTSize may be transmitted via an SPS. Embodiments may use boundary definitions as shown in Figure 12 or Figure 14, or other boundary definitions.

[0327] Other embodiments of the present disclosure are provided below. It should be noted that the numbering used in the following section does not necessarily need to agree with the numbering used in the previous sections.

[0328] Embodiment 1: A partitioning method comprising: determining whether the current block of an image is a boundary block; if the current block is a boundary block, determining whether the size of the current block is greater than a minimum allowable quaternary tree leaf node size; if the size of the current block is not greater than the minimum allowable quaternary tree leaf node size, applying forced binary tree partitioning to the current block.

[0329] Embodiment 2: The partitioning method of embodiment 1, wherein the forced binary tree partitioning is a recursive horizontal forced binary tree partitioning in case the current block is located at a lower boundary of the image, or is a recursive vertical forced boundary partitioning in case the current block is located at a right boundary of the image.

[0330] Embodiment 3: The partitioning method of embodiment 1 or 2, wherein the forced binary partitioning comprises recursively partitioning the current block by a horizontal forced boundary partitioning until a subpartition of the current block is located directly on the bottom boundary of the image, and recursively partitioning the subpartition by a vertical forced boundary partitioning until a leaf node is entirely located directly on the right boundary of the image, or vice versa.

[0331] Embodiment 4: The partitioning method of any one of embodiments 1 to 3, wherein the minimum allowed quaternary tree leaf node size is a minimum allowed quaternary tree leaf node size also applied to control the partitioning of a block that is not on the boundary.

[0332] Embodiment 5: A decoding method for decoding a block by partitioning the block according to the slicing method of any one of Embodiments 1 to 4.

[0333] Embodiment 6: The decoding method of embodiment 5, wherein the minimum allowed quaternary tree leaf node size is received via an SPS.

[0334] Embodiment 7: An encoding method for encoding a block by partitioning the block according to the slicing method of any one of embodiments 1 to 4.

[0335] Embodiment 8: The coding method of embodiment 7, wherein the minimum allowable quaternary tree leaf node size is transmitted via an SPS.

[0336] Embodiment 9: A decoding device, comprising a logic circuitry configured to perform any of the methods of embodiment 5 or 6.

[0337] Embodiment 10: An encoding device, comprising a logic circuitry configured to perform any of the methods of embodiment 7 or 8.

[0338] Embodiment 11: A non-transitory storage medium for storing instructions when executed by a processor causes the processor to perform any of the methods according to embodiments 1-8.

[0339] An apparatus comprises a memory element; and a processor element coupled to the memory element and configured to determine whether a current block of an image is a boundary block, determine, when the current block is a boundary block, whether a size of the current block is greater than a minimum allowed quaternary tree (QT) leaf node size (MinQTSize), and apply, when the current block size is not greater than MinQTSize, forced binary tree (BT) partitioning to the current block.

[0340] In summary, embodiments of the present application (or the present disclosure) provide apparatus and methods for encoding and decoding.

[0341] A first aspect relates to a partitioning method comprising determining whether a current block of an image is a boundary block and whether the current block size is greater than a minimum allowed quaternary tree leaf node size; and if the current block is the boundary block and the current block size is not greater than the minimum allowed quaternary tree leaf node size (MinQTSize), applying forced binary tree (BT) partitioning to the current block.

[0342] In a first form of implementation of the method according to the first aspect itself, the forced binary tree partitioning is a recursive horizontal forced binary tree partitioning in case the current block is located at a lower boundary of the image or a recursive vertical forced boundary partitioning in case the current block is located at a right boundary of the image.

[0343] In a second form of implementation of the method according to the first aspect itself or any prior form of implementation of the first aspect, the forced binary tree partitioning is continued until a leaf node block is within the image.

[0344] In a third form of implementation of the method according to the first aspect itself or any prior form of implementation of the first aspect, the forced binary partitioning comprises recursively partitioning the current block by a horizontal forced boundary partitioning until a subpartition of the current block is located at the bottom boundary of the image; and recursively partitioning the subpartition by a vertical forced boundary partitioning until a leaf node is located entirely at the right boundary of the image.

