WO2019194501A1 - Procédé de codage d'images sur la base d'un raffinement de vecteurs de mouvement et appareil associé - Google Patents

Procédé de codage d'images sur la base d'un raffinement de vecteurs de mouvement et appareil associé Download PDF

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WO2019194501A1
WO2019194501A1 PCT/KR2019/003809 KR2019003809W WO2019194501A1 WO 2019194501 A1 WO2019194501 A1 WO 2019194501A1 KR 2019003809 W KR2019003809 W KR 2019003809W WO 2019194501 A1 WO2019194501 A1 WO 2019194501A1
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motion vector
derived
amvr
prediction
unit
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Korean (ko)
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이재호
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LG Electronics Inc
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LG Electronics Inc
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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
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/102—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or selection affected or controlled by the adaptive coding
    • H04N19/103—Selection of coding mode or of prediction mode
    • H04N19/109—Selection of coding mode or of prediction mode among a plurality of temporal predictive coding modes
    • 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
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/102—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or selection affected or controlled by the adaptive coding
    • H04N19/132—Sampling, masking or truncation of coding units, e.g. adaptive resampling, frame skipping, frame interpolation or high-frequency transform coefficient masking
    • 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
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/169—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding
    • H04N19/17—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object
    • H04N19/176—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object the region being a block, e.g. a macroblock
    • 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
    • H04N19/50—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding
    • H04N19/503—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding involving temporal prediction
    • H04N19/51—Motion estimation or motion compensation
    • H04N19/53—Multi-resolution motion estimation; Hierarchical motion estimation
    • 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
    • H04N19/50—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding
    • H04N19/503—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding involving temporal prediction
    • H04N19/51—Motion estimation or motion compensation
    • H04N19/56—Motion estimation with initialisation of the vector search, e.g. estimating a good candidate to initiate a search
    • 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
    • H04N19/70—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals characterised by syntax aspects related to video coding, e.g. related to compression standards

Definitions

  • the present invention relates to an image coding technique, and more particularly, to an image coding method and apparatus based on motion vector refinement in an image coding system.
  • the demand for high resolution and high quality images such as high definition (HD) images and ultra high definition (UHD) images is increasing in various fields.
  • the higher the resolution and the higher quality of the image data the more information or bit rate is transmitted than the existing image data. Therefore, the image data can be transmitted by using a medium such as a conventional wired / wireless broadband line or by using a conventional storage medium. In the case of storage, the transmission cost and the storage cost are increased.
  • a high efficiency image compression technique is required to effectively transmit, store, and reproduce high resolution, high quality image information.
  • An object of the present invention is to provide a method and apparatus for improving image coding efficiency.
  • Another technical problem of the present invention is to provide a method and apparatus for increasing the efficiency of inter prediction.
  • Another technical problem of the present invention is to provide a method and apparatus for increasing the efficiency of inter prediction based on AMVP (Advanced Motion Vector Prediction).
  • AMVP Advanced Motion Vector Prediction
  • Another technical problem of the present invention is to provide a method and apparatus for increasing the efficiency of inter prediction based on adaptive motion vector resolution (AMVR).
  • AMVR adaptive motion vector resolution
  • Another technical problem of the present invention is to provide a method and apparatus for applying motion vector refinement in performing AMVR.
  • a picture decoding method performed by a decoding apparatus includes motion prediction information including information on an AMVR flag indicating whether to apply an Adaptive Motion Vector Resolution (AMVR) mode and information on an AMVR mode flag indicating a type of the AMVR mode.
  • AMVR Adaptive Motion Vector Resolution
  • a decoding device for performing picture decoding.
  • the decoding apparatus may include motion prediction information including information on an AMVR flag indicating whether to apply an Adaptive Motion Vector Resolution (AMVR) mode and information on an AMVR mode flag indicating a type of the AMVR mode.
  • An entropy decoding unit for obtaining information from a bitstream, and when the value of the AMVR flag is 1, a motion vector for the current block is derived based on the value of the AMVR mode flag, and the derived motion vector is refined.
  • a predictor that derives prediction samples for the current block based on the refined motion vector, and an adder that generates reconstruction samples for the current block based on the derived prediction samples.
  • the overall video / video compression efficiency can be improved.
  • the efficiency of inter prediction can be improved.
  • image coding efficiency can be improved by performing inter prediction based on AMVP.
  • image coding efficiency can be improved by performing inter prediction based on AMVR.
  • the accuracy of inter prediction can be improved by applying motion vector refinement in performing AMVR.
  • motion vector refinement may be applied depending on conditions in performing AMVR.
  • FIG. 1 is a diagram schematically illustrating a configuration of an encoding apparatus according to an embodiment.
  • FIG. 2 is a diagram schematically illustrating a configuration of a decoding apparatus according to an embodiment.
