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WO2012064083A2 - Procédé et appareil de filtrage de débouchage - Google Patents

Procédé et appareil de filtrage de débouchage Download PDF

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Publication number
WO2012064083A2
WO2012064083A2 PCT/KR2011/008463 KR2011008463W WO2012064083A2 WO 2012064083 A2 WO2012064083 A2 WO 2012064083A2 KR 2011008463 W KR2011008463 W KR 2011008463W WO 2012064083 A2 WO2012064083 A2 WO 2012064083A2
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WO
WIPO (PCT)
Prior art keywords
block
unit
chroma
edge
deblocking filter
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PCT/KR2011/008463
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English (en)
Korean (ko)
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WO2012064083A3 (fr
Inventor
최영희
김정선
박승욱
성재원
전병문
임재현
전용준
박준영
Original Assignee
엘지전자 주식회사
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Publication of WO2012064083A2 publication Critical patent/WO2012064083A2/fr
Publication of WO2012064083A3 publication Critical patent/WO2012064083A3/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/85—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using pre-processing or post-processing specially adapted for video compression
    • H04N19/86—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using pre-processing or post-processing specially adapted for video compression involving reduction of coding artifacts, e.g. of blockiness

Definitions

  • the present invention relates to image information compression technology, and more particularly, to a method of applying a deblocking filter to a chroma component in an in-loop.
  • High-efficiency image compression technology can be used to effectively transmit, store, and reproduce high-resolution and high-quality video information.
  • inter prediction and intra prediction may be used.
  • the inter prediction method predicts pixel values of a current picture by referring to information of another picture, and the intra prediction method predicts pixel values by using correlations between pixels within the same picture.
  • various methods are used to compensate for coding errors in an encoding process and to perform efficient image reconstruction.
  • the blocking artifacts as the transformation and prediction are performed on a block basis, and in the quantization process
  • a method of effectively compensating for a coding error occurring or the like has been considered.
  • One object of the present invention is to provide a method and apparatus for generating a reconstructed image closer to the original image.
  • Another technical problem of the present invention is to provide a method and apparatus for effectively removing undocking artifacts of a reconstructed image.
  • Another technical problem of the present invention is to provide a method and apparatus for effectively removing a blocking effect on a chroma component of a reconstructed image.
  • Another technical problem of the present invention is to provide a method and apparatus for effectively applying deblocking filtering on chroma components of a restored image in consideration of a sample.
  • Another object of the present invention so that the de-blocking filtering on a chroma component of the reconstructed image can be effectively performed, and to provide a method and apparatus to set the criteria for the chroma component of the deblocking filtering.
  • An embodiment of the present invention is a deblocking filtering method comprising: setting a bS (boundary, strength) for a block edge in a unit sample block composed of reconstructed chroma components; Determining a deblocking filtering for the and applying a deblocking filter to the chroma component in accordance with the deblocking filtering determination, wherein the unit The size of the sample block may be set according to the sampling format of the chroma sample.
  • the size of the unit sample block composed of chroma components may be set to 4 ⁇ 4.
  • the size of the unit sample block composed of chroma components may be set to 4x8 or 8x4.
  • the size of the unit sample block composed of chroma components may be set to 8x8.
  • the bS in the bS setting step, the bS may be set to a value greater than 1 when the block edge is an edge of a transform unit and the unit sample block includes a transform coefficient greater than zero.
  • the deblocking filtering determination step it may be determined that the deblocking filter is applied when the bS is greater than one.
  • left and right samples of the block edge may be encoded in an inter mode.
  • Another embodiment of the present invention is a deblocking filtering device comprising: a bS setting unit for setting a bSCboundary strength for a block edge in a unit sample block composed of reconstructed chroma components; A filtering deciding unit determining deblocking filtering for the filtering unit and a filtering applying unit applying the deblocking filter to the chroma component according to the deblocking filtering determination
  • the size of the unit sample block may be set according to a sampling format of the chroma sample.
  • the size of the unit sample block composed of chroma components may be 4 ⁇ 4.
  • the size of the unit sample block composed of chroma components may be 4x8 or 8x4.
  • the size of the unit sample block composed of chroma components may be 8x8.
  • the bS setting unit selects bS when the block edge is a transform unit edge and the unit sample block includes a transform coefficient greater than zero.
  • the filtering determiner may determine to apply the deblocking filter when the bS is greater than 1.
  • left and right samples of the block edge may be encoded in an inter mode.
  • a reconstruction image closer to the original image can be generated during the encoding / decoding process.
  • blocking artifacts (art if acts) of the reconstructed image can be effectively removed.
  • blocking artifacts for the chroma component of the reconstructed image can be effectively removed.
  • the effect of the deblocking filtering can be enhanced.
  • FIG. 1 is a block diagram schematically illustrating an image encoding apparatus (encoder) according to an embodiment of the present invention.
  • FIG. 2 is a block diagram schematically illustrating an image decoder according to an embodiment of the present invention.
