WO2018037919A1

WO2018037919A1 - Image decoding device, image coding device, image decoding method, and image coding method

Info

Publication number: WO2018037919A1
Application number: PCT/JP2017/028891
Authority: WO
Inventors: 知宏猪飼; 貴也山本
Original assignee: シャープ株式会社
Priority date: 2016-08-26
Filing date: 2017-08-09
Publication date: 2018-03-01

Abstract

An image decoding device (31) is provided with: a weight coefficient derivation unit (3030) that derives a weight coefficient from a weight candidate list (weightCandList) having weight coefficients (w) used for weight prediction as elements, according to the characteristic of a block used to generate a prediction image; and a weight prediction unit (3094) that performs weight prediction according to the weight coefficient derived by the weight coefficient derivation unit.

Description

Image decoding apparatus, image encoding apparatus, image decoding method, and image encoding method

Embodiments described herein relate generally to an image decoding device, an image encoding device, an image decoding method, and an image encoding method.

In order to efficiently transmit or record a moving image, a moving image encoding device that generates encoded data by encoding the moving image, and an image that generates a decoded image by decoding the encoded data A decoding device is used.

Specific examples of the moving image encoding method include a method proposed in H.264 / AVC and HEVC (High-Efficiency Video Coding).

In such a moving image coding system, an image (picture) constituting a moving image is a slice obtained by dividing the image, a coding unit obtained by dividing the slice (coding unit (Coding Unit : CU)), and a hierarchical structure consisting of a prediction unit (PU) and a transform unit (TU) that are obtained by dividing a coding unit. Decrypted.

In such a moving image coding method, a predicted image is usually generated based on a local decoded image obtained by encoding / decoding an input image, and the predicted image is generated from the input image (original image). A prediction residual obtained by subtraction (sometimes referred to as “difference image” or “residual image”) is encoded. Examples of the method for generating a predicted image include inter-screen prediction (inter prediction) and intra-screen prediction (intra prediction).

In addition, Non-Patent

Documents

1 and 2 can be cited as recent video encoding and decoding techniques.

(Bi prediction)
Bi-prediction is a technique for generating a predicted image predSample by the product sum (weighted average, weighted prediction) of two motion compensated images predSampleL0 and predSampleL1, as shown in the following equation.
predSample = (w * predSampleL0 + ((1 << shiftWP)-w) * predSampleL1) >> shiftWP
Here, “>>” is the right bit shift, “<<” is the left bit shift, and “shiftWP” is the number of bits to be shifted. Hereinafter, “w” is referred to as “weighting coefficient”.

In the prior art of Non-Patent Document 2, a bi-prediction weight coefficient (weight index weightIdx in the following equation) is explicitly encoded, and a weight prediction coefficient is derived as in the following equation.
w = weightTable [weightIdx]
weightTable [] = {-2, 2, 3, 4, 5, 6, 10}
Here, “weightTable” is a table of weight coefficients.

FIG. 32 is a flowchart showing the image decoding operation in the prior art of Non-Patent Document 2. The image decoding operation includes steps S101, S103, and S104.

In step S101, the weight index weightIdx is decoded. In step S103, a weight coefficient w is derived from the weight coefficient table weightTable based on the decoded weightIdx. In step S104, weight prediction is performed based on the weight coefficient w.

In the prior arts of

Non-Patent Documents

1 and 2, the encoding of the weight coefficient is not efficient. An object of the present invention is to realize an apparatus or the like capable of encoding weighting coefficients more efficiently than in the past.

Further, in the prior arts of

Non-Patent Documents

1 and 2, a method for deriving a weighting coefficient in the merge prediction mode is not disclosed. An object of the present invention is to realize an apparatus for deriving a weight coefficient with high prediction accuracy for the merge prediction mode.

In order to solve the above-described problem, an image decoding apparatus according to an aspect of the present invention provides a block of a block used for generating a predicted image from a weight candidate list including a weight coefficient used for weight prediction or an index indicating the weight coefficient as an element. A weighting factor deriving unit for deriving a weighting factor according to the feature; and a weight prediction unit for performing weight prediction using the weighting factor derived by the weighting factor deriving unit.

An image encoding device according to an aspect of the present invention derives a weighting factor from a weighting candidate list including a weighting factor used for weight prediction or an index indicating the weighting factor as an element according to a feature of a block used for generating a predicted image. A weight coefficient deriving unit that performs weight prediction using the weight coefficient derived by the weight coefficient deriving unit.

An image decoding method according to an aspect of the present invention derives a weighting factor from a weighting candidate list including elements of a weighting factor used for weight prediction or an index indicating the weighting factor in accordance with a feature of a block used for generating a predicted image. A weight coefficient deriving step, and a weight prediction step of performing weight prediction using the weight coefficient derived in the weight coefficient deriving step.

An image encoding method according to an aspect of the present invention derives a weighting factor from a weighting candidate list including a weighting factor used for weight prediction or an index indicating the weighting factor as an element according to a feature of a block used for generating a predicted image. A weight coefficient deriving step, and a weight prediction step of performing weight prediction using the weight coefficient derived in the weight coefficient deriving step.

According to each aspect of the present invention, there is an effect of reducing the code amount of the weight index.

It is a figure which shows the hierarchical structure of the data of the encoding stream which concerns on Embodiment 1. FIG. It is a figure which shows the pattern of PU division | segmentation mode. (A) to (h) respectively show the partition shapes when the PU partitioning modes are 2Nx2N, 2NxN, 2NxnU, 2NxnD, Nx2N, nLx2N, nRx2N, and NxN. It is a conceptual diagram which shows an example of a reference picture and a reference picture list. It is a block diagram which shows the structure of the image coding apparatus which concerns on Embodiment 1. FIG. 1 is a schematic diagram illustrating a configuration of an image decoding device according to Embodiment 1. FIG. It is the schematic which shows the structure of the inter estimated image generation part of the image coding apparatus which concerns on Embodiment 1. FIG. It is the schematic which shows the structure of the merge prediction parameter derivation | leading-out part which concerns on Embodiment 1. FIG. 3 is a schematic diagram illustrating a configuration of an AMVP prediction parameter derivation unit according to Embodiment 1. FIG. 6 is a flowchart illustrating an operation of motion vector decoding processing of the image decoding apparatus according to the first embodiment. It is the schematic which shows the structure of the inter prediction parameter encoding part of the image coding apparatus which concerns on Embodiment 1. FIG. It is the schematic which shows the structure of the inter estimated image generation part which concerns on Embodiment 1. FIG. It is the schematic which shows the structure of the inter prediction parameter decoding part which concerns on Embodiment 1. FIG. It is the figure shown about the structure of the transmitter which mounts the image coding apparatus which concerns on Embodiment 1, and the receiver which mounts an image decoding apparatus. (A) shows a transmission device equipped with an image encoding device, and (b) shows a reception device equipped with an image decoding device. It is the figure shown about the structure of the recording device carrying the image coding apparatus which concerns on Embodiment 1, and the reproducing | regenerating apparatus carrying an image decoding apparatus. (A) shows a recording device equipped with an image encoding device, and (b) shows a playback device equipped with an image decoding device. 1 is a schematic diagram illustrating a configuration of an image transmission system according to a first embodiment. FIG. 12 is a schematic diagram illustrating a detailed configuration of an inter prediction parameter decoding unit of a prediction parameter decoding unit of the image decoding device illustrated in FIG. 5 and an inter prediction image generation unit illustrated in FIG. 11. It is the schematic which shows the structure of the weighting coefficient derivation | leading-out part of the inter prediction parameter decoding part shown in FIG. It is a flowchart which shows operation | movement of the inter prediction parameter decoding part and inter prediction image generation part which are shown in FIG. FIG. 19 is a conceptual diagram illustrating a relationship between a reference block parameter and a reference block index in one step of the operation illustrated in FIG. 18. FIG. 18 is a schematic diagram illustrating a configuration of a weighting factor deriving unit different from the weighting factor deriving unit illustrated in FIG. 17. FIG. 20 is a conceptual diagram showing a correspondence relationship between a reference block parameter and a reference block index, which is different from the correspondence relationship shown in FIG. 19. It is the schematic which shows the detailed structure of the inter prediction parameter decoding part different from the inter prediction parameter decoding part shown in FIG. 16, and the inter estimated image production | generation part. It is the schematic which shows the structure of the weighting coefficient derivation | leading-out part of the inter prediction parameter decoding part shown in FIG. FIG. 19 is a conceptual diagram illustrating a correspondence relationship between a reference block parameter and a predicted value of a weight coefficient in one step of the operation illustrated in FIG. 18. It is a schematic diagram for demonstrating the bi-prediction based reference block index derivation method. FIG. 17 is a schematic diagram illustrating a detailed configuration of an inter prediction parameter decoding unit different from the inter prediction parameter decoding unit illustrated in FIG. 16 and an inter prediction image generation unit illustrated in FIG. 11 in the second embodiment. It is a flowchart which shows operation | movement of the inter prediction parameter decoding part and inter prediction image generation part which are shown in FIG. FIG. 27 is a schematic diagram illustrating adjacent blocks used when an adjacent base weight candidate list derivation unit of the inter prediction parameter decoding unit illustrated in FIG. 26 derives a weight candidate list. FIG. 27 is a schematic diagram for explaining scaling that is considered when the adjacent base weight candidate list deriving unit of the inter prediction parameter decoding unit illustrated in FIG. 26 derives a weight candidate list. It is the schematic which shows the detailed structure of the inter prediction parameter decoding part different from the inter prediction parameter decoding part shown in FIG. 11, and the inter prediction image generation part shown in FIG. 12 is a flowchart illustrating operations of the inter prediction parameter decoding unit of the prediction parameter decoding unit and the inter prediction image generation unit shown in FIG. 11 of the image decoding apparatus shown in FIG. 5 according to the third embodiment. 10 is a flowchart showing an image decoding operation in the prior art of Non-Patent Document 2.

Embodiment 1
Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 15 is a schematic diagram showing the configuration of the image transmission system 1 according to the present embodiment.

The image transmission system 1 is a system that transmits a code obtained by encoding an encoding target image, decodes the transmitted code, and displays an image. The image transmission system 1 includes an image encoding device 11, a network 21, an image decoding device 31, and an image display device 41.

The image encoding device 11 receives an image T indicating a single layer image or a plurality of layers. A layer is a concept used to distinguish a plurality of pictures when there are one or more pictures constituting a certain time. For example, when the same picture is encoded with a plurality of layers having different image quality and resolution, scalable encoding is performed, and when a picture of a different viewpoint is encoded with a plurality of layers, view scalable encoding is performed. When prediction is performed between pictures of a plurality of layers (inter-layer prediction, inter-view prediction), encoding efficiency is greatly improved. Further, even when prediction is not performed (simultaneous casting), encoded data can be collected.

The network 21 transmits the encoded stream Te generated by the image encoding device 11 to the image decoding device 31. The network 21 is the Internet, a wide area network (WAN: Wide Area Network), a small network (LAN: Local Area Network), or a combination thereof. The network 21 is not necessarily limited to a bidirectional communication network, and may be a one-way communication network that transmits broadcast waves such as terrestrial digital broadcast and satellite broadcast. The network 21 may be replaced with a storage medium that records an encoded stream Te such as a DVD (Digital Versatile Disc) or a BD (Blue-ray Disc).

The image decoding device 31 decodes each of the encoded streams Te transmitted by the network 21, and generates one or a plurality of decoded images Td decoded.

The image display device 41 displays all or part of one or more decoded images Td generated by the image decoding device 31. The image display device 41 includes, for example, a display device such as a liquid crystal display or an organic EL (Electro-luminescence) display. In addition, in the spatial scalable coding and SNR scalable coding, when the image decoding device 31 and the image display device 41 have a high processing capability, a high-quality enhancement layer image is displayed and only a lower processing capability is provided. Displays a base layer image that does not require higher processing capability and display capability as an extension layer.

<Operator>
The operators used in this specification are described below.

>> is right bit shift, << is left bit shift, & is bitwise AND, | is bitwise OR, | = is sum operation (OR) with another condition.

X? Y: z is a ternary operator that takes y when x is true (non-zero) and takes z when x is false (0).

Clip3 (a, b, c) is a function that clips c to a value between a and b, but returns a if c <a, returns b if c> b, otherwise Is a function that returns c (where a <= b).

<Structure of encoded stream Te>
Prior to detailed description of the image encoding device 11 and the image decoding device 31 according to the present embodiment, a data structure of an encoded stream Te generated by the image encoding device 11 and decoded by the image decoding device 31 will be described. .

FIG. 1 is a diagram showing a hierarchical structure of data in the encoded stream Te. The encoded stream Te illustratively includes a sequence and a plurality of pictures constituting the sequence. (A) to (f) of FIG. 1 respectively show an encoded video sequence defining a sequence SEQ, an encoded picture defining a picture PICT, an encoded slice defining a slice S, and an encoded slice defining a slice data It is a figure which shows the coding unit (Coding | unit: CU) contained in the coding tree unit contained in data and coding slice data, and a coding tree unit.

(Encoded video sequence)
In the encoded video sequence, a set of data referred to by the image decoding device 31 for decoding the sequence SEQ to be processed is defined. As shown in FIG. 1A, the sequence SEQ includes a video parameter set (Video Parameter Set), a sequence parameter set SPS (Sequence Parameter Set), a picture parameter set PPS (Picture Parameter Set), a picture PICT, and an addition. Includes SEI (Supplemental Enhancement Information). Here, the value indicated after # indicates the layer ID. Although FIG. 1 shows an example in which encoded data of # 0 and # 1, that is, layer 0 and layer 1, exists, the type of layer and the number of layers are not dependent on this.

The video parameter set VPS is a set of encoding parameters common to a plurality of moving images, a plurality of layers included in the moving image, and encoding parameters related to individual layers in a moving image composed of a plurality of layers. A set is defined.

The sequence parameter set SPS defines a set of encoding parameters that the image decoding device 31 refers to in order to decode the target sequence. For example, the width and height of the picture are defined. A plurality of SPSs may exist. In that case, one of a plurality of SPSs is selected from the PPS.

In the picture parameter set PPS, a set of encoding parameters referred to by the image decoding device 31 in order to decode each picture in the target sequence is defined. For example, a quantization width reference value (pic_init_qp_minus26) used for picture decoding and a flag (weighted_pred_flag) indicating application of weighted prediction are included. There may be a plurality of PPSs. In that case, one of a plurality of PPSs is selected from each picture in the target sequence.

(Encoded picture)
In the coded picture, a set of data referred to by the image decoding device 31 in order to decode the picture PICT to be processed is defined. As shown in FIG. 1B, the picture PICT includes slices S0 to S _NS-1 (NS is the total number of slices included in the picture PICT).

In the following description, if it is not necessary to distinguish each of the slices S0 to _SNS-1 , the subscripts may be omitted. The same applies to data included in an encoded stream Te described below and to which other subscripts are attached.

(Encoded slice)
In the coded slice, a set of data referred to by the image decoding device 31 for decoding the slice S to be processed is defined. As shown in FIG. 1C, the slice S includes a slice header SH and slice data SDATA.

The slice header SH includes an encoding parameter group that is referred to by the image decoding device 31 in order to determine a decoding method of the target slice. Slice type designation information (slice_type) for designating a slice type is an example of an encoding parameter included in the slice header SH.

As slice types that can be specified by the slice type specification information, (1) I slice using only intra prediction at the time of encoding, (2) P slice using unidirectional prediction or intra prediction at the time of encoding, (3) B-slice using unidirectional prediction, bidirectional prediction, or intra prediction at the time of encoding may be used.

Note that the slice header SH may include a reference (pic_parameter_set_id) to the picture parameter set PPS included in the encoded video sequence.

(Encoded slice data)
In the encoded slice data, a set of data referred to by the image decoding device 31 for decoding the slice data SDATA to be processed is defined. The slice data SDATA includes a coding tree unit (CTU) as shown in FIG. A CTU is a block of a fixed size (for example, 64x64) that constitutes a slice, and is sometimes called a maximum coding unit (LCU: Large Coding Unit).

(Encoding tree unit)
As shown in (e) of FIG. 1, a set of data referred to by the image decoding device 31 in order to decode the encoding tree unit to be processed is defined. The coding tree unit is divided by recursive quadtree division. A tree-structured node obtained by recursive quadtree partitioning is referred to as a coding node (CN). An intermediate node of the quadtree is an encoding node, and the encoding tree unit itself is defined as the highest encoding node. The CTU includes a split flag (cu_split_flag), and when cu_split_flag is 1, it is split into four coding nodes CN. When cu_split_flag is 0, the coding node CN is not divided and has one coding unit (CU: Coding Unit) as a node. The encoding unit CU is a terminal node of the encoding node and is not further divided. The encoding unit CU is a basic unit of the encoding process.

In addition, when the size of the coding tree unit CTU is 64 × 64 pixels, the size of the coding unit can be any of 64 × 64 pixels, 32 × 32 pixels, 16 × 16 pixels, and 8 × 8 pixels.

(Encoding unit)
As shown in (f) of FIG. 1, a set of data referred to by the image decoding device 31 in order to decode an encoding unit to be processed is defined. Specifically, the encoding unit includes a prediction tree, a conversion tree, and a CU header CUH. The CU header defines a prediction mode, a division method (PU division mode), and the like.

In the prediction tree, prediction information (a reference picture index, a motion vector, etc.) of each prediction unit (PU) obtained by dividing the coding unit into one or a plurality is defined. In other words, the prediction unit is one or a plurality of non-overlapping areas constituting the encoding unit. The prediction tree includes one or a plurality of prediction units obtained by the above-described division. Hereinafter, a prediction unit obtained by further dividing the prediction unit is referred to as a “sub-block”. The sub block is composed of a plurality of pixels. When the sizes of the prediction unit and the sub-block are equal, the number of sub-blocks in the prediction unit is one. If the prediction unit is larger than the size of the sub-block, the prediction unit is divided into sub-blocks. For example, when the prediction unit is 8 × 8 and the sub-block is 4 × 4, the prediction unit is divided into four sub-blocks that are divided into two horizontally and two vertically.

The prediction process may be performed for each prediction unit (sub block).

There are roughly two types of division in the prediction tree: intra prediction and inter prediction. Intra prediction is prediction within the same picture, and inter prediction refers to prediction processing performed between different pictures (for example, between display times and between layer images).

In the case of intra prediction, there are 2Nx2N (the same size as the encoding unit) and NxN division methods.

Also, in the case of inter prediction, the division method is encoded by the PU division mode (part_mode) of encoded data, 2Nx2N (same size as the encoding unit), 2NxN, 2NxnU, 2NxnD, Nx2N, nLx2N, nRx2N, and NxN etc. 2NxN and Nx2N indicate 1: 1 symmetrical division, and 2NxnU, 2NxnD and nLx2N and nRx2N indicate 1: 3 and 3: 1 asymmetric division. The PUs included in the CU are expressed as PU0, PU1, PU2, and PU3 in this order.

(A) to (h) of FIG. 2 specifically illustrate the shape of the partition (the position of the boundary of the PU partition) in each PU partition mode. 2A shows a 2Nx2N partition, and FIGS. 2B, 2C, and 2D show 2NxN, 2NxnU, and 2NxnD partitions (horizontal partitions), respectively. (E), (f), and (g) show partitions (vertical partitions) in the case of Nx2N, nLx2N, and nRx2N, respectively, and (h) shows an NxN partition. The horizontal partition and the vertical partition are collectively referred to as a rectangular partition, and 2Nx2N and NxN are collectively referred to as a square partition.