[0345] In a fourth form of implementation of the method according to the first aspect itself or any prior form of implementation of the first aspect, the forced BT partitioning comprises recursively partitioning the current block by a vertical forced boundary partitioning until a subpartition of the current block is located at the bottom boundary; and recursively partitioning the subpartition by a horizontal forced boundary partitioning until a leaf node is located entirely at the right boundary.

[0346] In a fifth implementation form of the method according to the first aspect itself or any prior implementation form of the first aspect, the method further comprises applying the minimum allowable quaternary tree leaf node size to control a partitioning of a non-boundary block.

[0347] In a sixth form of implementation of the method according to the first aspect itself or any prior form of implementation of the first aspect, the boundary block is a block that is not completely within the image and is not completely outside the image.

[0348] A second aspect relates to a decoding method for decoding a block by partitioning the block according to the first aspect itself or any prior implementation of the first aspect.

[0349] In a first form of implementation of the method according to the second aspect itself, the method further comprises receiving the minimum allowed quaternary tree leaf node size by means of a set of sequence parameters (SPS).

[0350] A third aspect relates to an encoding method for encoding a block by partitioning the block according to the first aspect itself or any prior implementation of the first aspect.

[0351] In a first form of implementation of the method according to the third aspect itself, the method further comprises transmitting the minimum allowed quaternary tree leaf node size via a set of sequence parameters (SPS).

[0352] A fourth aspect relates to a decoding device comprising logic circuitry configured to decode a block by partitioning the block according to the partitioning method of the first aspect itself or any prior implementation of the first aspect.

[0353] In a first form of implementation of the decoding device according to the fourth aspect itself, the logic circuitry is further configured to receive the minimum allowed quaternary tree leaf node size via a sequence parameter set (SPS).

[0354] A fifth aspect relates to an encoding device comprising logic circuitry configured to encode a block by partitioning the block according to the partitioning method of the first aspect itself or any prior implementation of the first aspect.

[0355] In a first form of implementation of the decoding device according to the fifth aspect itself, the logic circuitry is further configured to transmit the minimum allowable quaternary tree leaf node size via a sequence parameter set (SPS).

[0356] A sixth aspect relates to a non-transitory storage medium for storing instructions that when executed by a processor cause a processor to perform any of the first, second, or third aspect itself or any prior form of implementation of the first, second, or third aspect.

[0357] A seventh aspect relates to a method comprising making a determination that a current block of an image is a boundary block and that a size of the current block is less than or equal to a minimum allowed quaternary tree (QT) leaf node size (MinQTSize); and applying, in response to the determination, forced binary tree (BT) partitioning to the current block.

[0358] In a first form of implementation of the method according to the seventh aspect itself, the current block is located at a lower boundary of the image, and wherein the forced BT partitioning is a recursive horizontal forced BT partitioning.

[0359] In a second form of implementation of the method according to the seventh aspect itself or any prior form of implementation of the seventh aspect, the current block is located on a right-hand boundary of the image, and wherein the forced BT partitioning is a recursive vertical forced BT partitioning.

[0360] In a third form of implementation of the method according to the seventh aspect itself or any prior form of implementation of the seventh aspect, the forced BT partitioning comprises recursively partitioning the current block by a horizontal forced boundary partitioning until a subpartition of the current block is located on the bottom boundary; and recursively partitioning the subpartition by a vertical forced boundary partitioning until a leaf node is located entirely on the right boundary.

[0361] In a fourth form of implementation of the method according to the seventh aspect itself or any prior form of implementation of the seventh aspect, the forced BT partitioning comprises recursively partitioning the current block by a vertical forced boundary partitioning until a subpartition of the current block is located at the bottom boundary; and recursively partitioning the subpartition by a horizontal forced boundary partitioning until a leaf node is located entirely at the right boundary.

[0362] In a fifth form of implementation of the method according to the seventh aspect itself or any prior form of implementation of the seventh aspect, the method further comprises applying MinQTSize to control the partitioning of a block that is not on the boundary.

[0363] In a sixth form of implementation of the method according to the seventh aspect itself or any prior form of implementation of the seventh aspect, the method further comprises receiving MinQTSize via a sequence parameter set (SPS).

[0364] In a seventh form of implementation of the method according to the seventh aspect itself or any prior form of implementation of the seventh aspect, the method further comprises passing MinQTSize via a sequence parameter set (SPS).