  • FIG. 3 is a flowchart illustrating a method of operating a decoding apparatus, according to an exemplary embodiment.
  • FIG. 4 is a block diagram illustrating a configuration of a decoding apparatus according to an embodiment.
  • a picture decoding method performed by a decoding apparatus includes motion prediction information including information on an AMVR flag indicating whether to apply an Adaptive Motion Vector Resolution (AMVR) mode and information on an AMVR mode flag indicating a type of the AMVR mode.
  • AMVR Adaptive Motion Vector Resolution
  • each configuration in the drawings described in the present invention are shown independently for the convenience of description of the different characteristic functions, it does not mean that each configuration is implemented by separate hardware or separate software.
  • two or more of each configuration 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.
  • VVC Versatile Video Coding
  • HEVC High Efficiency Video Coding
  • a video may mean a series of images over time.
  • a picture generally refers to a unit representing one image in a specific time zone, and a slice is a unit constituting a part of a picture in coding.
  • One picture may be composed of a plurality of slices, and if necessary, the picture and the slice may be mixed with each other.
  • an "image” may mean a concept including a still image and a video, which is a set of a series of still images over time.
  • video does not necessarily mean a set of a series of still images over time, and in some embodiments, may be interpreted as a concept in which still images are included in video.
  • a pixel or a pel may refer to a minimum unit constituting one picture (or image). Also, 'sample' may be used as a term corresponding to a pixel.
  • a sample may generally represent a pixel or a value of a pixel, and may only represent pixel / pixel values of the luma component, or only pixel / pixel values of the chroma component.
  • a unit represents the basic unit of image processing.
  • the unit may include at least one of a specific region of the picture and information related to the region.
  • the unit may be used interchangeably with terms such as block or area in some cases.
  • an M ⁇ N block may represent a set of samples or transform coefficients composed of M columns and N rows.
  • the encoding / decoding device may include a video encoding / decoding device and / or an image encoding / decoding device, and the video encoding / decoding device is used as a concept including the image encoding / decoding device, or the image encoding / decoding device is It may be used in a concept including a video encoding / decoding device.
  • the (video) encoding apparatus 100 may include a picture partitioning module 105, a prediction module 110, a residual processing module 120, and an entropy encoding unit (
  • the entropy encoding module 130 may include an adder 140, a filtering module 150, and a memory 160.
  • the residual processor 120 may include a substractor 121, a transform module 122, a quantization module 123, a rearrangement module 124, and a dequantization module 125. ) And an inverse transform module 126.
  • the picture divider 105 may divide the input picture into at least one processing unit.
  • the processing unit may be called a coding unit (CU).
  • the coding unit may be recursively split from the largest coding unit (LCU) according to a quad-tree binary-tree (QTBT) structure.
  • QTBT quad-tree binary-tree
  • one coding unit may be divided into a plurality of coding units of a deeper depth based on a quad tree structure, a binary tree structure, and / or a ternary tree structure.
  • the quad tree structure may be applied first, and the binary tree structure and the ternary tree structure may be applied later.
  • the binary tree structure / tunary tree structure may be applied first.
  • the coding procedure according to the present invention may be performed based on the final coding unit that is no longer split.
  • the maximum coding unit may be used as the final coding unit immediately based on coding efficiency according to the image characteristic, or if necessary, the coding unit is recursively divided into coding units of lower depths and optimized.
  • a coding unit of size may be used as the final coding unit.
  • the coding procedure may include a procedure of prediction, transform, and reconstruction, which will be described later.
  • the processing unit may include a coding unit (CU) prediction unit (PU) or a transform unit (TU).
  • the coding unit may be split from the largest coding unit (LCU) into coding units of deeper depths along the quad tree structure.
  • LCU largest coding unit
  • the maximum coding unit may be used as the final coding unit immediately based on coding efficiency according to the image characteristic, or if necessary, the coding unit is recursively divided into coding units of lower depths and optimized.
  • a coding unit of size may be used as the final coding unit. If a smallest coding unit (SCU) is set, the coding unit may not be split into smaller coding units than the minimum coding unit.
  • the final coding unit refers to a coding unit that is the basis of partitioning or partitioning into a prediction unit or a transform unit.
  • the prediction unit is a unit partitioning from the coding unit and may be a unit of sample prediction. In this case, the prediction unit may be divided into sub blocks.
  • the transform unit may be divided along the quad tree structure from the coding unit, and may be a unit for deriving a transform coefficient and / or a unit for deriving a residual signal from the transform coefficient.
  • a coding unit may be called a coding block (CB)
  • a prediction unit is a prediction block (PB)
  • a transform unit may be called a transform block (TB).
  • a prediction block or prediction unit may mean a specific area in the form of a block within a picture, and may include an array of prediction samples.