Also, in the conversion tree, the encoding unit is divided into one or a plurality of conversion units, and the position and size of each conversion unit are defined. In other words, a transform unit is one or more non-overlapping areas that make up a coding unit. The conversion tree includes one or a plurality of conversion units obtained by the above division.

The division in the conversion tree includes a case where an area having the same size as that of the encoding unit is assigned as a conversion unit, and a case where recursive quadtree division is used, as in the case of the CU division described above.

Conversion processing is performed for each conversion unit.

(Prediction parameter)
A prediction image of a prediction unit (PU: Prediction Unit) is derived from a prediction parameter associated with the PU. The prediction parameters include a prediction parameter for intra prediction or a prediction parameter for inter prediction. Hereinafter, prediction parameters for inter prediction (inter prediction parameters) will be described. The inter prediction parameter includes prediction list use flags predFlagL0 and predFlagL1, reference picture indexes refIdxL0 and refIdxL1, and motion vectors mvL0 and mvL1. The prediction list use flags predFlagL0 and predFlagL1 are flags indicating whether or not reference picture lists called L0 list and L1 list are used, respectively, and a reference picture list corresponding to a value of 1 is used. In this specification, when “flag indicating whether or not it is XX” is described, when the flag is not 0 (for example, 1) is XX, 0 is not XX, and logical negation, logical product, etc. 1 is treated as true and 0 is treated as false (the same applies hereinafter). However, other values can be used as true values and false values in an actual apparatus or method.

Syntax elements for deriving inter prediction parameters included in the encoded data include, for example, PU partition mode part_mode, merge flag merge_flag, merge index merge_idx, inter prediction identifier inter_pred_idc, reference picture index refIdxLX, prediction vector index mvp_LX_idx, There is a difference vector mvdLX.

(Reference picture list)
The reference picture list is a list including reference pictures stored in the reference picture memory 306. FIG. 3 is a conceptual diagram illustrating an example of a reference picture and a reference picture list. In FIG. 3A, a rectangle is a picture, an arrow is a picture reference relationship, a horizontal axis is time, I, P, and B in the rectangle are intra pictures, uni-predictive pictures, bi-predictive pictures, and numbers in the rectangles are decoded. Indicates the order. As shown in the figure, the decoding order of pictures is I0, P1, B2, B3, and B4, and the display order is I0, B3, B2, B4, and P1. FIG. 3B shows an example of the reference picture list. The reference picture list is a list representing candidate reference pictures, and one picture (slice) may have one or more reference picture lists. In the illustrated example, the target picture B3 has two reference picture lists, an L0 list RefPicList0 and an L1 list RefPicList1. When the target picture is B3, the reference pictures are I0, P1, and B2, and the reference picture has these pictures as elements. In each prediction unit, which picture in the reference picture list RefPicListX is actually referred to is specified by the reference picture index refIdxLX. The figure shows an example in which reference pictures P1 and B2 are referenced by refIdxL0 and refIdxL1.

(Merge prediction and AMVP prediction)
The prediction parameter decoding (encoding) method includes a merge prediction (merge) mode and an AMVP (Adaptive Motion Vector Prediction) mode. The merge flag merge_flag is a flag for identifying these. The merge prediction mode is a mode in which the prediction list use flag predFlagLX (or inter prediction identifier inter_pred_idc), the reference picture index refIdxLX, and the motion vector mvLX are not included in the encoded data and are derived from the prediction parameters of already processed neighboring PUs. The AMVP mode is a mode in which the inter prediction identifier inter_pred_idc, the reference picture index refIdxLX, and the motion vector mvLX are included in the encoded data. The motion vector mvLX is encoded as a prediction vector index mvp_LX_idx for identifying the prediction vector mvpLX and a difference vector mvdLX.

The inter prediction identifier inter_pred_idc is a value indicating the type and number of reference pictures, and takes one of PRED_L0, PRED_L1, and PRED_BI. PRED_L0 and PRED_L1 indicate that reference pictures managed by the reference picture lists of the L0 list and the L1 list are used, respectively, and that one reference picture is used (single prediction). PRED_BI indicates that two reference pictures are used (bi-prediction BiPred), and reference pictures managed by the L0 list and the L1 list are used. The prediction vector index mvp_LX_idx is an index indicating a prediction vector, and the reference picture index refIdxLX is an index indicating a reference picture managed in the reference picture list. Note that LX is a description method used when L0 prediction and L1 prediction are not distinguished from each other. By replacing LX with L0 and L1, parameters for the L0 list and parameters for the L1 list are distinguished.

The merge index merge_idx is an index that indicates whether one of the prediction parameter candidates (merge candidates) derived from the processed PU is used as the prediction parameter of the decoding target PU.

(Motion vector)
The motion vector mvLX indicates a shift amount between blocks on two different pictures. A prediction vector and a difference vector related to the motion vector mvLX are referred to as a prediction vector mvpLX and a difference vector mvdLX, respectively.

(Inter prediction identifier inter_pred_idc and prediction list use flag predFlagLX)
The relationship between the inter prediction identifier inter_pred_idc and the prediction list use flags predFlagL0 and predFlagL1 is as follows and can be converted into each other.

inter_pred_idc = (predFlagL1 << 1) + predFlagL0
predFlagL0 = inter_pred_idc & 1
predFlagL1 = inter_pred_idc >> 1
Note that a prediction list use flag or an inter prediction identifier may be used as the inter prediction parameter. Further, the determination using the prediction list use flag may be replaced with the determination using the inter prediction identifier. Conversely, the determination using the inter prediction identifier may be replaced with the determination using the prediction list use flag.

(Determination of bi-prediction biPred)
The flag biPred as to whether it is a bi-prediction BiPred can be derived depending on whether the two prediction list use flags are both 1. For example, it can be derived by the following formula.

biPred = (predFlagL0 == 1 && predFlagL1 == 1)
The flag biPred can also be derived depending on whether or not the inter prediction identifier is a value indicating that two prediction lists (reference pictures) are used. For example, it can be derived by the following formula.

biPred = (inter_pred_idc == PRED_BI)? 1: 0
The above formula can also be expressed by the following formula.

biPred = (inter_pred_idc == PRED_BI)
For example, a value of 3 can be used for PRED_BI.

(Configuration of image decoding device)
Next, the configuration of the image decoding device 31 according to the present embodiment will be described. FIG. 5 is a schematic diagram illustrating a configuration of the image decoding device 31 according to the present embodiment. The image decoding device 31 includes an entropy decoding unit 301, a prediction parameter decoding unit (prediction image decoding device) 302, a loop filter 305, a reference picture memory 306, a prediction parameter memory 307, a prediction image generation unit (prediction image generation device) 308, and inversely. A quantization / inverse DCT unit 311 and an addition unit 312 are included.

The prediction parameter decoding unit 302 includes an inter prediction parameter decoding unit 303 and an intra prediction parameter decoding unit 304. The predicted image generation unit 308 includes an inter predicted image generation unit 309 and an intra predicted image generation unit 310.

The entropy decoding unit 301 performs entropy decoding on the coded stream Te input from the outside, and separates and decodes individual codes (syntax elements). The separated codes include prediction information for generating a prediction image and residual information for generating a difference image.

The entropy decoding unit 301 outputs a part of the separated code to the prediction parameter decoding unit 302. Some of the separated codes are, for example, a prediction mode predMode, a PU partition mode part_mode, a merge flag merge_flag, a merge index merge_idx, an inter prediction identifier inter_pred_idc, a reference picture index refIdxLX, a prediction vector index mvp_LX_idx, and a difference vector mvdLX. Control of which code is decoded is performed based on an instruction from the prediction parameter decoding unit 302. The entropy decoding unit 301 outputs the quantization coefficient to the inverse quantization / inverse DCT unit 311. The quantization coefficient is a coefficient obtained by performing quantization by performing DCT (Discrete Cosine Transform) on the residual signal in the encoding process.

The inter prediction parameter decoding unit 303 decodes the inter prediction parameter with reference to the prediction parameter stored in the prediction parameter memory 307 based on the code input from the entropy decoding unit 301.

The inter prediction parameter decoding unit 303 outputs the decoded inter prediction parameter to the prediction image generation unit 308 and stores it in the prediction parameter memory 307. Details of the inter prediction parameter decoding unit 303 will be described later.

The intra prediction parameter decoding unit 304 refers to the prediction parameter stored in the prediction parameter memory 307 on the basis of the code input from the entropy decoding unit 301 and decodes the intra prediction parameter. The intra prediction parameter is a parameter used in a process of predicting a CU within one picture, for example, an intra prediction mode IntraPredMode. The intra prediction parameter decoding unit 304 outputs the decoded intra prediction parameter to the prediction image generation unit 308 and stores it in the prediction parameter memory 307.

The intra prediction parameter decoding unit 304 may derive different intra prediction modes for luminance and color difference. In this case, the intra prediction parameter decoding unit 304 decodes the luminance prediction mode IntraPredModeY as the luminance prediction parameter and the color difference prediction mode IntraPredModeC as the color difference prediction parameter. The luminance prediction mode IntraPredModeY is a 35 mode, and corresponds to planar prediction (0), DC prediction (1), and direction prediction (2 to 34). The color difference prediction mode IntraPredModeC uses one of the planar prediction (0), the DC prediction (1), the direction prediction (2 to 34), and the LM mode (35). The intra prediction parameter decoding unit 304 decodes a flag indicating whether IntraPredModeC is the same mode as the luminance mode. If the flag indicates that the mode is the same as the luminance mode, IntraPredModeC is assigned to IntraPredModeC and the flag is If the mode is different from the mode, planar prediction (0), DC prediction (1), direction prediction (2 to 34), and LM mode (35) may be decoded as IntraPredModeC.

The loop filter 305 applies filters such as a deblocking filter, a sample adaptive offset (SAO), and an adaptive loop filter (ALF) to the decoded image of the CU generated by the adding unit 312.

The reference picture memory 306 stores the decoded image of the CU generated by the adding unit 312 at a predetermined position for each decoding target picture and CU.

The prediction parameter memory 307 stores the prediction parameter in a predetermined position for each decoding target picture and prediction unit (or sub-block, fixed-size block, pixel). Specifically, the prediction parameter memory 307 stores the inter prediction parameter decoded by the inter prediction parameter decoding unit 303, the intra prediction parameter decoded by the intra prediction parameter decoding unit 304, and the prediction mode predMode separated by the entropy decoding unit 301. . The stored inter prediction parameters include, for example, a prediction list utilization flag predFlagLX (inter prediction identifier inter_pred_idc), a reference picture index refIdxLX, and a motion vector mvLX.

The prediction image generation unit 308 receives the prediction mode predMode input from the entropy decoding unit 301 and the prediction parameter from the prediction parameter decoding unit 302. Further, the predicted image generation unit 308 reads a reference picture (reference picture block) from the reference picture memory 306. The prediction image generation unit 308 generates a prediction image of a PU or sub-block using the input prediction parameter and the read reference picture (reference picture block) in the prediction mode indicated by the prediction mode predMode.

Here, when the prediction mode predMode indicates the inter prediction mode, the inter prediction image generation unit 309 uses the inter prediction parameter input from the inter prediction parameter decoding unit 303 and the read reference picture to perform prediction of the PU by inter prediction. Is generated.

The inter prediction image generation unit 309 performs a motion vector on the basis of the decoding target PU from the reference picture indicated by the reference picture index refIdxLX for a reference picture list (L0 list or L1 list) having a prediction list use flag predFlagLX of 1. The reference picture block at the position indicated by mvLX is read from the reference picture memory 306. The inter prediction image generation unit 309 performs prediction based on the read reference picture block to generate a prediction image of the PU. The inter prediction image generation unit 309 outputs the generated prediction image of the PU to the addition unit 312. Here, a reference picture block is a set of pixels on a reference picture (usually called a block because it is a rectangle), and is an area that is referred to in order to generate a predicted image of a PU or sub-block. Hereinafter, it is also simply referred to as “reference block”.

When the prediction mode predMode indicates the intra prediction mode, the intra predicted image generation unit 310 performs intra prediction using the intra prediction parameter input from the intra prediction parameter decoding unit 304 and the read reference picture. Specifically, the intra predicted image generation unit 310 reads, from the reference picture memory 306, neighboring PUs that are pictures to be decoded and are in a predetermined range from the decoding target PUs among the PUs that have already been decoded. The predetermined range is, for example, one of the left, upper left, upper, and upper right adjacent PUs when the decoding target PU sequentially moves in the so-called raster scan order, and differs depending on the intra prediction mode. The raster scan order is an order in which each row is sequentially moved from the left end to the right end in each picture from the upper end to the lower end.

The intra predicted image generation unit 310 performs prediction in the prediction mode indicated by the intra prediction mode IntraPredMode for the read adjacent PU, and generates a predicted image of the PU. The intra predicted image generation unit 310 outputs the generated predicted image of the PU to the adding unit 312.

When the intra prediction parameter decoding unit 304 derives an intra prediction mode different in luminance and color difference, the intra prediction image generation unit 310 performs planar prediction (0), DC prediction (1), direction according to the luminance prediction mode IntraPredModeY. Prediction image of luminance PU is generated by any of prediction (2 to 34), and planar prediction (0), DC prediction (1), direction prediction (2 to 34), LM mode according to color difference prediction mode IntraPredModeC A predicted image of the color difference PU is generated by any of (35).

The inverse quantization / inverse DCT unit 311 inversely quantizes the quantization coefficient input from the entropy decoding unit 301 to obtain a DCT coefficient. The inverse quantization / inverse DCT unit 311 performs inverse DCT (Inverse Discrete Cosine Transform) on the obtained DCT coefficient to calculate a residual signal. The inverse quantization / inverse DCT unit 311 outputs the calculated residual signal to the addition unit 312.

The addition unit 312 adds the prediction image of the PU input from the inter prediction image generation unit 309 or the intra prediction image generation unit 310 and the residual signal input from the inverse quantization / inverse DCT unit 311 for each pixel, Generate a decoded PU image. The adding unit 312 stores the generated decoded image of the PU in the reference picture memory 306, and outputs a decoded image Td in which the generated decoded image of the PU is integrated for each picture to the outside.

(Configuration of inter prediction parameter decoding unit)
Next, the configuration of the inter prediction parameter decoding unit 303 will be described.

FIG. 12 is a schematic diagram illustrating a configuration of the inter prediction parameter decoding unit 303 according to the present embodiment. The inter prediction parameter decoding unit 303 includes an inter prediction parameter decoding control unit 3031, an AMVP prediction parameter derivation unit 3032, an addition unit 3035, a merge prediction parameter derivation unit 3036, and a sub-block prediction parameter derivation unit 3037.

The inter prediction parameter decoding control unit 3031 instructs the entropy decoding unit 301 to decode a code (syntax element) related to inter prediction, and a code (syntax element) included in the encoded data, for example, PU partition mode part_mode , Merge flag merge_flag, merge index merge_idx, inter prediction identifier inter_pred_idc, reference picture index refIdxLX, prediction vector index mvp_LX_idx, and difference vector mvdLX are extracted.

The inter prediction parameter decoding control unit 3031 first extracts a merge flag merge_flag. When the inter prediction parameter decoding control unit 3031 expresses that a certain syntax element is to be extracted, it means that the entropy decoding unit 301 is instructed to decode a certain syntax element, and the corresponding syntax element is read from the encoded data. To do.

When the merge flag merge_flag is 0, that is, indicates the AMVP prediction mode, the inter prediction parameter decoding control unit 3031 uses the entropy decoding unit 301 to extract the AMVP prediction parameter from the encoded data. Examples of AMVP prediction parameters include an inter prediction identifier inter_pred_idc, a reference picture index refIdxLX, a prediction vector index mvp_LX_idx, and a difference vector mvdLX. The AMVP prediction parameter derivation unit 3032 derives a prediction vector mvpLX from the prediction vector index mvp_LX_idx. Details will be described later. The inter prediction parameter decoding control unit 3031 outputs the difference vector mvdLX to the addition unit 3035. The adding unit 3035 adds the prediction vector mvpLX and the difference vector mvdLX to derive a motion vector.

When the merge flag merge_flag is 1, that is, indicates the merge prediction mode, the inter prediction parameter decoding control unit 3031 extracts the merge index merge_idx as a prediction parameter related to merge prediction. The inter prediction parameter decoding control unit 3031 outputs the extracted merge index merge_idx to the merge prediction parameter derivation unit 3036 (details will be described later), and outputs the sub-block prediction mode flag subPbMotionFlag to the sub-block prediction parameter derivation unit 3037. The subblock prediction parameter deriving unit 3037 divides the PU into a plurality of subblocks according to the value of the subblock prediction mode flag subPbMotionFlag, and derives a motion vector in units of subblocks. That is, in the sub-block prediction mode, the prediction block is predicted in units of blocks as small as 4x4 or 8x8. In the image encoding device 11 to be described later, a sub-block prediction mode is used for a method in which a CU is divided into a plurality of partitions (PUs such as 2NxN, Nx2N, and NxN) and the syntax of prediction parameters is encoded in units of partitions. Since a plurality of sub-blocks are grouped into a set and the syntax of the prediction parameter is encoded for each set, motion information of a large number of sub-blocks can be encoded with a small amount of code.

FIG. 7 is a schematic diagram illustrating the configuration of the merge prediction parameter deriving unit 3036 according to the present embodiment. The merge prediction parameter derivation unit 3036 includes a merge candidate derivation unit 30361, a merge candidate selection unit 30362, and a merge candidate storage unit 30363. The merge candidate storage unit 30363 stores the merge candidates input from the merge candidate derivation unit 30361. The merge candidate includes a prediction list use flag predFlagLX, a motion vector mvLX, and a reference picture index refIdxLX. In the merge candidate storage unit 30363, an index is assigned to the stored merge candidate according to a predetermined rule.

The merge candidate derivation unit 30361 derives a merge candidate using the motion vector of the adjacent PU that has already been decoded and the reference picture index refIdxLX as they are. In addition, merge candidates may be derived using affine prediction. This method is described in detail below. The merge candidate derivation unit 30361 may use affine prediction for a spatial merge candidate derivation process, a temporal merge candidate derivation process, a combined merge candidate derivation process, and a zero merge candidate derivation process described later. Affine prediction is performed in units of sub-blocks, and prediction parameters are stored in the prediction parameter memory 307 for each sub-block. Alternatively, the affine prediction may be performed on a pixel basis.

(Spatial merge candidate derivation process)
As the spatial merge candidate derivation process, the merge candidate derivation unit 30361 reads and reads the prediction parameters (prediction list use flag predFlagLX, motion vector mvLX, reference picture index refIdxLX) stored in the prediction parameter memory 307 according to a predetermined rule. The predicted parameters are derived as merge candidates. The prediction parameter to be read is a prediction parameter related to each of the PUs within a predetermined range from the decoding target PU (for example, all or part of the PUs in contact with the lower left end, the upper left end, and the upper right end of the decoding target PU, respectively). is there. The merge candidates derived by the merge candidate deriving unit 30361 are stored in the merge candidate storage unit 30363.

(Time merge candidate derivation process)
As the temporal merge derivation process, the merge candidate derivation unit 30361 reads the prediction parameter of the PU in the reference image including the lower right coordinate of the decoding target PU from the prediction parameter memory 307 and sets it as a merge candidate. The reference picture designation method may be, for example, the reference picture index refIdxLX designated in the slice header, or may be designated using the smallest reference picture index refIdxLX of the PU adjacent to the decoding target PU. The merge candidates derived by the merge candidate deriving unit 30361 are stored in the merge candidate storage unit 30363.