[0365] An eighth aspect relates to an apparatus comprising a memory; and a processor coupled to the memory and configured to determine whether a current block of an image is a boundary block, determine, when the current block is a boundary block, whether a size of the current block is greater than a minimum allowed quaternary tree (QT) leaf node size (MinQTSize), and apply, when the current block size is not greater than MinQTSize, forced binary tree (BT) partitioning to the current block.

[0366] In a first form of implementation of the apparatus according to the eighth aspect itself, the forced BT partitioning is a recursive horizontal forced BT partitioning when the current block is located at a bottom boundary of the image or a recursive vertical forced BT partitioning when the current block is located at a right boundary of the image.

[0367] In a second form of implementation of the apparatus according to the eighth aspect itself or any prior form of implementation of the eighth aspect, the forced BT partitioning comprises recursively partitioning the current block by a horizontal forced boundary partitioning until a subpartition of the current block is located on the bottom boundary; and recursively partitioning the subpartition by a vertical forced boundary partitioning until a leaf node is located entirely on the right boundary.

[0368] In a third form of implementation of the apparatus according to the eighth aspect itself or any prior form of implementation of the eighth aspect, the forced BT partitioning comprises recursively partitioning the current block by a vertical forced boundary partitioning until a subpartition of the current block is located on the bottom boundary; and recursively partitioning the subpartition by a horizontal forced boundary partitioning until a leaf node is located entirely on the right boundary.

[0369] In a fourth form of implementation of the apparatus according to the eighth aspect itself or any prior form of implementation of the eighth aspect, the processor is further configured to apply MinQTSize to control the partitioning of a block that is not on the boundary.

[0370] In a fifth form of implementation of the apparatus according to the eighth aspect itself or any prior form of implementation of the eighth aspect, the apparatus further comprises a receiver coupled to the processor and configured to receive MinQTSize via a sequence parameter set (SPS).

[0371] In a sixth form of implementation of the apparatus according to the eighth aspect itself or any prior form of implementation of the eighth aspect, the apparatus further comprises a transmitter coupled to the processor and configured to transmit MinQTSize via a sequence parameter set (SPS).

[0372] A ninth aspect relates to a computer program product comprising computer-executable instructions stored on a non-transitory medium that, when executed by a processor, causes an apparatus to determine whether a current block of an image is a boundary block; determine, when the current block is a boundary block, whether a size of the current block is greater than a minimum allowable quaternary tree (QT) leaf node size (MinQTSize); and apply, when the current block size is not greater than MinQTSize, forced binary tree (BT) partitioning to the current block.

[0373] In a first form of implementation of the apparatus according to the eighth aspect itself, the forced BT partitioning is a recursive horizontal forced BT partitioning when the current block is located at a bottom boundary of the image or a recursive vertical forced BT partitioning when the current block is located at a right boundary of the image.

[0374] In a second form of implementation of the apparatus according to the ninth aspect itself or any prior form of implementation of the ninth aspect, the forced BT partitioning comprises recursively partitioning the current block by a horizontal forced boundary partitioning until a subpartition of the current block is located on the bottom boundary; and recursively partitioning the subpartition by a vertical forced boundary partitioning until a leaf node is located entirely on the right boundary.

[0375] In a third form of implementation of the apparatus according to the ninth aspect itself or any prior form of implementation of the ninth aspect, the forced BT partitioning comprises recursively partitioning the current block by a vertical forced boundary partitioning until a subpartition of the current block is located on the bottom boundary; and recursively partitioning the subpartition by a horizontal forced boundary partitioning until a leaf node is located entirely on the right boundary.

[0376] In a fourth form of implementation of the apparatus according to the ninth aspect itself or any prior form of implementation of the ninth aspect, the instructions further cause the apparatus to apply MinQTSize to control the partitioning of a block that is not on the boundary.

[0377] In a fifth form of implementation of the apparatus according to the ninth aspect itself or any prior form of implementation of the ninth aspect, the instructions further cause the apparatus to receive MinQTSize via a sequence parameter set (SPS).

[0378] In a sixth form of implementation of the apparatus according to the ninth aspect itself or any prior form of implementation of the ninth aspect, the instructions further cause the apparatus to transmit MinQTSize via a sequence parameter set (SPS).