  • a transform block or a transform unit may mean a specific area in a block form within a picture, and may include an array of transform coefficients or residual samples.
  • the prediction unit 110 performs prediction on a block to be processed (hereinafter, may mean a current block or a residual block), and generates a predicted block including prediction samples for the current block. can do.
  • the unit of prediction performed by the prediction unit 110 may be a coding block, a transform block, or a prediction block.
  • the prediction unit 110 may determine whether intra prediction or inter prediction is applied to the current block. As an example, the prediction unit 110 may determine whether intra prediction or inter prediction is applied on a CU basis.
  • the prediction unit 110 may derive a prediction sample for the current block based on reference samples outside the current block in the picture to which the current block belongs (hereinafter, referred to as the current picture). In this case, the prediction unit 110 may (i) derive the prediction sample based on the average or interpolation of neighboring reference samples of the current block, and (ii) the neighbor reference of the current block.
  • the prediction sample may be derived based on a reference sample present in a specific (prediction) direction with respect to the prediction sample among the samples. In case of (i), it may be called non-directional mode or non-angle mode, and in case of (ii), it may be called directional mode or angular mode.
  • the prediction mode may have, for example, 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).
  • the prediction unit 110 may determine the prediction mode applied to the current block by using the prediction mode applied to the neighboring block.
  • the prediction unit 110 may derive the prediction sample for the current block based on the sample specified by the motion vector on the reference picture.
  • the prediction unit 110 may apply one of a skip mode, a merge mode, and a motion vector prediction (MVP) mode to derive a prediction sample for the current block.
  • the prediction unit 110 may use the motion information of the neighboring block as the motion information of the current block.
  • the skip mode unlike the merge mode, the difference (residual) between the prediction sample and the original sample is not transmitted.
  • the MVP mode the motion vector of the current block may be derived using the motion vector of the neighboring block as a motion vector predictor.
  • the neighboring block may include a spatial neighboring block existing in the current picture and a temporal neighboring block present in the reference picture.
  • a reference picture including the temporal neighboring block may be called a collocated picture (colPic).
  • the motion information may include a motion vector and a reference picture index.
  • Information such as prediction mode information and motion information may be encoded (entropy) and output in the form of a bitstream.
  • the highest picture on the reference picture list may be used as the reference picture.
  • Reference pictures included in a reference picture list may be sorted based on a difference in a picture order count (POC) between a current picture and a corresponding reference picture.
  • POC picture order count
  • the subtraction unit 121 generates a residual sample which is a difference between the original sample and the prediction sample.
  • residual samples may not be generated as described above.
  • the transform unit 122 generates transform coefficients by transforming the residual sample in units of transform blocks.
  • the transform unit 122 may perform the transform according to the size of the transform block and the prediction mode applied to the coding block or the prediction block that spatially overlaps the transform block. For example, if intra prediction is applied to the coding block or the prediction block that overlaps the transform block, and the transform block is a 4 ⁇ 4 residual array, the residual sample is configured to perform a discrete sine transform (DST) transform kernel.
  • the residual sample may be transformed using a discrete cosine transform (DCT) transform kernel.
  • DST discrete sine transform
  • DCT discrete cosine transform
  • the quantization unit 123 may quantize the transform coefficients to generate quantized transform coefficients.
  • the reordering unit 124 rearranges the quantized transform coefficients.
  • the reordering unit 124 may reorder the quantized transform coefficients in the form of a block into a one-dimensional vector form through a coefficient scanning method. Although the reordering unit 124 has been described in a separate configuration, the reordering unit 124 may be part of the quantization unit 123.
  • the entropy encoding unit 130 may perform entropy encoding on the quantized transform coefficients.
  • Entropy encoding may include, for example, encoding methods such as exponential Golomb, context-adaptive variable length coding (CAVLC), context-adaptive binary arithmetic coding (CABAC), and the like.
  • the entropy encoding unit 130 may encode information necessary for video reconstruction other than the quantized transform coefficients (for example, a value of a syntax element) together or separately according to entropy encoding or a predetermined method.
  • the encoded information may be transmitted or stored in units of network abstraction layer (NAL) units in the form of bitstreams.
  • the bitstream may be transmitted over a network or may be stored in a digital storage medium.
  • the network may include a broadcasting network and / or a communication network, and the digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, and the like.
  • the inverse quantization unit 125 inverse quantizes the quantized values (quantized transform coefficients) in the quantization unit 123, and the inverse transformer 126 inverse transforms the inverse quantized values in the inverse quantization unit 125 to obtain a residual sample.
  • the adder 140 reconstructs the picture by combining the residual sample and the predictive sample.
  • the residual sample and the predictive sample may be added in units of blocks to generate a reconstructed block.
  • the adder 140 may be part of the predictor 110.
  • the adder 140 may also be called a reconstruction module or a restore block generator.