  • FIG. 3 is a diagram schematically illustrating three formats for sampling a luma signal and a chroma signal.
  • FIG. 4 is a diagram schematically illustrating an example of a boundary of a transform unit or a boundary of a prediction unit derived as described above.
  • 5 schematically shows a sample block to which a multiblocking filter is applied.
  • 6 is a diagram comparing the original image on the left side with the reconstructed image on the right side.
  • FIG. 7 is a diagram comparing the original image on the left side with the luma reconstruction image on the right side.
  • 8 is a diagram comparing an original image on the left side with a chroma (U) reconstructed image on the right side.
  • FIG. 9 is a diagram comparing the original image on the left side with the chroma (V) reconstructed image on the right side.
  • FIG. 10 illustrates a deblocking filter for chroma components in a system to which the present invention is applied. It is a figure explaining a sample block to apply.
  • FIG. 11 is a flowchart schematically illustrating a method of applying a deblocking filter to chroma components in a system to which the present invention is applied.
  • FIG. 12 is a view schematically showing the effect of applying a deblocking filter to chroma in accordance with the present invention.
  • each of the components in the drawings described in the present invention are shown independently for the convenience of description of the different characteristic functions in the image encoding / decoding apparatus, each component is implemented in separate hardware or separate software ⁇ 1 does not mean.
  • two or more of each It may be combined to form one configuration, or one configuration may be divided into a plurality of configurations.
  • Embodiments in which each configuration is integrated and / or separated are also included in the scope of the present invention without departing from the spirit of the present invention.
  • the image encoding apparatus 100 may include a picture splitter 105, a predictor 110, a transformer 115, a quantizer 120, a reordering unit 125, and an entropy encoding unit 130. And an inverse quantization unit 135, an inverse transform unit 140, a filter unit 145, and a memory 150.
  • the picture division unit 105 may divide the input picture into at least one processing unit.
  • the processing unit may be a prediction unit (hereinafter referred to as a PU), a transform unit (hereinafter referred to as a "TIT”), or a coding unit (hereinafter referred to as "CIT"). )
  • the predictor 110 includes an inter-screen predictor that performs inter-prediction and an intra-screen predictor that performs intra-prediction, as described below.
  • the prediction unit 110 generates a prediction block by performing prediction on the processing unit of the picture in the picture division unit 105.
  • the processing unit of the picture in the prediction unit 110 may be a CU, a TU, or a PU.
  • the content eg, prediction mode, etc.
  • the processing unit in which the prediction is performed may differ from the processing unit in which the prediction method and the specific content are determined.
  • the prediction method and the prediction mode may be determined in units of PUs, and the prediction may be performed in units of TUs.
  • a prediction block may be generated by performing prediction based on information of at least one picture of a previous picture and / or a subsequent picture of the current picture.
  • a prediction block may be generated by performing prediction based on pixel information in a current picture through intra prediction.
  • a reference picture may be selected for a PU and a reference block having the same size as that of the PU may be selected in integer pixel sample units. Subsequently, the residual signal with the current PU is minimized, and the prediction block generates a minimum motion vector size.
  • a skip mode a merge mode, an MVP (Motion Vector Predtiction), and the like can be used.
  • the prediction block may be generated in sub-integer sample units, such as 1/2 pixel sample unit and 1/4 pixel sample unit.
  • the motion vector may also be expressed in units of integer pixels or less.
  • the luminance pixel may be expressed in units of 1/4 pixels
  • the chrominance pixel may be expressed in units of 1/8 pixels.
  • Information such as an index, a motion vector predictor, and a residual signal of a reference picture selected through inter prediction is entropy encoded and transmitted to a decoder.
  • the prediction mode is determined in units of PUs, The prediction may be performed in units. In addition, a prediction mode may be determined in units of PUs, and intra prediction may be performed in units of TUs.
  • a prediction mode may have 33 directional prediction modes and at least two non-directional modes.
  • the non-directional mode may include a DC prediction mode and a planner mode (Planar mode).
  • a prediction block may be generated after applying an adaptive intra smoothing (AIS) filter to a reference pixel according to a prediction mode.
  • AIS adaptive intra smoothing
  • the type of AIS filter applied to the reference pixel may be different.
  • the prediction may be performed by interpolating the reference pixel in units of 1/8 pixels according to the prediction mode of the current block.
  • the PU may have various sizes / shapes, for example, in case of inter prediction, the PU may have a size of 2NX2N, 2NXN, NX2N, or NXN. In the case of intra prediction, the PU may have a size of 2NX2N or NXN (where N is an integer). At this time, the NXN size PU may be configured to apply only in a specific case. For example, the NxN PU may be used only for the minimum size coding unit, or only for intra prediction. In addition to the pu of the size described above,
  • a PU having a size of NXmN, mNXN, 2NXmN, or mNx2N (m ⁇ l) may be further defined and used.