(Join merge candidate derivation process)
As the merge merge derivation process, the merge candidate derivation unit 30361 uses two different derived merge candidate motion vectors and reference picture indexes already derived and stored in the merge candidate storage unit 30363 as the motion vectors of L0 and L1, respectively. Combined merge candidates are derived by combining them. The merge candidates derived by the merge candidate deriving unit 30361 are stored in the merge candidate storage unit 30363.

(Zero merge candidate derivation process)
As the zero merge candidate derivation process, the merge candidate derivation unit 30361 derives a merge candidate in which the reference picture index refIdxLX is 0 and both the X component and the Y component of the motion vector mvLX are 0. The merge candidates derived by the merge candidate deriving unit 30361 are stored in the merge candidate storage unit 30363.

The merge candidate selection unit 30362 selects, from the merge candidates stored in the merge candidate storage unit 30363, a merge candidate to which an index corresponding to the merge index merge_idx input from the inter prediction parameter decoding control unit 3031 is assigned. As an inter prediction parameter. The merge candidate selection unit 30362 stores the selected merge candidate in the prediction parameter memory 307 and outputs it to the prediction image generation unit 308.

FIG. 8 is a schematic diagram showing the configuration of the AMVP prediction parameter derivation unit 3032 according to this embodiment. The AMVP prediction parameter derivation unit 3032 includes a vector candidate derivation unit 3033, a vector candidate selection unit 3034, and a vector candidate storage unit 3035. The vector candidate derivation unit 3033 reads the already processed PU motion vector mvLX stored in the prediction parameter memory 307 based on the reference picture index refIdx, derives a prediction vector candidate, and sends the prediction vector candidate to the vector candidate storage unit 3035. Store in candidate list mvpListLX [].

The vector candidate selection unit 3034 selects the motion vector mvpListLX [mvp_LX_idx] indicated by the prediction vector index mvp_LX_idx from the prediction vector candidates in the prediction vector candidate list mvpListLX [] as the prediction vector mvpLX. The vector candidate selection unit 3034 outputs the selected prediction vector mvpLX to the addition unit 3035.

Note that a prediction vector candidate is a PU for which decoding processing has been completed, and is derived by scaling a motion vector of a PU (for example, an adjacent PU) within a predetermined range from the decoding target PU. The adjacent PU includes a PU that is spatially adjacent to the decoding target PU, for example, the left PU and the upper PU, and an area that is temporally adjacent to the decoding target PU, for example, the same position as the decoding target PU. It includes areas obtained from prediction parameters of PUs with different times.

The addition unit 3035 adds the prediction vector mvpLX input from the AMVP prediction parameter derivation unit 3032 and the difference vector mvdLX input from the inter prediction parameter decoding control unit 3031 to calculate a motion vector mvLX. The adding unit 3035 outputs the calculated motion vector mvLX to the predicted image generation unit 308 and the prediction parameter memory 307.

(Inter prediction image generation unit 309)
FIG. 11 is a schematic diagram illustrating a configuration of an inter predicted image generation unit 309 included in the predicted image generation unit 308 according to the present embodiment. The inter prediction image generation unit 309 includes a motion compensation unit (prediction image generation device) 3091 and a weight prediction unit 3094.

(Motion compensation)
The motion compensation unit 3091 receives the reference picture index refIdxLX from the reference picture memory 306 based on the inter prediction parameters (prediction list use flag predFlagLX, reference picture index refIdxLX, motion vector mvLX) input from the inter prediction parameter decoding unit 303. In the reference picture specified in (2), an interpolation image (motion compensation image) is generated by reading out a block at a position shifted by the motion vector mvLX starting from the position of the decoding target PU. Here, when the accuracy of the motion vector mvLX is not integer accuracy, a motion compensation image is generated by applying a filter for generating a pixel at a decimal position called a motion compensation filter.

(Weight prediction)
The weight prediction unit 3094 generates a prediction image of the PU by multiplying the input motion compensation image predSamplesLX by a weight coefficient. When one of the prediction list use flags (predFlagL0 or predFlagL1) is 1 (in the case of single prediction) and the weight prediction is not used, the input motion compensated image predSamplesLX (LX is L0 or L1) is represented by the number of pixel bits bitDepth The following equation is processed to match

predSamples [X] [Y] = Clip3 (0, (1 << bitDepth)-1, (predSamplesLX [X] [Y] + offset1) >> shift1)
Here, shift1 = 14−bitDepth, offset1 = 1 << (shift1-1).
When both of the reference list use flags (predFlagL0 and predFlagL1) are 1 (in the case of bi-prediction BiPred) and weight prediction is not used, the input motion compensation images predSamplesL0 and predSamplesL1 are averaged and the number of pixel bits The following equation is processed to match

predSamples [X] [Y] = Clip3 (0, (1 << bitDepth)-1, (predSamplesL0 [X] [Y] + predSamplesL1 [X] [Y] + offset2) >> shift2)
Here, shift2 = 15-bitDepth, offset2 = 1 << (shift2-1).

Furthermore, in the case of single prediction, when performing weight prediction, the weight prediction unit 3094 derives the weight prediction coefficient w0 and the offset o0 from the encoded data, and performs the processing of the following equation.

predSamples [X] [Y] = Clip3 (0, (1 << bitDepth)-1, ((predSamplesLX [X] [Y] * w0 + 2 ^ (log2WD-1)) >> log2WD) + o0)
Here, log2WD is a variable indicating a predetermined shift amount.

Furthermore, in the case of bi-prediction BiPred, when performing weight prediction, the weight prediction unit 3094 derives weight prediction coefficients w0, w1, o0, o1 from the encoded data, and performs the processing of the following equation.

predSamples [X] [Y] = Clip3 (0, (1 << bitDepth)-1, (predSamplesL0 [X] [Y] * w0 + predSamplesL1 [X] [Y] * w1 + ((o0 + o1 + 1) << log2WD)) >> (log2WD + 1))
<Motion vector decoding process>
Below, with reference to FIG. 9, the motion vector decoding process which concerns on this embodiment is demonstrated concretely.

As is clear from the above description, the motion vector decoding process according to the present embodiment includes a process of decoding syntax elements related to inter prediction (also referred to as motion syntax decoding process) and a process of deriving a motion vector ( Motion vector derivation process).

(Motion syntax decoding process)
FIG. 9 is a flowchart illustrating a flow of inter prediction syntax decoding processing performed by the inter prediction parameter decoding control unit 3031. In the following description of FIG. 9, each process is performed by the inter prediction parameter decoding control unit 3031 unless otherwise specified.

First, in step S101, the merge flag merge_flag is decoded, and in step S102,
merge_flag! = 0 (whether merge_flag is not 0)
Is judged.

If merge_flag! = 0 is true (Y in S102), the merge index merge_idx is decoded in S103, and the motion vector derivation process (S111) in the merge prediction mode is executed.

When merge_flag! = 0 is false (N in S102), the inter prediction identifier inter_pred_idc is decoded in S104.

When inter_pred_idc is other than PRED_L1 (PRED_L0 or PRED_BI), the reference picture index refIdxL0, the difference vector parameter mvdL0, and the prediction vector index mvp_L0_idx are decoded in S105, S106, and S107, respectively.

When inter_pred_idc is other than PRED_L0 (PRED_L1 or PRED_BI), the reference picture index refIdxL1, the difference vector parameter mvdL1, and the prediction vector index mvp_L1_idx are decoded in S108, S109, and S110. Subsequently, a motion vector derivation process (S112) in the AMVP mode is executed.

(Configuration of image encoding device)
Next, the configuration of the image encoding device 11 according to the present embodiment will be described. FIG. 4 is a block diagram illustrating a configuration of the image encoding device 11 according to the present embodiment. The image encoding device 11 includes a prediction image generation unit 101, a subtraction unit 102, a DCT / quantization unit 103, an entropy encoding unit 104, an inverse quantization / inverse DCT unit 105, an addition unit 106, a loop filter 107, and a prediction parameter memory. (Prediction parameter storage unit, frame memory) 108, reference picture memory (reference image storage unit, frame memory) 109, encoding parameter determination unit 110, and prediction parameter encoding unit 111. The prediction parameter encoding unit 111 includes an inter prediction parameter encoding unit 112 and an intra prediction parameter encoding unit 113.

The predicted image generation unit 101 generates, for each picture of the image T, a predicted image P of the prediction unit PU for each encoding unit CU that is an area obtained by dividing the picture. Here, the predicted image generation unit 101 reads a decoded block from the reference picture memory 109 based on the prediction parameter input from the prediction parameter encoding unit 111. The prediction parameter input from the prediction parameter encoding unit 111 is, for example, a motion vector in the case of inter prediction. The predicted image generation unit 101 reads a block at a position on the reference image indicated by the motion vector with the target PU as a starting point. In the case of intra prediction, the prediction parameter is, for example, an intra prediction mode. A pixel value of an adjacent PU used in the intra prediction mode is read from the reference picture memory 109, and a predicted image P of the PU is generated. The predicted image generation unit 101 generates a predicted image P of the PU using one prediction method among a plurality of prediction methods for the read reference picture block. The predicted image generation unit 101 outputs the generated predicted image P of the PU to the subtraction unit 102.

Note that the predicted image generation unit 101 performs the same operation as the predicted image generation unit 308 already described. For example, FIG. 6 is a schematic diagram illustrating a configuration of an inter predicted image generation unit 1011 included in the predicted image generation unit 101. The inter prediction image generation unit 1011 includes a motion compensation unit 10111 and a weight prediction unit 10112. Since the motion compensation unit 10111 and the weight prediction unit 10112 have the same configurations as the motion compensation unit 3091 and the weight prediction unit 3094 described above, description thereof is omitted here.

The predicted image generation unit 101 generates a predicted image P of the PU based on the pixel value of the reference picture (reference picture block) read from the reference picture memory, using the parameter input from the prediction parameter encoding unit. The predicted image generated by the predicted image generation unit 101 is output to the subtraction unit 102 and the addition unit 106.

The subtraction unit 102 subtracts the signal value of the predicted image P of the PU input from the predicted image generation unit 101 from the pixel value of the corresponding PU of the image T, and generates a residual signal. The subtraction unit 102 outputs the generated residual signal to the DCT / quantization unit 103.

The DCT / quantization unit 103 performs DCT on the residual signal input from the subtraction unit 102 and calculates a DCT coefficient. The DCT / quantization unit 103 quantizes the calculated DCT coefficient to obtain a quantization coefficient. The DCT / quantization unit 103 outputs the obtained quantization coefficient to the entropy coding unit 104 and the inverse quantization / inverse DCT unit 105.

The entropy encoding unit 104 receives the quantization coefficient from the DCT / quantization unit 103 and receives the encoding parameter from the prediction parameter encoding unit 111. Examples of input encoding parameters include codes such as a reference picture index refIdxLX, a prediction vector index mvp_LX_idx, a difference vector mvdLX, a prediction mode predMode, and a merge index merge_idx.

The entropy encoding unit 104 generates an encoded stream Te by entropy encoding the input quantization coefficient and encoding parameter, and outputs the generated encoded stream Te to the outside.

The inverse quantization / inverse DCT unit 105 inversely quantizes the quantization coefficient input from the DCT / quantization unit 103 to obtain a DCT coefficient. The inverse quantization / inverse DCT unit 105 performs inverse DCT on the obtained DCT coefficient to calculate a residual signal. The inverse quantization / inverse DCT unit 105 outputs the calculated residual signal to the addition unit 106.

The addition unit 106 adds the signal value of the prediction image P of the PU input from the prediction image generation unit 101 and the signal value of the residual signal input from the inverse quantization / inverse DCT unit 105 for each pixel, and performs decoding. Generate an image. The adding unit 106 stores the generated decoded image in the reference picture memory 109.

The loop filter 107 performs a deblocking filter, a sample adaptive offset (SAO), and an adaptive loop filter (ALF) on the decoded image generated by the adding unit 106.

The prediction parameter memory 108 stores the prediction parameter generated by the encoding parameter determination unit 110 at a predetermined position for each encoding target picture and CU.

The reference picture memory 109 stores the decoded image generated by the loop filter 107 at a predetermined position for each picture to be encoded and each CU.

The encoding parameter determination unit 110 selects one set from among a plurality of sets of encoding parameters. The encoding parameter is a parameter to be encoded that is generated in association with the above-described prediction parameter or the prediction parameter. The predicted image generation unit 101 generates a predicted image P of the PU using each of these encoding parameter sets.

The encoding parameter determination unit 110 calculates a cost value indicating the amount of information and the encoding error for each of a plurality of sets. The cost value is, for example, the sum of a code amount and a square error multiplied by a coefficient λ. The code amount is the information amount of the encoded stream Te obtained by entropy encoding the quantization error and the encoding parameter. The square error is the sum between pixels regarding the square value of the residual value of the residual signal calculated by the subtracting unit 102. The coefficient λ is a real number larger than a preset zero. The encoding parameter determination unit 110 selects a set of encoding parameters that minimizes the calculated cost value. As a result, the entropy encoding unit 104 outputs the selected set of encoding parameters to the outside as the encoded stream Te, and does not output the set of unselected encoding parameters. The encoding parameter determination unit 110 stores the determined encoding parameter in the prediction parameter memory 108.

The prediction parameter encoding unit 111 derives a format for encoding from the parameters input from the encoding parameter determination unit 110 and outputs the format to the entropy encoding unit 104. Deriving the format for encoding is, for example, deriving a difference vector from a motion vector and a prediction vector. Also, the prediction parameter encoding unit 111 derives parameters necessary for generating a prediction image from the parameters input from the encoding parameter determination unit 110 and outputs the parameters to the prediction image generation unit 101. The parameter necessary for generating the predicted image is, for example, a motion vector in units of sub-blocks.

The inter prediction parameter encoding unit 112 derives an inter prediction parameter such as a difference vector based on the prediction parameter input from the encoding parameter determination unit 110. The inter prediction parameter encoding unit 112 derives parameters necessary for generating a prediction image to be output to the prediction image generating unit 101, and an inter prediction parameter decoding unit 303 (see FIG. 5 and the like) derives inter prediction parameters. Some of the configurations are the same as the configuration to be performed. The configuration of the inter prediction parameter encoding unit 112 will be described later.

The intra prediction parameter encoding unit 113 derives a format (for example, MPM_idx, rem_intra_luma_pred_mode) for encoding from the intra prediction mode IntraPredMode input from the encoding parameter determination unit 110.

(Configuration of inter prediction parameter encoding unit)
Next, the configuration of the inter prediction parameter encoding unit 112 will be described. The inter prediction parameter encoding unit 112 is a unit corresponding to the inter prediction parameter decoding unit 303 in FIG. 12, and the configuration is shown in FIG.

The inter prediction parameter encoding unit 112 includes an inter prediction parameter encoding control unit 1121, an AMVP prediction parameter derivation unit 1122, a subtraction unit 1123, a sub-block prediction parameter derivation unit 1125, and a partition mode derivation unit and a merge flag derivation unit (not shown). , An inter prediction identifier deriving unit, a reference picture index deriving unit, a vector difference deriving unit, etc., and a split mode deriving unit, a merge flag deriving unit, an inter prediction identifier deriving unit, a reference picture index deriving unit, and a vector difference deriving unit Respectively derive a PU partition mode part_mode, a merge flag merge_flag, an inter prediction identifier inter_pred_idc, a reference picture index refIdxLX, and a difference vector mvdLX. The inter prediction parameter encoding unit 112 outputs the motion vector (mvLX, subMvLX), the reference picture index refIdxLX, the PU partition mode part_mode, the inter prediction identifier inter_pred_idc, or information indicating these to the prediction image generating unit 101. Also, the inter prediction parameter encoding unit 112 entropy PU partition mode part_mode, merge flag merge_flag, merge index merge_idx, inter prediction identifier inter_pred_idc, reference picture index refIdxLX, prediction vector index mvp_LX_idx, difference vector mvdLX, sub-block prediction mode flag subPbMotionFlag. The data is output to the encoding unit 104.

The inter prediction parameter encoding control unit 1121 includes a merge index deriving unit 11211 and a vector candidate index deriving unit 11212. The merge index derivation unit 11211 compares the motion vector and reference picture index input from the encoding parameter determination unit 110 with the motion vector and reference picture index of the merge candidate PU read from the prediction parameter memory 108, and performs merge An index merge_idx is derived and output to the entropy encoding unit 104. A merge candidate is a reference PU (for example, a reference PU that touches the lower left end, upper left end, and upper right end of the encoding target block) within a predetermined range from the encoding target CU to be encoded. The PU has been processed. The vector candidate index deriving unit 11212 derives a prediction vector index mvp_LX_idx.

When the encoding parameter determination unit 110 determines to use the sub-block prediction mode, the sub-block prediction parameter derivation unit 1125 includes any of spatial sub-block prediction, temporal sub-block prediction, affine prediction, and matching prediction according to the value of subPbMotionFlag. A motion vector and a reference picture index for subblock prediction are derived. As described in the description of the image decoding apparatus, the motion vector and the reference picture index are derived by reading out the motion vector and the reference picture index such as the adjacent PU and the reference picture block from the prediction parameter memory 108.

The AMVP prediction parameter derivation unit 1122 has the same configuration as the AMVP prediction parameter derivation unit 3032 (see FIG. 12).

That is, when the prediction mode predMode indicates the inter prediction mode, the motion vector mvLX is input from the encoding parameter determination unit 110 to the AMVP prediction parameter derivation unit 1122. The AMVP prediction parameter derivation unit 1122 derives a prediction vector mvpLX based on the input motion vector mvLX. The AMVP prediction parameter derivation unit 1122 outputs the derived prediction vector mvpLX to the subtraction unit 1123. Note that the reference picture index refIdx and the prediction vector index mvp_LX_idx are output to the entropy encoding unit 104.

The subtraction unit 1123 subtracts the prediction vector mvpLX input from the AMVP prediction parameter derivation unit 1122 from the motion vector mvLX input from the coding parameter determination unit 110 to generate a difference vector mvdLX. The difference vector mvdLX is output to the entropy encoding unit 104.

For convenience of explanation, members having the same functions as those described above will be given the same reference numerals and explanation thereof will be omitted.

(A1: Configuration for deriving weighting factors in consideration of features of reference blocks)
In the prior art described in Non-Patent Document 2, there is room for improvement in coding efficiency because the characteristics of the reference block are not taken into account in the derivation of the weighting coefficient. Therefore, in the present embodiment, the weighting factor is derived according to the reference block parameter representing the feature of the reference block.

FIG. 16 is a schematic diagram illustrating a detailed configuration of the inter prediction parameter decoding unit 303 of the prediction parameter decoding unit 302 of the image decoding device 31 illustrated in FIG. 5 and the inter prediction image generation unit 309 illustrated in FIG.

16, the inter prediction parameter decoding unit 303 includes a weight index decoding unit 3038, a reference block parameter derivation unit 3039, and a weight coefficient derivation unit 3030.

<Weight Index Decoding Unit 3038>
The weight index decoding unit 3038 decodes the weight index weightIdx from the encoded data supplied by the entropy decoding unit 301. The decoded weight index weightIdx is supplied to the weight coefficient deriving unit 3030. Here, the weight index weightIdx is an index that is referred to in order to derive a bi-prediction weight coefficient.

<Reference block parameter deriving unit 3039>
The reference block parameter deriving unit 3039 refers to the prediction parameter memory 307 and derives the reference block parameter of the reference block. Here, the reference block parameter is derived from reference block information (for example, POC (Picture Order Count) of a reference picture, a motion vector to the reference block, a quantization parameter (QP)) of the reference block. It is a parameter and is referenced to generate a predicted image. More specifically, the reference block parameter may be referred to in order to derive a weight candidate list described later. Hereinafter, a configuration in which the reference block parameter deriving unit 3039 derives the reference block parameters Xval0 and Xval1 will be described.