  • the filter unit 150 may apply a deblocking filter and / or a sample adaptive offset to the reconstructed picture. Through deblocking filtering and / or sample adaptive offset, the artifacts of the block boundaries in the reconstructed picture or the distortion in the quantization process can be corrected.
  • the sample adaptive offset may be applied on a sample basis and may be applied after the process of deblocking filtering is completed.
  • the filter unit 150 may apply an adaptive loop filter (ALF) to the reconstructed picture. ALF may be applied to the reconstructed picture after the deblocking filter and / or sample adaptive offset is applied.
  • ALF adaptive loop filter
  • the memory 160 may store reconstructed pictures (decoded pictures) or information necessary for encoding / decoding.
  • the reconstructed picture may be a reconstructed picture after the filtering process is completed by the filter unit 150.
  • the stored reconstructed picture may be used as a reference picture for (inter) prediction of another picture.
  • the memory 160 may store (reference) pictures used for inter prediction.
  • pictures used for inter prediction may be designated by a reference picture set or a reference picture list.
  • FIG. 2 is a diagram schematically illustrating a configuration of a video / video decoding apparatus to which the present invention can be applied.
  • the video decoding apparatus may include an image decoding apparatus.
  • the (video) decoding apparatus 200 may include an entropy decoding module 210, a residual processing module 220, a prediction module 230, and an adder. , 240, a filtering module 250, and a memory 260.
  • the residual processor 220 may include a rearrangement module 221, a dequantization module 222, and an inverse transform module 223.
  • the video decoding apparatus 200 may include a receiver that receives a bitstream including video information. The receiver may be configured as a separate module or may be included in the entropy decoding unit 210.
  • the (video) decoding apparatus 200 may restore the video / image / picture in response to a process in which the video / image information is processed in the (video) encoding apparatus. .
  • the video decoding apparatus 200 may perform video decoding using a processing unit applied in the video encoding apparatus.
  • the processing unit block of video decoding may be, for example, a coding unit, and in another example, a coding unit, a prediction unit, or a transform unit.
  • the coding unit may be split along the quad tree structure, binary tree structure and / or ternary tree structure from the largest coding unit.
  • the prediction unit and the transform unit may be further used in some cases, in which case the prediction block is a block derived or partitioned from the coding unit and may be a unit of sample prediction. At this point, the prediction unit may be divided into subblocks.
  • the transform unit may be divided along the quad tree structure from the coding unit, and may be a unit for deriving a transform coefficient or a unit for deriving a residual signal from the transform coefficient.
  • the entropy decoding unit 210 may parse the bitstream and output information necessary for video reconstruction or picture reconstruction. For example, the entropy decoding unit 210 decodes information in a bitstream based on a coding method such as exponential Golomb coding, CAVLC, or CABAC, quantized values of syntax elements necessary for video reconstruction, and residual coefficients. Can be output.
  • a coding method such as exponential Golomb coding, CAVLC, or CABAC, quantized values of syntax elements necessary for video reconstruction, and residual coefficients. Can be output.
  • the CABAC entropy decoding method receives a bin corresponding to each syntax element in a bitstream, and decodes syntax element information and decoding information of neighboring and decoding target blocks or information of symbols / bins decoded in a previous step.
  • the context model is determined using the context model, the probability of occurrence of a bin is predicted according to the determined context model, and arithmetic decoding of the bin is performed to generate a symbol corresponding to the value of each syntax element. can do.
  • the CABAC entropy decoding method may update the context model by using the information of the decoded symbol / bin for the context model of the next symbol / bin after determining the context model.
  • the information related to the prediction among the information decoded by the entropy decoding unit 210 is provided to the prediction unit 230, and the residual value on which the entropy decoding has been performed by the entropy decoding unit 210, that is, the quantized transform coefficient, is used as a reordering unit ( 221 may be input.
  • the reordering unit 221 may rearrange the quantized transform coefficients in a two-dimensional block form.
  • the reordering unit 221 may perform reordering in response to coefficient scanning performed by the encoding apparatus.
  • the rearrangement unit 221 has been described in a separate configuration, but the rearrangement unit 221 may be part of the inverse quantization unit 222.
  • the inverse quantization unit 222 may dequantize the quantized transform coefficients based on the (inverse) quantization parameter and output the transform coefficients.
  • information for deriving a quantization parameter may be signaled from the encoding apparatus.
  • the inverse transform unit 223 may inversely transform transform coefficients to derive residual samples.
  • the prediction unit 230 may perform prediction on the current block and generate a predicted block including prediction samples for the current block.
  • the unit of prediction performed by the prediction unit 230 may be a coding block, a transform block, or a prediction block.
  • the prediction unit 230 may determine whether to apply intra prediction or inter prediction based on the information about the prediction.
  • a unit for determining which of intra prediction and inter prediction is to be applied and a unit for generating a prediction sample may be different.