  • the residual value (the residual block or the residual signal) between the generated prediction block and the original block is input to the converter 115.
  • the prediction used for the prediction Mode information, motion vector information, and the like are encoded by the entropy encoder 130 along with the residual values and transmitted to the decoder.
  • the transform unit 115 performs transform on the residual blot in transform units and generates transform coefficients.
  • the transform unit in the transform unit 115 may be a TU and may have a quad tree structure. In this case, the size of the transform unit may be determined within a range of a predetermined maximum and minimum size.
  • the transform unit 115 may convert the residual block using a discrete cosine transform (DCT) and / or a discrete sine transform (DST).
  • DCT discrete cosine transform
  • DST discrete sine transform
  • the quantization unit 120 may generate quantization coefficients by quantizing the residual values transformed by the transformation unit 115.
  • the value calculated by the quantization unit 120 is provided to the inverse quantization unit 135 and the reordering unit 125.
  • the reordering unit 125 rearranges the quantization coefficients provided from the quantization unit 120. By reordering the quantization coefficients, the efficiency of the encoding in the entropy encoder 130 may be increased.
  • the reordering unit 125 may rearrange the quantization coefficients in the form of a two-dimensional block into a one-dimensional vector form through a coefficient scanning method.
  • the reordering unit 125 may increase the entropy coding efficiency of the entropy encoder 130 by changing the order of coefficient scanning based on probabilistic statistics of coefficients transmitted from the quantizer.
  • the entropy encoder 130 may perform entropy encoding on the quantization coefficients redefined by the reordering unit 125.
  • Entropy coding includes, for example, Exponential Golomb and Context-Adaptive Variable Length. Coding (Coding), CABAC (Corit ext-Adaptive Binary Arithmetic Coding) can be used.
  • the entropy encoder 130 may include quantization coefficient information, block type information, prediction mode information, partition unit information, PU information, transmission unit information, motion vector information, etc. of a CU received from the reordering unit 125 and the prediction unit 110.
  • Various information such as reference picture information, interpolation information of a block, and filtering information can be encoded.
  • the entropy encoder 130 may apply a constant change to a parameter set or syntax to be transmitted.
  • the inverse quantization unit 135 is the value quantized by the quantization unit 120, inverse quantization, and inverse transform unit 140 inverse transform the dequantized value from the inverse quantization section 135.
  • the residual values generated by the inverse quantizer 135 and the inverse transformer 140 may be combined with the predicted block predicted by the predictor 110 to generate a reconstructed block.
  • the filter unit 145 is a deblocking filter, ALF (Adaptive Loop Filter), SAO (Sample)
  • Adaptive Offset can be applied to the reconstructed picture.
  • the deblocking filter may remove block distortion generated at the boundary between blocks in the reconstructed picture.
  • the adaptive loop filter may perform filtering based on a value obtained by comparing the reconstructed image with the original image after the block is filtered through the deblocking filter.
  • ALF may be performed only when high efficiency is applied.
  • SA0 restores the offset difference from the original image on a pixel-by-pixel basis for the residual block to which the deblocking filter is applied, and is applied in the form of a band offset and an edge offset. Meanwhile, the filter unit 145 may not apply filtering to the reconstructed block used for inter prediction.
  • the memory 150 may store the reconstructed block or the picture calculated by the filter unit 145.
  • the reconstructed block or picture stored in the memory 150 may be provided to the predictor 110 that performs inter prediction.
  • 2 is a block diagram schematically illustrating an image decoder according to an embodiment of the present invention.
  • the image decoder 200 includes an entropy decoder 210, a reordering unit 215, an inverse quantizer 220, an inverse transform unit 225, a predictor 230, and a filter unit 235.
  • Memory 240 may be included.
  • the input bit stream may be decoded according to a procedure in which image information is processed by the image encoder.
  • VLC variable length coding
  • 'VLC' variable length coding
  • CABAC CABAC
  • Information for generating the prediction block among the information decoded by the entropy decoder 210 is provided to the predictor 230, and entropy decoding is performed by the entropy decoder.
  • the performed residual value may be input to the reordering unit 215.
  • the reordering unit 215 may reorder the entropy-decoded bit stream by the entropy decoding unit 210 based on the reordering method in the image encoder.
  • the reordering unit 215 may reorder the coefficients expressed in the form of a one-dimensional vector back to the coefficients in the form of a two-dimensional block.
  • the reordering unit 215 may receive the information related to the coefficient scanning performed by the encoder and perform the rearrangement by performing a reverse scanning method based on the scanning order performed by the corresponding encoder.
  • the inverse quantization unit 220 may perform inverse quantization based on the quantization parameter provided by the encoder and the coefficient values of the rearranged block.
  • the inverse transformer 225 may perform inverse DCT and / or inverse DST on the DCT and DST performed by the encoder of the encoder for the quantization result performed by the image encoder.
  • the inverse transform may be performed based on a transmission unit determined by the encoder or a division unit of an image.