[0379] According to some embodiments, a set-top box is provided, comprising one or more processors; and a non-transitory computer-readable storage medium coupled to the processors and storing programming for execution by the processors, wherein the programming, when executed by the processors, configures the set-top box to perform any of the methods described above with reference to embodiments 1-4.

[0380] Furthermore, an encoder is provided, comprising one or more processors; and a non-transitory computer-readable storage medium coupled to the processors and storing programming for execution by the processors, wherein the programming, when executed by the processors, configures the encoder to perform any of the methods described above with reference to embodiments 1-4.

[0381] The following is an explanation of the applications of the encoding method as well as the decoding method as shown in the aforementioned embodiments, and a system using them.

[0382] Figure 17 is a block diagram showing a content supply system 3100 for performing content distribution service. This content supply system 3100 includes capture device 3102, terminal device 3106, and optionally includes display 3126. The capture device 3102 communicates with the terminal device 3106 via the communication link 3104. The communication link may include the communication channel 13 described above. The communication link 3104 includes, but is not limited to, WIFI, Ethernet, cable, wireless (3G/4G/5G), USB, or any type of combination thereof, or the like.

[0383] The capture device 3102 generates data, and may encode the data by the encoding method as shown in the above embodiments. Alternatively, the capture device 3102 may distribute the data to a streaming server (not shown in the Figures), and the server encodes the data and transmits the encoded data to the terminal device 3106. The capture device 3102 includes, but is not limited to, the camera, smartphone or Pad, computer or laptop, video conferencing system, PDA, vehicle-mounted device, or a combination of any of these, or the like. For example, the capture device 3102 may include the source device 12 as described above. When the data includes video, the video encoder 20 included in the capture device 3102 may actually perform the video encoding processing. When the data includes audio (i.e., voice), an audio encoder included in the capture device 3102 may actually perform the audio encoding processing. For some practical scenarios, capture device 3102 distributes the encoded video and audio data by multiplexing them together. For other practical scenarios, for example, in a videoconferencing system, the encoded audio data and the encoded video data are not multiplexed. Capture device 3102 distributes the encoded audio data and the encoded video data to the terminal device 3106 separately.

[0384] In the content delivery system 3100, the terminal device 310 receives and plays back the encoded data. The terminal device 3106 could be a device capable of receiving and retrieving data, such as a smartphone or Pad 3108, a computer or laptop 3110, a network video recorder (NVR)/digital video recorder (DVR) 3112, a TV 3114, a set top box (STB) 3116, a video conferencing system 3118, a video surveillance system 3120, a personal digital assistant (PDA) 3122, a vehicle-mounted device 3124, or a combination of any of them, or the like capable of decoding the aforementioned encoded data. For example, the terminal device 3106 may include the destination device 14 as described above. When the encoded data includes video, the video decoder 30 included in the terminal device is prioritized to perform video decoding. When the encoded data includes audio, an audio decoder included in the terminal device is prioritized to perform audio decoding processing.

[0385] For a terminal device with its display, e.g., smartphone or Pad 3108, computer or laptop 3110, network video recorder (NVR)/digital video recorder (DVR) 3112, TV 3114, personal digital assistant (PDA) 3122, or vehicle-mounted device 3124, the terminal device may feed the decoded data to its display. For a terminal device equipped without a display, e.g., STB 3116, video conferencing system 3118, or video surveillance system 3120, an external monitor 3126 is contacted thereto to receive and display the decoded data.

[0386] When each device in this system performs encoding or decoding, the image encoding device or the image decoding device as shown in the above-mentioned embodiments can be used.

[0387] Figure 18 is a diagram showing a structure of an example terminal device 3106. After terminal device 3106 receives stream from capture device 3102, protocol processing unit 3202 analyzes the transmission protocol of the stream. The protocol includes, but is not limited to, Real-Time Streaming Protocol (RTSP), Hypertext Transfer Protocol (HTTP), HTTP live streaming protocol (HLS), MPEG-DASH, Real-Time Transport Protocol (RTP), Real-Time Messaging Protocol (RTMP), or any combination thereof, or the like.