  • the unit for generating a prediction sample in inter prediction and intra prediction may also be different.
  • whether to apply inter prediction or intra prediction may be determined in units of CUs.
  • a prediction mode may be determined and a prediction sample may be generated in PU units
  • intra prediction a prediction mode may be determined in PU units and a prediction sample may be generated in TU units.
  • the prediction unit 230 may derive the prediction sample for the current block based on the neighbor reference samples in the current picture.
  • the prediction unit 230 may derive the prediction sample for the current block by applying the directional mode or the non-directional mode based on the neighbor reference samples of the current block.
  • the prediction mode to be applied to the current block may be determined using the intra prediction mode of the neighboring block.
  • the prediction unit 230 may derive the prediction sample for the current block based on the sample specified on the reference picture by the motion vector on the reference picture.
  • the prediction unit 230 may apply any one of a skip mode, a merge mode, and an MVP mode to derive a prediction sample for the current block.
  • motion information required for inter prediction of the current block provided by the video encoding apparatus for example, information about a motion vector, a reference picture index, and the like may be obtained or derived based on the prediction information.
  • the motion information of the neighboring block may be used as the motion information of the current block.
  • the neighboring block may include a spatial neighboring block and a temporal neighboring block.
  • the prediction unit 230 may construct a merge candidate list using motion information of available neighboring blocks, and may use information indicated by the merge index on the merge candidate list as a motion vector of the current block.
  • the merge index may be signaled from the encoding device.
  • the motion information may include a motion vector and a reference picture. When the motion information of the temporal neighboring block is used in the skip mode and the merge mode, the highest picture on the reference picture list may be used as the reference picture.
  • the difference (residual) between the prediction sample and the original sample is not transmitted.
  • the motion vector of the current block may be derived using the motion vector of the neighboring block as a motion vector predictor.
  • the neighboring block may include a spatial neighboring block and a temporal neighboring block.
  • a merge candidate list may be generated by using a motion vector of a reconstructed spatial neighboring block and / or a motion vector corresponding to a Col block, which is a temporal neighboring block.
  • the motion vector of the candidate block selected from the merge candidate list is used as the motion vector of the current block.
  • the information about the prediction may include a merge index indicating a candidate block having an optimal motion vector selected from candidate blocks included in the merge candidate list.
  • the prediction unit 230 may derive the motion vector of the current block by using the merge index.
  • a motion vector predictor candidate list may be generated using a motion vector of a reconstructed spatial neighboring block and / or a motion vector corresponding to a Col block, which is a temporal neighboring block.
  • the prediction information may include a prediction motion vector index indicating an optimal motion vector selected from the motion vector candidates included in the list.
  • the prediction unit 230 may select the predicted motion vector of the current block from the motion vector candidates included in the motion vector candidate list using the motion vector index.
  • the prediction unit of the encoding apparatus may obtain a motion vector difference (MVD) between the motion vector of the current block and the motion vector predictor, and may encode the output vector in a bitstream form. That is, MVD may be obtained by subtracting the motion vector predictor from the motion vector of the current block.
  • the prediction unit 230 may obtain a motion vector difference included in the information about the prediction, and derive the motion vector of the current block by adding the motion vector difference and the motion vector predictor.
  • the prediction unit may also obtain or derive a reference picture index or the like indicating a reference picture from the information about the prediction.
  • the adder 240 may reconstruct the current block or the current picture by adding the residual sample and the predictive sample.
  • the adder 240 may reconstruct the current picture by adding the residual sample and the predictive sample in block units. Since the residual is not transmitted when the skip mode is applied, the prediction sample may be a reconstruction sample.
  • the adder 240 has been described in a separate configuration, the adder 240 may be part of the predictor 230.
  • the adder 240 may also be called a reconstruction module or a reconstruction block generator.
  • the filter unit 250 may apply the deblocking filtering sample adaptive offset, and / or ALF to the reconstructed picture.
  • the sample adaptive offset may be applied in units of samples and may be applied after deblocking filtering.
  • ALF may be applied after deblocking filtering and / or sample adaptive offset.
  • the memory 260 may store reconstructed pictures (decoded pictures) or information necessary for decoding.
  • the reconstructed picture may be a reconstructed picture after the filtering process is completed by the filter unit 250.
  • the memory 260 may store pictures used for inter prediction.
  • pictures used for inter prediction may be designated by a reference picture set or a reference picture list.
  • the reconstructed picture can be used as a reference picture for another picture.
  • the memory 260 may output the reconstructed picture in an output order.
  • a predicted block including prediction samples of the current block which is a coding target block
  • the predicted block comprises prediction samples in the spatial domain (or pixel domain).