  • the DCT and / or DST may be selectively performed according to a plurality of pieces of information, such as a prediction method, a size and a prediction direction of the current block, and the inverse transformer 225 of the decoder is performed by the encoder of the encoder.
  • Inverse transformation may be performed based on the transformation information.
  • the prediction unit 230 may generate the prediction block based on the prediction block specific generation related information provided by the entropy decoder 210 and previously decoded blocks and / or picture information provided by the memory 240.
  • the reconstruction block may be generated using the prediction block generated by the predictor 230 and the residual block provided by the inverse transform unit 225. have.
  • intra prediction mode intra prediction mode
  • intra prediction may be performed to generate a prediction block based on pixel information in the current picture.
  • the inter screen for the current PU based on information included in at least one of a previous picture or a subsequent picture of the current picture. You can make predictions.
  • motion information required for inter-prediction prediction of the current PU provided by the image encoder for example, a motion vector, a reference picture index, and the like, may be derived by checking a skip flag, a merge flag, and the like received from the encoder.
  • the reconstructed blot and / or picture may be provided to the filter unit 235.
  • the filter unit 235 applies deblocking filtering, SACXSample Adaptive Offset, and / or adaptive loop filtering to the reconstructed blocks and / or pictures.
  • the memory 240 may store the reconstructed picture or block to use as the reference picture or the reference block, and may provide the reconstructed picture to the output unit.
  • a color image e.g., a color video such as a color TV
  • R Red
  • Green Green
  • B Can be represented by the [Y, Cb, Cr] signal equivalent to the [R, G, B] signal expressed in Blue
  • sampling of the X, Cb, and Cr signals is performed in one of three formats.
  • 3 is a diagram schematically illustrating three formats for sampling a luma signal and a chroma signal.
  • the three formats are divided into 4: 4: 4, 4: 2: 2, and 4: 2: 0 according to sampling rates between Y, Cb, and Cr based on 2x2 blocking of the toma signal.
  • 3A schematically illustrates sampling the luma signal Y and the chroma signals Cb and Cr in a 4: 4: 4 format.
  • the -roma component of the original image can be preserved as it is. Therefore, it is used for images of medical care, movies, and the like.
  • 3B schematically illustrates sampling the luma signal Y and the chroma signals Cb and Cr in a 4: 2: 2 format.
  • the 4: 2: 2 format is used to reproduce high quality color images.
  • the chroma component has the same resolution as the luma component in the horizontal direction, but has a resolution equivalent to 1/2 of the luma component in the vertical direction.
  • the number of chroma pixels in the horizontal direction is 1/2 of the 4: 4: 4 format when compared to the 4: 4: 4 format. .
  • 3C schematically illustrates sampling the luma signal Y and the chroma signals Cb and Cr in a 4: 2: 0 format.
  • 4: 2: 0 is the sampling between X, Cb and Cr signals Rather than a ratio, it is a sampling format that is distinguished from 4: 4: 4 format and 4: 2: 2 format.
  • the 4: 2: 0 format is used for video such as digital TV, digital versatile disk (DVD), and video conferencing.
  • the chroma component in the 4: 2: 0 format has a data amount and resolution corresponding to 1/2 of the luma component when compared to the 4: 4: 4 format.
  • the number of chroma pixels in the vertical direction is 1/2 of the 4: 2: 2 format when compared to the 4: 2: 2 format.
  • an in-loof filter is applied to the reconstructed image to compensate for a difference between the original image and the reconstructed image due to an error occurring in a compression encoding process such as quantization.
  • in-loop filtering may be performed in the filter unit of the encoder and the decoder, and at least one of a deblocking filter, a SAOCSample Adaptive Offset (ALF), and an ALF (Adaptive Loop Filter) is applied.
  • the deblocking filter process can be applied to all prediction unit edges and transform unit edges in the picture, as described above. However, it may not be applied to the edge at the border of the picture.
  • the decoder may not apply the deblocking filter to an edge designated as inactive by an indicator such as disable_deblocking_filter_idc or a slice boundary indicated that the deblocking filter is not applied by information such as loop_fiUer_slice_flag.
  • a minimum size of a block to which the deblocking filter is applied may be set.
  • the block of size may be set to the minimum size to which the deblocking filter is applied, and in the case of a block smaller than the 8x8 size, the deblocking filter may be applied only when the edge is located on the 8x8 sample grid.
  • the chroma component of this edge may also be filtered by the chroma filter.
  • the encoder / decoder may determine an area to which the deblocking filter is to be applied before determining bS. Specifically, the encoder / decoder is based on the information of the current block (position, width, height, depth, size, prediction partition width (PartMODE, etc.), and the boundary and prediction unit of the transform unit to which the deblocking filter is to be applied in the current block. The boundary of can be determined.
  • the decision unit boundary may be determined for the blocks in the coding unit.
  • the boundary of the transform unit may be derived for square blocks or for non-square (rectangular) blocks.