More specifically, the reference block parameter Xval0 (first reference block parameter) is a parameter determined according to the POC of a picture including a reference block L0 (first reference block) described later and the POC of a picture including the target block. Yes, it is the absolute value of the difference between the POC of the picture including the reference block L0 and the POC of the picture including the target block. The reference block parameter Xval1 (second reference block parameter) is a parameter determined according to the POC of a picture including a reference block L1 (second reference block) to be described later and the POC of a picture including the target block. This is the absolute value of the difference between the POC of the picture containing L1 and the POC of the picture containing the target block. The POC is a value indicating a temporal order of a picture including a reference block or a picture including a target block, and is used for deriving a parameter indicating the priority of the reference block in the present application.

Furthermore, the reference block parameter deriving unit 3039 derives a value (reference block index) fIdx indicating the characteristics of the reference block according to the reference block parameters Xval0 and Xval1. The derived reference block index fIdx is supplied to the weighting factor deriving unit 3030. Here, the reference block index fIdx is an index that is referred to in order to derive a weight candidate list to be described later.

<Weighting factor deriving unit 3030>
The weighting factor deriving unit 3030 derives the weighting factor w from the weighting index weightIdx and the reference block index fIdx. Here, the weight coefficient w is a coefficient for obtaining a value to be multiplied to the motion compensated image in the weight prediction.

FIG. 17 is a schematic diagram illustrating a configuration of the weight coefficient deriving unit 3030 of the inter prediction parameter decoding unit 303 illustrated in FIG. As shown in FIG. 17, the weighting factor derivation unit 3030 includes a weight candidate list derivation unit 30301 and a weighting factor selection unit 30302.

The weight candidate list deriving unit 30301 derives a weight candidate list weightCandList from the reference block index fIdx supplied by the reference block parameter deriving unit 3039. The derived weight candidate list weightCandList is supplied to the weight coefficient selection unit 30302. Here, the weight candidate list weightCandList is a list having a plurality of weighting factors w as elements.

The weight coefficient selection unit 30302 derives the weight coefficient w according to the weight candidate list weightCandList and the weight index weightIdx. The derived weight coefficient w is supplied to the weight prediction unit 3094.

(A1: Operation for deriving a weighting factor considering the characteristics of the reference block)
FIG. 18 is a flowchart showing operations of the inter prediction parameter decoding unit 303 and the inter prediction image generation unit 309 shown in FIG. As shown in FIG. 18, the operations of the inter prediction parameter decoding unit 303 and the inter prediction image generation unit 309 include steps S1 to S4. Step S3 includes steps S31 and S32.

<Step S1>
The weight index decoding unit 3038 decodes the weight index weightIdx.

<Step S2>
Reference blocks that the motion compensation unit 3091 refers to when deriving the motion compensated images predSamplesL0 and predSamplesL1 are referred to as a reference block L0 and a reference block L1, respectively.

The reference block parameter derivation unit 3039 derives the reference block parameter Xval0 of the reference block L0 and the reference block parameter Xval1 of the reference block L1 (the derivation method is “X: derivation of reference block parameter, similarity, and priority” described later) Method ”).

Note that the reference block parameter is a parameter indicating the priority of the reference block, and is derived from the POC, the motion vector, the quantization parameter, and the like. The reference block parameters can also be called temporal distance, dissimilarity (similarity), and priority.

The reference block parameter deriving unit 3039 derives reference block parameters Xval0 and Xval1 by the following equation.
Xval0 = | PicOrderCount (refPic0)-PicOrderCount (currPic) |
Xval1 = | PicOrderCount (refPic1)-PicOrderCount (currPic) |
refPic0: Picture of reference block L0
refPic1: Picture of reference block L1
currPic: Target picture
PicOrderCount (pic): A function that returns the POC of the picture pic. Also simply described as POC (pic).

Furthermore, the reference block parameter deriving unit 3039 derives a reference block index fIdx according to the reference block parameters Xval0 and Xval1 (refer to “F: Reference block index fIdx derivation method” described later for the derivation method).

FIG. 19 is a conceptual diagram showing a correspondence relationship between the reference block parameters Xval0 and Xval1 and the reference block index fIdx in step S2 of the operation shown in FIG. The reference block parameter deriving unit 3039 derives the reference block index fIdx by the following equation using the correspondence shown in FIG.
if (Xval0 * 2> Xval1 * 6) fIdx = 0
else if (Xval0 * 3> Xval1 * 5) fIdx = 1
else if (Xval0 * 4> Xval1 * 4) fIdx = 2
else if (Xval0 * 5> Xval1 * 3) fIdx = 3
else if (Xval0 * 6> Xval1 * 2) fIdx = 4
else fIdx = 5
<Step S3>
The weight candidate list derivation unit 30301 derives a weight candidate list according to the reference block parameters Xval0 and Xval1 (step S31). Then, the weight coefficient selection unit 30302 derives the weight coefficient w from the weight index weightIdx decoded by the weight index decoding unit 3038 and the weight candidate list derived by the weight candidate list deriving unit 30301 (step S32). Hereinafter, the “ordered set of elements” is called a list (weight candidate list), but may be called a table (weight candidate table). Similarly, hereinafter, the weight candidate list derivation unit may be referred to as a weight candidate table derivation unit.

Here, the weight candidate list deriving unit 30301 derives the weight candidate list weightCandListW according to the reference block index fIdx.
if (fIdx == 0) weightCandListW [] = {2, 3, 4, 5, 6, -2, 10}
else if (fIdx == 1) weightCandListW [] = {3, 4, 2, 5, 6, -2, 10}
else if (fIdx == 2) weightCandListW [] = {4, 3, 5, 2, 6, -2, 10}
else if (fIdx == 3) weightCandListW [] = {4, 5, 3, 6, 2, 10, -2}
else if (fIdx == 4) weightCandListW [] = {5, 4, 6, 3, 2, 10, -2}
else if (fIdx == 5) weightCandListW [] = {6, 5, 4, 3, 2, 10, -2}
The elements of the weight candidate list are weight coefficients, and the coefficients are arranged in the order of priority (as shown in “Modified example of step S3” described later, another form of weight candidate list may be used). Further, the weight candidate list deriving unit 30301 may derive the weight candidate list weightCandListW by referring to the table as follows. That is, the weighting factor table weightCandListW is derived by referring to the weight candidate list table weightCandListWTable [] [] with fIdx.
weightCandListW = weightCandListWTable [fIdx]
weightCandListWTable [] [] =
{
{2, 3, 4, 5, 6, -2, 10},
{3, 4, 2, 5, 6, -2, 10},
{4, 3, 5, 2, 6, -2, 10},
{4, 5, 3, 6, 2, 10, -2},
{5, 4, 6, 3, 2, 10, -2},
{6, 5, 4, 3, 2, 10, -2}
}
The table can also be described as follows.
weightCandListWTable [0] [] = {2, 3, 4, 5, 6, -2, 10}
weightCandListWTable [1] [] = {3, 4, 2, 5, 6, -2, 10}
weightCandListWTable [2] [] = {4, 3, 5, 2, 6, -2, 10}
weightCandListWTable [3] [] = {4, 5, 3, 6, 2, 10, -2}
weightCandListWTable [4] [] = {5, 4, 6, 3, 2, 10, -2}
weightCandListWTable [5] [] = {6, 5, 4, 3, 2, 10, -2}
The weight coefficient selection unit 30302 derives the weight coefficient w by the following equation.
w = weightCandListW [weightIdx]
<Modification of Step S3>
In step S3, the element e of the weight candidate list is a weighting coefficient (for example, any of e∈ {-2,2,3,4,5,6,10}). May be a parameter (index) indicating a weighting factor. For example, e is any one of 0 to 6. In this case, the weight candidate list deriving unit 30301 selects one of the weight candidate list tables weightCandListITable [0] to weightCandListITable [5] as the weight candidate list according to the reference block index fIdx. The weight candidate list deriving unit 30301 derives a weight candidate list weightCandListI by the following equation.

weightCandListI = weightCandListITable [fIdx]
For example, the following can be used as the weight candidate list weightCandListI.
weightCandListITable [0] [] = {1, 2, 3, 4, 5, 0, 6}
weightCandListITable [1] [] = {2, 3, 1, 4, 5, 0, 6}
weightCandListITable [2] [] = {3, 2, 4, 1, 5, 0, 6}
weightCandListITable [3] [] = {3, 4, 2, 5, 1, 6, 0}
weightCandListITable [4] [] = {4, 3, 5, 2, 1, 6, 0}
weightCandListITable [5] [] = {5, 4, 3, 2, 1, 6, 0}
Then, the weight coefficient selection unit 30302 derives a parameter (here, posIdx) indicating the weight coefficient from the weight candidate list weightCandListI selected by the reference block parameter fIdx and the weight index weightIdx.

posIdx = weightCandListI [weightIdx]
Here, the parameter posIdx indicating the weighting factor is the position posIdx of the weighting factor table weightTable that is a table of weighting factors.

The weighting factor selection unit 30302 derives the weighting factor w from the weighting factor table weightTable and the parameter posIdx by the following equation.
w = weightTable [posIdx]
Here, for example, the weight coefficient table weightTable is weightTable [] = {− 2,2,3,4,5,6,10}.

<Step S4>
The weight prediction unit 3094 generates predicted images predSamples from the weighted average of the two motion compensated images predSamplesL0 and predSamplesL1 according to the weighting factor w derived by the weighting factor deriving unit 3030. The weight prediction unit 3094 generates predicted images predSamples as in the following equation.
w0 = w
w1 = (1 << shiftWP) -w0
offset = 1 << (shiftWP-1)
predSamples [x] [y] = (w0 * predSamplesL0 [x] [y] + w1 * predSamplesL1 [x] [y] + offset) >> shiftWP
ShiftWP is a shift value for treating the weighting coefficient as an integer. (1/2) ^shiftWP is a unit of weighting factor. For example, 5 (in this case, 1/32 unit weight coefficient) is used as shiftWP. Moreover, it is not always necessary to add offset in the generation of a predicted image. The method for calculating w0 and w1 may be as follows.
w0 = (1 << shiftWP) -w1
w1 = w
Note that in the generation of a predicted image, the right shift by shiftWP may not be performed here, but may be performed in a subsequent process. In this case, the following calculation is performed.
predSamples [x] [y] = (w0 * predSamplesL0 [x] [y] + w1 * predSamplesL1 [x] [y] + offset)
Further, in the generation of the predicted image, a small shift may be performed using a predetermined number M less than shiftWP, and adjustment may be performed by shifting rightward by M again in the subsequent stage. In this case, the following calculation is performed.
predSamples [x] [y] = (w0 * predSamplesL0 [x] [y] + w1 * predSamplesL1 [x] [y] + offset) >> (shiftWP-M)
(A1: Effect of derivation of weighting factors considering characteristics of reference block)
As described above, by deriving the weight candidate list from the reference block parameter and deriving the weighting factor according to the weight candidate list, the selection probability is increased according to the ratio of the temporal distance between the target picture and the reference image. A list in which weighting factors are arranged in descending order can be derived.

The above decoding process can also be applied to the encoding process. Then, in the encoding process, by encoding the weighting coefficient derived as described above, the weighting coefficient can be encoded with a smaller weight index than in the conventional case. Therefore, the effect of reducing the code amount of the weight index is achieved.

Note that the above configuration is not limited to a configuration in which a list in which the weighting coefficients are arranged is derived according to the ratio of the temporal distance between the target picture and the reference image, and the direction of the reference image and the magnitude of the motion vector are not limited. A list in which the weighting factors are arranged may be derived according to the ratio of the length or the size of the quantization parameter. Also in this case, there is an effect of reducing the code amount of the weight index.

(A2: Configuration and operation for deriving weighting factors considering the characteristics of reference blocks)
FIG. 20 is a schematic diagram showing a configuration of a weighting factor deriving unit 3030a different from the weighting factor deriving unit 3030 shown in FIG. As shown in FIG. 20, the weighting factor deriving unit 3030a is different from the weighting factor deriving unit 3030 in that it further includes a weighting factor correcting unit 30303. In the inter prediction parameter decoding unit 303 shown in FIG. 16, the weighting factor deriving unit 3030 can be replaced with a weighting factor deriving unit 3030a.

The weighting factor selection unit 30302 derives the weighting factor w and supplies it to the weighting factor correction unit 30303. The weighting coefficient correction unit 30303 corrects the weighting coefficient w and supplies it to the weight prediction unit 3094.

<Step S2 in A2>
FIG. 21 is a conceptual diagram showing the correspondence between reference block parameters Xval0 and Xval1 and the reference block index fIdx, which is different from the correspondence shown in FIG. In FIG. 21, the reference block index fIdx is 0 or 1, and is determined only by the magnitude relationship between the reference block parameters Xval0 and Xval1.

The reference block parameter deriving unit 3039 derives the reference block index fIdx by the following equation using the correspondence shown in FIG.
if (Xval0> Xval1) fIdx = 0
else fIdx = 1
In addition, not only an inequality sign (>) but also ≧ including an equal sign can be used for the comparison of the magnitude relation. Also, <and ≦ can be used. The same applies hereinafter.

<Step S3 in A2>
The weight candidate list deriving unit 30301 derives a weight candidate list (weight coefficient table) weightTable. In this configuration, the weight candidate list is derived without depending on the reference block parameters Xval0 and Xval1 and the reference block index fIdx.
weightTable [] = {4, 3, 5, 2, 6, -2, 10}
The weighting factor selection unit 30302 derives the weighting factor w from the weighting factor table weightTable and the parameter weightIdx by the following equation.
w = weightTable [weightIdx]
<Step S4 in A2>
Next, the weighting factor correction unit 30303 updates the weighting factor w according to the reference block index fIdx. Specifically, when the reference block index fIdx is a predetermined value (for example, fIdx = X 0 indicating Xval0> Xval1), the weight coefficient is used as it is. Conversely, when the reference block index fIdx is other than a predetermined value (for example, a value fIdx indicating Xval0 ≦ Xval1 == 1), the weight w0 (first weight) of the motion compensated image predSamplesL0 (first motion compensated image) ) And the weight w1 (second weight) of the motion compensated image predSamplesL1 (second motion compensated image) are swapped.

At this time, the value of w is updated by the following equation.
w = (1 << shiftWP)-w
Alternatively, the weights w0 and w1 are swapped by the following equation. In the following equation, tmp is a temporary variable used for swapping the weights w0 and w1.
tmp = w0
w0 = w1
w1 = tmp
That is, the swap can be described as: In the following equation, swap is a function that takes weights w0 and w1 as arguments and returns two values obtained by swapping weights w0 and w1.
(w0, w1) = swap (w0, w1)
Hereinafter, the weighting factors w0 and w1 obtained from the weighting factor w will be referred to as weights w0 and w1.

(A2: Effect of derivation of weighting factors considering characteristics of reference block)
As described above, the weighting factor can be derived by a normal method (a method that does not depend on the reference block parameter), and then the weighting factor can be updated according to the reference block parameter. The swap is one method for updating the weighting factor. As described above, even when the same weight coefficient table is used according to the ratio of the temporal distance between the target picture and the reference image, the weight coefficient can be encoded with a small weight index. This produces an effect of reducing the code amount of the weight index.

(A3: Configuration for deriving a weighting factor considering the characteristics of the reference block)
FIG. 22 is a schematic diagram illustrating a detailed configuration of an inter prediction parameter decoding unit 303b and an inter prediction image generation unit 309 different from the inter prediction parameter decoding unit 303 illustrated in FIG.

The inter prediction parameter decoding unit 303b is different from the inter prediction parameter decoding unit 303 in the following points.
Reference block parameter deriving unit 3039 is a reference block parameter deriving unit 3039b.
The weight coefficient deriving unit 3030 is a weight coefficient deriving unit 3030b.
The value that the reference block parameter deriving unit 3039b supplies to the weighting factor deriving unit 3030b is the prediction weighting factor wpIdx.

And in FIG. 5, the inter prediction parameter decoding part 303 can be replaced with the inter prediction parameter decoding part 303b.

<Reference block parameter deriving unit 3039b>
The reference block parameter deriving unit 3039b refers to the prediction parameter memory 307, derives reference block parameters Xval0 and Xval1 of the reference block, and further indicates a value (prediction weight coefficient) indicating the characteristics of the reference block according to the reference block parameters Xval0 and Xval1. ) Derive wpIdx. The derived prediction weight coefficient wpIdx is supplied to the weight coefficient deriving unit 3030b. Here, the prediction weight coefficient wpIdx is a coefficient referred to in order to derive a weight candidate list described later.

<Weighting factor deriving unit 3030b>
The weighting factor deriving unit 3030b derives the weighting factor w from the weighting index weightIdx and the prediction weighting factor wpIdx.

FIG. 23 is a schematic diagram illustrating a configuration of the weight coefficient deriving unit 3030b of the inter prediction parameter decoding unit 303b illustrated in FIG. As shown in FIG. 23, the weighting factor deriving unit 3030b includes a weight candidate list deriving unit 30301b and a weighting factor selecting unit 30302. The weight candidate list deriving unit 30301b derives a weight candidate list weightCandList from the prediction weight coefficient wpIdx supplied by the reference block parameter deriving unit 3039b.