  • the predicted block is derived identically in the encoding apparatus and the decoding apparatus, and the encoding apparatus decodes information (residual information) about the residual between the original block and the predicted block, not the original sample value itself of the original block. Signaling to an apparatus may increase image coding efficiency.
  • the decoding apparatus may derive a residual block including residual samples based on the residual information, generate the reconstructed block including reconstructed samples by adding the residual block and the predicted block, and generate reconstructed blocks. A reconstructed picture may be generated.
  • the residual information may be generated through a transform and quantization procedure.
  • the encoding apparatus derives a residual block between the original block and the predicted block, and performs transform procedure on residual samples (residual sample array) included in the residual block to derive transform coefficients.
  • the quantized transform coefficients may be derived by performing a quantization procedure on the transform coefficients to signal related residual information to the decoding device (via a bitstream).
  • the residual information may include information such as value information of the quantized transform coefficients, position information, a transform scheme, a transform kernel, and a quantization parameter.
  • the decoding apparatus may perform an inverse quantization / inverse transformation procedure and derive residual samples (or residual blocks) based on the residual information.
  • the decoding apparatus may generate a reconstructed picture based on the predicted block and the residual block.
  • the encoding apparatus may then dequantize / inverse transform the quantized transform coefficients for reference for inter prediction of the picture to derive a residual block, and generate a reconstructed picture based thereon.
  • Inter prediction of video encoding may be performed based on motion compensation using motion information.
  • motion information such as Advanced Motion Vector Prediction (AMVP), which directly encodes / decodes motion information
  • Merge mode which transmits only an optimal index by listing peripheral motion information of the current block.
  • AMVP mode the motion information to be encoded / decoded includes a prediction direction (bi or uni), a reference picture index, a motion vector information (for example, a motion vector predictor index, and a motion vector (MVD).
  • the motion information may include a prediction direction (bi or uni), a reference picture index, a motion vector, and the like.
  • motion vector information of AMVP may be expressed up to a decimal point unit.
  • motion vector information may be expressed up to a decimal point based on a quarter pixel unit, a 1/8 pixel unit, and the like.
  • the motion vector information may be inefficient to decode / decode the motion vector information of AMVP in the unit of decimal pixels.
  • the motion vector information may be encoded / decoded in the unit of decimal pixels. May be inefficient. Therefore, in order to solve the above-mentioned problem, it is possible to use adaptive motion vector resolution (AMVR) that adaptively selects the resolution of the motion vector information.
  • AMVR adaptive motion vector resolution
  • a signal for determining whether to express motion information in units of fractional pixels or in units of integer pixels may be explicitly encoded / decoded.
  • a signal for determining whether to express in 1 pixel unit or 4 pixel unit may be explicitly encoded / decoded.
  • Tables 1 and 2 below show the syntax of the AMVP mode when AMVR is applied, and Table 2 shows the decoding process in that case.
  • skip_flag represents a flag for specifying whether or not a skip mode. If the value of skip_flag is 1, the skip mode is performed. If the value of skip_flag is 0, the skip mode is not performed.
  • merge_flag represents a flag for specifying whether the merge mode or not. If the merge_flag value is 1, the merge mode is performed. If the merge_flag value is 0, the merge mode is not performed.
  • amvr_flag represents a flag for specifying whether to be in AMVR mode or not. If the value of amvr_flag is 1, the AMVR mode is executed. If the value of amvr_flag is 0, the AMVR mode is not performed.
  • amvr_mode represents a flag for specifying whether to perform a 1 pixel reference AMVR or a 4 pixel reference AMVR.
  • the motion vector is derived (or determined) by performing AMVR on the basis of 1 pixel, and when the value of amvr_mode is 1, the motion vector is derived (or determined) on the basis of 4 pixels.
  • motion vector refinement for AMVR can be based on the following three methods.
  • the motion vector may be determined based on the similarity between the peripheral pixels of the predetermined area of the current block and the peripheral pixels of the predefined area of the reference block. At this time, the neighboring pixels of the current block must satisfy the decodable condition.
  • a motion vector may be determined based on the similarity between two reference blocks.
  • the motion vector in each direction may be determined based on the similarity with the average block of the two prediction blocks.
  • a method of applying motion vector refinement to an AMVR may be a method of applying to an AMVR mode first, a method of applying to an AMVR mode of a second pixel, and a third of There may be a method applied to the AMVR mode in the 4-pixel unit.
  • motion vector refinement can be applied to the AMVR.
  • the motion vector refinement may be performed after encoding the motion vector.
  • An example of the decoding process in which the motion vector refinement is applied to the AMVR is shown in Table 3 below.
  • motion vector refinement may be applied to an AMVR mode in one pixel.