  • information indicating the presence of the horizontal block edge to which the deblocking block filter is to be applied and the existence of the vertical block edge to each block which derived the boundary of the transform unit (eg, a horizontal block edge exists) Flag indicating whether or not there is a flag indicating whether a vertical block edge exists.
  • the blocks in the sub-code unit from which the boundary of the transform unit is derived may be a transform unit.
  • the 'deblocking filter applied to the block edge' here means that the deblocking filter is applied to a predetermined sample on the left and right bordering the block edge.
  • the 'deblocking filter for the block edge' means a deblocking filter applied to left and right predetermined samples on the block edge boundary.
  • the edge of the prediction unit to which the deblocking filter is to be applied is determined according to the prediction partition mode (PartMODE). For example, when the coding unit is split into 2NxN or NxN prediction units, it is determined whether or not to apply deblocking filtering to the horizontal edges inside the coding unit, and black is derived, and the coding unit is split into Nx2N or NxN prediction units. If there is, it can be determined or derived whether to apply the deblocking filtering with respect to the vertical edge of the internal encoding unit.
  • N is an integer of 1 or more, and N or 2N represents the number of pixels.
  • the deblocking filter is applied to the horizontal edge inside the coding unit according to the shape of the prediction unit.
  • Deblocking filter on the vertical edge inside the coding unit according to the shape of the prediction unit when the coding unit is nLx2N L is an integer of 1 or more, nL represents the number of pixels. Determining whether to apply black may lead to 4 is a diagram schematically illustrating an example of a boundary of a transform unit or a boundary of a prediction unit derived as described above.
  • FIG. 4A schematically illustrates an example of a square block as an example of a luma block 410.
  • the minimum unit to which the deblocking filter is applied to the luma component is an 8 ⁇ 8 block
  • the boundary of the block can be derived.
  • the deblocking filter is applied to an 8x8 block
  • a boundary with the block 445 may be derived.
  • the sample block 440 to which the filtering, which is the object of the deblocking filter, is applied may be set at the boundary between the two blocks 435 and 445.
  • FIG. 4B schematically illustrates an example of a grass block and a square block for the chroma block 450.
  • the boundary of the block is determined in consideration of the vertical edge 460 and the horizontal edge 470 as shown. Can be induced.
  • the boundary of the block 485 may be derived. Accordingly, the sample block 480 to which the filtering, which is the object of the deblocking filter, is applied, may be set at the boundary between the two blocks 475 and 485.
  • FIG. 5 schematically illustrates a sample block to which the deblocking filter is applied, and more specifically illustrates the sample block 440 of FIG. 4A and the sample block 480 of FIG. 4B.
  • the samples (p) belonging to the left region 445 and 475 and the samples q of the right region 435 and 485 are each 4x8 relative to the center boundary. It is arranged in the form.
  • the block 510 on the left is called block P and the block 520 on the right is called block Q based on the boundary to which the deblocking filter is applied.
  • a sample belonging to is called q.
  • an encoder / decoder determines a boundary strength (bS) for an inter-block boundary or an edge of a block.
  • Bs represents the filtering strength for the horizontal edge and the vertical edge.
  • an 'edge' of a block may mean 'boundary' between blocks.
  • the encoder / decoder decides whether to filter. Whether to apply filtering may be determined in units of blocks. For example, referring to FIG. 5, when bS is greater than 0, filtering based on the degree of linearity between a predetermined sample line in the block P and a predetermined sample line in the block Q is shown between the boundary 515.
  • the encoder / decoder selects a filter to apply to the edge 515 in the sample block 500.
  • the filter can be divided into a strong filter and a weak filter.
  • the filter may be selected according to the bS value.
  • the filter may also be selected depending on whether it is a deblocking filter for luma or a deblocking filter for chroma. For example, for chroma, only one predetermined filter may be applied instead of the strong filter and the weak filter.
  • the encoder / decoder may apply a filter as defined above to the edge 515 in the sample block 500.
  • the deblocking filter is applied to a grid of 8x8 blocks that are boundaries of the transform unit or the prediction unit. Also, the deblocking filter has (1) block P and Q in both inter modes, (2) block P and Q have no non-zero transform coefficients, and (3) block P and block Q have the same reference picture. If the motion vector is not similar, it can be applied.
  • the similarity of the motion vectors means that the difference between the motion vectors of the block P and the block Q is smaller than the predetermined difference.
  • the deblocking filter may also be applied to chroma components.
  • the application unit of the deblocking filter may be set to be the same as the luma component.
  • the deblocking filter for the chroma component may also be applied to a grid of 8x8 blocks that are boundaries of the prediction unit or transform unit.
  • the deblocking filter may be further limited.
  • the deblocking filter is further applied.
  • the edge of the sample block is the edge of the prediction unit, and the block P and the block Q are both in planner mode, the deblocking filter may not be applied.