[0388] After the protocol processing unit 3202 processes the stream, the stream file is generated. The file is output to a demultiplexing unit 3204. The demultiplexing unit 3204 may separate the multiplexed data into encoded audio data and encoded video data. As described above, for some practical scenarios, e.g., in the video conferencing system, the encoded audio data and the encoded video data are not multiplexed. In this situation, the encoded data is transmitted to the video decoder 3206 and external audio decoder 3208 via the demultiplexing unit 3204.

[0389] Through demultiplexing processing, video elementary stream (ES), audio ES, and optionally, caption are generated. Video decoder 3206, which includes video decoder 30 as explained in the above-mentioned embodiments, decodes video ES by decoding method as shown in the above-mentioned embodiments to generate video frame, and feeds this data to synchronous unit 3212. Audio decoder 3208 decodes audio ES to generate audio frame, and feeds this data to synchronous unit 3212. Alternatively, the video frame may store in a buffer (not shown in Figure 18) before feeding it to synchronous unit 3212. Similarly, the audio frame may store in a buffer (not shown in Figure 18) before feeding it to synchronous unit 3212.

[0390] The synchronous unit 3212 synchronizes the video frame and the audio frame and supplies the video/audio to a video/audio display 3214. For example, the synchronous unit 3212 synchronizes the presentation of the video and audio information. The information may encode in syntax using timestamps relative to the presentation of encoded audio and visual data and timestamps relative to the delivery of the data stream itself.

[0391] If the caption is included in the stream, the caption decoder 3210 decodes the caption, and synchronizes it with the video frame and the audio frame, and outputs the video/audio/caption to a video/audio/caption display 3216.

[0392] The present invention is not limited to the above-mentioned system, and either the image encoding device or the image decoding device in the above-mentioned embodiments may be incorporated into another system, for example, a car system.

[0393] Although embodiments of the invention have been described primarily based on video coding, it should be noted that embodiments of the coding system 10, encoder 20, and decoder 30 (and correspondingly of the system 10) and the other embodiments described herein may also be configured for processing or coding still images, i.e., processing or coding an individual image independent of any preceding or consecutive images as in video coding. In general only inter prediction units 244 (encoder) and 344 (decoder) may not be available in case the image processing coding is limited to a single image 17. All other functionalities (also referred to as tools or technologies) of video encoder 20 and video decoder 30 may equally be used for still image processing, e.g., residual calculation 204/304, transform 206, quantization 208, inverse quantization 210/310, (inverse) transform 212/312, partitioning 262/362, intra prediction 254/354 and/or loop filtering 220, 320, and entropy encoding 270 and entropy decoding 304.

[0394] Embodiments, for example, of encoder 20 and decoder 30, and functions described herein, for example, with reference to encoder 20 and decoder 30, may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on a computer-readable medium or transmitted over communication media as one or more instructions or code and executed by a hardware-based processing unit. Computer-readable media may include computer-readable storage media, which corresponds to a tangible medium such as data storage media, or communication media, including any media that facilitates the transfer of a computer program from one place to another, for example, in accordance with a communication protocol. Thus, computer-readable media generally may correspond to (1) tangible computer-readable storage media that is non-transitory, or (2) a communication medium, such as a signal or carrier wave. Data storage media may be any readily available media that can be accessed by one or more computers or one or more processors to retrieve instructions, code, and/or data structures for implementing the techniques described in this disclosure. A computer program product may include computer-readable media.

[0395] In one or more examples, the described functions may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored or transmitted as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media may include computer-readable storage media, which correspond to a tangible medium, such as data storage media, or communications media, including any media that facilitates the transfer of a computer program from one place to another, for example, in accordance with a communications protocol. Thus, computer-readable media generally may correspond to (1) tangible computer-readable storage media that is non-transitory, or (2) a communications medium such as a signal or carrier wave. Data storage media may be any readily available media that can be accessed by one or more computers or one or more processors to retrieve instructions, code, and/or data structures for implementing the techniques described in this disclosure. A computer program product may include computer-readable media.