  • Motion vector refinement has a trade-off relationship between complexity and coding efficiency. Therefore, refinement can be performed by selecting a specific mode among AMVR modes. In general, when the AMVR mode is selected, most of the 1-pixel unit AMVR mode can be selected. Therefore, in order to design the motion vector refinement process in the direction of reducing the coding complexity while maintaining the maximum coding efficiency, refinement may be performed only in the 1-pixel AMVR mode. Table 4 below shows the decoding process.
  • motion vector refinement may be applied to a 4-pixel AMVR mode.
  • the 4-pixel AMVR has low reliability in motion vectors when compared to the 1-pixel AMVR mode. Therefore, it can be designed to perform the motion vector refinement only in the 4-pixel AMVR mode.
  • Table 5 shows the decoding process of the method.
  • the search range (SR) of the motion vector refinement technique for AMVR may be considered.
  • the search range has a trade-off relationship between coding complexity and coding performance. If the search range is too large, the coding performance improvement may be small compared to the coding complexity. If the search range is too small, the absolute coding performance may be small. Therefore, the search range needs to be determined in consideration of coding complexity and efficiency.
  • the search range for AMVR can be defined as follows.
  • Equation 1 may be expressed as in Equation 2, and m and n values may be determined in consideration of encoding complexity and encoding performance.
  • Equation 2 m, n or 1 / m, 1 / n may be transmitted in a high level syntax such as Picture Parameter Set (PPS) or Sequence Parameter Set (SPS), or may be determined at the frame or coding block level. Can be.
  • PPS Picture Parameter Set
  • SPS Sequence Parameter Set
  • FIG. 3 is a flowchart illustrating a method of operating a decoding apparatus according to an embodiment
  • FIG. 4 is a block diagram illustrating a configuration of a decoding apparatus according to an embodiment.
  • the decoding apparatus according to FIGS. 3 and 4 and the operating method of the decoding apparatus may be similarly applied to the encoding apparatus according to FIG. 1.
  • Each step disclosed in FIG. 3 may be performed by the decoding apparatus 200 disclosed in FIG. 2. More specifically, S300 may be performed by the entropy decoding unit 210 shown in FIG. 2, S310 to S330 may be performed by the predictor 230 shown in FIG. 2, and S340 may be added as shown in FIG. 2. It may be performed by the unit 240. Therefore, detailed descriptions that overlap with the foregoing description in FIG. 2 will be omitted or simply described.
  • the decoding apparatus may include an entropy decoding unit 210, a predictor 230, and an adder 240.
  • the decoding apparatus may be implemented by more or fewer components than those illustrated in FIG. 4.
  • the entropy decoding unit 210, the prediction unit 230, and the adder 240 are each implemented as separate chips, or at least two or more components are implemented through one chip. May be
  • a decoding apparatus includes: motion prediction including information on an AMVR flag indicating whether to apply an adaptive motion vector resolution (AMVR) mode and information on an AMVR mode flag indicating a type of the AMVR mode; Motion prediction information may be obtained from the bitstream (S300). More specifically, the entropy decoding unit 210 of the decoding apparatus may provide information on an AMVR flag indicating whether to apply an Adaptive Motion Vector Resolution (AMVR) mode and information on an AMVR mode flag indicating a type of the AMVR mode. Motion prediction information including may be obtained from the bitstream.
  • AMVR adaptive motion vector resolution
  • AMVR Adaptive Motion Vector Resolution
  • the decoding apparatus may derive a motion vector for the current block based on the value of the AMVR mode flag (S310). More specifically, when the value of the AMVR flag is 1, the prediction unit 230 of the decoding apparatus may derive a motion vector for the current block based on the value of the AMVR mode flag.
  • the motion vector when the value of the AMVR mode flag is 0, the motion vector is derived based on 1 pixel unit, and when the value of the AMVR mode flag is 1, the motion vector is derived based on 4 pixel unit. Can be.
  • the decoding apparatus may refine the derived motion vector (S320). More specifically, the prediction unit 230 of the decoding apparatus may refine the derived motion vector.
  • the decoding apparatus may refine the motion vector when the motion vector is derived based on the one pixel unit or the four pixel unit.
  • the decoding apparatus may refine the motion vector when the motion vector is derived based on the one pixel unit.
  • the decoding apparatus may refine the motion vector when the motion vector is derived based on the 4 pixel unit.
  • the decoding apparatus may refine the derived motion vector based on a similarity between neighboring pixels of the predefined area of the current block and neighboring pixels of the predefined area of the reference block with respect to the current block. Can be.
  • the decoding apparatus may refine the derived motion vector based on the similarity between the bidirectional reference blocks with respect to the current block.
  • the decoding apparatus may refine the derived motion vector based on the similarity of the average block of the bidirectional reference blocks to the current block.
  • the decoding apparatus may refine the derived motion vector within a search range.
  • the search range may be determined as a value between -1 and 1.
  • the search range may be determined as a value between -4 and 4.