  • 6 is a diagram comparing the original image on the left side with the reconstructed image on the right side. The reconstructed image on the right is an image to which the deblocking filter has not yet been applied.
  • blocking artifacts are prominent in the circled portion.
  • a reconstructed image is generated using only the luma component ⁇ component, and the reconstructed image using only the chroma components U and V, respectively.
  • FIG. 7 is a diagram comparing the original image on the left side with the luma reconstruction image on the right side.
  • the luma reconstructed image is an image reconstructed using only a luma signal and no deblocking filter is applied.
  • the luma reconstructed image of FIG. 7 may confirm that blocking artifacts are not prominent.
  • FIG. 8 is a diagram comparing an original image on the left side with a chroma (U) reconstructed image on the right side.
  • the chroma (U) reconstructed picture is a picture reconstructed only with a U component signal, and the deblocking filter is not applied.
  • the chroma (V) reconstructed image is an image reconstructed using only the signal of the V component, and the deblocking filter is not applied.
  • the omission of the deblocking filter for the chroma component, or as a secondary process according to the deblocking filter for the luma component, does not simply apply the deblocking filter for the chroma component, and the fire due to the characteristics of the chroma component and the chroma component.
  • it is necessary to apply a deblocking filter for the chroma components Specifically, the chroma component needs to be adjusted in consideration of the sampling mode of the chroma component instead of simply setting the unit of the sample block to which the deblocking filter is applied as the luma component.
  • the conditions for restricting the application of the deblocking filter to the chroma component are applied only when the blocks on both sides of the boundary are both in the intra mode or the application is excluded in the planner mode. Need to be alleviated.
  • the sampling format used in the image processing technique is 4: 4: 4 format, 4: 2: 2 format or 4: 2: 0 format. According to this sampling format, the size ratio between the luma component block and the chroma component block can be determined.
  • FIG. 10 is a diagram schematically illustrating a sample block applying a deblocking filter to chroma components in a system to which the present invention is applied.
  • a block P 1010 and a block Q 1015 form an 8 ⁇ 8 sample block 1000 with a block edge 1005 interposed therebetween.
  • a block P 1030 and a block Q 1035 form a 4 ⁇ 8 sample block 1025 with a block edge 1025 interposed therebetween.
  • the block edge 1045 is interposed, and blocks P L050 and Q 1055) are 8x4 samples.
  • Configure block 1040 a block POL070 and a block CK1075 constitute a sample block 1060 with a block edge 1065 interposed therebetween.
  • the deblocking filter may be applied to the chroma component in units of 8 ⁇ 8 sample blocks 1000.
  • sampling format when the sampling format is 4: 2: 2 format, it is highly likely that a prediction unit and / or a transform unit are set in 4x8 or 8x4 block units. Therefore, when the sampling format is 4: 2: 2 format, as shown in FIG. 10 (B) or FIG. 10 (C), the 4x8 size sample block 1020 or the black is chroma in 8x4 size sample block 1040 units.
  • the deblocking filter can be applied to the component.
  • the deblocking filter may be applied to the chroma component in units of a 4 ⁇ 4 sample block 1060.
  • the deblocking filter to the chroma component not only when the blocks on both sides of the block edge, for example, the blocks p and the block Q are intra modes, but also in other cases.
  • the bS of the block edge may be set according to the mode of the block P and the block Q, and the bS of the block edge is the same but in more cases, the deblocking filter is It can also be applied.
  • the deblocking filter may be applied in more cases.
  • the bS determined for the same block edge may be applied to the luma component and the chroma component together.
  • bS of a luma component and bS of a chroma component can also be set separately with respect to the said block edge.
  • FIG. 11 is a flowchart schematically illustrating a method of applying a deblocking filter to chroma components in a system to which the present invention is applied.
  • the encoder / decoder determines a boundary strength (bS) for a block edge (1110). .
  • the candidate / decoder determines the bS of the block edge for each sample block in consideration of the filter direction, that is, the direction of the blocking edge.
  • bS may be determined using the direction of the block edge and the position of the block as parameters.
  • the block edge for example, the boundaries 1005, 1025, 1045, and 1065 between blocks P and Q in FIG. 10 may be vertical edges or horizontal edges.
  • the boundary (block edge) between block P and block Q is an encoding U edge, and when referring to FIG. 10 described above, block P or block Q is encoded in intra prediction mode. If so, the bS value of the block edge can be set to 4. If the block edge is not the edge of the coding unit, but the block P or the block Q is encoded in the intra mode, Bs of the block edge can be set to three.
  • bS can be set to 2.
  • bS may be set to zero.
  • bS for the luma component and bS for the chroma component are separately set, deblocking filtering is performed for the luma component based on the bS for the luma component, and based on the bS for the chroma component. It is also possible to perform deblocking filtering on the chroma component.
  • the block edge ( If 515 is the edge of the coding unit, bS may be set to 4, and if the block edge 515 is not the edge of the coding unit, bS may be set to 3.