[0396] By way of example, and not limitation, such computer-readable storage media may comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage, or other magnetic storage devices, flash memory, or any other media that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer. Furthermore, any connection is properly termed a computer-readable media. For example, if instructions are transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of media. It should be understood, however, that computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other transient media, but are instead intended for non-transitory tangible storage media. Magnetic disc and optical disc, as used herein, include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray Disc, where magnetic discs generally reproduce data magnetically, while optical discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

[0397] The instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general-purpose microprocessors, application-specific integrated circuits (ASICs), field-programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuits. Accordingly, the term "processor" as used herein may refer to any of the foregoing structures or any other structure suitable for implementing the techniques described herein. Furthermore, in some aspects, the described functionality may be provided in dedicated hardware and/or software modules configured for encoding and decoding, or incorporated into a combined codec. Furthermore, the techniques may be implemented entirely in one or more circuit or logic element sets.

[0398] The techniques of this disclosure can be implemented in a wide variety of devices or apparatus, including a wireless handset, an integrated circuit (IC), or a set of ICs (e.g., a chipset). Various components, modules, or units are described in this disclosure to emphasize functional aspects of devices configured to perform the disclosed techniques, but do not necessarily require implementation by different hardware units. Rather, as described above, multiple units can be combined into a codec hardware unit or provided by a collection of interoperable hardware units, including one or more processors as described above, in conjunction with suitable software and/or firmware.

[0399] The following logical operators or Mathematical Operators are defined as follows:

[0400] The mathematical operators used in this application are similar to those used in the C programming language. However, the results of integer division and arithmetic shift operations are defined more precisely, and additional operations are defined, such as exponentiation and real-valued division. Numbering and counting conventions generally start at 0, e.g., "the first" is equivalent to 0, "the second" is equivalent to 1st, etc.

[0401] Arithmetic operators

[0402] The following arithmetic operators are defined as follows:+ Addition- Subtraction (as a two-argument operator) or negation (as a unary prefix operator)* Multiplication, including matrix multiplication xy Exponentiation. Specifies x raised to the y power. In other contexts, this notation is used for superscripting, not intended for interpretation as exponentiation./ Division by an integer with truncation of the result towards zero. For example, 7/4 and −7 / −4 are truncated to 1, and −7 / 4 and 7 / −4 are truncated to −1.÷ Used to denote division in mathematical equations where no truncation or rounding is intended. Used to denote division in mathematical equations where no truncation or rounding is intended. The sum of f(i) with i taking all integer values from x to y and including yx % y Modulus. Remainder of x divided by y, defined only for integers with x>=0 and y>0.

[0403] Logical operators

[0404] The following logical operators are defined as follows:x && y Boolean "and" of x and yx | | y Boolean "or" of x and y ! Boolean "not"x ? y : z If x is TRUE or not equal to 0, evaluates to the value of y; otherwise, evaluates to the value of z.

[0405] Relational operators

[0406] The following relational operators are defined as follows: > Greater than > = Greater than or equal to > Less than <= Less than or equal to = = Equal to ! = Not equal to

[0407] When a relational operator is applied to a syntax element or variable that has been assigned the value "na" (not applicable), the value "na" is treated as a distinct value for the syntax element or variable. The value "na" is not considered equal to any other value.

[0408] Bitwise operators

[0409] The following bit-wise operators are defined as follows:& bit-wise "and". When operating on integer arguments, operates on a two's complement representation of the integer value. When operating on a binary argument that contains fewer bits than another argument, the shorter argument is extended by adding more significant bits equal to 0.| bit-wise "or". When operating on integer arguments, operates on a two's complement representation of the integer value. When operating on a binary argument that contains fewer bits than another argument, the shorter argument is extended by adding more significant bits equal to 0.A bit-wise "exclusive or". When operating on integer arguments, operates on a two's complement representation of the integer value. When operating on a binary argument that contains fewer bits than another argument, the shorter argument is extended by adding more significant bits equal to 0.x >> y Arithmetic right shift of a two's complement integer representation of x by y binary digits. This function is defined only for non-negative integer values of y. Bits shifted to the most significant bits (MSBs) as a result of the right shift have a value equal to the MSB of x before the shift operation. x << y Arithmetic left shift of a binary two's complement integer representation of x by y. This function is defined only for non-negative integer values of y. Bits shifted to the least significant bits (LSBs) as a result of the left shift have a value equal to 0.