  • the search range is determined as a value between -1 / m and 1 / m, wherein the value of m is determined by the motion prediction information. May be included.
  • the search range is determined as a value between -4 / n and 4 / n, wherein the value of n is determined in the motion prediction information. May be included.
  • the decoding apparatus may derive prediction samples for the current block based on the refined motion vector (S330). More specifically, the prediction unit 230 of the decoding apparatus may derive the prediction samples for the current block based on the refined motion vector.
  • the decoding apparatus may generate reconstruction samples for the current block based on the derived prediction samples (S340). More specifically, the adder 240 of the decoding apparatus may generate reconstruction samples for the current block based on the derived prediction samples.
  • Motion prediction information including information on the indicated AMVR mode flag is obtained from the bitstream (S300).
  • the current block is determined based on the value of the AMVR mode flag.
  • Derive a motion vector for the current block (S310), refine the derived motion vector (S320), and derive prediction samples for the current block based on the refined motion vector (S330).
  • Reconstruction samples for the current block may be generated (S340) based on prediction samples. That is, the accuracy of inter prediction can be improved by applying motion vector refinement in performing AMVR.
  • the above-described method according to the present invention may be implemented in software, and the encoding device and / or the decoding device according to the present invention may perform image processing of, for example, a TV, a computer, a smartphone, a set-top box, a display device, and the like. It can be included in the device.
  • the above-described method may be implemented as a module (process, function, etc.) for performing the above-described function.
  • the module may be stored in memory and executed by a processor.
  • the memory may be internal or external to the processor and may be coupled to the processor by various well known means.
  • the processor may include an application-specific integrated circuit (ASIC), other chipsets, logic circuits, and / or data processing devices.
  • the memory may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium and / or other storage device.

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Abstract

La présente invention concerne un procédé de décodage d'images réalisé par un appareil de décodage, comportant les étapes consistant à: obtenir, à partir d'un flux binaire, des informations sur un fanion de résolution adaptative de vecteurs de mouvement (AMVR) indiquant s'il convient d'appliquer un mode d'AMVR et des informations de prédiction de mouvement comprenant des informations sur un fanion de mode d'AMVR indiquant un type du mode d'AMVR; élaborer un vecteur de mouvement pour un bloc courant d'après la valeur du fanion de mode d'AMVR lorsque la valeur du fanion d'AMVR est 1; raffiner le vecteur de mouvement élaboré; élaborer des échantillons de prédiction pour le bloc courant d'après le vecteur de mouvement raffiné; et générer des échantillons de reconstruction pour le bloc courant d'après les échantillons de prédiction élaborés.
PCT/KR2019/003809 2018-04-01 2019-04-01 Procédé de codage d'images sur la base d'un raffinement de vecteurs de mouvement et appareil associé Ceased WO2019194501A1 (fr)

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Publication number Priority date Publication date Assignee Title
US20120170660A1 (en) * 2007-11-29 2012-07-05 Pavel Novotny Refinement of motion vectors in hierarchical motion estimation
KR20160106127A (ko) * 2014-01-08 2016-09-09 마이크로소프트 테크놀로지 라이센싱, 엘엘씨 인코딩된 비트 스트림에서의 움직임 벡터 표현
WO2017052000A1 (fr) * 2015-09-24 2017-03-30 엘지전자 주식회사 Procédé et appareil de prédiction inter basée sur le raffinement des vecteurs de mouvement dans un système de codage d'images
KR20170113513A (ko) * 2015-06-05 2017-10-12 인텔렉추얼디스커버리 주식회사 움직임 벡터 정밀성을 이용하는 영상 부호화 및 복호화 방법과 영상 복호화 장치
KR20180004147A (ko) * 2015-05-11 2018-01-10 퀄컴 인코포레이티드 비디오 데이터의 특정 픽처 내의 인터 코딩을 위한 검색 영역 결정

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120170660A1 (en) * 2007-11-29 2012-07-05 Pavel Novotny Refinement of motion vectors in hierarchical motion estimation
KR20160106127A (ko) * 2014-01-08 2016-09-09 마이크로소프트 테크놀로지 라이센싱, 엘엘씨 인코딩된 비트 스트림에서의 움직임 벡터 표현
KR20180004147A (ko) * 2015-05-11 2018-01-10 퀄컴 인코포레이티드 비디오 데이터의 특정 픽처 내의 인터 코딩을 위한 검색 영역 결정
KR20170113513A (ko) * 2015-06-05 2017-10-12 인텔렉추얼디스커버리 주식회사 움직임 벡터 정밀성을 이용하는 영상 부호화 및 복호화 방법과 영상 복호화 장치
WO2017052000A1 (fr) * 2015-09-24 2017-03-30 엘지전자 주식회사 Procédé et appareil de prédiction inter basée sur le raffinement des vecteurs de mouvement dans un système de codage d'images

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