(A3: Operation for deriving a weighting factor considering the characteristics of the reference block)
<Step S2 in A3>
FIG. 24 is a conceptual diagram showing a correspondence relationship between the reference block parameters Xval0 and Xval1 and the predicted value of the weighting coefficient (predicted weighting coefficient) wpIdx in step S2 of the operation shown in FIG. The reference block parameter deriving unit 3039b derives a prediction weight coefficient wpIdx by the following equation using the correspondence shown in FIG.
if (Xval0 * 2> Xval1 * 6) wpIdx = 2
else if (Xval0 * 3> Xval1 * 5) wpIdx = 3
else if (Xval0 * 5> Xval1 * 3) wpIdx = 4
else if (Xval0 * 6> Xval1 * 2) wpIdx = 5
else wpIdx = 6
<Step S3 in A3>
The weight candidate list deriving unit 30301b derives a weight candidate list weightCandListW according to the prediction weight coefficient wpIdx. Here, a weight candidate list weightCandListW having the prediction weight coefficient wpIdx as the head element is derived by the following equation so that the priority of the prediction weight coefficient wpIdx is the highest.
if (wpIdx == 2) weightCandListW [] = {2, 3, 4, 5, 6, -2, 10}
else if (wpIdx == 3) weightCandListW [] = {3, 4, 2, 5, 6, -2, 10}
else if (wpIdx == 4) weightCandListW [] = {4, 3, 5, 2, 6, -2, 10}
else if (wpIdx == 5) weightCandListW [] = {5, 4, 6, 3, 2, 10, -2}
else if (wpIdx == 6) weightCandListW [] = {6, 5, 4, 3, 2, 10, -2}
The weight coefficient selection unit 30302 derives the weight coefficient w from the weight candidate list weightCandListW and the weight index weightIdx as in the following equation.
w = weightCandListW [weightIdx]
The weighting factor deriving unit 3030b (weight candidate list deriving unit 30301b) may derive the weight candidate list weightCandListW by referring to the table as follows. That is, the weight candidate list weightCandListW is derived by referring to the weight candidate list table weightCandListWTable [] [] with wpIdx.
weightCandListW = weightCandListWTable [wpIdx-2]
weightCandListWTable [] [] =
{
{2, 3, 4, 5, 6, -2, 10},
{3, 4, 2, 5, 6, -2, 10},
{4, 3, 5, 2, 6, -2, 10},
{5, 4, 6, 3, 2, 10, -2},
{6, 5, 4, 3, 2, 10, -2}
}
<Modification of step S2 in A3>
The reference block parameter deriving unit 3039b may derive the reference block parameters Xval0 and Xval1, and may derive the prediction weight coefficient wpIdx according to the reference block parameters Xval0 and Xval1, as in the following equation.
if (Xval0 * 2> Xval1 * 6) wpIdx = 1
else if (Xval0 * 3> Xval1 * 5) wpIdx = 2
else if (Xval0 * 5> Xval1 * 3) wpIdx = 3
else if (Xval0 * 6> Xval1 * 2) wpIdx = 4
else wpIdx = 5
<Modification of Step S3 in A3>
The weight candidate list deriving unit 30301b may derive a weight candidate list weightCandListI having elements of an order index representing the order of the weight coefficients, as in the following equation, according to the prediction weight coefficient wpIdx. Here, the weight candidate list weightCandListI [] has the predicted value of the order index as the top element so that the order index that becomes the prediction weight coefficient wpIdx has the highest priority.
if (wpIdx == 1)
weightCandListI [] = {1, 2, 3, 4, 5, 0, 6}
else if (wpIdx == 2)
weightCandListI [] = {2, 3, 1, 4, 5, 0, 6}
else if (wpIdx == 3)
weightCandListI [] = {3, 2, 4, 1, 5, 0, 6}
else if (wpIdx == 4)
weightCandListI [] = {4, 3, 5, 2, 1, 6, 0}
else if (wpIdx == 5)
weightCandListI [] = {5, 4, 3, 2, 1, 6, 0}
Alternatively, the weight candidate list deriving unit 30301b may derive the weight candidate list weightCandListI by referring to the table as follows.
weightCandListI = weightCandListITable [wpIdx-1]
weightCandListITable [] =
{
{1, 2, 3, 4, 5, 0, 6}
{2, 3, 1, 4, 5, 0, 6},
{3, 2, 4, 1, 5, 0, 6},
{4, 3, 5, 2, 1, 6, 0},
{5, 4, 3, 2, 1, 6, 0}
}
The weight coefficient selection unit 30302 derives a parameter (here, posIdx) indicating a weight coefficient from the weight candidate list weightCandListI [wpIdx] and the weight index weightIdx by the following equation.
posIdx = weightCandListI [wpIdx] [weightIdx]
The weight coefficient selection unit 30302 derives the weight coefficient w from the weight coefficient table weightTable and the parameter posIdx indicating the weight coefficient by the following equation.
w = weightTable [posIdx]
Here, for example, the weight coefficient table weightTable is weightTable [] = {− 2,2,3,4,5,6,10}.

(A3: Effect of deriving weighting factors considering the characteristics of the reference block)
As described above, the prediction weight coefficient can be derived from the reference block parameter, and the weight coefficient can be derived according to the derived prediction weight coefficient. More specifically, a weight candidate list can be derived according to the derived prediction weight coefficient. Accordingly, a list in which weighting factors are arranged in descending order of selection probability can be derived according to the ratio of the temporal distance between the target picture and the reference image.

(X: Reference block parameter, similarity, and priority derivation method)
Hereinafter, a method for deriving the reference block parameters Xval0 and Xval1 will be described. Since the weight coefficient w of the weight prediction tends to decrease as the distance between the reference picture including the reference block multiplied by the weight coefficient w and the target picture increases (dissimilarity increases), the reference block and the target A parameter corresponding to the temporal distance (dissimilarity) with the block can be used to derive the weighting factor w. Further, since the weighting factor w tends to decrease as the image quality of the reference block improves, a parameter corresponding to the image quality of the reference block can be used.

<X1: Time reference block parameter and time difference>
The reference block parameter Xval0 is derived from the absolute value of the difference between the POC of the reference picture refPic0 including the reference block L0 and the POC of the picture currPic including the target block. Further, the reference block parameter Xval1 is derived from the absolute value of the difference between the POC of the reference picture refPic1 including the reference block L1 and the POC of the picture currPic.
Xval0 = | PicOrderCount (refPic0)-PicOrderCount (currPic) |
Xval1 = | PicOrderCount (refPic1)-PicOrderCount (currPic) |
Note that a difference that does not take the absolute value may be used as the reference block parameters Xval0 and Xval1 as in the following equation.
Xval0 = PicOrderCount (refPic0)-PicOrderCount (currPic)
Xval1 = PicOrderCount (refPic1)-PicOrderCount (currPic)
Further, the left side and the right side in the case of calculating the POC difference as in the following expression may be interchanged.
Xval0 = PicOrderCount (refPic0)-PicOrderCount (currPic)
Xval1 = PicOrderCount (currPic)-PicOrderCount (refPic1)
Further, a predetermined constant D may be added to the absolute value in order to calculate the ratio between the reference block parameters Xval0 and Xval1 as a relatively small value as in the following equation.
Xval0 = | PicOrderCount (refPic0)-PicOrderCount (currPic) | + D
Xval1 = | PicOrderCount (refPic1)-PicOrderCount (currPic) | + D
Further, the absolute value may be subtracted from a predetermined constant as in the following equation.
Xval0 = D-(| PicOrderCount (refPic0)-PicOrderCount (currPic) |)
Xval1 = D-(| PicOrderCount (refPic1)-PicOrderCount (currPic) |)
Further, as shown in the following equation, the reference block parameter Xval0 may be derived from the difference between the POC of the current picture and the POC of one reference picture, and the reference block parameter Xval1 may be derived from the POC difference between the reference pictures.
Xval0 = PicOrderCount (refPic0)-PicOrderCount (currPic)
Xval1 = PicOrderCount (refPic1)-PicOrderCount (refPic0)
<X2: Motion vector length reference block parameter>
A reference block parameter is derived from the motion vector length mvL0 that is the length of the motion vector from the target block to the reference block L0 and the motion vector length mvL1 that is the length of the motion vector from the target block to the reference block L1. At this time, it may be derived from the sum of the absolute value of the horizontal direction component (mvLX [0]) and the absolute value of the vertical direction component (mvLX [1]) as in the following equation. Note that X in mvLX [] is 0 or 1.
Xval0 = | mvL0 [0] | + | mvL0 [1] |
Xval1 = | mvL1 [0] | + | mvL1 [1] |
Further, a predetermined constant D may be added to the sum as follows.
Xval0 = | mvL0 [0] | + | mvL0 [1] | + D
Xval1 = | mvL1 [0] | + | mvL1 [1] | + D
Further, the sum may be subtracted from a predetermined constant D as follows.
Xval0 = D-(| mvL0 [0] | + | mvL0 [1] |)
Xval1 = D-(| mvL1 [0] | + | mvL1 [1] |)
<X3: Quantization coefficient reference block parameter>
A reference block parameter (priority) is derived from the quantization parameter qpL0 of the reference block L0 and the quantization parameter qpL1 of the reference block L1.
Xval0 = qpL1
Xval1 = qpL0
Here, the quantization parameter qpL1 of the reference block L1 is used as the reference block parameter Xval0 of the reference block L0. This is because the smaller the value of the quantization parameter qpL1 of the reference block L1, the higher the image quality of the reference block L1, so that the weighting factor of the reference block L1 is increased. As the value of the reference block parameter Xval0 is larger, the weight coefficient of the reference block L0 is relatively smaller (the weight of the reference block L1 is larger). Depending on the configuration, the following may be used.
Xval0 = qpL0
Xval1 = qpL1
Further, a predetermined constant D may be added to the quantization parameter as in the following equation.
Xval0 = qpL1 + D
Xval1 = qpL0 + D
(F: Reference block index fIdx derivation method)
<F1: Derivation of reference block index fIdx based on reference block parameter ratio>
[Comparison method a]
FIdx is derived by repeatedly comparing Xval0 * M and Xval1 * N based on a previously defined set of M and N. If Xval0 * M> Xval1 * N (or Xval0 * M ≧ Xval1 * N), it can be seen that Xval0 / Xval1> N / M (or Xval0 / Xval1 ≧ N / M).

Specifically, fIdx = 0 to n−1 is derived by performing the following comparison in {M _i , N _i } from i = 1 to n−1.
if (Xval0 * M ₁ > Xval1 * N ₁ ) fIdx = 0
else if (Xval0 * M ₂ > Xval1 * N ₂ ) fIdx = 1
else if (Xval0 * M ₃ > Xval1 * N ₃ ) fIdx = 2
else if (Xval0 * M ₄ > Xval1 * N ₄ ) fIdx = 3
...
else if (Xval0 * M _n-1 > Xval1 * N _n-1 ) fIdx = n-2
else fIdx = n-1
For example, a specific example in the case of using (M _i , N _i ) = (2, 6), (3, 5), (4, 4), (5, 3), (6, 2) is shown below.
if (Xval0 * 2> Xval1 * 6) fIdx = 0
else if (Xval0 * 3> Xval1 * 5) fIdx = 1
else if (Xval0 * 4> Xval1 * 4) fIdx = 2
else if (Xval0 * 5> Xval1 * 3) fIdx = 3
else if (Xval0 * 6> Xval1 * 2) fIdx = 4
else fIdx = 5
[Comparison b]
In addition, when repeatedly comparing an integer multiple of Xval0 (Xval0 * M _i ) and an integer multiple of Xval1 (Xval1 * N _i ), comparison processing of Xval0 and Xval1 is performed according to the magnitude of M _i and N _i. It may be changed. For example, when M _i <N _i , Xval 0 * M _i > Xval 1 * N _i may be compared, and when M _i > N _i , Xval 0 * M _i <Xval 1 * N _i may be compared. In the case of M _i = N _i , either comparison may be used. For example, the following processing may be performed.
if (Xval0 * M ₁ > Xval1 * N ₁ ) fIdx = 0
else if (Xval0 * M ₂ > Xval1 * N ₂ ) fIdx = 1
else if (Xval0 * M ₃ > Xval1 * N ₃ ) fIdx = 2
...
_{else if (Xval0 * M m>} Xval1 * N m) fIdx = m-1
else if (Xval0 * M _n-1 <Xval1 * N _n-1 ) fIdx = n-1
else if (Xval0 * M _n-2 <Xval1 * N _n-2 ) fIdx = n-2
...
else if (Xval0 * M _{m + 1} <Xval1 * N _{m + 1} ) fIdx = m + 1
else fIdx = m
Here, m = n / 2. When n = 9 and m = 4:
if (Xval0 * M ₁ > Xval1 * N ₁ ) fIdx = 0
else if (Xval0 * M ₂ > Xval1 * N ₂ ) fIdx = 1
else if (Xval0 * M ₃ > Xval1 * N ₃ ) fIdx = 2
else if (Xval0 * M ₄ > Xval1 * N ₄ ) fIdx = 3 (= m-1)
else if (Xval0 * M ₈ <Xval1 * N ₈ ) fIdx = 8 (= n-1)
else if (Xval0 * M ₇ <Xval1 * N ₇ ) fIdx = 7
else if (Xval0 * M ₆ <Xval1 * N ₆ ) fIdx = 6
_{else if (Xval0 * M 5 <} Xval1 * N 5) fIdx = 5
else fIdx = 4 (= m)
Furthermore, (M _i , N _i ) = (1, 4), (1, 3), (1, 2), (2, 3), (3, 2), (2, 1), (3, 1 ), (4, 1):
if (Xval0> Xval1 * 4) fIdx = 0
else if (Xval0> Xval1 * 3) fIdx = 1
else if (Xval0> Xval1 * 2) fIdx = 2
else if (Xval0 * 2> Xval1 * 3) fIdx = 3
else if (Xval0 * 4 <Xval1) fIdx = 8
else if (Xval0 * 3 <Xval1) fIdx = 7
else if (Xval0 * 2 <Xval1) fIdx = 6
else if (Xval0 * 3 <Xval1 * 2) fIdx = 5
else fIdx = 4
[Comparison method c]
After Xval0 and Xval1 are rearranged according to the magnitude of Xval0 and Xval1, the integer multiple of Xval0 and the integer multiple of Xval1 are repeatedly compared. Here, an example is shown in which magnitude comparison is performed after swapping values so that Xval0> = Xval1. The index is modified according to whether it was last swapped (the number of comparisons is reduced by aligning the large and small orders).
m = n / 2
if (Xval1> Xval0) {tmp = Xval0; Xval0 = Xval1; Xval1 = tmp; swap = 1}
if (Xval0 * M ₁ > Xval1 * N ₁ ) fIdx = 0
else if (Xval0 * M ₂ > Xval1 * N ₂ ) fIdx = 1
...
else if (Xval0 * M _m > Xval1 * N _m ) fIdx = m-1
else fIdx = m
if (swap) fIdx = n -1-fIdx
When (M _i , N _i ) = (2, 6), (3, 5), (4, 4), (5, 3), (6, 2), n = 6, so .
m = 6/2 = 3
if (Xval1> Xval0) {tmp = Xval0; Xval0 = Xval1; Xval1 = tmp; swap = 1}
if (Xval0 * 2> Xval1 * 6) fIdx = 0
else if (Xval0 * 3> Xval1 * 5) fIdx = 1
else fIdx = 2
if (swap) fIdx = 5-fIdx
(M _i , N _i ) = (1, 4), (1, 3), (1, 2), (2, 3), (3, 2), (2, 1), (3, 1), In the case of (4, 1), since n = 9, the following equation is obtained.
if (Xval1> Xval0) {tmp = Xval0; Xval0 = Xval1; Xval1 = tmp; swap = 1}
if (Xval0> Xval1 * 4) fIdx = 0
else if (Xval0> Xval1 * 3) fIdx = 1
else if (Xval0> Xval1 * 2) fIdx = 2
else if (Xval0 * 2> Xval1 * 3) fIdx = 3
else fIdx = 4
if (swap) fIdx = 8-fIdx
[Division method a]
FIdx is derived according to a value corresponding to Xval1 / (Xval0 + Xval1) (or Xval0 / (Xval0 + Xval1)). K is a constant for deriving fIdx as an integer value. Then, before fIdx is derived, clip processing may be performed, or table reference may be performed. In the following formula, “nume” means a number. “Denom” means denominator.
nume = Xval1
denom = Xval0 + Xval1
fIdx = Clip3 (0, K-1, (K * nume) / denom)
From the above, fIdx = 0 to K−1 can be derived. Here, when K = 8, the numerator and denominator are derived by adding a predetermined constant D according to fIdx = 0,1,2,3,4,5,6,7 as shown in the following equation. May be.
nume = Xval1 + D
denom = Xval0 + Xval1 + D
fIdx = Clip3 (0, 7, (8 * nume) / denom)
Further, fIdx may be derived from the value of Xval0 / (Xval0 + Xval1) using Xval0 as a numerator instead of the value of Xval1 / (Xval0 + Xval1) using Xval1 as a numerator.
nume = Xval0 + D
denom = Xval0 + Xval1 + D
Further, as shown in the following equation, deom / 2 may be added during division to perform a kind of rounding (round control). Note that the value added for round control is not limited to denom / 2, but may be denom / 2 + 1, denom / 3, or denom / 4.
nume = Xval1
denom = Xval0 + Xval1
fIdx = Clip3 (0, K-1, (K * nume + denom / 2) / denom)
When round control such as rounding is performed, clipping may be performed between 0 and K as follows. In this case, naturally, fIdx = 0 to K can be derived.
fIdx = Clip3 (0, K, (K * nume + denom / 2) / denom)
[Division method b]
FIdx is derived according to the value corresponding to Xval1 / Xval0 (or Xval0 / Xval1). In the division method a, the ratio of Xval0 + Xval1 is derived using Xval0 + Xval1 as the denominator, but in the division method b, the ratio of Xval0 and Xval1 is derived. Divide after K * Xval0 to derive by integer arithmetic. Clipping may be performed after deriving K * Xval0 / Xval1. Specifically, fIdx = 0 to K−1 is derived as in the following equation.
nume = Xval1
denom = Xval0
fIdx = Clip3 (0, K-1, (K * nume + round) / denom)
Note that round is a variable for round control and is, for example, any of round = 0, denom / 2, denom / 2 + 1, denom / 3, and denom / 4. When round control is performed (when round> 0), clipping may be performed between 0 and K as follows. In this case, fIdx = 0 to K can be derived.
fIdx = Clip3 (0, K, (K * nume + denom / 2) / denom)
<F2: Bi-prediction based reference block index fIdx derivation>
When two pictures including a reference block (reference picture) are in the same direction with respect to a picture including the target block (target picture), a weighting factor of 1: 1 is used regardless of the ratio of the reference block parameters. There are many cases. Therefore, it is desirable to switch the derivation method of the reference block index fIdx related to the derivation of the weighting coefficient depending on whether the direction of the reference picture is equal to or different from the direction of the target picture.

The weighting factor of 1: 1 is the first weight and the second weight for the first weight multiplied by the first motion compensated image and the second weight multiplied by the second motion compensated image in the weight prediction. It means the weighting factor when the weights are equal. For example, when shiftWP = 3 and weighting factor w = 4, the first weight is 4, and the second weight is 1 << shiftWP − w = 4.

FIG. 25 is a schematic diagram for explaining a bi-prediction-based reference block index fIdx derivation method. An arrow attached with “POC” indicates that the POC of the picture written on the direction side of the arrow is larger than the POC of the picture written on the side opposite to the direction of the arrow. That is, it can be said that the direction of the arrow is the time direction.

FIG. 25 (a) shows a situation in which the target picture currPic is between the two reference pictures refPic0 and refPic1 (the two reference pictures are in different time directions as viewed from the target picture). In FIGS. 25B and 25C, the target picture currPic is at the end, that is, not between the two reference pictures refPic0 and refPic1 (the two reference pictures are the same in the time direction as viewed from the target picture). Means that.

Specifically, as shown in FIGS. 25B and 25C, when the time directions of two reference pictures with respect to the target picture are equal (a true value dirSame described later is true), fIdx is set to a predetermined value. The value of As shown in (a) of FIG. 25, when the time directions of the two reference pictures for the target picture are different (a true value dirSame described later is false), fIdx is compared with the above-described comparison methods a to c and division. Derived by any of the methods a and b.