[0410] Assignment operators

[0411] The following arithmetic operators are defined as follows:= Assignment operator+ + Increment, that is, x + + is equivalent to x = x + 1; when used in an array index, evaluates to the value of the variable before the increment operation.- - Decrement, that is, x - - is equivalent to x = x - 1; when used in an array index, evaluates to the value of the variable before the decrement operation.+ = Increment by the specified amount, that is, x += 3 is equivalent to x = x + 3, and x + = (-3) is equivalent to x = x + (-3).- = Decrement by the specified amount, that is, x - = 3 is equivalent to x = x - 3, and x - = (-3) is equivalent to x = x - (-3).

[0412] Range notation

[0413] The following notation is used to specify a range of values:x = y..z x takes on integer values starting from y to z, inclusive, with x, y, and z being integers and z being greater than y.

[0414] Mathematical functions

[0415] The following mathematical functions are defined: Asin(x) the trigonometric inverse sine function, operating on an argument x that is in the range −1.0 to 1.0 inclusive, with an output value in the range −π ÷ 2 to π ÷ 2 inclusive, in radian unitsAtan(x) the trigonometric inverse tangent function, operating on an argument x, with an output value in the range −π * 2 to π * 2 inclusive, in radian units Ceil(x) the smallest integer greater than or equal to x.Clip1Y(x) = Clip3(0, (1 << BitDepthY) - 1, x)Clip1C(x) = Clip3(0, (1 << BitDepthC) - 1, x) Cos(x) the trigonometric cosine function operating on an argument x in units of radians. Floor(x) the largest integer less than or equal to x. Ln(x) the natural logarithm of x (the logarithm to base e, where e is the constant natural logarithm to base 2.718 281 828 ...).Log2(x) the logarithm to base 2 of x.Log10(x) the logarithm to base 10 of x. Round(x) = Sign(x) * Floor( Abs (x) + 0.5) Sin(x) the trigonometric sine function operating on an argument x in units of radiansSqrt( x ) = √xSwap(x, y) = (y, x)Tan(x) the trigonometric tangent function operating on an argument x in units of radians

[0416] Order of precedence of operation

[0417] When an order of precedence in an expression is not explicitly indicated by the use of parentheses, the following rules apply:- Operations of higher precedence are evaluated before any operations of lower precedence.- Operations of the same precedence are evaluated sequentially from left to right.

[0418] The table below specifies the precedence of operations from highest to lowest; a higher position in the table indicates a higher precedence.

[0419] For those operators that are also used in the C programming language, the order of precedence used in this Report is the same as that used in the C programming language.Table: Operation precedence from highest (at the top of the table) to lowest (at the bottom of the table)

[0420] Text description of logical operations

[0421] In the text, a statement of logical operations as would be described mathematically in the following form:if( condition 0 )statement 0else if( condition 1 ) statement 1 ...else /* informative remark on remaining condition */ statement ncan be described in the following way:... in the following form / ...the following applies:- If condition 0, statement 0- Otherwise, if condition 1, statement 1 - ...- Otherwise (informative remark on remaining condition), statement n

[0422] Each "If... Otherwise, if... Otherwise,..." statement in the text is introduced with "... as follows" or "... The following applies" immediately followed by "If... ". The last condition of the "If... Otherwise, if... Otherwise,..." is always an "Otherwise,...". Interleaved "If... Otherwise, if... Otherwise,..." statements can be identified by pairing "... as follows" or "... the following applies" with the ending "Otherwise,...".

[0423] In the text, a statement of logical operations such as would be described mathematically in the following form:if( condition 0a && condition 0b )statement 0else if( condition 1a | | condition 1b ) statement 1 ...elsestatement ncan be described in the following way:... as follows / ...the following applies: - If all of the following conditions are true, statement 0:- condition 0a- condition 0b- Otherwise, if one or more of the following conditions are true, statement 1:- condition 1a- condition 1b- ...- Otherwise, statement n

[0424] In the text, a statement of logical operations such as would be described mathematically in the following form:if( condition 0 )statement 0if( condition 1 ) statement 1can be described in the following manner:When condition 0, statement 0When condition 1, statement 1

[0425] In summary, the present disclosure relates to methods and devices to be employed for encoding and decoding an image or video signal. They include determining whether the size of a current block is greater than a minimum allowable quaternary tree leaf node size. If the size of the current block is not greater than the minimum allowable quaternary tree leaf node size, multi-type tree splitting is applied to the current block. The minimum allowable quaternary tree leaf node size is not greater than the maximum allowable binary tree root node size, or the minimum allowable quaternary tree leaf node size is not greater than a maximum allowable ternary tree root node size.