  • block edge 515 is the edge of the transform unit, and block P 510 or block
  • bS may be set to two.
  • the vertical component or the horizontal component has a predetermined difference value, eg, 4 pixels, in the motion vector of the two prediction units.
  • BS may be set to 1 when there is a greater difference.
  • bS for the block edge of the luma component may be set to zero.
  • the boundary (block edge) between the block P and the block Q is the encoding unit edge and the block P or the block Q is encoded in the intra prediction mode, referring to FIG.
  • the bS value of the block edge for the chroma (Cb, Cr) component can be set to 4.
  • Bs of the block edge for the chroma (Cb, Cr) component can be set to three.
  • bS for chroma can be set to two.
  • bS of the block edge for the Cb block can be set to two.
  • the Cr block if the block edge is the edge of the transform unit, and the block P or the block Q includes a non-zero transform coefficient for Cr, bS of the block edge for Cr can be set to two.
  • bS for the chroma component may be set to zero.
  • the bS value for the block edge can be set according to each case of FIG. 10.
  • the sampling format when the sampling format is 4: 4: 4 format, as shown in FIG. 10 (A), the block edge 1005 is determined in units of 8x8 chroma sample blocks 1000.
  • bS can be set.
  • the sampling format is 4: 2: 2 format
  • bS for the block edge 1025 is set in units of 4x8 size chroma sample blocks 1020 as shown in FIG. 10 (B), or as shown in FIG. 10 (C).
  • the sampling format is the 4: 2: 0 format
  • bS for the block edge 1065 may be set in units of 4x4 chroma sample blocks 1060 as shown in FIG. 10 (D).
  • the encoder / decoder determines filtering for the chroma component (S1120).
  • the encoder / decoder may determine the filtering by distinguishing the Cr component from the Cb component. For example, an index of color cldx may allow a color index value of 1 to indicate a chroma sample for Cb and a color index value 2 to indicate a chroma sample for Cr.
  • the requirements for applying the deblocking filter to the chroma component are alleviated so that the deblocking filter for the chroma component may be applied even when both the block P and the block Q having the block edge are encoded in the inter mode. can do. For example, if the encoder / decoder has bS greater than 1, the deblocking filter can be applied to the chroma component.
  • block edge is the boundary of the coding unit
  • bS of the block edge is set to 4
  • block edge is not the boundary of the coding unit
  • bS of the block edge is set.
  • Block edge is the edge of the transform unit, and block P or block Q If included, bS can be set to 2. If the mode does not correspond to the above-described case, bS may be set to 0.
  • a bS value larger than 1 may be set if the block P or the block Q has a non-zero transform coefficient. Therefore, when the deblocking filter is set to be applied when the bS value is greater than 1, the deblocking filter may be applied to the chroma component even when both the block P and the block Q are not in the intra mode.
  • a plurality of rows of samples in block p and block Q may be used to determine the application of the deblocking filter. Equation 1 is an example for determining the deblocking filtering, and is an example of using samples adjacent to the block edges of the second and third columns in the block P and the block Q.
  • the deblocking filter may be applied to the block edge for the chroma.
  • the determination of this deblocking filtering can be determined for the horizontal edge and the vertical edge, respectively. Therefore, when the bS value for the block edge of the Cb block is greater than 1 and the d value is less than the T threshold for the horizontal edge, the deblocking filter may be applied to the block edge of the Cb block. Also for the vertical edge, for the block edge of Cb blot If the bS value is larger than 1 and the d value is smaller than the T threshold , the deblocking filter may be applied to the block edge of the Cb block.
  • the deblocking filter is to be applied to the block edge of the Cr block.
  • the deblocking filter may be applied to the block edge of the Cr block.
  • the encoder / decoder applies the deblocking filter to the target block edge (S1130).
  • a deblocking filter is applied to the block edge of the chroma component in the coding unit.
  • the size of the coding unit to which the deblocking filter is applied may be set to a predetermined size.
  • the deblocking filter may be applied in units of 8 ⁇ 8 size.
  • the deblocking filter for chroma when the sampling format is 4: 4: 4 format, the deblocking filter for chroma may be applied in units of 8x8 size sample blocks, and the sampling format is 4: 4: 4 format. In this case, the deblocking filter for chroma may be applied in units of 8x4 or 4x8 sample blocks. In addition, when the sampling format is 4: 2: 0 format, a deblocking filter for chroma may be applied in units of 4 ⁇ 4 sample blocks.
  • X is determined based on the position of the chroma block in the coding unit with respect to the horizontal block edge.
  • the deblocking filter may be applied by checking whether the bS and the deblocking filter are applied every 4 pixels in the direction.
  • the chroma position of a coding unit For example, the chroma position of a coding unit, the position of a 4x4 chroma sample block, information about the existence of a horizontal block edge (for example, a flag indicating whether there is a vertical block edge), a value of cldx indicating whether Cr or Cb, a vertical block edge
  • the deblocking filtering may be performed based on whether or not the deblocking filter is applied to the horizontal block edge for every 4 ⁇ 4 block (the position of every 4 pixels in the coding unit) based on the bS value.