When dirSame is true, both of the two reference pictures are temporally before the target picture, or when both of the reference pictures are temporally after the target picture (POC0, PIC1 <currPOC or curPOC <POC0, PIC1), so it can be derived as:
dirSame =
(PicOrderCount (refPic0) <PicOrderCount (currPic) &&
PicOrderCount (refPic1) <PicOrderCount (currPic)) ||
(PicOrderCount (refPic0)> PicOrderCount (currPic) &&
PicOrderCount (refPic1)> PicOrderCount (currPic))
DirSame can also be derived as follows:
dirSame = (PicOrderCount (refPic0)-PicOrderCount (currPic)) x (PicOrderCount (refPic1)-PicOrderCount (currPic))> 0
Further, as in the following equation, the case where the POC of the reference picture is equal to the POC of the target picture may be included when the time directions of the two reference pictures with respect to the target picture are equal.
dirSame = (PicOrderCount (refPic0)-PicOrderCount (currPic)) x (PicOrderCount (refPic1)-PicOrderCount (currPic)) ≥ 0
Of course, the determination may be made based on whether or not the time directions of the two reference pictures with respect to the target picture are different (! DirSame meaning negation of dirSame).
! dirSame = (PicOrderCount (refPic0)-PicOrderCount (currPic)) x (PicOrderCount (refPic1)-PicOrderCount (currPic)) <0
(L: List / table format configuration)
<L1: Highest priority table>
In the weight candidate list derivation unit 30301, the weight candidate list tables weightCandListWTable [] [] and weightCandListITable [] [], which are options, are represented by the weight candidate lists of the following (1-1) and (1-2) as shown in the following equation. It is preferable to include.
(1-1) Weight candidate list (1-2) having a weighting factor when the weighting factor multiplied by the motion compensated image predSamplesL0 and the weighting factor multiplied by the motion compensated image predSamplesL1 are 1: 1, ) Weighting candidate list deriving unit having a weighting coefficient when the weighting coefficient multiplied by the motion compensated image predSamplesL0 and the weighting coefficient multiplied by the motion compensated image predSamplesL1 are other than 1: 1 as a leading element. In step S3 of 30301, the following weight candidate list table may be used.
weightCandListWTable [] [] =
{
{2, 3, 4, 5, 6, -2, 10} // The weight of the first element is not 1: 1 (w0F! = W1F)
{3, 4, 2, 5, 6, -2, 10} // The weight of the first element is not 1: 1 (w0F! = W1F)
{4, 3, 5, 2, 6, -2, 10} // The weight of the first element is 1: 1 (w0F == w1F)
{4, 5, 3, 6, 2, 10, -2} // The weight of the first element is 1: 1 (w0F == w1F)
{5, 4, 6, 3, 2, 10, -2} // The weight of the first element is not 1: 1 (w0F! = W1F)
{6, 5, 4, 3, 2, 10, -2} // The weight of the first element is not 1: 1 (w0F! = W1F)
}
w0F: Weight coefficient to be multiplied by the motion compensation image predSamplesL0 or its index in the weight coefficient selected by the first element (First) of the weight candidate list
w1F: Weight coefficient to be multiplied by the motion compensation image predSamplesL1 in the weight coefficient selected by the first element (First) of the weight candidate list, or its index. Here, shiftWP = 3. In this case, when the weight coefficient w is 4, the first weight w0 multiplied by the first motion compensated image and the second weight w1 multiplied by the second motion compensated image are respectively w0 = w = 4, w1 = (1 << shiftWP) -w = 8-4 = 4, which is equal.

For example, the following weight candidate list table may be used in the modification of step S3 of the weight candidate list deriving unit 30301.
weightCandListITable [] [] =
{
{1, 2, 3, 4, 5, 0, 6} // The weight of the first element is not 1: 1 (w0F! = W1F)
{2, 3, 1, 4, 5, 0, 6} // The weight of the first element is not 1: 1 (w0F! = W1F)
{3, 2, 4, 1, 5, 0, 6} // The weight of the first element is 1: 1 (w0F == w1F)
{3, 4, 2, 5, 1, 6, 0} // The weight of the first element is 1: 1 (w0F == w1F)
{4, 3, 5, 2, 1, 6, 0} // The weight of the first element is not 1: 1 (w0F! = W1F)
{5, 4, 3, 2, 1, 6, 0} // The weight of the first element is not 1: 1 (w0F! = W1F)
}
Here, when the weight index is 3, the weight is 1: 1. For example, if a weight coefficient table weightTableW for deriving a weight coefficient from a weight index that is an element e of weightCandListITable [] [] is the following table, shiftWP = 3, when the weight index is 3, w = weightTableW [3] = 4, w1 = w = 4, w2 = (1 << shiftWP) −w = 4, and the first weight w0 and the second weight w1 are equal.
weightTableW [] = {-2,2,3,4,5,6,10}
<L2: Secondary priority table>
As shown in the following equation, it is preferable that the weightCandListWTable [] [] and weightCandListITable [] [] as options include a weight candidate list that satisfies the following conditions (2-1) and (2-2). (2-1) The weighting factor when the weighting factor multiplied by the motion compensated image predSamplesL0 and the weighting factor multiplied by the motion compensated image predSamplesL1 is other than 1: 1 is set as the head element.
(2-2) The weighting factor when the weighting factor multiplied by the motion compensated image predSamplesL0 and the weighting factor multiplied by the motion compensated image predSamplesL1 is 1: 1 is the second element from the top.

For example, the following weight candidate list table may be used in step S3 of the weight candidate list deriving unit 30301.
weightCandListWTable [] [] =
{
{2, 3, 4, 5, 6, -2, 10}
{3, 4, 2, 5, 6, -2, 10} // The weight of the first element is not 1: 1 and the weight of the second element is 1: 1 (w0F! = W1F && w0S == w1S)
{4, 3, 5, 2, 6, -2, 10}
{4, 5, 3, 6, 2, 10, -2}
{5, 4, 6, 3, 2, 10, -2} // The weight of the first element is not 1: 1 and the weight of the second element is 1: 1 (w0F! = W1F && w0S == w1S)
{6, 5, 4, 3, 2, 10, -2}
}
w0S: Weighting coefficient to be multiplied by the motion compensation image predSamplesL0 in the weighting coefficient selected by the second element (Second) from the top of the weight candidate list
w1S: Weight coefficient to be multiplied by motion compensation image predSamplesL1 in the weight coefficient selected by the second element (Second) from the top of the weight candidate list For example, when fIdx = 2, weightCandListW [fIdx] [] = {3, 4, 2, 5, 6, -2, 10} is selected. In this case, 4 which is a weighting factor of 1: 1 is the second element. In the case of the above example, the following weight candidate list table may be used in the modification of step S3 of the weight candidate list deriving unit 30301.
weightCandListITable [] [] =
{
{1, 2, 3, 4, 5, 0, 6}
{2, 3, 1, 4, 5, 0, 6} // The weight of the first element is not 1: 1 and the weight of the second element is 1: 1
{3, 2, 4, 1, 5, 0, 6}
{3, 4, 2, 5, 1, 6, 0}
{4, 3, 5, 2, 1, 6, 0} // The weight of the first element is not 1: 1 and the weight of the second element is 1: 1
{5, 4, 3, 2, 1, 6, 0}
}
In the case of the above example, when fIdx = 2, weightCandListI [fIdx] [] = {2, 3, 1, 4, 5, 0, 6} is selected. In this case, the weight coefficient index is 1: 1. A certain 3 is the second element.

<L3: Highest priority / secondary priority table 1>
As in the following equation, weightCandListWTable [] [] and weightCandListITable [] [] preferably include the following weight candidate lists (3-1) and (3-2).
(3-1) A weight candidate list that satisfies the following conditions (a) and (b).
(A) A weighting factor with which the relationship between the weight w0 multiplied by the motion compensated image predSamplesL0 and the weight w1 multiplied by the motion compensated image predSamplesL1 is w0 <w1 is set as the leading element.
(B) The weighting factor that satisfies the relationship w0 <w1 is the second element from the top.
(3-2) A weight candidate list that satisfies the following conditions (c) and (d).
(C) A weighting factor with which the relationship is w0> w1 is set as a head element.
(D) A weighting factor that satisfies the relationship w0> w1 is the second element from the top.

For example, the following weight candidate list table may be used in step S3 of the weight candidate list deriving unit 30301.
weightCandListWTable [] [] =
{
{2, 3, 4, 5, 6, -2, 10} // The relation derived from the first element and the relation derived from the second element are w0 <w1 (w0F <w1F && w0S <w1S )
{3, 4, 2, 5, 6, -2, 10}
{4, 3, 5, 2, 6, -2, 10}
{4, 5, 3, 6, 2, 10, -2}
{5, 4, 6, 3, 2, 10, -2}
{6, 5, 4, 3, 2, 10, -2} // The relationship derived from the first element and the relationship derived from the second element are w0> w1 (w0F> w1F &&w0S> w1S )
}
Here shiftWP = 3. In the above example, when fIdx = 0, weightCandListITable [0] [] = {2, 3, 4, 5, 6, -2, 10} is selected. In this case, (w1, w2) = (2, 6), (w1, w2) of the second element is (3, 5), both satisfy w1 <w2. Similarly, when fIdx = 5, (w1, w2) = (6, 2) in the first element, (w1, w2) in the second element is (5, 3), and both satisfy w1> w2.

For example, in the modified example of step S3 of the weight candidate list deriving unit 30301, the following weight candidate list table may be used.
weightCandListITable [] [] =
{
{1, 2, 3, 4, 5, 0, 6} // The relation derived from the first element and the relation derived from the second element are w0 <w1
{2, 3, 1, 4, 5, 0, 6}
{3, 2, 4, 1, 5, 0, 6}
{3, 4, 2, 5, 1, 6, 0}
{4, 3, 5, 2, 1, 6, 0}
{5, 4, 3, 2, 1, 6, 0} // The relation derived from the first element and the relation derived from the second element are w0> w1
}
<L4: Highest priority / secondary priority table 2>
In the above weightCandListWTable [] [] and weightCandListITable [] [], w0F, w1F, w0S, and w1S preferably satisfy w0F <w0S <w1S <w1F.

Ww0F <w0S <w1S <w1F is equivalent to the configuration of “L3: Highest priority / secondary priority table 1” (w0Fw <w1F && w0S <w1S) with the addition of w0F <w1S.

0w0F <w0S <w1S <w1F is equivalent to a configuration in which w0F 最> w1S is added to one of the configurations (w0F> w1F && w0S> w1S) of “L3: Highest priority / secondary priority table 1”.

For example, the following weight candidate list table may be used in step S3 of the weight candidate list deriving unit 30301.
weightCandListWTable [] [] =
{
{2, 3, 4, 5, 6, -2, 10} // w0F (= 2) <w0S (= 3) <w1S (= 5) <w1F (= 6)
{3, 4, 2, 5, 6, -2, 10}
{4, 3, 5, 2, 6, -2, 10}
{4, 5, 3, 6, 2, 10, -2}
{5, 4, 6, 3, 2, 10, -2}
{6, 5, 4, 3, 2, 10, -2} // w0F (= 6)> w0S (= 5)> w1S (= 3)> w1F (= 2)
}
Here, shiftWP = 3.

(A1L: Relationship between reference block parameter and weight candidate list)
In the above-mentioned “A1: Operation for deriving a weighting factor considering the characteristics of the reference block”, the weight candidate list deriving unit 30301 derives a weight candidate list table weightCandListWTable as shown in the following equation.
weightCandListWTable [0] [] = {2, 3, 4, 5, 6, -2, 10}
weightCandListWTable [1] [] = {3, 4, 2, 5, 6, -2, 10}
weightCandListWTable [2] [] = {4, 3, 5, 2, 6, -2, 10}
weightCandListWTable [3] [] = {4, 5, 3, 6, 2, 10, -2}
weightCandListWTable [4] [] = {5, 4, 6, 3, 2, 10, -2}
weightCandListWTable [5] [] = {6, 5, 4, 3, 2, 10, -2}
w = weightCandListWTable [fIdx] [weightIdx]
In FIG. 19, in the weight candidate lists weightCandListWTable [0] [] and weightCandListWTable [1] [] when fIdx is 0 and 1, the temporal distance Xval0 between RefPic0 and currPic is the temporal relationship between RefPic1 and currPic. More than a predetermined distance Xval1. Here, the predetermined degree is, for example, half of the temporal distance between RefPic0 and RefPic1. At this time, the top element of the weight candidate lists weightCandListWTable [0] [] and weightCandListWTable [1] [] is a weighting coefficient when the weight w0 of RefPic0 is smaller than the weight w1 of RefPic1.

In the weight candidate lists weightCandListWTable [2] [] and weightCandListWTable [3] [] when fIdx is 2 and 3, the temporal distance Xval0 between RefPic0 and currPic and the temporal distance Xval1 between RefPic1 and currPic Are comparable (Xval0 and Xval1 do not have to match exactly). At this time, the top elements of the weight candidate lists weightCandListWTable [2] [] and weightCandListWTable [3] [] are weight coefficients when the weight w0F of RefPic0 and the weight w1F of RefPic1 are equal (1: 1). . The second element from the top of the weight candidate lists weightCandListWTable [2] [] and weightCandListWTable [3] [] is a weighting factor (4 in this case) with a weight w0S of RefPic0 of 1: 1 when Xval0> Xval1. Is smaller than 3 (here, 3), and when the relationship between Xval0 and Xval1 is Xval0 <Xval1, the weight w0S of RefPic0 is larger than the weighting factor of 1: 1 (here 4). Then 5).

In the weight candidate lists weightCandListWTable [4] [] and weightCandListWTable [5] [] when fIdx is 4 and 5, the temporal distance Xval0 between RefPic0 and currPic is the temporal distance Xval1 between RefPic1 and currPic. Smaller than the predetermined degree. At this time, the top element of the weight candidate lists weightCandListWTable [4] [] and weightCandListWTable [5] [] is a weighting coefficient when the weight of RefPic0 is larger than the weight of RefPic1.

As described above, there is also a configuration for deriving a weight candidate list such that the weight of motion compensated image predSamplesL0 derived by referring to RefPic0 becomes smaller as Xval0> Xval1 (the smaller weight is near the top of the list) Are included in the present invention.

(A3L: Relationship between reference block parameter and prediction weight coefficient)
In the above-described “A1: Operation for deriving a weighting factor considering the characteristics of the reference block”, the weight candidate list deriving unit 30301 derives a weight candidate list weightCandListW as shown in the following equation.
if (wpIdx == 2) weightCandListW [] = {2, 3, 4, 5, 6, -2, 10}
else if (wpIdx == 3) weightCandListW [] = {3, 4, 2, 5, 6, -2, 10}
else if (wpIdx == 4) weightCandListW [] = {4, 3, 5, 2, 6, -2, 10}
else if (wpIdx == 5) weightCandListW [] = {5, 4, 6, 3, 2, 10, -2}
else if (wpIdx == 6) weightCandListW [] = {6, 5, 4, 3, 2, 10, -2}
w = weightCandListW [weightIdx]
In the weight candidate list weightCandListW [] when wpIdx is 2 and 3 in FIG. 24, Xval0 is larger than Xval1 by the above-mentioned predetermined degree or more. At this time, the head element of the weight candidate list weightCandListW [] is a weighting coefficient when the weight of RefPic0 is smaller than the weight of RefPic1.

In the weight candidate list weightCandListW [] when wpIdx is 4, Xval0 and Xval1 are the same level (Xval0 and Xval1 do not have to match exactly). At this time, the leading element of the weight candidate list weightCandListW [] is a weighting coefficient when the weight of RefPic0 and the weight of RefPic1 are equal.

In addition, in the weight candidate list weightCandListW [] when wpIdx is 5 and 6, the temporal distance Xval0 between RefPic0 and currPic is greater than the predetermined degree than the temporal distance Xval1 between RefPic1 and currPic. small. At this time, the head element of the weight candidate lists weightCandListW [4] [] and weightCandListW [] is a weighting coefficient when the weight of RefPic0 is larger than the weight of RefPic1.

[Embodiment 2]
In the first embodiment, the characteristics of the reference block are considered in the decoding process and the encoding process. The present embodiment is different from the first embodiment in that the characteristics of adjacent blocks are considered in each process.

(B1: Configuration for deriving weighting factors in consideration of features of adjacent blocks)
FIG. 26 is a schematic diagram illustrating a detailed configuration of the inter prediction parameter decoding unit 303c different from the inter prediction parameter decoding unit 303 illustrated in FIG. 16 and the inter prediction image generation unit 309 illustrated in FIG. 11 in the present embodiment.

26, the inter prediction parameter decoding unit 303c includes a weight index decoding unit 3038, an adjacent base weight candidate list derivation unit 30301c, and a weight coefficient selection unit 30302c.

<Adjacent Base Weight Candidate List Deriving Unit 30301c>
The adjacent base weight candidate list deriving unit 30301c refers to the prediction parameter memory 307 and derives a weight candidate list weightCandList using the weight coefficient (or weight index) of the adjacent block.

<Weighting coefficient selection unit 30302c>
The weighting coefficient selection unit 30302c derives the weighting coefficient w according to the weight candidate list weightCandList and the weight index weightIdx.

(B1: Operation for deriving weighting factors in consideration of features of adjacent blocks)
FIG. 27 is a flowchart showing operations of the inter prediction parameter decoding unit 303c and the inter prediction image generation unit 309 shown in FIG. As illustrated in FIG. 27, the operations of the inter prediction parameter decoding unit 303c and the inter prediction image generation unit 309 include steps S1, S12, S13, and S4.

<Step S12>
The adjacent base weight candidate list deriving unit 30301c derives adjacent block weight coefficients (wIdxLXA, wIdxLXB) as adjacent block parameters.

<Step S13>
The adjacent base weight candidate list deriving unit 30301c derives a weight candidate list weightCandListW from the derived adjacent block weight coefficients (wIdxLXA, wIdxLXB). FIG. 28 is a schematic diagram illustrating adjacent blocks A and B used when the adjacent base weight candidate list deriving unit 30301c of the inter prediction parameter decoding unit 303c illustrated in FIG. 26 derives the weight candidate list weightCandListW. In FIG. 28, the adjacent block A is located to the left of the target block T. The adjacent block B is located on the target block T.

The block coordinates are expressed as (x, y) in a two-dimensional plane coordinate system. The x coordinate increases from the left to the right of the block. The y coordinate increases from the top to the bottom of the block.

Suppose that the position of the target block T is (xP, yP). The length of the target block in the x-axis direction is nPbW. The length of the target block in the y-axis direction is nPbH. At this time, the adjacent block A is a block including coordinates (xP-1, yP + nPbH-1). The adjacent block B is a block including coordinates (xP + nPbW-1, yP-1).

If the weight coefficient wIdxLXA of the adjacent block A is available (availableFlagLXA = 1), the adjacent base weight candidate list derivation unit 30301c adds the weight to the weight candidate list weightCandListW []. Furthermore, if the weight coefficient wIdxLXB of the adjacent block B is available (availableFlagLXB = 1), it is added to the weight candidate list weightCandListW [].
i = 0
if (availableFlagLXA) {
weightCandListW [i ++] = wIdxLXA; wpUsed [wIdxLXA] = 1
}
if (availableFlagLXB) {
weightCandListW [i ++] = wIdxLXB; wpUsed [wIdxLXB] = 1
}
Here, wpUsed [wIdx] is information for indicating whether a certain weighting factor wIdx has been stored in the weight candidate list, and wpUsed [wIdx] is true when a certain weighting factor wIdx has been stored, conversely! wpUsed [wIdx] (described later) is true when a certain weight coefficient wIdx is not stored.

Subsequently, if the number of elements in the derived weight candidate list weightCandListW [] does not reach a predetermined number wN (for example, 5), the adjacent base weight candidate list deriving unit 30301c uses the elements in the predetermined table weightCandListWDefault as the weight candidate list weightCandListW [ ] Is added to the weight candidate list weightCandListW [] so that the number of elements becomes wN. If the element wp of the table weightCandListWDefault has already been added to the weight candidate list weightCandListW [] at the time of adding the element of the table weightCandListWDefault to the weight candidate list weightCandListW [], that element wp is not added to weightCandList [].
while (i <wN) {
for (j = 0; j <sizeof (weightCandListW); j ++) {
wpIdx = weightCandListWDefault [j]
if (! wpUsed [wpIdx]) {weightCandListW [i ++] = wpIdx; wpUsed [wpIdx] = 1}
}}
As the predetermined table weightCandListWDefault [], for example, the following is used.
weightCandListWDefault [] = {4, 3, 5, 2, 6, -2, 10}
If an element wp of the predetermined table weightCandListWDefault has already been added to the weight candidate list weightCandListW [] at the time of adding an element of the predetermined table weightCandListWDefault to the weight candidate list weightCandListW [] (wpUsed [wp] == 1 ), The element wp is not added to weightCandListW [].