Claims (13)

1. An encoding method comprising: determining whether a size of a current block is greater than a minimum allowable quaternary tree leaf node size; provided that the current block size is not greater than the minimum allowable quaternary tree leaf node size, applying binary tree splitting to the current block based on a maximum allowable binary tree root node size, wherein the maximum allowable binary tree root node size is determined based on the minimum allowable quaternary tree leaf node size, and the minimum allowable quaternary tree leaf node size is not greater than the maximum allowable binary tree root node size. 2. The encoding method of claim 1, further comprising the steps of: determining whether the current block of an image is a boundary block; wherein on condition that the current block size is not greater than the minimum allowable quaternary tree leaf node size, applying binary tree split to the current block; and wherein on condition that the current block size is not greater than the minimum allowable quaternary tree leaf node size. 3. The encoding method of claim 2, further comprising the steps of: dividing an image into blocks, wherein the blocks comprise the current block; wherein applying binary tree splitting to the current block comprises: applying binary tree splitting to the boundary block with a maximum boundary multi-type partition depth, wherein the maximum boundary multi-type partition depth is a sum of at least a maximum multi-type tree depth and a maximum multi-type tree depth offset, wherein the maximum multi-type tree depth is greater than 0. 4. The encoding method of claim 3, wherein the maximum multi-type tree depth is greater than 0 when applying binary tree splitting to the boundary block. 5. The encoding method of any one of claims 1 to 4, further comprising: dividing an image into blocks, wherein the blocks comprise the current block; wherein applying binary tree splitting to the current block comprises: applying binary tree splitting to the current block of the blocks with a final maximum multi-type tree depth, wherein the final maximum multi-type tree depth is a sum of at least a maximum multi-type tree depth and a maximum multi-type tree depth offset, wherein the maximum multi-type tree depth is greater than or equal to subtracting the minimum allowed coding block size Log2 value from the minimum allowed quaternary tree leaf node size Log2 value. 6. The encoding method of claim 5, wherein the current block is a non-boundary block. 7. The coding method of claim 5 or 6, wherein the maximum multi-type tree depth offset is 0. 8. A decoding device comprising: a circuitry configured to: determine whether a current block size is greater than a minimum allowable quaternary tree leaf node size; provided that the current block size is not greater than the minimum allowable quaternary tree leaf node size, apply binary tree splitting to the current block based on a maximum allowable binary tree root node size, wherein the maximum allowable binary tree root node size is determined based on the minimum allowable quaternary tree leaf node size, and the minimum allowable quaternary tree leaf node size is not greater than the maximum allowable binary tree root node size. 9. A coding device comprising: a circuitry configured to: determine whether a current block size is greater than a minimum allowable quaternary tree leaf node size; provided that the current block size is not greater than the minimum allowable quaternary tree leaf node size, apply binary tree splitting to the current block based on a maximum allowable binary tree root node size, wherein the maximum allowable binary tree root node size is determined based on the minimum allowable quaternary tree leaf node size, and the minimum allowable quaternary tree leaf node size is not greater than the maximum allowable binary tree root node size. 10. A non-transitory computer-readable storage medium that stores programming for execution by a set of processing circuits, wherein the programming, when executed by the set of processing circuits, configures the set of processing circuits to perform the method as defined in any one of claims 1 to 7. 11. A set-top box comprising: one or more processors; and a non-transitory computer-readable storage medium coupled to the processors and storing programming for execution by the processors, wherein the programming, when executed by the processors, configures the set-top box to perform the method as defined in any one of claims 1 to 7. 12. An encoder comprising: one or more processors; and a non-transitory computer-readable storage medium coupled to the processors and storing programming for execution by the processors, wherein the programming, when executed by the processors, configures the encoder to perform the method as defined in any one of claims 1 to 7. 13. Non-transitory storage media, CHARACTERIZED by the fact that it includes a computer program, which when executed by a processor, causes the processor to perform the method as defined in any one of claims 1 to 7 to generate a bit stream.