  • the deblocking filter may be applied to the vertical block edge by checking whether bS and the deblocking filter are applied in every 4 pixels in the y direction. For example, as in the case of the horizontal block edge, also in the case of the vertical block edge, information about the chroma position of the coding unit, the position of the 4x4 chroma sample block, and the existence of the horizontal block edge (for example, a flag indicating whether there is a horizontal block edge). Based on the value of cldx indicating Cr or Cb, the bS value for the horizontal block edge, etc., whether or not the deblocking filter is applied to the horizontal blocking edge for every 4x4 block (the position of every 4 pixels in the coding unit). Thus, deblocking filtering can be performed.
  • the deblocking filtering may be performed in a similar manner to the above-described method for the 4x4 block.
  • the deblocking filtering is applied in the same manner as the aforementioned 4x4 block, but the parameters for applying the deblocking filtering are 4x8 blocks. Determined in units. Therefore, deblocking filtering may be performed based on whether filtering is applied and bS for each 4x8 block in the blowing unit. That is, the deblocking filter may be applied according to whether or not filtering is applied every 8 pixels for the vertical block edge and every 4 pixels for the horizontal block edge.
  • deblocking filtering may be performed based on whether filtering is applied and bS for each 8x4 block in the coding unit. That is, the deblocking filter may be applied according to whether or not filtering is applied every 4 pixels for the vertical block edge and every 8 pixels for the male block edge.
  • deblocking filtering When the deblocking filter is applied in units of 8 ⁇ 8 block-specific blocks, the deblocking filtering is applied in the same manner as described above, but the parameters for applying the deblocking filtering are determined in units of 8 ⁇ 8 blocks. Accordingly, deblocking filtering may be performed based on whether filtering is applied and bS for each 8x8 blocks in the bursting unit. That is, the deblocking filter may be applied to the vertical block edge and the horizontal block edge according to whether filtering is applied every 8 pixels, bS, and the like. In this case, the deblocking filter may be set to modify a predetermined sample by using a predetermined number of samples. For example, referring to the sample blot of FIG.
  • the type of deblocking filter for the chroma component may be classified into a strong filter and a weak filter based on the bS value. Strong filters can apply weaker filters and different coefficients to make filtering more effective.
  • the deblocking filter for chroma components may not distinguish between a strong filter and a weak filter. That is, when deblocking filtering is applied to the chroma component, only one predetermined filter may be applied. For example, as described above, if bS is greater than 1, a predetermined correction value ⁇ may be used to modify the values of two pixels pO and pi at the boundary. For example, the correction may be performed by adding or subtracting the correction value ⁇ to the original pixel value. In this case, the predetermined correction value ⁇ may be limited within a certain range.
  • Equation 2 shows an example of generating the modified value ⁇ and the modified pO ′ and q0 ′.
  • ⁇ is a correction value generated by using two samples pO, pi, q0, and ql for each line in block P and block Q. Yale of corrections
  • ⁇ may have various values by various methods based on pixel state information, sampling format, and the like.
  • the correction value ⁇ given to pixel ⁇ and pixel qO can be clipped between a predetermined range ( ⁇ t c , to).
  • t c is a value that defines a range of pixel values that can be modified by the deblocking filter.
  • FIG. 12 is a view schematically showing the effect of the case in accordance with the present invention, applying the deblocking filter to the chroma.
  • the image on the left side applies a deblocking filter for chroma on the basis of 8x8 blocks only when at least one of the left and right blocks of the sample edge is encoded in the intra mode according to a conventional method.
  • the image on the right side of FIG. 12 applies a deblocking filter when bS is larger than 1 even when both the left and right blots of the sample edge are encoded in the inter mode, and applies the deblocking filter as a 4x4 block. It is.

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Abstract

La présente invention porte sur un procédé de filtrage de débouchage et sur un appareil de filtrage de débouchage. Le procédé de filtrage de débouchage selon la présente invention comprend les étapes suivantes, consistant à : établir une force limite (bS) pour un bord de bloc dans un bloc échantillon unitaire constitué par des composants chromatiques récupérés ; déterminer un filtrage de débouchage pour ledit bord de bloc sur la base de la force limite ; et appliquer un filtre de débouchage auxdits composants chromatiques en fonction de la détermination de filtrage de débouchage. Selon la présente invention, la taille dudit bloc échantillon unitaire peut être établie en fonction d'un format d'échantillonnage d'un échantillon chromatique.
PCT/KR2011/008463 2010-11-08 2011-11-08 Procédé et appareil de filtrage de débouchage WO2012064083A2 (fr)

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WO2020224581A1 (fr) * 2019-05-05 2020-11-12 Beijing Bytedance Network Technology Co., Ltd. Harmonisation de dégroupage de chrominance pour codage vidéo

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