<Consideration of Scaling in Step S13>
FIG. 29 is a schematic diagram for explaining scaling that is considered when the adjacent base weight candidate list deriving unit 30301c of the inter prediction parameter decoding unit 303c illustrated in FIG. 26 derives the weight candidate list weightCandListW. In FIG. 29, the correspondence between the symbols and their meanings is as follows.
Pcurr: Target picture
Pnref: Reference picture of adjacent block
Pref: Reference picture of the target block
mvLX: Reference picture motion vector of adjacent block
mvpLX: Scaled motion vector of the reference picture of the neighboring block (ie, the prediction vector of the target block)
In FIG. 29, the target picture and the reference picture are schematically shown as line segments. In the prediction motion vector derivation, when the reference picture Pnref of the adjacent block is different from the reference picture Pref of the target picture Pcurr, the motion vector mvLX is scaled while maintaining the direction of the motion vector mvLX. The motion vector mvpLX obtained by scaling the motion vector mvLX has a length according to the temporal distance between the target picture Pcurr and the reference picture Pref.

When the motion vector mvLX is scaled, the weighting factor of the adjacent block cannot be used as it is as the weighting factor added to the weight candidate list weightCandListW (the weighting factor does not become an appropriate value even if it is scaled). Therefore, in this case, the weight coefficient of the adjacent block is not stored in the weight candidate list weightCandListW. When the motion vector mvLX is scaled, a default weight coefficient may be used as a weight coefficient to be added to the weight candidate list weightCandListW. In this case, the configuration may be such that the elements of the predetermined table weightCandListWDefault are stored in order.

In other words, the case where the motion vector mvLX is scaled can be said to be the case where Pref! = Pnref. Alternatively, the case where the motion vector mvLX is scaled can be said to be a case where POC (Pref)! = POC (Pnref).

Specifically, in the weight candidate list weightCandListW, as shown below, the adjacent block A is available (the truth value availableFlagLXA is true (non-zero)), and the prediction vector of the adjacent block A is scaled in the prediction vector list derivation. If not (if the true / false value scaledLXA indicating that it is scaled is false (0)), the weight coefficient wIdxLXA of the adjacent block A is added to the weightCandListW. Further, 1 is set to the variable wpUsed [wIdxLXA] indicating that the weight coefficient wIdxLXA has been added.

Similarly, in the prediction vector list derivation, if the prediction vector of the adjacent block B is not scaled (if the true / false value scaledLXB indicating that it is scaled is false (0)), the weight of the adjacent block B in the weightCandList Add coefficient wIdxLXB.

Finally, if the derived weightCandListW has not reached a predetermined number wN (for example, 5), the elements of the predetermined table weightCandListWDefault are added to the list so that the number of elements of weightCandListW [] is wN.
i = 0
if (availableFlagLXA &&! scaledLXA) {
weightCandListW [i ++] = wIdxLXA
wpUsed [wIdxLXA] = 1
}
if (availableFlagLXB &&! scaledLXB) {
weightCandListW [i ++] = wIdxLXB
wpUsed [wIdxLXB] = 1
}
while (i <wN) {
for (j = 0; j <sizeof (weightCandListW); j ++) {
wpIdx = weightCandListWDefault [j]
if (! wpUsed [wpIdx]) {weightCandListW [i ++] = wpIdx; wpUsed [wpIdx] = 1}
}}
The weighting candidate list weightCandList does not need to store the weighting coefficient itself, and may be a label (eg, A, B,...) Of an adjacent block that refers to the weighting coefficient. An index indicating a weighting factor may be used. In the case of an index indicating a weight coefficient, that is, the weight candidate list weightCandListI [] can be processed as follows. In the following, wIdxLXA and wIdxLXB are weight indexes of adjacent blocks A and B.
i = 0
if (availableFlagLXA &&! scaledLXA) {
weightCandListI [i ++] = wIdxLXA
wpUsed [wIdxLXA] = 1
}
if (availableFlagLXB &&! scaledLXB) {
weightCandListI [i ++] = wIdxLXB
wpUsed [wIdxLXB] = 1
}
while (i <wN) {
for (j = 0; j <sizeof (weightCandListI); j ++) {
wpIdx = weightCandListIDefault [j]
if (! wpUsed [wpIdx]) {weightCandListI [i ++] = wpIdx; wpUsed [wpIdx] = 1}
}}
Then, the weight coefficient selection unit 30302c derives a weight coefficient w from the derived weight candidate list weightCandListW and the weight index weightIdx.
w = weightCandListW [weightIdx]
(B1: Effect of derivation of weighting factors considering features of adjacent blocks)
As described above, a list in which weighting factors are arranged in descending order of selection probability can be derived according to the weighting factors of adjacent blocks. The above weight candidate list derivation process can also be applied to the encoding process. Then, in the encoding process, by encoding the weighting coefficient derived as described above, the weighting coefficient can be encoded with a smaller weight index than in the conventional case. Therefore, the effect of reducing the code amount of the weight index is achieved.

(B1L: Modification Example 1 for Deriving Weighting Factors Considering Features of Adjacent Blocks)
A weighting factor is derived as follows.
(1) A weight candidate list is derived from the weight coefficient wIdxLXA of the adjacent block A and the weight coefficient wIdxLXB of the adjacent block B. At this time, candidates close to the weighting factor wEq of 1: 1 (in this case, close to wEq = wIdx = 4) are added to the weight candidate list first). The absolute value of the difference between the weighting factors wIdxLXA and wIdxLXB of each adjacent block and the weighting factor wEq of 1: 1 | wIdxLXA-wEq | and | wIdxLXB-wEq | If the difference between and is smaller, the weight coefficient wIdxLXA of the adjacent block A is added to the weight candidate list, and if not, the weight coefficient wIdxLXB of the adjacent block B is added to the weight candidate list first.
(2) If there is a vacancy in the candidate list (i <wN), a weighting factor of a predetermined table weightCandListWDefault is added.
wEq = 4
i = 0
if (availableFlagLXA && availableFlagLXB) {
if (| wIdxLXA-wEq | <| wIdxLXB-wEq |) {
weightCandListW [i ++] = wIdxLXA; wpUsed [wIdxLXA] = 1
weightCandListW [i ++] = wIdxLXB; wpUsed [wIdxLXB] = 1
} else {
weightCandListW [i ++] = wIdxLXB; wpUsed [wIdxLXB] = 1
weightCandListW [i ++] = wIdxLXA; wpUsed [wIdxLXA] = 1
}
} else if (availableFlagLXA) {
weightCandListW [i ++] = wIdxLXA; wpUsed [wIdxLXA] = 1
} else if (availableFlagLXB) {
weightCandListW [i ++] = wIdxLXB; wpUsed [wIdxLXB] = 1
}
while (i <wN) {
for (j = 0; j <sizeof (weightCandListW); j ++) {
wpIdx = weightCandListWDefault [j]
if (! wpUsed [wpIdx]) {weightCandListW [i ++] = wpIdx; wpUsed [wpIdx] = 1}
}}
In the following, an example different from that described above is shown.
i = 0
scaledLXA = (POC (Pref)! = POC (PnAref)) // PnAref Reference image of adjacent block A
if (availableFlagLXA &&! scaledLXA) {
weightCandListW [i ++] = wIdxLXA
wpUsed [wIdxLXA] = 1
}
scaledLXB = (POC (Pref)! = POC (PnBref)) // PnBref Reference image of adjacent block B
if (availableFlagLXB &&! scaledLXB) {
weightCandListW [i ++] = wIdxLXB
wpUsed [wIdxLXB] = 1
}
while (i <wN) {
for (j = 0; j <sizeof (weightCandListW); j ++) {
wpIdx = weightCandListWDefault [j]
if (! wpUsed [wpIdx]) {weightCandListW [i ++] = wpIdx; wpUsed [wpIdx] = 1}
}}
The determination of (| wIdxLXA−wEq | <| wIdxLXB−wEq |) may be made as wIdxLXA <wIdxLXB.

(B1b: Modified example 2 of derivation of weighting factors considering features of adjacent blocks)
The derivation of the weighting factor of this item is different from the above-described derivation of the weighting factor in that the weight candidate list is derived by referring to the index indicating the weighting factor of the adjacent block instead of the weighting factor of the adjacent block. Specifically, step S12 and step S13 are modified as follows.

<Modification of Step S12>
The adjacent base weight candidate list deriving unit 30301c derives the weight coefficient index (wIdxLXA, wIdxLXB) of the adjacent block as the adjacent block parameter.

<Modification of Step S13>
The adjacent base weight candidate list deriving unit 30301c derives a weight candidate list weightCandListI from the weight indexes (wIdxLXA, wIdxLXB) of adjacent blocks.
i = 0
if (availableFlagLXA &&! scaledLXA) {
weightCandListI [i ++] = wIdxLXA
wpUsed [wIdxLXA] = 1
}
if (availableFlagLXB &&! scaledLXB) {
weightCandListI [i ++] = wIdxLXB
wpUsed [wIdxLXB] = 1
}
while (i <wN) {
for (j = 0; j <sizeof (weightCandListI); j ++) {
wpIdx = weightCandListIDefault [j]
if (! wpUsed [wpIdx]) {weightCandListI [i ++] = wpIdx; wpUsed [wpIdx] = 1}
}}
If the derived weightCandListI does not reach the predetermined number wN, it is filled with elements of the predetermined table weightCandListIDefault. At this time, if the element wpIdx of weightCandListIDefault has already been stored in weightCandListI (wpUsed [wpIdx] == 1), wpIdx is not stored in the table.
while (i <wN) {
for (j = 0; j <sizeof (weightCandListI); j ++) {
wpIdx = weightCandListIDefault [j]
if (! wpUsed [wpIdx]) {weightCandListI [i ++] = wpIdx; wpUsed [wpIdx] = 1}
}}
Further, the weight coefficient selection unit 30302c derives the position posIdx of the weight coefficient table weightTable from the derived weight candidate list weightCandListI and the weight index weightIdx, and derives the weight coefficient w from the derived weight index as follows. To do.

posIdx = weightCandListI [weightIdx]
w = weightTable [posIdx]
Here, for example, the weighting coefficient table is weightTable [] = {− 2,2,3,4,5,6,10}.

(B2: Configuration for deriving weighting factors in consideration of features of adjacent blocks)
30 is a schematic diagram illustrating a detailed configuration of an inter prediction parameter decoding unit 303d different from the inter prediction parameter decoding unit 303 illustrated in FIG. 16 and an inter prediction image generation unit 309 illustrated in FIG.

As illustrated in FIG. 30, the inter prediction parameter decoding unit 303d includes a weight index decoding unit 3038, a prediction weight candidate list derivation unit 30301d, a prediction weight candidate selection unit 30302d, and a weight coefficient derivation unit 3030b. The

<Prediction weight candidate list derivation unit 30301d>
The prediction weight candidate list deriving unit 30301d refers to the prediction parameter memory 307 and derives a prediction weight candidate list using the weight coefficient (or weight index) of the adjacent block.

<Prediction weight candidate selection unit 30302d>
The prediction weight candidate selection unit 30302d selects an element of the prediction weight candidate list derived by the prediction weight candidate list deriving unit 30301d using the prediction vector index mvp_LX_idx used in AMVP.

Specifically, as shown in FIG. 28, the prediction weight candidate list wpCandList [2] is created using the weight coefficients wIdxLXA and wIdxLXB of the left adjacent block A and the upper adjacent block B of the target block.

wpCandList [2] = {wIdxLXA, wIdxLXB}
Next, a prediction weight coefficient wpIdx is derived.

wpIdx = wpCandList [mvp_LX_idx]
Here, mvp_LX_idx is a parameter for designating a prediction vector in a prediction vector candidate set.

<Step S13 in B2>
The prediction weight candidate list deriving unit 30301d derives a 1: 1 weighting factor when the motion vector is scaled. If the motion vector is not scaled, the prediction weight candidate list derivation unit 30301d uses the weight coefficient of the adjacent block. When the motion vector mvLX is scaled, a default weight coefficient w_default (w_default = (1 << shiftWP) >> 1, w_default = 4 if shiftWP = 3) is added as a weight coefficient to be added to the prediction weight candidate list wpCandListLX. May be used. In this case, the configuration may be such that the elements of the predetermined table weightCandListWDefault are stored in order.
i = 0, j = 0
if (availableFlagLXA) {
mvpListLX [i ++] = mvLXA
scaledLXA = (POC (Pref)! = POC (PnAref)) // PnAref Reference image of adjacent block A wpCandListLX [j ++] =! scaledLXA? wIdxLXA: w_default
if (availableFlagLXB && (mvLXA! = mvLXB)) {
mvpListLX [i ++] = mvLXB
scaledLXB = (POC (Pref)! = POC (PnBref)) // PnBref Reference image of adjacent block B wpCandListLX [j ++] =! scaledLXB? wIdxLXB: w_default
}
} else if (availableFlagLXB) {
mvpListLX [i ++] = mvLXB
wpCandListLX [j ++] =! scaledLXB? wIdxLXB: w_default
}
if (i <2 && availableFlagLXCol) {
mvpListLX [i ++] = mvLXCol
wpCandListLX [j ++] = w_default
}
while (i <2) {
mvpListLX [i] [0] = 0
mvpListLX [i] [1] = 0
wpCandListLX [j ++] = w_default
i ++
}
The prediction weight candidate selection unit 30302d derives the weighting factor of the adjacent block according to mvp_LX_idx, and derives a table according to the derived weighting factor (basically, the derived weighting factor is derived so that it becomes the head. ).
wpIdxL0 = wpCandListL0 [mvp_L0_idx]
wpIdxL1 = wpCandListL1 [mvp_L1_idx]
[Modification]
A configuration in which the weighting factor is derived in consideration of the feature of the reference block as in the first embodiment and a configuration in which the weighting factor is derived in consideration of the feature of the adjacent block as in the second embodiment may be combined.

[Embodiment 3]
The present embodiment is different in that the weighting factor is derived in consideration of at least one of the feature of the reference block and the feature of the adjacent block in the merge prediction mode in the decoding process and the coding process.

(C1: Configuration and effect for deriving weighting coefficient depending on reference block parameter)
The prediction weight coefficient wpIdx is derived in the same manner as the above-described “modified example of step S2 in A3”.
if (Xval0 * 2> Xval1 * 6) wpIdx = 1
else if (Xval0 * 3> Xval1 * 5) wpIdx = 2
else if (Xval0 * 5> Xval1 * 3) wpIdx = 3
else if (Xval0 * 6> Xval1 * 2) wpIdx = 4
else wpIdx = 5
In this case, the weighting coefficient w is derived using the prediction weighting coefficient wpIdx as the weighting coefficient in the merge prediction mode.
w = wpIdx
Alternatively, the weighting factor w is derived by referring to the weighting factor table weightTable using the prediction weighting factor wpIdx as an index.
w = weightTable [wpIdx]
In the merge prediction mode, a list of merge candidates that are motion compensation parameter candidates is generated, and motion compensation of the predicted image is performed using a motion vector candidate selected from the list by an index.

FIG. 31 is a flowchart illustrating operations of the inter prediction parameter decoding unit of the prediction parameter decoding unit and the inter prediction image generation unit illustrated in FIG. 11 of the image decoding apparatus illustrated in FIG. 5 according to the third embodiment.

As shown in (a) of FIG. 31, since it is a merge prediction mode, the weight index weightIdx, which is an index referred to in order to derive a bi-prediction weight coefficient, is not decoded.

Then, when the merge candidate is a join merge candidate, a weighting factor derived according to the reference block parameter can be used. As a result, different L0 reference pictures and L1 reference pictures are used for each merge candidate in the combined merge mode in which bi-prediction is used. By using a reference block parameter such as a temporal distance between each of these reference pictures and the target picture, the prediction accuracy of each merged merge candidate can be further improved.

Also, when the merge candidate is a zero merge candidate, the weighting factor derived according to the reference block parameter is used. As a result, bi-prediction is used as a zero merge candidate derived when the slice type is B (in the case of a B picture). In each zero merge candidate, a different reference picture of L0 and a reference picture of L1 are used. By using reference block parameters such as the temporal distance between each reference picture and the target picture, the prediction accuracy of each zero merge candidate can be further improved.

(C2: Configuration and effect for deriving weighting factors depending on adjacent block parameters)
A weighting factor is derived in the same manner as in “B1L: Modification Example 1 of Deriving Weighting Factor Considering Features of Adjacent Block” described above.
(1) A weighting factor is derived from the weighting factor wIdxLXA of the adjacent block A and the weighting factor wIdxLXB of the adjacent block B. At this time, a candidate that is close to a weighting factor of 1: 1 (in this case, close to wIdxLXA and wIdxLXB) is preferentially set as a weighting factor. For 5 and 4, 4 is preferentially used as the weighting factor first.
(2) When the adjacent block A is not available and the adjacent block B is available, the default list weight coefficient is derived.
if (availableFlagLXA && availableFlagLXB) {
wpIdx = (| wIdxLXA-wEq | <| wIdxLXB-wEq |)? wIdxLXA: wIdxLXB
} else if (availableFlagLXA) {
wpIdx = wIdxLXA;
} else if (availableFlagLXB) {
wpIdx = wIdxLXB;
} else {
wpIdx = wpIdxDefault
}
The determination of (| wIdxLXA−wEq | <| wIdxLXB−wEq |) may be made as wIdxLXA <wIdxLXB.

Further, as wpIdxDefault, the prediction weight coefficient derived according to the reference block parameter (for example, the prediction weight coefficient wpIdx obtained in “Step S2 in A3” described above) may be used.

Also, as shown in FIG. 31 (b), since it is a merge prediction mode, the weight index weightIdx, which is an index referred to in order to derive a bi-prediction weight coefficient, is not decoded.

Then, when the merge candidate is a join merge candidate, the weighting factor derived according to the adjacent block can be used. Thereby, in each merge candidate of the merge merge mode in which bi-prediction is used, a suitable weighting factor according to an adjacent block can be used, and the prediction accuracy of each merge merge candidate can be further improved.

Also, when the merge candidate is a zero merge candidate, the weighting factor derived according to the adjacent block is used. Thereby, the zero merge candidate derived when the slice type is B (in the case of B picture) is used for bi-prediction, and in each zero merge candidate, a suitable weighting factor according to the adjacent block can be used, The prediction accuracy of each zero merge candidate can be further improved.

[Embodiment 4]
(Image Coding Device, Image Decoding Method, and Image Coding Method Corresponding to Image Decoding Device)
The image decoding device 31 described in the first to third embodiments uses a weight candidate list weightCandList whose elements are a weighting factor w used for weight prediction or an index indicating a weighting factor according to the feature of a block used for generating a predicted image. A weight coefficient deriving unit 3030 for deriving a coefficient and a weight prediction unit 3094 for performing weight prediction using the weight coefficient derived by the weight coefficient deriving unit 3030 are provided.

As described above, the above decoding process can also be applied to the encoding process. Specifically, the weight prediction unit 10112 (FIG. 6) of the inter prediction image generation unit 1011 (FIG. 5) of the prediction image generation unit 101 of the image encoding device 11 (FIG. 4) in the encoding process is used as the weight in the decoding process. The prediction unit 3094 can be replaced. The image encoding device 11 in this case is also included in the present invention.

In addition, in the decoding process, an image decoding method including a weight coefficient derivation process that is a process representing the process performed by the weight coefficient derivation unit 3030 and a weight prediction process that is a process representing the process performed by the weight prediction unit 3094 is also disclosed in the present invention. include.

Also, in the encoding process, an image encoding method including a weight coefficient deriving process that is a process representing the process performed by the weight coefficient deriving unit 3030 and a weight prediction process that is a process representing the process performed by the weight predicting unit 10112 is also provided. It is included in the present invention.

The image encoding device 11, the image decoding method, and the image encoding method described above have the same effects as the effects exhibited by the image decoding device 31.

[Others]
Note that a part of the image encoding device 11 and the image decoding device 31 in the above-described embodiment, for example, the entropy decoding unit 301, the prediction parameter decoding unit 302, the loop filter 305, the predicted image generation unit 308, the inverse quantization / inverse DCT. Unit 311, addition unit 312, predicted image generation unit 101, subtraction unit 102, DCT / quantization unit 103, entropy encoding unit 104, inverse quantization / inverse DCT unit 105, loop filter 107, encoding parameter determination unit 110, You may make it implement | achieve the prediction parameter encoding part 111 and the block which each part contains with a computer. In that case, the program for realizing the control function may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read by the computer system and executed. Here, the “computer system” is a computer system built in either the image encoding device 11 or the image decoding device 31 and includes hardware such as an OS and peripheral devices. The “computer-readable recording medium” refers to a storage device such as a portable medium such as a flexible disk, a magneto-optical disk, a ROM, a CD-ROM, or a hard disk built in a computer system. Furthermore, the “computer-readable recording medium” is a medium that dynamically holds a program for a short time, such as a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line, In this case, a volatile memory inside a computer system that serves as a server or a client may be included that holds a program for a certain period of time. The program may be a program for realizing a part of the above-described functions, or may be a program that can realize the above-described functions in combination with a program already recorded in a computer system.

Further, part or all of the image encoding device 11 and the image decoding device 31 in the above-described embodiment may be realized as an integrated circuit such as an LSI (Large Scale Integration). Each functional block of the image encoding device 11 and the image decoding device 31 may be individually made into a processor, or a part or all of them may be integrated into a processor. Further, the method of circuit integration is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor. In addition, when an integrated circuit technology that replaces LSI appears due to the advancement of semiconductor technology, an integrated circuit based on the technology may be used.

As described above, the embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to the above, and various design changes and the like can be made without departing from the scope of the present invention. It is possible to

(Application examples)
The image encoding device 11 and the image decoding device 31 described above can be used by being mounted on various devices that perform transmission, reception, recording, and reproduction of moving images. The moving image may be a natural moving image captured by a camera or the like, or an artificial moving image (including CG and GUI) generated by a computer or the like.

First, it will be described with reference to FIG. 13 that the above-described image encoding device 11 and image decoding device 31 can be used for transmission and reception of moving images.

(A) of FIG. 13 is a block diagram showing a configuration of a transmission device PROD_A in which the image encoding device 11 is mounted. As illustrated in FIG. 13A, the transmission apparatus PROD_A modulates a carrier wave with an encoding unit PROD_A1 that obtains encoded data by encoding a moving image, and with the encoded data obtained by the encoding unit PROD_A1. Thus, a modulation unit PROD_A2 that obtains a modulation signal and a transmission unit PROD_A3 that transmits the modulation signal obtained by the modulation unit PROD_A2 are provided. The above-described image encoding device 11 is used as the encoding unit PROD_A1.

Transmission device PROD_A, as a source of moving images to be input to the encoding unit PROD_A1, a camera PROD_A4 that captures moving images, a recording medium PROD_A5 that records moving images, an input terminal PROD_A6 for inputting moving images from the outside, and An image processing unit A7 that generates or processes an image may be further provided. FIG. 13A illustrates a configuration in which the transmission apparatus PROD_A includes all of these, but some of them may be omitted.

Note that the recording medium PROD_A5 may be a recording of a non-encoded moving image, or a recording of a moving image encoded by a recording encoding scheme different from the transmission encoding scheme. It may be a thing. In the latter case, a decoding unit (not shown) for decoding the encoded data read from the recording medium PROD_A5 in accordance with the recording encoding method may be interposed between the recording medium PROD_A5 and the encoding unit PROD_A1.

(B) of FIG. 13 is a block diagram illustrating a configuration of the receiving device PROD_B in which the image decoding device 31 is mounted. As illustrated in FIG. 13B, the receiving device PROD_B includes a receiving unit PROD_B1 that receives a modulated signal, a demodulating unit PROD_B2 that obtains encoded data by demodulating the modulated signal received by the receiving unit PROD_B1, and a demodulator. A decoding unit PROD_B3 that obtains a moving image by decoding the encoded data obtained by the unit PROD_B2. The above-described image decoding device 31 is used as the decoding unit PROD_B3.

The receiving device PROD_B is a display destination PROD_B4 for displaying a moving image, a recording medium PROD_B5 for recording a moving image, and an output terminal for outputting the moving image to the outside as a supply destination of the moving image output by the decoding unit PROD_B3 PROD_B6 may be further provided. In FIG. 13B, a configuration in which all of these are provided in the receiving device PROD_B is illustrated, but a part may be omitted.

Note that the recording medium PROD_B5 may be used for recording a non-encoded moving image, or is encoded using a recording encoding method different from the transmission encoding method. May be. In the latter case, an encoding unit (not shown) for encoding the moving image acquired from the decoding unit PROD_B3 according to the recording encoding method may be interposed between the decoding unit PROD_B3 and the recording medium PROD_B5.

Note that the transmission medium for transmitting the modulation signal may be wireless or wired. Further, the transmission mode for transmitting the modulated signal may be broadcasting (here, a transmission mode in which the transmission destination is not specified in advance) or communication (here, transmission in which the transmission destination is specified in advance). Refers to the embodiment). That is, the transmission of the modulation signal may be realized by any of wireless broadcasting, wired broadcasting, wireless communication, and wired communication.

For example, a terrestrial digital broadcast broadcasting station (broadcasting equipment, etc.) / Receiving station (such as a television receiver) is an example of a transmitting device PROD_A / receiving device PROD_B that transmits and receives a modulated signal by wireless broadcasting. A broadcasting station (such as broadcasting equipment) / receiving station (such as a television receiver) of cable television broadcasting is an example of a transmitting device PROD_A / receiving device PROD_B that transmits and receives a modulated signal by cable broadcasting.

In addition, a server (workstation, etc.) / Client (television receiver, personal computer, smartphone, etc.) such as a VOD (Video On Demand) service or a video sharing service using the Internet is a transmission device that transmits and receives modulated signals via communication. This is an example of PROD_A / receiving device PROD_B (normally, either a wireless or wired transmission medium is used in a LAN, and a wired transmission medium is used in a WAN). Here, the personal computer includes a desktop PC, a laptop PC, and a tablet PC. The smartphone also includes a multi-function mobile phone terminal.

In addition to the function of decoding the encoded data downloaded from the server and displaying it on the display, the video sharing service client has a function of encoding a moving image captured by the camera and uploading it to the server. That is, the client of the video sharing service functions as both the transmission device PROD_A and the reception device PROD_B.

Next, the fact that the above-described image encoding device 11 and image decoding device 31 can be used for recording and reproduction of moving images will be described with reference to FIG.

(A) of FIG. 14 is a block diagram showing a configuration of a recording apparatus PROD_C in which the above-described image encoding device 11 is mounted. As shown in FIG. 14 (a), the recording apparatus PROD_C has an encoding unit PROD_C1 that obtains encoded data by encoding a moving image, and the encoded data obtained by the encoding unit PROD_C1 on the recording medium PROD_M. A writing unit PROD_C2 for writing. The above-described image encoding device 11 is used as the encoding unit PROD_C1.

The recording medium PROD_M may be of a type built into the recording device PROD_C, such as (1) HDD (Hard Disk Drive) or SSD (Solid State Drive), or (2) SD memory. It may be of the type connected to the recording device PROD_C, such as a card or USB (Universal Serial Bus) flash memory, or (3) DVD (Digital Versatile Disc) or BD (Blu-ray Disc: registration) Or a drive device (not shown) built in the recording device PROD_C.

In addition, the recording device PROD_C is a camera PROD_C3 that captures moving images as a source of moving images to be input to the encoding unit PROD_C1, an input terminal PROD_C4 for inputting moving images from the outside, and a reception for receiving moving images A unit PROD_C5 and an image processing unit PROD_C6 for generating or processing an image may be further provided. FIG. 14A illustrates a configuration in which the recording apparatus PROD_C includes all of these, but some of them may be omitted.

The receiving unit PROD_C5 may receive a non-encoded moving image, or may receive encoded data encoded by a transmission encoding scheme different from the recording encoding scheme. You may do. In the latter case, a transmission decoding unit (not shown) that decodes encoded data encoded by the transmission encoding method may be interposed between the reception unit PROD_C5 and the encoding unit PROD_C1.

Examples of such a recording device PROD_C include a DVD recorder, a BD recorder, an HDD (Hard Disk Drive) recorder, and the like (in this case, the input terminal PROD_C4 or the receiver PROD_C5 is a main source of moving images). . In addition, a camcorder (in this case, the camera PROD_C3 is a main source of moving images), a personal computer (in this case, the receiving unit PROD_C5 or the image processing unit C6 is a main source of moving images), a smartphone (this In this case, the camera PROD_C3 or the reception unit PROD_C5 is a main source of moving images), and the like is also an example of such a recording apparatus PROD_C.

(B) of FIG. 14 is a block showing a configuration of a playback device PROD_D equipped with the image decoding device 31 described above. As shown in FIG. 14B, the playback device PROD_D reads a moving image by decoding a read unit PROD_D1 that reads encoded data written to the recording medium PROD_M and a read unit PROD_D1 that reads the encoded data. And a decoding unit PROD_D2 to obtain. The above-described image decoding device 31 is used as the decoding unit PROD_D2.

The recording medium PROD_M may be of the type built into the playback device PROD_D, such as (1) HDD or SSD, or (2) such as an SD memory card or USB flash memory. It may be of the type connected to the playback device PROD_D, or (3) may be loaded into a drive device (not shown) built in the playback device PROD_D, such as a DVD or BD. Good.

In addition, the playback device PROD_D has a display unit PROD_D3 that displays a moving image as a supply destination of the moving image output by the decoding unit PROD_D2, an output terminal PROD_D4 that outputs the moving image to the outside, and a transmission unit that transmits the moving image. PROD_D5 may be further provided. FIG. 14B illustrates a configuration in which the playback apparatus PROD_D includes all of these, but some of them may be omitted.

The transmission unit PROD_D5 may transmit a non-encoded moving image, or transmits encoded data encoded by a transmission encoding scheme different from the recording encoding scheme. You may do. In the latter case, it is preferable to interpose an encoding unit (not shown) that encodes a moving image using a transmission encoding method between the decoding unit PROD_D2 and the transmission unit PROD_D5.

Examples of such a playback device PROD_D include a DVD player, a BD player, and an HDD player (in this case, an output terminal PROD_D4 to which a television receiver or the like is connected is a main moving image supply destination). . In addition, a television receiver (in this case, the display PROD_D3 is a main supply destination of moving images), a digital signage (also referred to as an electronic signboard or an electronic bulletin board), and the display PROD_D3 or the transmission unit PROD_D5 is the main supply of moving images Desktop PC (in this case, output terminal PROD_D4 or transmission unit PROD_D5 is the main video source), laptop or tablet PC (in this case, display PROD_D3 or transmission unit PROD_D5 is video) A smartphone (which is a main image supply destination), a smartphone (in this case, the display PROD_D3 or the transmission unit PROD_D5 is a main moving image supply destination), and the like are also examples of such a playback device PROD_D.

(Hardware implementation and software implementation)
Each block of the image decoding device 31 and the image encoding device 11 described above may be realized in hardware by a logic circuit formed on an integrated circuit (IC chip), or may be a CPU (Central Processing Unit). You may implement | achieve by software using.

In the latter case, each device includes a CPU that executes instructions of a program that realizes each function, a ROM (Read （Memory) that stores the program, a RAM (RandomAccess Memory) that expands the program, the program, and various data A storage device (recording medium) such as a memory for storing the. The object of the embodiment of the present invention is to record the program code (execution format program, intermediate code program, source program) of the control program for each device, which is software for realizing the functions described above, so as to be readable by a computer. This can also be achieved by supplying a medium to each of the above devices, and reading and executing the program code recorded on the recording medium by the computer (or CPU or MPU).

Examples of the recording medium include tapes such as magnetic tapes and cassette tapes, magnetic disks such as floppy (registered trademark) disks / hard disks, CD-ROMs (Compact Disc-Read-Only Memory) / MO discs (Magneto-Optical discs). ) / MD (Mini Disc) / DVD (Digital Versatile Disc) / CD-R (CD Recordable) / Blu-ray Disc (Blu-ray Disc: registered trademark) and other optical disks, IC cards (including memory cards) / Cards such as optical cards, Mask ROM / EPROM (Erasable Programmable Read-Only Memory) / EEPROM (Electrically Erasable and Programmable Read-Only Memory: registered trademark) / Semiconductor memories such as flash ROM, or PLD (Programmable logic device ) Or FPGA (Field Programmable Gate Gate Array) or the like.

Further, each device may be configured to be connectable to a communication network, and the program code may be supplied via the communication network. The communication network is not particularly limited as long as it can transmit the program code. For example, Internet, intranet, extranet, LAN (Local Area Network), ISDN (Integrated Services Digital Network), VAN (Value-Added Network), CATV (Community Area Antenna / television / Cable Television), Virtual Private Network (Virtual Private Network) Network), telephone line network, mobile communication network, satellite communication network, and the like. The transmission medium constituting the communication network may be any medium that can transmit the program code, and is not limited to a specific configuration or type. For example, IEEE (Institute of Electrical and Electronic Engineers) 1394, USB, power line carrier, cable TV line, telephone line, ADSL (Asymmetric Digital Subscriber Line) line, etc. wired such as IrDA (Infrared Data Association) or remote control , BlueTooth (registered trademark), IEEE802.11 wireless, HDR (High Data Rate), NFC (Near Field Communication), DLNA (Digital Living Network Alliance: registered trademark), mobile phone network, satellite line, terrestrial digital broadcasting network, etc. It can also be used wirelessly. The embodiment of the present invention can also be realized in the form of a computer data signal embedded in a carrier wave in which the program code is embodied by electronic transmission.

[Additional Notes]
The embodiments of the present invention are not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention.
(Cross-reference of related applications)
This application claims the benefit of priority to the Japanese patent application filed on Aug. 26, 2016: Japanese Patent Application No. 2016-166317. Included in this document.

Embodiments of the present invention can be preferably applied to an image decoding apparatus that decodes encoded data in which image data is encoded, and an image encoding apparatus that generates encoded data in which image data is encoded. it can. Further, the present invention can be suitably applied to the data structure of encoded data generated by an image encoding device and referenced by the image decoding device.

DESCRIPTION OF SYMBOLS 1 Image transmission system 11 Image coding apparatus 31 Image decoding apparatus 41 Image display apparatus 101,308 Predictive image generation part 303,303b, 303c, 303d Inter prediction

parameter decoding part

309,1011 Inter prediction

image generation part

3030,3030a, 3030b Weight Coefficient derivation unit 3038 Weight

index decoding unit

3039, 3039b Reference block

parameter derivation unit

3094, 10112

Weight prediction unit

30301, 30301b Weight candidate list derivation unit 30301c Adjacent base weight candidate list derivation unit 30301d Prediction weight candidate

list derivation unit

30302, 30302c Weight coefficient Selection unit 30302d Prediction weight candidate selection unit 30303 Weight coefficient correction unit

Claims

A weighting factor deriving unit for deriving a weighting factor according to a feature of a block used for generation of a predicted image, from a weighting candidate list including a weighting factor used for weight prediction or an index indicating the weighting factor as an element;
A weight prediction unit that performs weight prediction using the weighting factor derived by the weighting factor deriving unit;
An image decoding apparatus comprising:
A reference block parameter deriving unit for deriving a reference block parameter representing a feature of the reference block referred to for generating a predicted image;
The image decoding apparatus according to claim 1, wherein the weighting factor deriving unit derives the weighting factor according to the reference block parameter.
The weighting factor derivation unit includes:
From the plurality of weight candidate lists having a weighting factor as an element, select a weight candidate list according to the reference block parameter derived by the reference block parameter deriving unit,
The image decoding apparatus according to claim 2, wherein a weight coefficient is derived from the selected weight candidate list.
The weighting factor derivation unit includes:
A weight candidate list is selected from a plurality of weight candidate lists having an index indicating a weighting factor as an element according to a reference block parameter derived by the reference block parameter deriving unit,
The image decoding apparatus according to claim 2, wherein a weighting factor is derived by deriving an index from the selected weight candidate list.
The reference block parameter derivation unit includes:
A first reference block parameter that is a reference block parameter of the first reference block;
Deriving a second reference block parameter that is a reference block parameter of the second reference block;
The weighting factor deriving unit reduces the elements of the weight candidate list as the absolute value of the difference between the first reference block parameter and the second reference block parameter is larger. The image decoding device described.
3. The image decoding apparatus according to claim 2, wherein the weighting factor deriving unit swaps elements of the weight candidate list according to the reference block parameter derived by the reference block parameter deriving unit.
The weighting factor derivation unit includes:
From the reference block parameter derived by the reference block parameter deriving unit, a prediction weight coefficient that is a predicted value of the weight coefficient is derived,
Deriving the weight candidate list according to the prediction weight coefficient,
The image decoding apparatus according to claim 2, wherein a weighting factor is derived from the derived weight candidate list.
The reference block parameter derivation unit includes:
A first reference block parameter that is a reference block parameter of the first reference block;
Deriving a second reference block parameter that is a reference block parameter of the second reference block;
The image decoding according to claim 7, wherein the weighting factor deriving unit decreases the prediction weighting factor as the absolute value of the difference between the first reference block parameter and the second reference block parameter increases. apparatus.
The weighting factor deriving unit derives the weighting factor according to a weighting factor used for weight prediction of an adjacent block adjacent to a target block that is a target for generating a predicted image. Image decoding apparatus.
The image decoding device according to claim 9, wherein the weighting factor deriving unit adds the weighting factor of the adjacent block to the weighting candidate list and derives the weighting factor from the weighting candidate list.
The weighting factor deriving unit derives the weighting factor by adding an index indicating the order of the weighting factors of the adjacent blocks to the weighting candidate list and deriving the index from the weighting candidate list. The image decoding apparatus according to claim 9.
The first element of the weight candidate list includes first and second weights that have the same value for the first weight multiplied by the first motion compensated image and the second weight multiplied by the second motion compensated image in weight prediction. The image decoding device according to claim 10 or 11, wherein the image decoding device is an element capable of obtaining the second weight.
12. The image decoding device according to claim 9, wherein the weighting factor deriving unit derives the weighting factor when a motion vector of a reference picture is not scaled.
The weighting factor deriving unit derives a weighting factor from the weighting candidate list according to an index of the prediction vector candidate list when a prediction vector candidate list is used for motion vector prediction. The image decoding device according to claim 9.
10. The image decoding apparatus according to claim 1, wherein the weighting factor deriving unit derives a weighting factor when the prediction mode of the weight prediction is a merge prediction mode.
A weighting factor deriving unit for deriving a weighting factor according to a feature of a block used for generation of a predicted image, from a weighting candidate list including a weighting factor used for weight prediction or an index indicating the weighting factor as an element;
A weight prediction unit that performs weight prediction using the weighting factor derived by the weighting factor deriving unit;
An image encoding device comprising:
A weighting factor deriving step for deriving a weighting factor according to the feature of the block used for generation of the predicted image from the weighting candidate list including the weighting factor used for weight prediction or the index indicating the weighting factor as an element;
A weight prediction step of performing weight prediction using the weighting factor derived in the weighting factor derivation step;
An image decoding method comprising:
A weighting factor deriving step for deriving a weighting factor according to the feature of the block used for generation of the predicted image from the weighting candidate list including the weighting factor used for weight prediction or the index indicating the weighting factor as an element;
A weight prediction step of performing weight prediction using the weighting factor derived in the weighting factor derivation step;
An image encoding method comprising: