WO2023043223A1 - 비디오 신호 부호화/복호화 방법, 그리고 비트스트림을 저장한 기록 매체 - Google Patents
비디오 신호 부호화/복호화 방법, 그리고 비트스트림을 저장한 기록 매체 Download PDFInfo
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Definitions
- the present disclosure relates to a video signal processing method and apparatus.
- High-resolution and high-quality images such as high definition (HD) images and ultra high definition (UHD) images is increasing in various application fields.
- image data becomes higher resolution and higher quality, the amount of data increases relatively compared to existing image data. Therefore, when image data is transmitted using a medium such as an existing wired/wireless broadband line or stored using an existing storage medium, transmission cost and Storage costs increase.
- High-efficiency video compression technologies can be used to solve these problems that occur as video data becomes high-resolution and high-quality.
- An inter-prediction technique for predicting pixel values included in the current picture from pictures before or after the current picture as an image compression technique an intra-prediction technique for predicting pixel values included in the current picture using pixel information within the current picture
- image compression technology can be used to effectively compress and transmit or store image data.
- An object of the present disclosure is to provide a method for performing motion estimation based on a previously reconstructed picture at the decoder side and an apparatus for performing the same.
- An object of the present disclosure is to provide a method for increasing prediction accuracy by combining a plurality of inter prediction modes and an apparatus for performing the same.
- An object of the present disclosure is to provide a method for adaptively determining a search range for motion estimation and an apparatus for performing the same.
- An object of the present disclosure is to provide a method for correcting motion information signaled from an encoder through motion estimation at the decoder side, and an apparatus for performing the same.
- An image decoding method includes obtaining a first prediction block for a current block based on a first inter prediction mode, and obtaining a second prediction block for the current block based on a second inter prediction mode. Obtaining, and obtaining a final prediction block for the current block based on the first prediction block and the second prediction block.
- An image encoding method includes obtaining a first prediction block for a current block based on a first inter prediction mode, and obtaining a second prediction block for the current block based on a second inter prediction mode. Obtaining, and obtaining a final prediction block for the current block based on the first prediction block and the second prediction block.
- At least one of the first inter prediction mode and the second inter prediction mode uses a previously reconstructed reference picture, and a decoder performs motion estimation in the same manner as the encoder. It may be a motion estimation mode on the decoder side.
- the motion estimation is performed using an optimal cost among combinations of a current template composed of a reconstructed region around the current block and a reference template having the same size as the current template in the reference picture. It may include a process of searching for a combination having.
- the motion estimation may be performed for each reference picture having a reference picture index in a reference picture list smaller than a threshold value.
- the motion estimation may be performed for each reference picture whose output order difference from a current picture in a reference picture list is equal to or less than a threshold value.
- the reference template is searched within a search range set for the reference picture, and the search range may be set based on initial motion information of the current block.
- the initial motion information may be motion information for a region larger than the current block.
- the reference template is searched within a search range set for the reference picture, the search range is determined based on motion characteristics of a region including the current block, The motion characteristic of the area may be set to one of a strong motion area and a strong motion area.
- the motion estimation is performed by searching for a combination having an optimal cost among combinations of an L0 reference block included in an L0 reference picture and an L1 reference block included in an L1 reference picture. process may be included.
- the output order of the current picture may be located between the output order of the L0 reference picture and the output order of the L1 reference picture.
- the first inter prediction mode may be used for L0 direction prediction of the current block
- the second inter prediction mode may be used for L1 direction prediction of the current block.
- the final prediction block is derived based on a weighted sum operation of the first prediction block and the second prediction block, and during the weighted sum operation, the first prediction block A first weight assigned to and a second weight assigned to the second prediction block may be adaptively determined according to the type of the first inter prediction mode or the second prediction mode.
- the first weight is the second inter prediction mode. It can have a value greater than the weight.
- signaling overhead can be reduced by performing motion estimation on the decoder side based on a previously reconstructed picture.
- prediction accuracy can be improved by combining a plurality of inter prediction modes.
- complexity of an encoder and/or a decoder can be reduced by providing a method for adaptively determining a search range for motion estimation.
- prediction accuracy can be improved by correcting motion information signaled from an encoder through motion estimation on the decoder side.
- FIG. 1 is a block diagram illustrating an image encoding apparatus according to an embodiment of the present disclosure.
- FIG. 2 is a block diagram illustrating an image decoding apparatus according to an embodiment of the present disclosure.
- 4 and 5 illustrate an example in which a prediction block of a current block is generated based on motion information generated through motion estimation.
- FIG. 6 shows a referenced position for deriving a motion vector prediction value.
- FIG. 7 is a diagram for explaining a template-based motion estimation method.
- FIG. 9 is a diagram for explaining a motion estimation method based on a bilateral matching method.
- FIG. 10 is a diagram for explaining a motion estimation method based on a unidirectional matching method.
- FIG 13 illustrates an example in which prediction samples are generated under the DC mode.
- FIG. 14 illustrates an example in which prediction samples are generated under the directional intra prediction mode.
- 15 is a flowchart illustrating a method of deriving a prediction block of a current block by a combined prediction method.
- 16 shows an example in which a plurality of prediction blocks are generated under the combined prediction method.
- FIG. 17 illustrates various examples in which a current block is divided according to a partition type.
- 19 is an example showing the position of the dividing line.
- FIG. 20 illustrates an example in which a current block is divided according to the description of FIGS. 18 and 19 .
- 21 illustrates an example of deriving prediction samples in a weighted sum region and an unweighted sum region.
- FIG. 22 illustrates an example in which a filter is applied centered on a boundary between a weighted sum region and an unweighted sum region.
- FIG. 23 is a flowchart of a method for adjusting a search range according to an embodiment of the present disclosure.
- 24 and 25 illustrate examples in which a current picture is divided into a plurality of regions.
- 26 illustrates an example in which a search range is set around a reference point.
- FIG. 27 illustrates an example of determining motion characteristics of a current picture.
- FIG. 28 illustrates an example of dividing a current picture and a reference picture into a plurality of regions.
- 29 is a diagram for explaining an example in which motion information for each sub-block is corrected.
- first and second may be used to describe various components, but the components should not be limited by the terms. These terms are only used for the purpose of distinguishing one component from another. For example, a first element may be termed a second element, and similarly, a second element may be termed a first element, without departing from the scope of the present disclosure.
- the terms and/or include any combination of a plurality of related recited items or any of a plurality of related recited items.
- FIG. 1 is a block diagram illustrating an image encoding apparatus according to an embodiment of the present disclosure.
- an image encoding apparatus 100 includes a picture division unit 110, prediction units 120 and 125, a transform unit 130, a quantization unit 135, a rearrangement unit 160, an entropy encoding unit ( 165), an inverse quantization unit 140, an inverse transform unit 145, a filter unit 150, and a memory 155.
- each component shown in FIG. 1 is shown independently to represent different characteristic functions in the video encoding device, and does not mean that each component is made of separate hardware or a single software component. That is, each component is listed and included as each component for convenience of explanation, and at least two components of each component can be combined to form one component, or one component can be divided into a plurality of components to perform a function, and each of these components can be divided into a plurality of components. Integrated embodiments and separated embodiments of components are also included in the scope of the present disclosure unless departing from the essence of the present disclosure.
- components may be optional components for improving performance rather than essential components that perform essential functions in the present disclosure.
- the present disclosure may be implemented by including only components essential to implement the essence of the present disclosure, excluding components used for performance improvement, and a structure including only essential components excluding optional components used for performance enhancement. Also included in the scope of the present disclosure.
- the picture divider 110 may divide an input picture into at least one processing unit.
- the processing unit may be a prediction unit (PU), a transform unit (TU), or a coding unit (CU).
- the picture divider 110 divides one picture into a plurality of combinations of coding units, prediction units, and transformation units, and combines one coding unit, prediction unit, and transformation unit according to a predetermined criterion (eg, a cost function). You can encode a picture by selecting .
- a predetermined criterion eg, a cost function
- one picture may be divided into a plurality of coding units.
- a recursive tree structure such as a quad tree, a ternary tree, or a binary tree may be used.
- a coding unit divided into other coding units using a coding unit as a root may be divided with as many child nodes as the number of divided coding units.
- a coding unit that is not further divided according to a certain limit becomes a leaf node. For example, when it is assumed that quad tree splitting is applied to one coding unit, one coding unit may be split into up to four different coding units.
- a coding unit may be used as a unit for performing encoding or a unit for performing decoding.
- the prediction unit may be divided into at least one square or rectangular shape having the same size within one coding unit, and one of the prediction units divided within one coding unit predicts another prediction unit. It may be divided to have a shape and/or size different from the unit.
- a conversion unit and a prediction unit may be set identically. In this case, after dividing the encoding unit into a plurality of transformation units, intra-prediction may be performed for each transformation unit. Coding units may be divided horizontally or vertically. The number of transformation units generated by dividing the coding unit may be 2 or 4 according to the size of the coding unit.
- the prediction units 120 and 125 may include an inter prediction unit 120 that performs inter prediction and an intra prediction unit 125 that performs intra prediction. It is possible to determine whether to use inter-prediction or intra-prediction for a coding unit, and determine specific information (eg, intra-prediction mode, motion vector, reference picture, etc.) according to each prediction method. In this case, a processing unit in which prediction is performed and a processing unit in which a prediction method and specific details are determined may be different. For example, a prediction method and a prediction mode may be determined in a coding unit, and prediction may be performed in a prediction unit or a transformation unit. A residual value (residual block) between the generated prediction block and the original block may be input to the transform unit 130 .
- an inter prediction unit 120 that performs inter prediction
- an intra prediction unit 125 that performs intra prediction. It is possible to determine whether to use inter-prediction or intra-prediction for a coding unit, and determine specific information (eg, intra-prediction mode, motion vector, reference
- prediction mode information and motion vector information used for prediction may be encoded in the entropy encoding unit 165 together with residual values and transmitted to a decoding device.
- a specific encoding mode it is also possible to encode an original block as it is and transmit it to a decoder without generating a prediction block through the prediction units 120 and 125 .
- the inter-prediction unit 120 may predict a prediction unit based on information on at least one picture among pictures before or after the current picture, and in some cases based on information on a partially coded region within the current picture. You can also predict prediction units.
- the inter-prediction unit 120 may include a reference picture interpolation unit, a motion estimation unit, and a motion compensation unit.
- the reference picture interpolator may receive reference picture information from the memory 155 and generate pixel information of an integer pixel or less in the reference picture.
- a DCT-based 8-tap interpolation filter with different filter coefficients may be used to generate pixel information of an integer pixel or less in units of 1/4 pixels.
- a DCT-based 4-tap interpolation filter with different filter coefficients may be used to generate pixel information of an integer pixel or less in units of 1/8 pixels.
- the motion predictor may perform motion prediction based on the reference picture interpolated by the reference picture interpolator.
- various methods such as full search-based block matching algorithm (FBMA), three step search (TSS), and new three-step search algorithm (NTS) may be used.
- FBMA full search-based block matching algorithm
- TSS three step search
- NTS new three-step search algorithm
- the motion vector may have a motion vector value in units of 1/2 or 1/4 pixels based on interpolated pixels.
- the motion estimation unit may predict the current prediction unit by using a different motion estimation method.
- Various methods such as a skip method, a merge method, an advanced motion vector prediction (AMVP) method, and an intra block copy method may be used as motion prediction methods.
- AMVP advanced motion vector prediction
- intra block copy method may be used as motion prediction methods.
- the intra-prediction unit 125 may generate a prediction block based on reference pixel information that is pixel information in the current picture.
- Reference pixel information may be derived from a selected one of a plurality of reference pixel lines.
- the N-th reference pixel line may include left pixels having an x-axis difference between them and the upper-left pixel in the current block of N, and upper pixels having a y-axis difference of N between them and the upper-left pixel in the current block.
- the number of reference pixel lines that can be selected by the current block may be 1, 2, 3 or 4.
- a block adjacent to the current prediction unit is a block on which inter-prediction is performed
- the reference pixel is a pixel on which inter-prediction is performed
- the reference pixel included in the block on which inter-prediction is performed performs inter-prediction. It can be used by replacing it with the reference pixel information of the block. That is, when the reference pixel is unavailable, information on the unavailable reference pixel may be replaced with at least one information among available reference pixels.
- Prediction modes in intra-prediction may include a directional prediction mode in which reference pixel information is used according to a prediction direction, and a non-directional prediction mode in which directional information is not used during prediction.
- a mode for predicting luminance information and a mode for predicting chrominance information may be different, and intra-prediction mode information or predicted luminance signal information used for predicting luminance information may be used to predict chrominance information. .
- the picture for the prediction unit is based on the pixel on the left, the top left, and the top of the prediction unit. I can do my predictions.
- a prediction block may be generated after applying a smoothing filter to a reference pixel according to a prediction mode. Whether to apply a smoothing filter may be determined according to the selected reference pixel line.
- the intra prediction mode of the current prediction unit may be predicted from the intra prediction modes of prediction units existing around the current prediction unit.
- the current prediction unit and the neighboring prediction using predetermined flag information Information that the prediction modes of the units are the same may be transmitted, and if the prediction modes of the current prediction unit and the neighboring prediction units are different, entropy encoding may be performed to encode prediction mode information of the current block.
- a residual block may be generated that includes residual information that is a difference between a prediction unit performed prediction based on the prediction unit generated by the prediction units 120 and 125 and an original block of the prediction unit.
- the generated residual block may be input to the transform unit 130 .
- the residual block including the original block and the residual information of the prediction unit generated through the prediction units 120 and 125 is converted into DCT (Discrete Cosine Transform), DST (Discrete Sine Transform), KLT and It can be converted using the same conversion method. Whether DCT, DST, or KLT is applied to transform the residual block is based on at least one of the size of the transformation unit, the shape of the transformation unit, the prediction mode of the prediction unit, or the intra-prediction mode information of the prediction unit. can be determined by
- the quantization unit 135 may quantize the values converted to the frequency domain by the transform unit 130 .
- a quantization coefficient may change according to a block or an importance of an image.
- the value calculated by the quantization unit 135 may be provided to the inverse quantization unit 140 and the rearrangement unit 160 .
- the rearrangement unit 160 may rearrange the coefficient values for the quantized residual values.
- the reordering unit 160 may change a 2D block-type coefficient into a 1-D vector form through a coefficient scanning method. For example, the reordering unit 160 may scan DC coefficients to high-frequency coefficients using a zig-zag scan method and change them into a one-dimensional vector form.
- zig-zag scan vertical scan that scans two-dimensional block-shaped coefficients in the column direction, horizontal scan that scans two-dimensional block-shaped coefficients in the row direction, or two-dimensional block-shaped coefficients in the row direction.
- Diagonal scan which scans block shape coefficients in a diagonal direction, may also be used. That is, it is possible to determine which scan method among zig-zag scan, vertical scan, horizontal scan, and diagonal scan is used according to the size of the transformation unit and the intra-prediction mode.
- the entropy encoding unit 165 may perform entropy encoding based on the values calculated by the reordering unit 160 .
- Entropy encoding may use various encoding methods such as, for example, exponential Golomb, context-adaptive variable length coding (CAVLC), and context-adaptive binary arithmetic coding (CABAC).
- the entropy encoding unit 165 receives residual value coefficient information and block type information of a coding unit from the reordering unit 160 and the prediction units 120 and 125, prediction mode information, division unit information, prediction unit information and transmission unit information, motion Various information such as vector information, reference frame information, block interpolation information, and filtering information can be encoded.
- the entropy encoding unit 165 may entropy-encode the coefficient value of the coding unit input from the reordering unit 160 .
- the inverse quantization unit 140 and the inverse transform unit 145 inversely quantize the values quantized by the quantization unit 135 and inverse transform the values transformed by the transform unit 130 .
- the residual value (Residual) generated by the inverse quantization unit 140 and the inverse transform unit 145 is combined with the prediction unit predicted through the motion estimation unit, motion compensation unit, and intra prediction unit included in the prediction units 120 and 125.
- a Reconstructed Block can be created.
- the filter unit 150 may include at least one of a deblocking filter, an offset correction unit, and an adaptive loop filter (ALF).
- a deblocking filter may include at least one of a deblocking filter, an offset correction unit, and an adaptive loop filter (ALF).
- ALF adaptive loop filter
- the deblocking filter can remove block distortion caused by a boundary between blocks in a reconstructed picture.
- it may be determined whether to apply the deblocking filter to the current block based on pixels included in several columns or rows included in the block.
- a strong filter or a weak filter may be applied according to the required deblocking filtering strength.
- horizontal filtering and vertical filtering may be processed in parallel.
- the offset correction unit may correct an offset of the deblocked image from the original image in units of pixels.
- pixels included in the image are divided into a certain number of areas, then the area to be offset is determined and the offset is applied to the area, or the offset is performed considering the edge information of each pixel method can be used.
- Adaptive Loop Filtering may be performed based on a value obtained by comparing the filtered reconstructed image with the original image. After dividing the pixels included in the image into predetermined groups, filtering may be performed differentially for each group by determining one filter to be applied to the corresponding group. Information related to whether or not to apply ALF may be transmitted for each coding unit (CU) of a luminance signal, and the shape and filter coefficients of an ALF filter to be applied may vary according to each block. In addition, the ALF filter of the same form (fixed form) may be applied regardless of the characteristics of the block to be applied.
- ALF Adaptive Loop Filtering
- the memory 155 may store a reconstructed block or picture calculated through the filter unit 150, and the stored reconstructed block or picture may be provided to the prediction units 120 and 125 when inter prediction is performed.
- FIG. 2 is a block diagram illustrating an image decoding apparatus according to an embodiment of the present disclosure.
- the image decoding apparatus 200 includes an entropy decoding unit 210, a reordering unit 215, an inverse quantization unit 220, an inverse transform unit 225, a prediction unit 230 and 235, a filter unit ( 240), memory 245 may be included.
- the input bitstream may be decoded by a procedure opposite to that of the image encoding device.
- the entropy decoding unit 210 may perform entropy decoding by a procedure opposite to that performed by the entropy encoding unit of the image encoding apparatus. For example, various methods such as exponential Golomb, CAVLC (Context-Adaptive Variable Length Coding), and CABAC (Context-Adaptive Binary Arithmetic Coding) may be applied corresponding to the method performed by the image encoding device.
- various methods such as exponential Golomb, CAVLC (Context-Adaptive Variable Length Coding), and CABAC (Context-Adaptive Binary Arithmetic Coding) may be applied corresponding to the method performed by the image encoding device.
- the entropy decoding unit 210 may decode information related to intra-prediction and inter-prediction performed by the encoding device.
- the rearrangement unit 215 may perform rearrangement based on a method in which the encoding unit rearranges the entropy-decoded bitstream in the entropy decoding unit 210 . Coefficients expressed in the form of one-dimensional vectors may be reconstructed into coefficients in the form of two-dimensional blocks and rearranged. The rearrangement unit 215 may perform rearrangement through a method of receiving information related to the coefficient scanning performed by the encoder and performing reverse scanning 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 encoding device and the rearranged coefficient value of the block.
- the inverse transform unit 225 may perform inverse transforms, that is, inverse DCT, inverse DST, and inverse KLT, on the transforms performed by the transform unit, that is, DCT, DST, and KLT, on the quantization result performed by the video encoding apparatus. Inverse transformation may be performed based on the transmission unit determined by the video encoding apparatus. In the inverse transformation unit 225 of the video decoding apparatus, transformation techniques (eg, DCT, DST, KLT) are selectively performed according to a plurality of pieces of information such as prediction method, size and shape of the current block, prediction mode, and intra-prediction direction. It can be.
- transformation techniques eg, DCT, DST, KLT
- the prediction units 230 and 235 may generate a prediction block based on information related to prediction block generation provided from the entropy decoding unit 210 and previously decoded block or picture information provided from the memory 245 .
- Intra-prediction is performed on a prediction unit based on a pixel existing in , but when performing intra-prediction, if the size of the prediction unit and the size of the transformation unit are different, a reference pixel based on the transformation unit is used to screen the picture. I can do my predictions.
- intra prediction using NxN division may be used only for the smallest coding unit.
- the prediction units 230 and 235 may include a prediction unit determination unit, an inter prediction unit, and an intra prediction unit.
- the prediction unit determination unit receives various information such as prediction unit information input from the entropy decoding unit 210, prediction mode information of the intra prediction method, and motion prediction related information of the inter prediction method, and classifies the prediction unit from the current coding unit. , it is possible to determine whether the prediction unit performs inter-prediction or intra-prediction.
- the inter-prediction unit 230 uses information necessary for inter-prediction of the current prediction unit provided from the video encoding device, based on information included in at least one picture among pictures before or after the current picture that includes the current prediction unit. It is possible to perform inter-prediction for the current prediction unit. Alternatively, inter prediction may be performed based on information of a pre-reconstructed partial region in the current picture including the current prediction unit.
- the motion prediction methods of the prediction unit included in the corresponding coding unit based on the coding unit are skip mode, merge mode, AMVP mode, intra-block copy It is possible to determine which of the modes is used.
- the intra prediction unit 235 may generate a prediction block based on pixel information in the current picture.
- intra prediction may be performed based on intra prediction mode information of the prediction unit provided by the video encoding device.
- the intra prediction unit 235 may include an Adaptive Intra Smoothing (AIS) filter, a reference pixel interpolation unit, and a DC filter.
- the AIS filter is a part that performs filtering on reference pixels of the current block, and can be applied by determining whether to apply the filter according to the prediction mode of the current prediction unit.
- AIS filtering may be performed on the reference pixels of the current block using the prediction mode of the prediction unit and AIS filter information provided by the image encoding apparatus.
- AIS filter may not be applied.
- the reference pixel interpolator may interpolate the reference pixel to generate a reference pixel in pixel units having an integer value or less.
- the prediction mode of the current prediction unit is a prediction mode for generating a prediction block without interpolating reference pixels
- the reference pixels may not be interpolated.
- the DC filter may generate a prediction block through filtering when the prediction mode of the current block is the DC mode.
- the reconstructed block or picture may be provided to the filter unit 240 .
- the filter unit 240 may include a deblocking filter, an offset correction unit, and an ALF.
- Information on whether a deblocking filter is applied to a corresponding block or picture and, when a deblocking filter is applied, information on whether a strong filter or a weak filter is applied may be provided from the video encoding device.
- the deblocking filter of the video decoding apparatus receives information related to the deblocking filter provided by the video encoding apparatus, and the video decoding apparatus may perform deblocking filtering on the corresponding block.
- the offset correction unit may perform offset correction on the reconstructed image based on the type and offset value information of the offset correction applied to the image during encoding.
- ALF may be applied to a coding unit based on ALF application information, ALF coefficient information, etc. provided from an encoding device. Such ALF information may be included in a specific parameter set and provided.
- the memory 245 may store a reconstructed picture or block so that it can be used as a reference picture or reference block, and may also provide the reconstructed picture to an output unit.
- a coding unit is used as a coding unit, but it may be a unit that performs not only encoding but also decoding.
- the current block indicates a block to be encoded/decoded, and according to encoding/decoding steps, a coding tree block (or coding tree unit), a coding block (or coding unit), a transform block (or transform unit), and a prediction block (or a prediction unit) or a block to which an in-loop filter is applied.
- a 'unit' may represent a basic unit for performing a specific encoding/decoding process
- a 'block' may represent a pixel array of a predetermined size.
- 'block' and 'unit' can be used interchangeably.
- a coding block (coding block) and a coding unit (coding unit) may be understood as equivalent to each other.
- a picture including the current block will be referred to as a current picture.
- Inter prediction may be performed in units of blocks.
- a prediction block of the current block may be generated from a reference picture using motion information of the current block.
- the motion information may include at least one of a motion vector, a reference picture index, and a prediction direction.
- Motion information of the current block may be generated through motion estimation.
- a search range for motion estimation may be set from the same position as the reference point of the current block in the reference picture.
- the reference point may be the location of the top left sample of the current block.
- a rectangle having a size of (w0+w01) and (h0+h1) centered on a reference point is set as a search range.
- w0, w1, h0, and h1 may have the same value.
- at least one of w0, w1, h0 and h1 may be set to have a different value from the other one.
- the sizes of w0, w1, h0, and h1 may be determined so as not to exceed a coding tree unit (CTU) boundary, slice boundary, tile boundary, or picture boundary.
- CTU coding tree unit
- a cost with respect to the current block may be measured for each reference block.
- the cost may be calculated using the similarity between the two blocks.
- a cost may be calculated based on an absolute sum of difference values between original samples in the current block and original samples (or reconstructed samples) in the reference block. The smaller this absolute value sum is, the lower the cost can be.
- a reference block having an optimal cost may be set as a prediction block of the current block.
- a distance between the current block and the reference block may be set as a motion vector.
- the x-coordinate difference and the y-coordinate difference between the current block and the reference block may be set as motion vectors.
- an index of a picture including a reference block specified through motion estimation is set as a reference picture index.
- a prediction direction may be set based on whether the reference picture belongs to the L0 reference picture list or the L1 reference picture list.
- motion estimation may be performed for each of the L0 and L1 directions.
- motion information in the L0 direction and motion information in the L1 direction may be respectively generated.
- 4 and 5 illustrate an example in which a prediction block of a current block is generated based on motion information generated through motion estimation.
- FIG. 4 shows an example of generating a prediction block through unidirectional (ie, L0 direction) prediction
- FIG. 5 shows an example of generating a prediction block through bidirectional (ie, L0 and L1 directions) prediction.
- a prediction block of the current block is generated using one piece of motion information.
- the motion information may include an L0 motion vector, an L0 reference picture index, and prediction direction information covering the L0 direction.
- a prediction block is generated using two pieces of motion information. For example, a reference block in the L0 direction specified based on motion information (L0 motion information) in the L0 direction is set as an L0 prediction block, and an L1 direction specified based on the motion information (L1 motion information) in the L1 direction.
- a reference block of can generate an L1 prediction block.
- a prediction block of the current block may be generated by performing a weighted sum of the L0 prediction block and the L1 prediction block.
- the L0 reference picture exists in the previous direction of the current picture (ie, the POC value is smaller than that of the current picture), and the L1 reference picture exists in the direction after the current picture (ie, the current picture). POC value is greater than that of the picture).
- the L0 reference picture may exist in a later direction of the current picture, or the L1 reference picture may exist in a previous direction of the current picture.
- both the L0 reference picture and the L1 reference picture may exist in a direction before the current picture, or both may exist in a direction after the current picture.
- bidirectional prediction may be performed using an L0 reference picture existing in a later direction of the current picture and an L1 reference picture existing in a previous direction of the current picture.
- Motion information of a block on which inter prediction is performed may be stored in a memory.
- motion information may be stored in units of samples.
- motion information of a block to which a specific sample belongs may be stored as motion information of a specific sample.
- the stored motion information may be used to derive motion information of a neighboring block to be encoded/decoded later.
- the encoder may signal information encoding a residual sample corresponding to a difference between a sample of the current block (ie, an original sample) and a prediction sample and motion information necessary for generating a prediction block to the decoder.
- the decoder may derive a difference sample by decoding information on the signaled difference value, and may generate a reconstructed sample by adding a prediction sample within a prediction block generated using motion information to the difference sample.
- one of a plurality of inter prediction modes may be selected.
- the plurality of inter prediction modes may include a motion information merging mode and a motion vector prediction mode.
- the motion vector prediction mode is a mode in which a difference value between a motion vector and a predicted motion vector is encoded and signaled.
- the motion vector prediction value may be derived based on motion information of neighboring blocks or neighboring samples adjacent to the current block.
- FIG. 6 shows a referenced position for deriving a motion vector prediction value.
- the current block has a size of 4x4.
- 'LB' represents samples included in the leftmost column and the lowest row in the current block.
- 'RT' represents samples included in the rightmost column and the topmost row in the current block.
- A0 to A4 indicate samples neighboring the left side of the current block, and B0 to B5 indicate samples neighboring the top side of the current block.
- A1 represents a sample neighboring to the left of LB, and B1 represents a sample neighboring to the top of RT.
- Col indicates the position of a sample adjacent to the lower right corner of the current block in a co-located picture.
- a collocated picture is a picture different from the current picture, and information for specifying the collocated picture may be explicitly coded in a bitstream and signaled.
- a reference picture having a predefined reference picture index may be set as a collocated picture.
- a motion vector prediction value of the current block may be derived from at least one motion vector prediction candidate included in a motion vector prediction list.
- the number of motion vector prediction candidates (ie, the size of the list) that can be inserted into the motion vector prediction list may be predefined in the encoder and decoder.
- the maximum number of motion vector prediction candidates may be two.
- a motion vector stored in a position of a neighboring sample adjacent to the current block or a scaled motion vector derived by scaling the motion vector may be inserted into the motion vector prediction list as a motion vector prediction candidate.
- a motion vector prediction candidate may be derived by scanning neighboring samples adjacent to the current block in a predefined order.
- an available motion vector found first may be inserted into the motion vector prediction list as a motion vector prediction candidate.
- a motion vector prediction candidate may be derived based on the first available vector found. Specifically, after scaling an available motion vector found first, the scaled motion vector may be inserted into the motion vector prediction list as a motion vector prediction candidate.
- scaling may be performed based on an output order difference between the current picture and a reference picture (ie, a POC difference) and an output order difference between the current picture and a reference picture of a neighboring sample (ie, a POC difference).
- a motion vector prediction candidate may be derived based on the first available vector found. Specifically, after scaling an available motion vector found first, the scaled motion vector may be inserted into the motion vector prediction list as a motion vector prediction candidate.
- scaling may be performed based on an output order difference between the current picture and a reference picture (ie, a POC difference) and an output order difference between the current picture and a reference picture of a neighboring sample (ie, a POC difference).
- a motion vector prediction candidate may be derived from a sample adjacent to the left side of the current block, and a motion vector prediction candidate may be derived from a sample adjacent to the top side of the current block.
- the motion vector prediction candidate derived from the left sample may be inserted into the motion vector prediction list prior to the motion vector prediction candidate derived from the upper sample.
- an index assigned to the motion vector prediction candidate derived from the left sample may have a value smaller than that of the motion vector prediction candidate derived from the upper sample.
- the motion vector prediction candidate derived from the upper sample may be inserted into the motion vector prediction list before the motion vector prediction candidate derived from the left sample.
- a motion vector prediction candidate having the highest coding efficiency among motion vector prediction candidates included in the motion vector prediction list may be set as a motion vector predictor (MVP) of the current block.
- index information indicating a motion vector prediction candidate set as a motion vector prediction value of a current block among a plurality of motion vector prediction candidates may be encoded and signaled to a decoder.
- the index information may be a 1-bit flag (eg, MVP flag).
- a motion vector difference (MVD) which is a difference between a motion vector of a current block and a motion vector prediction value, may be encoded and signaled to a decoder.
- the decoder may construct a motion vector prediction list in the same way as the encoder. Also, index information may be decoded from the bitstream, and one of a plurality of motion vector prediction candidates may be selected based on the decoded index information. The selected motion vector prediction candidate may be set as a motion vector prediction value of the current block.
- a motion vector difference value may be decoded from the bitstream. Thereafter, the motion vector of the current block may be derived by adding the motion vector prediction value and the motion vector difference value.
- a motion vector prediction list may be generated for each of the L0 direction and the L1 direction. That is, the motion vector prediction list may be composed of motion vectors in the same direction. Accordingly, the motion vector of the current block and the motion vector prediction candidates included in the motion vector prediction list have the same direction.
- reference picture index and prediction direction information may be explicitly encoded and signaled to a decoder.
- reference picture index and prediction direction information may be explicitly encoded and signaled to a decoder. For example, when a plurality of reference pictures exist on a reference picture list and motion estimation is performed on each of the plurality of reference pictures, a method for specifying a reference picture from which motion information of a current block is derived among the plurality of reference pictures A reference picture index may be explicitly coded and signaled to a decoder.
- the prediction direction information may be an index indicating one of L0 unidirectional prediction, L1 unidirectional prediction, and bidirectional prediction.
- the L0 flag indicating whether prediction in the L0 direction is performed and the L1 flag indicating whether prediction in the L1 direction are performed may be encoded and signaled.
- the motion information merging mode is a mode in which motion information of a current block is set to be the same as motion information of a neighboring block.
- motion information may be encoded/decoded using a motion information merging list.
- a motion information merging candidate may be derived based on motion information of neighboring blocks or neighboring samples adjacent to the current block. For example, after pre-defining a location to be referenced around the current block, it is possible to check whether motion information exists in the pre-defined reference location. When motion information exists in a predefined reference position, the motion information of the corresponding position may be inserted into the motion information merging list as a motion information merging candidate.
- the predefined reference positions may include at least one of A0, A1, B0, B1, B5, and Col.
- motion information merging candidates may be derived in the order of A1, B1, B0, A0, B5, and Col.
- motion information of a motion information merging candidate having an optimal cost may be set as motion information of the current block.
- index information eg, merge index
- a motion information merging candidate selected from among a plurality of motion information merging candidates may be encoded and transmitted to the decoder.
- a motion information merging list may be configured in the same way as in the encoder. And, based on the merge index decoded from the bitstream, a motion information merge candidate may be selected. Motion information of the selected motion information merging candidate may be set as motion information of the current block.
- the motion information merging list is composed of a single list regardless of prediction direction. That is, the motion information merging candidates included in the motion information merging list may have only L0 motion information or L1 motion information, or may have bi-directional motion information (ie, L0 motion information and L1 motion information).
- Motion information of the current block may be derived using a reconstructed sample area around the current block.
- a reconstructed sample region used to derive motion information of the current block may be referred to as a template.
- FIG. 7 is a diagram for explaining a template-based motion estimation method.
- the prediction block of the current block is determined based on the cost between the current block and the reference block within the search range.
- motion estimation for the current block can be performed.
- the cost may be calculated based on the sum of absolute differences between reconstructed samples in the current template and reconstructed samples in the reference block. The smaller the absolute value sum, the lower the cost can be.
- a reference block neighboring the reference template may be set as a prediction block of the current block.
- Motion information of the current block may be set based on the distance between the current block and the reference block, the index of the picture to which the reference block belongs, and whether the reference picture is included in the L0 or L1 reference picture list.
- the decoder itself can perform motion estimation in the same way as the encoder. Accordingly, when motion information is derived using a template, there is no need to encode and signal motion information other than information indicating whether or not the template is used.
- the current template may include at least one of an area adjacent to the top of the current block or an area adjacent to the left side of the current block.
- an area adjacent to the top may include at least one row
- an area adjacent to the left side may include at least one column.
- the current template can be configured.
- the template may be configured only with an area adjacent to the left side of the current block or only with an area adjacent to the top of the current block.
- the size and/or shape of the current template may be predefined in the encoder and decoder.
- index information specifying one of the plurality of template candidates may be encoded and signaled to a decoder.
- one of a plurality of template candidates may be adaptively selected based on at least one of the size, shape, or location of the current block. For example, when the current block is in contact with the upper boundary of the CTU, the current template may be configured only with an area adjacent to the left side of the current block.
- Motion estimation based on a template may be performed on each of the reference pictures stored in the reference picture list.
- motion estimation may be performed on only some of the reference pictures. For example, motion estimation is performed only for a reference picture having a reference picture index of 0, motion estimation is performed only for reference pictures having a reference picture index smaller than a threshold value, or reference pictures having a POC difference from the current picture smaller than the threshold value. can be done
- motion estimation may be performed only on a reference picture indicated by the reference picture index.
- motion estimation may be performed targeting a reference picture of a neighboring block corresponding to the current template. For example, if the template is composed of a left neighboring region and an upper neighboring region, at least one reference picture may be selected using at least one of a reference picture index of a left neighboring block or a reference picture index of an upper neighboring block. Then, motion estimation may be performed on at least one selected reference picture.
- Information indicating whether template-based motion estimation is applied may be encoded and signaled to a decoder.
- the information may be a 1-bit flag. For example, when the flag is true (1), it indicates that template-based motion estimation is applied to the L0 and L1 directions of the current block. On the other hand, if the flag is false (0), it indicates that template-based motion estimation is not applied. In this case, motion information of the current block may be derived based on the motion information merging mode or the motion vector prediction mode.
- template-based motion estimation may be applied only when it is determined that the motion information merging mode and the motion vector prediction mode are not applied to the current block. For example, when both the first flag indicating whether the motion information merging mode is applied and the second flag indicating whether the motion vector prediction mode is applied are 0, motion estimation based on the template may be performed.
- template-based motion estimation For each of the L0 and L1 directions, information indicating whether template-based motion estimation is applied may be signaled. That is, whether template-based motion estimation is applied to the L0 direction and whether template-based motion estimation is applied to the L1 direction may be independently determined. Accordingly, template-based motion estimation may be applied to one of the L0 direction and the L1 direction, while another mode (eg, motion information merging mode or motion vector prediction mode) may be applied to the other direction.
- another mode eg, motion information merging mode or motion vector prediction mode
- a prediction block of the current block may be generated based on a weighted sum operation of the L0 prediction block and the L1 prediction block.
- the prediction block of the current block this can be created. This will be described later through Equation 2.
- a motion estimation method based on a template may be inserted as a motion information merging candidate in a motion information merging mode or a motion vector prediction candidate in a motion vector prediction mode.
- whether to apply the template-based motion estimation method may be determined based on whether the selected motion information merging candidate or the selected motion vector prediction candidate indicates the template-based motion estimation method.
- motion information of the current block may be generated.
- FIG. 9 is a diagram for explaining a motion estimation method based on a bilateral matching method.
- the bilateral matching method can be performed only when the temporal order (ie, POC) of the current picture exists between the temporal order of the L0 reference picture and the temporal order of the L1 reference picture.
- search ranges may be set for each of the L0 reference picture and the L1 reference picture.
- an L0 reference picture index for identifying the L0 reference picture and an L1 reference picture index for identifying the L1 reference picture may be coded and signaled.
- the L1 reference picture may be selected based on the distance between the current picture and the L0 reference picture (hereinafter referred to as the L0 POC difference).
- the L1 POC difference the absolute value of the distance from the current picture (hereinafter referred to as the L1 POC difference) is equal to the absolute value of the distance between the current picture and the L0 reference picture. You can select a picture. If an L1 reference picture having the same L1 POC difference as the L0 POC difference does not exist, an L1 reference picture having the most similar L1 POC difference to the L0 POC difference may be selected from among the L1 reference pictures.
- an L1 reference picture having a different temporal direction from the L0 reference picture among the L1 reference pictures may be used for bilateral matching. For example, when the POC of the L0 reference picture is smaller than that of the current picture, one of L1 reference pictures having a POC greater than that of the current picture may be selected.
- the L1 reference picture index may be coded and signaled, and the L0 reference picture may be selected based on the distance between the current picture and the L1 reference picture.
- the bilateral matching method may be performed using an L0 reference picture having the closest distance to the current picture among L0 reference pictures and an L1 reference picture having the closest distance to the current picture among L1 reference pictures.
- both A matching method may also be performed.
- the LX (X is 0 or 1) reference picture is selected based on an explicitly signaled reference picture index, and the L
- reference picture list may be selected.
- L0 and/or L1 reference pictures may be selected based on motion information of neighboring blocks of the current block.
- an L0 and/or L1 reference picture to be used for bilateral matching may be selected using a reference picture index of a left or upper neighboring block of the current block.
- the search range may be set within a predetermined range from the collocated block in the reference picture.
- a search range may be set based on initial motion information.
- Initial motion information may be derived from a neighboring block of the current block. For example, motion information of a left neighboring block or an upper neighboring block of the current block may be set as initial motion information of the current block.
- the L0 motion vector and the motion vector in the L1 direction are set in opposite directions. This indicates that the sign of the L0 motion vector and the motion vector in the L1 direction have opposite signs to each other.
- the size of the LX motion vector may be proportional to the distance between the current picture and the LX reference picture (ie, the POC difference).
- L0 reference block a reference block belonging to the search range of the L0 reference picture
- L1 reference block a reference block belonging to the search range of the L1 reference picture
- an L1 reference block spaced apart from the current block by (-Dx, -Dy) may be selected.
- D may be determined by a ratio of a distance between the current picture and the L0 reference picture and a distance between the L1 reference picture and the current picture.
- the absolute value of the distance between the current picture (T) and the L0 reference picture (T-1) and the distance between the current picture (T) and the L1 reference picture (T+1) Absolute values are equal to each other. Accordingly, in the illustrated example, the L0 motion vector (x0, y0) and the L1 motion vector (x1, y1) have the same magnitude but opposite distances. If an L1 reference picture with a POC of (T+2) is used, the L1 motion vector (x1, y1) will be set to (-2*x0, -2*y0).
- each of the L0 reference block and the L1 reference block may be set as the L0 prediction block and the L1 prediction block of the current block. Thereafter, a final prediction block of the current block may be generated through a weighted sum operation of the L0 reference block and the L1 reference block. For example, according to Equation 2 to be described later, a prediction block of the current block may be generated.
- the decoder may perform motion estimation in the same way as the encoder. Accordingly, while information indicating whether the bilateral motion matching method is applied is explicitly encoded/decoded, encoding/decoding of motion information such as motion vectors may be omitted. As described above, at least one of the L0 reference picture index and the L1 reference picture index may be explicitly encoded/decoded.
- the L0 motion vector or the L1 motion vector may be explicitly encoded and signaled.
- the L0 motion vector When the L0 motion vector is signaled, the L1 motion vector can be derived based on the POC difference between the current picture and the L0 reference picture and the POC difference between the current picture and the L1 reference picture.
- the L0 motion vector When the L1 motion vector is signaled, the L0 motion vector can be derived based on the POC difference between the current picture and the L0 reference picture and the POC difference between the current picture and the L1 reference picture.
- the encoder may explicitly encode the smaller one of the L0 motion vector and the L1 motion vector.
- Information indicating whether the bilateral matching method is applied may be a 1-bit flag. For example, when the flag is true (eg, 1), it may indicate that the bilateral matching method is applied to the current block. When the flag is false (eg, 0), it may indicate that the bilateral matching method is not applied to the current block. In this case, a motion information merging mode or a motion vector prediction mode may be applied to the current block.
- the bilateral matching method may be applied only when it is determined that the motion information merging mode and the motion vector prediction mode are not applied to the current block. For example, when both the first flag indicating whether the motion information merging mode is applied and the second flag indicating whether the motion vector prediction mode is applied are 0, the bilateral matching method may be applied.
- the bilateral matching method may be inserted as a motion information merging candidate in the motion information merging mode or a motion vector prediction candidate in the motion vector prediction mode.
- whether to apply the bilateral matching method may be determined based on whether the selected motion information merging candidate or the selected motion vector prediction candidate indicates the bilateral matching method.
- a prediction block of the current block may be generated by applying a unidirectional matching method to which the above bidirectional matching method does not apply.
- a unidirectional matching method two reference pictures having a smaller temporal order (ie, POC) than the current block or two reference pictures having a greater temporal order than the current block may be used.
- both reference pictures may be derived from the L0 reference picture list or the L1 reference picture list.
- one of the two reference pictures may be derived from the L0 reference picture list and the other may be derived from the L1 reference picture list.
- FIG. 10 is a diagram for explaining a motion estimation method based on a unidirectional matching method.
- the unidirectional matching method may be performed based on two reference pictures having a smaller POC than the current picture (ie, forward reference pictures) or two reference pictures having a higher POC than the current picture (ie, backward reference pictures).
- FIG. 10 it is illustrated that motion estimation based on a unidirectional matching method is performed based on the first reference picture (T-1) and the second reference picture (T-2) having smaller POCs than the current picture (T).
- a first reference picture index for identifying the first reference picture and a second reference picture index for identifying the second reference picture may be coded and signaled.
- a reference picture having a smaller POC difference from the current picture may be set as the first reference picture.
- only reference pictures having a greater POC difference from the current picture than the first reference picture among the reference pictures included in the reference picture list may be set as the second reference picture.
- the second reference picture index is obtained by rearranging reference pictures having the same temporal direction as the first reference picture and having a greater POC difference from the current picture than the first reference picture, and then obtaining an index of one of the rearranged reference pictures. It can be set to point.
- a reference picture having a greater POC difference from the current picture may be set as the first reference picture.
- the second reference picture index is obtained by rearranging reference pictures having the same temporal direction as the first reference picture and having a smaller POC difference from the current picture than the first reference picture, and then selecting one of the rearranged reference pictures. It can be set to point to the index of
- the unidirectional matching method may be performed using a reference picture to which a predefined index is assigned in the reference picture list and a reference picture having the same temporal direction as the reference picture.
- a reference picture having an index of 0 in the reference picture list is set as a first reference picture
- a reference picture having the smallest index among reference pictures in the same temporal direction as the first reference picture in the reference picture list is used as a second reference picture.
- Both the first reference picture and the second reference picture can be selected from the L0 reference picture list or the L1 reference picture list.
- FIG. 10 it is shown that two L0 reference pictures are used for the unidirectional matching method.
- the first reference picture may be selected from the L0 reference picture list
- the second reference picture may be selected from the L1 reference picture list.
- Information indicating whether the first reference picture and/or the second reference picture belongs to the L0 reference picture list or the L1 reference picture list may be additionally encoded/decoded.
- unidirectional matching may be performed using one of the L0 reference picture list and the L1 reference picture list set as default.
- two reference pictures may be selected from among the L0 reference picture list and the L1 reference picture list having a greater number of reference pictures.
- search ranges within the first reference picture and the second reference picture may be set.
- the search range may be set within a predetermined range from the collocated block in the reference picture.
- a search range may be set based on initial motion information.
- Initial motion information may be derived from a neighboring block of the current block. For example, motion information of a left neighboring block or an upper neighboring block of the current block may be set as initial motion information of the current block.
- motion estimation may be performed using a cost between a first reference block belonging to the search range of the first reference picture and a second reference block belonging to the search range of the second reference picture.
- the size of the motion vector should be set to increase in proportion to the distance between the current picture and the reference picture.
- the second reference block when a first reference block having a vector of (x, y) with the current picture is selected, the second reference block must be spaced apart from the current block by (Dx, Dy).
- D may be determined by a ratio of a distance between the current picture and the first reference picture and a distance between the current picture and the second reference picture.
- the distance between the current picture and the first reference picture is 1, and the distance between the current picture and the second reference picture (ie, the POC difference) is 2. Accordingly, when the first motion vector for the first reference block in the first reference picture is (x0, y0), the second motion vector (x1, y1) for the second reference block in the second reference picture is ( 2x0, 2y0).
- each of the first reference block and the second reference block may be set as the first prediction block and the second prediction block of the current block. Thereafter, a final prediction block of the current block may be generated through a weighted sum operation of the first prediction block and the second prediction block. For example, according to Equation 2 to be described later, a prediction block of the current block may be generated.
- the decoder may perform motion estimation in the same way as the encoder. Accordingly, information indicating whether the unidirectional motion matching method is applied may be explicitly encoded/decoded, while encoding/decoding of motion information such as motion vectors may be omitted. As described above, at least one of the first reference picture index and the second reference picture index may be explicitly encoded/decoded.
- information indicating whether the unidirectional matching method is applied is explicitly encoded/decoded, but when the unidirectional matching method is applied, the first motion vector or the second motion vector may be explicitly encoded and signaled.
- the second motion vector may be derived based on the POC difference between the current picture and the first reference picture and the POC difference between the current picture and the second reference picture.
- the first motion vector may be derived based on a POC difference between the current picture and the first reference picture and a POC difference between the current picture and the second reference picture.
- the encoder may explicitly encode a smaller one of the first motion vector and the second motion vector.
- Information indicating whether the one-way matching method is applied may be a 1-bit flag. For example, when the flag is true (eg, 1), it may indicate that the one-way matching method is applied to the current block. When the flag is false (eg, 0), it may indicate that the one-way matching method is not applied to the current block. In this case, a motion information merging mode or a motion vector prediction mode may be applied to the current block.
- the unidirectional matching method can be applied only when it is determined that the motion information merging mode and the motion vector prediction mode are not applied to the current block. For example, when both the first flag indicating whether the motion information merging mode is applied and the second flag indicating whether the motion vector prediction mode is applied are 0, the unidirectional matching method may be applied.
- the unidirectional matching method may be inserted as a motion information merging candidate in the motion information merging mode or a motion vector prediction candidate in the motion vector prediction mode.
- whether to apply the unidirectional matching method may be determined based on whether the selected motion information merging candidate or the selected motion vector prediction candidate indicates the unidirectional matching method.
- Intra prediction is a method of obtaining a prediction block of a current block by using reference samples having spatial similarity with the current block.
- Reference samples used for intra prediction may be reconstructed samples.
- a reconstructed sample obtained by reconstructing a current block periphery may be set as a reference sample.
- an adjacent reconstructed sample may be set as a reference sample of the specific location.
- the original sample may be set as a reference sample.
- At least one of a method for performing motion estimation in a decoder in the same manner as an encoder may be defined as an inter prediction mode.
- a method for performing motion estimation in a decoder in the same manner as an encoder may be defined as an inter prediction mode.
- a plurality of decoder-side motion estimation methods are defined as an inter prediction mode, specifying one of the plurality of decoder-side motion estimation methods together with a flag indicating whether the decoder-side motion estimation method is applied.
- An index may be encoded and signaled. For example, an index indicating at least one of a template-based motion estimation method, a bilateral estimation method, and a unidirectional estimation method may be encoded and signaled.
- Intra prediction may be performed based on at least one of a plurality of intra prediction modes predefined in an encoder and a decoder.
- Intra prediction modes predefined in the encoder and decoder may include non-directional intra prediction modes and directional prediction modes.
- mode 0 represents a planar mode, which is a non-directional mode
- mode 1 represents a DC mode, which is a non-directional mode.
- 65 directional intra prediction modes (2-66) are illustrated.
- a larger number of intra prediction modes or a smaller number of intra prediction modes than shown may be predefined in the encoder and decoder.
- One of predefined intra prediction modes may be selected, and a prediction block for a current block may be obtained based on the selected intra prediction mode.
- the number and locations of reference samples used to generate prediction samples in the prediction block may be adaptively determined according to the selected intra prediction mode.
- a reference sample T adjacent to the upper right corner and a reference sample L adjacent to the lower left corner of the current block may be used.
- P1 represents a prediction sample in a horizontal direction
- P2 represents a prediction sample in a vertical direction
- P1 may be generated by linearly interpolating a reference sample having the same y-coordinate as P1 (ie, a reference sample located in the horizontal direction of P1) and a reference sample T.
- P2 may be generated by linearly interpolating a reference sample having the same x-coordinate as P2 (ie, a reference sample located in the vertical direction of P2) and a reference sample L.
- Equation 1 shows an example of generating a final prediction sample.
- ⁇ represents a weight assigned to the horizontal direction prediction sample P1
- ⁇ represents a weight assigned to the vertical direction prediction sample P2.
- Weight ⁇ and weight ⁇ may be determined based on the width and height of the current block. Depending on the width and height of the current block, the weights ⁇ and ⁇ may have the same or different values. For example, when one side of a block is longer than the other side, a weight assigned to a prediction sample in a direction parallel to the long side may be set to have a higher value. Alternatively, contrary to the above, a weight assigned to a prediction sample in a direction parallel to the long side may be set to have a smaller value.
- FIG 13 illustrates an example in which prediction samples are generated under the DC mode.
- an average value of reference samples around the current block may be calculated.
- Figure 13 shows the range of reference samples used to use the mean value. As in the example shown in FIG. 13 , the average value may be calculated based on the top reference samples and the left reference samples.
- the average value may be calculated using only the top reference samples or the average value may be calculated using only the left reference samples. For example, when the width of the current block is greater than the height, or when the ratio between the width and height of the current block is equal to or greater than (or less than) a predefined value, an average value may be calculated using only upper reference samples. .
- the average value can be calculated using only the left reference samples.
- FIG. 14 illustrates an example in which prediction samples are generated under the directional intra prediction mode.
- projection may be performed in the direction in which the reference sample is placed, according to the angle of the directional intra prediction mode, at each sample position in the current block.
- the reference sample at the corresponding position may be set as a prediction sample.
- reference samples around the projected position may be interpolated, and the interpolated value may be set as the predicted sample.
- reference sample R3 when angle-based projection of the directional intra prediction mode is performed at the position of sample B in the current block, reference sample R3 exists at the projected position. Accordingly, reference sample R3 may be set as a predicted sample for the sample B position.
- integer position reference samples existing around the projected position may be interpolated, and the interpolated value may be set as a predicted sample for the sample A position.
- a value generated by interpolating integer position reference samples may be referred to as a fractional position reference sample (r in FIG. 14 ).
- the prediction block of the current block may be generated through inter prediction or intra prediction.
- inter prediction may be generated based on at least one of a plurality of inter prediction modes, and the plurality of inter prediction modes include a motion vector merging mode, a motion vector prediction mode, a motion estimation method based on a template, and a bilateral matching method.
- at least one of the unidirectional matching methods may be included.
- an inter prediction mode in which a decoder performs motion estimation in the same way as an encoder to generate a prediction block ie, a motion estimation method based on a template, a bilateral matching method
- a decoder-side motion estimation mode an inter prediction mode in which information generated by motion estimation in an encoder is explicitly encoded and signaled (ie, a motion information merging mode and/or a motion vector prediction mode) is a motion information signaling mode.
- a prediction block of a current block may be generated by combining two or more of inter prediction methods. For example, after generating a plurality of prediction blocks based on each of a plurality of inter prediction methods, a final prediction block of the current block may be generated based on the plurality of prediction blocks.
- the above inter prediction method may be referred to as a combined prediction method.
- Information indicating whether the combined prediction method is applied may be explicitly coded and signaled.
- the information may be a 1-bit flag.
- information identifying each of the two inter-prediction modes may be additionally encoded/decoded. For example, a flag indicating whether template-based motion estimation is applied, a flag indicating whether bilateral matching method is applied, a flag indicating whether unidirectional matching method is applied, a flag indicating whether motion information merging mode is applied, or Two or more of the flags indicating whether the motion vector prediction mode is applied may be coded and signaled.
- a plurality of combination candidates configured by combining two of the inter prediction modes may be previously defined, and an index specifying one of the plurality of combination candidates may be coded and signaled.
- 15 is a flowchart illustrating a method of deriving a prediction block of a current block by a combined prediction method.
- a first prediction block may be generated by applying the first inter prediction mode to the current block (S1510).
- the first prediction mode may be any one of a motion vector merging mode, a motion vector prediction mode, a motion estimation method based on a template, a bilateral matching method, and a unidirectional matching method.
- a second prediction block may be generated by applying the second inter prediction mode to the current block (S1520).
- the second inter prediction mode may be any one different from the first inter prediction mode among a motion vector merging mode, a motion vector prediction mode, a template-based motion estimation method, a bilateral matching method, and a unidirectional matching method.
- one of the first inter-prediction mode and the second inter-prediction mode may be set as a decoder-side motion estimation mode, and the other may be forced to be set as a motion information signaling mode.
- 16 shows an example in which a plurality of prediction blocks are generated under the combined prediction method.
- the template-based motion estimation method is applied to the L0 direction
- the general motion estimation method of searching for a reference block similar to the current block is applied to the L1 direction.
- the first prediction block (ie, the L0 prediction block) for the current block may be generated by applying the template-based motion estimation method to the L0 direction.
- the current template within the search range of the L0 reference picture and the reference template with the lowest cost may be searched.
- a distance between the current template and the reference template may be set as a motion vector in the L0 direction.
- a reference block neighboring the reference template may be set as the first prediction block (ie, L0 prediction block) of the current block.
- a second prediction block (ie, an L1 prediction block) for the current block may be generated by applying a general motion estimation method to the L1 direction. Specifically, a current block within the search range of the L1 reference picture and a reference block having the lowest cost may be searched for. When a reference block having the lowest cost is determined, a distance between the current block and the reference template may be set as a motion vector in the L1 direction.
- the reference block may be set as the second prediction block (ie, L1 prediction block) of the current block.
- the decoder can determine whether the template-based motion estimation method is applied based on the information. When it is determined that the motion estimation method based on the template is applied, the motion vector and/or the first prediction block may be generated through the motion estimation method based on the template in the same way as the encoder.
- the decoder may generate a first prediction block by setting the template-based motion estimation method to the first inter prediction mode and performing template-based motion estimation.
- the decoder sets the motion information merging mode or the motion vector prediction mode to the second inter prediction mode, and generates a second prediction block based on motion information derived based on information parsed from the bitstream.
- the second inter prediction mode is a motion information merging mode
- motion information may be derived based on a motion information merging index parsed from a bitstream.
- motion information may be derived based on a motion vector prediction flag and a motion vector difference parsed from a bitstream.
- the combined prediction method may be performed by applying different inter prediction modes to L0 inter prediction and L1 inter prediction, respectively.
- bidirectional prediction ie, L0 and L1 prediction
- unidirectional prediction ie, L0 or L1 prediction
- bidirectional prediction ie, L0 and L1 prediction
- uni-prediction may be performed through the first inter-prediction mode
- bi-prediction may be performed through the second inter-prediction mode.
- both the first inter-prediction mode and the second inter-prediction mode may be set to perform bidirectional prediction.
- the prediction direction of the second inter prediction mode may be set according to the prediction direction of the first inter prediction mode.
- the second inter-prediction mode may be set to be applied to L1-direction prediction or bi-directional prediction.
- the first inter-prediction mode and the second inter-prediction mode may be selected regardless of the prediction direction.
- the L0 reference picture is a forward reference picture with a smaller POC than the current picture
- the L1 reference picture is a backward reference picture with a larger POC than the current picture.
- the first inter-prediction mode can be forced to be performed using a forward reference picture
- the second inter-prediction mode to be performed using a backward reference picture.
- forward reference pictures may be used in both the L0 and L1 directions, or backward reference pictures may be used in both the L0 and L1 directions.
- a final prediction block of the current block may be generated through a weighted sum operation of the first prediction block and the second prediction block (S1530).
- Equation 2 shows an example of generating a final prediction block of a current block through a weighted sum operation.
- Equation 2 P means the last prediction block of the current block, and P0 and P1 mean the first prediction block and the second prediction block, respectively.
- [x, y] represents the coordinates of the sample in the current block.
- W represents the width of the current block, and H represents the height of the current block.
- the weight applied to the first prediction block P0 is w0 and the weight applied to the second prediction block P1 is (1-w0). Conversely, a weight of (1-w0) may be applied to the first prediction block P0 and a weight of w0 may be applied to the second prediction block P1.
- the same weight may be assigned to each of P0 and P1. That is, by setting w0 to 1/2, the average value of P0 and P1 may be set as the final prediction block.
- a weight assigned to each prediction block may be adaptively set according to an inter prediction mode used to generate each prediction block. For example, a weight assigned to a prediction block generated by a motion estimation mode on the decoder side may be set to a greater value than a weight assigned to a prediction block generated based on a motion information signaling mode.
- the first prediction block ie, the L0 prediction block
- the second prediction block ie, the L1 prediction block
- the weight assigned to the first prediction block may have a greater value than the weight assigned to the second prediction block.
- the weight may be determined based on the POC of the first reference picture used to generate the first prediction block and the POC of the second reference picture used to generate the second prediction block.
- the weight w0 may be determined based on the ratio between the absolute value of the POC difference between the first reference picture and the current picture and the absolute value of the POC difference between the second reference picture and the current picture.
- a higher weight may be assigned to a prediction block derived from a reference picture having a smaller absolute value of the POC difference from the current picture among the first reference picture and the second reference picture.
- a weight applied to each prediction block may be determined based on a predefined weight table.
- the weight table may be a lookup table in which different indices are assigned to each of the weight candidates that may be set to the weight w0.
- lookup tables to which different indices are assigned to each of the five weight candidates may be pre-stored in the encoder and the decoder.
- a weight table [4/8, 5/8, 3/8, 10/8, -2/8] including 5 weight candidates to which indices 0 to 4 are assigned in the enumerated order may be predefined.
- Index information identifying a candidate value having the same value as w0 in the lookup table may be explicitly encoded and signaled.
- the number of weight candidates included in the weight table and/or the value of the weight candidates may be at least one of the inter prediction mode, the size of the current block, the shape of the current block, the temporal direction of the reference picture(s), or the temporal order of the reference picture(s). It can be adaptively determined based on one.
- a weight w0 may be selected from N weight candidates.
- a weight w0 may be selected from among M weight candidates.
- M may be a natural number different from N.
- a combined prediction method is applied by combining a first inter prediction mode and a second inter prediction mode different from the first inter prediction mode.
- the final prediction block of the current block may be generated by generating two prediction blocks based on one inter prediction mode.
- the same inter prediction mode may be applied to both the L0 direction and the L1 direction.
- a template-based motion estimation method may be applied to both the L0 direction and the L1 direction.
- information eg, a flag
- indicating whether the template-based motion estimation method is applied to each of the L0 and L1 directions may be explicitly encoded and signaled.
- two prediction blocks may be generated by applying a template-based motion estimation method to each of two forward reference pictures or two backward reference pictures.
- two prediction blocks may be generated by selecting a plurality of motion information merging candidates from the motion information merging list. For example, a first prediction block is derived based on first motion information derived from a first motion information merging candidate, and a second prediction block is derived based on second motion information derived from a second motion information merging candidate.
- the decoder-side motion estimation mode when the decoder-side motion estimation mode is inserted into the motion information merging list as one of the motion information merging candidates, at least one of the first motion information merging candidate and the second motion information merging candidate is the decoder-side motion estimation mode. It may be forced to indicate a motion information merging candidate corresponding to .
- a total of three prediction blocks may be generated for the current block.
- the first inter-prediction mode is the motion information merging mode and the motion information derived based on the motion information merging list has bi-directional motion information
- an L0 prediction block and an L1 prediction block are formed using the motion information.
- the second inter prediction mode is the template-based motion estimation method and the template-based motion estimation method is applied only to the L0 direction
- one L0 prediction block may be generated.
- three prediction blocks ie, two L0 prediction blocks and one L1 prediction block
- a prediction block generated by a weighted sum (or average) of the L0 prediction block and the L1 prediction block generated through the first inter prediction mode is set as the first prediction block, and L0 generated through the second inter prediction mode
- a final prediction block of the current block may be generated through Equation 2.
- a prediction block generated by a weighted sum (or average) of two L0 prediction blocks is set as the first prediction block, and one L1 prediction block is set as the second prediction block, and through Equation 2, the current It is also possible to generate the final prediction block of the block.
- the final prediction block of the current block can be generated in the same manner as above.
- the first inter-prediction mode is the motion information merging mode and the motion information derived based on the motion information merging list has bi-directional motion information
- an L0 prediction block and an L1 prediction block are formed using the motion information.
- the second inter prediction mode is the template-based motion estimation method and the template-based motion estimation method is applied to each of the L0 direction and the L1 direction
- an L0 prediction block and an L1 prediction block may be generated.
- four prediction blocks ie, two L0 prediction blocks and two L1 prediction blocks
- a prediction block generated by a weighted sum (or average) of the L0 prediction block and the L1 prediction block generated based on the first inter prediction mode is set as the first prediction block, and generated based on the second inter prediction mode
- a prediction block generated by a weighted sum (or average) of the L0 prediction block and the L1 prediction block may be set as the second prediction block.
- a prediction block generated by a weighted sum (or average) of the L0 prediction block generated based on the first inter prediction mode and the L0 prediction block generated based on the second inter prediction mode is set as the first prediction block;
- a prediction block generated by a weighted sum (or average) of the L1 prediction block generated based on the first inter prediction mode and the L1 prediction block generated based on the second inter prediction mode may be set as the second prediction block.
- a combined prediction method may be performed using three or more inter prediction modes.
- three or more prediction blocks may be generated for the current block, and a final prediction block of the current block may be generated by performing a weighted sum of the three prediction blocks.
- each of the three prediction blocks may be generated based on a motion estimation mode or a motion information signaling mode on the decoder side.
- a weighted sum (or average) of the L0 prediction blocks may be set as the first prediction block, and a weighted sum (or average) of the L1 prediction blocks may be set as the second prediction block.
- a weighted sum (or average) of prediction blocks derived based on the motion estimation mode of the decoding side is set as the first prediction block, and the prediction blocks derived based on the motion information signaling mode
- a weighted sum (or average) may be set as the second prediction block.
- a final prediction block of the current block may be derived based on a weighted sum operation between three or more prediction blocks.
- the weight applied to each prediction block may be determined based on a predefined weight table.
- information identifying one of the weight candidates included in the weight table may be explicitly encoded and signaled.
- a plurality of prediction blocks may be generated for the current block by applying the template-based motion estimation method multiple times.
- a template-based motion estimation method may be applied to each of reference pictures available for the current block, and based on this, up to N reference block(s) may be selected from each reference picture.
- N represents 1 or an integer larger than 1. For example, when N is 1, as many reference blocks as the number of reference pictures may be generated.
- M reference blocks may be derived based on costs with a current template by applying a template-based motion estimation method to each of the reference pictures. For example, it is assumed that template-based motion estimation is applied to each of the L reference pictures, and as a result, a reference block having an optimal cost within each reference picture is selected.
- M reference blocks may be selected in order of lowest cost with the current template.
- M represents an integer greater than or equal to 1.
- N and/or M may have predefined values in the encoder and decoder.
- N and/or M may be determined based on at least one of the size of the current block, the shape of the current block, or the number of samples in the current block.
- a final prediction block for the current block may be obtained by weighting a plurality of reference blocks derived through the above process.
- a weight assigned to each reference block may be determined based on a cost ratio between reference templates. For example, when it is assumed that the final prediction block for the current block is obtained by weighting two reference blocks, the weight assigned to each of the first reference block and the second reference block is a first reference template adjacent to the first reference block It may be determined as a ratio between a cost a for and a cost b for a second reference template adjacent to the second reference block. For example, a weight of b/(a+b) may be applied to the first reference block, and a weight of a/(a+b) may be applied to the second reference block.
- the first reference block and the second reference block are applied.
- weight can be determined. For example, when the above ratio or the above difference does not exceed a threshold value, the same weight may be applied to the first reference block and the second reference block. Otherwise, the weight for the first reference block and the weight for the second reference block may be determined differently.
- a reference block having an optimal cost among a plurality of reference blocks may be selected as a prediction block of the current block.
- the final prediction sample included in the first region of the current block may be obtained through a weighted sum operation between prediction samples included in the first prediction block and prediction samples included in the second prediction block.
- the final prediction sample included in the second region of the current block may be set to a prediction sample included in the first prediction block or a prediction sample included in the second prediction block. That is, in a region where weighted sum is not performed, a value obtained by copying a reference sample in the first reference picture or the second reference picture may be set as the final prediction sample.
- the area to which the weighted sum operation is applied is the distance from a specific boundary of the current block, the distance from the reconstructed pixels around the current block, the size of the current block, the shape of the current block, the number of samples in the current block, and the motion of the current block. It may be determined based on at least one of an inter-prediction mode used to obtain a vector or whether bi-directional prediction is applied to the current block.
- information for specifying a region to which a weighted sum operation is applied may be explicitly encoded and signaled through a bitstream.
- the information may include at least one of a position or an angle of a dividing line dividing a region to which a weighted sum operation is applied (hereinafter referred to as a weighted sum region) and an area other than the region (hereinafter referred to as a non-weighted sum region). It may be to specify one.
- FIG. 17 illustrates various examples in which a current block is divided according to a partition type.
- At least one of the following may be determined according to the partition type of the current block.
- Each of the above four elements can be coded with a 1-bit flag and signaled. That is, the partition type of the current block may be determined by a plurality of flags.
- the division direction flag may be set to indicate the horizontal direction
- the symmetrical division flag may be set to indicate that the ratio is not 1:1.
- the second (ie, right) partition of the two partitions is designated as the weighted sum area. Accordingly, the flag indicating the ratio of the weighted sum area to the unweighted sum area is set to indicate 3:1, and the flag indicating the position of the weighted sum area is set to indicate the second partition.
- the division direction flag may be set to indicate a horizontal direction
- the symmetrical division flag may be set to indicate a 1:1 ratio.
- encoding/decoding of a flag indicating a ratio of the weighted and unweighted regions may be omitted.
- the flag indicating the location of the weighted sum area is set to indicate the second partition.
- an index indicating one of a plurality of partition type candidates may be coded and signaled.
- a plurality of partition type candidates may be configured as shown in FIG. 17 .
- more or fewer partition type candidates may be defined than those shown in FIG. 17 .
- Encoding/decoding of information indicating a ratio between a weighted sum region and an unweighted sum region may be omitted, and a larger or smaller partition among the two partitions may be set as the weighted sum region. For example, in the above example, when the current block is divided at a ratio of 1:3 or 3:1, the encoding/decoding of the flag indicating the position of the weighted sum region is omitted, and the larger or smaller of the two partitions It can be set as a weighted sum area.
- the ratio between the weighted combined area and the unweighted combined area is 1:1, 1:3 or 3:1.
- the current block is divided so that the ratio between the weighted and unweighted areas is 1:15 or 15:1, or the ratio between the weighted and unweighted areas is 1:31 or 31:1.
- the current block may be divided as much as possible.
- information indicating the ratio occupied by the weighted and unweighted regions in the current block is coded and signaled, or a plurality of ratio values Among them, an index corresponding to the ratio may be coded and signaled.
- the weighted sum area and the unweighted sum area may be divided by a diagonal line or an oblique line.
- FIG. 18 is an example showing a direction in which a dividing line dividing a current block is placed
- FIG. 19 is an example showing a position of a dividing line.
- a different mode number is assigned to each splitting direction.
- the dividing line passing through the center point of the current block is named a distance 0 dividing line, and it is assumed that there are dividing lines of distances 1 to 3 depending on the distance from the center line.
- the current block may be divided by a division line orthogonal to the division direction shown in FIG. 18 .
- it may be set that a distance 0 division line is used as a candidate for only one of the modes having opposite division directions.
- the partition type of the current block may be determined based on the division direction and the distance of the division line.
- information representing the division direction of the current block and information representing the distance of the division line may be encoded and signaled.
- FIG. 20 illustrates an example in which a current block is divided according to the description of FIGS. 18 and 19 .
- the current block may be divided into two areas.
- information indicating a weighted sum region among the two regions may be additionally encoded and signaled.
- the larger or smaller one of the two regions may be designated as the weighted sum region by default.
- a prediction sample is obtained by a weighted sum operation of the first prediction block and the second prediction block, and in the unweighted sum region, the prediction sample is obtained using only the first prediction block or the second prediction block. This is illustrated as being obtained.
- information indicating whether the first prediction block or the second prediction block is used in deriving the prediction sample of the unweighted region may be explicitly encoded and signaled.
- a prediction block used to derive a prediction sample of an unweighted region may be determined according to a priority order between the first prediction block and the second prediction block.
- the priority between the first prediction block and the second prediction block is at least one of the temporal distance between the current picture and the reference picture, the temporal direction of the reference picture, the inter prediction mode, the location of the unweighted region, or the cost with the current template. can be determined on the basis of
- a prediction block derived from a reference picture having a smaller distance from the current picture may have a higher priority. That is, if the temporal distance between the first reference picture and the current picture is smaller than the temporal distance between the current picture and the second reference picture, the prediction sample of the unweighted region may be derived using the first prediction block. .
- one of the first prediction block and the second prediction block may be selected in consideration of a cost between the current template and the reference template. For example, a cost between the current template and a first reference template composed of restoration regions around the first prediction block (ie, the first reference block) and a cost between the current template and the second prediction block (ie, the second reference block) After comparing costs between the second reference templates composed of reconstruction regions, a prediction block adjacent to a reference template having a lower cost may be used to derive a prediction sample of an unweighted region.
- 21 illustrates an example of deriving prediction samples in a weighted sum region and an unweighted sum region.
- the prediction samples included in the weighted sum region may be derived by weighting the prediction samples included in the first prediction block and the prediction samples included in the second prediction block. For example, as in the example shown in FIG. 21, by applying a weight w0 to the prediction sample included in the first prediction block and applying a weight w1 to the prediction sample included in the second prediction block, prediction in the weighted sum region samples can be derived.
- Prediction samples of the unweighted region may be generated by copying prediction samples included in the first prediction block or the second prediction block.
- the prediction sample of the unweighted region is generated by copying the prediction sample included in the first prediction block.
- Filtering may be performed at the boundary between the weighted sum region and the unweighted sum region.
- the filtering may be performed for smoothing between prediction samples included in the weighted sum region and prediction samples included in the unweighted sum region.
- Filtering may be performed by assigning a first weight to a first prediction sample included in the weighted sum region and assigning a second weight to a second prediction sample included in the unweighted sum region.
- the first prediction sample is generated by a weighted sum of prediction samples included in the first prediction block and the second prediction block
- the second prediction sample is a prediction sample included in the first prediction block or the second prediction block It may have been created by copying.
- weights assigned to the first prediction sample and the second prediction sample may be adaptively determined according to locations.
- FIG. 22 illustrates an example in which a filter is applied centered on a boundary between a weighted sum region and an unweighted sum region.
- mode 5 is applied to an 8x8 block.
- a number marked on each sample indicates a weight assigned to the first prediction sample.
- the weight applied to the second prediction sample may be derived by differentiating the weight assigned to the first prediction sample from an integer.
- the first weight and the second weight are adaptively determined according to the distance of the dividing line and the position of the sample.
- a final prediction sample may be obtained through a weighted sum operation of the first prediction sample and the second prediction sample. Equations 3 to 5 below represent examples of obtaining filtered prediction samples.
- Equation 3 P0 means the first prediction sample, and P1 means the second prediction sample.
- W denotes a weight matrix
- W_Max denotes the sum of the maximum and minimum values in the weight matrix.
- W_Max may be set to 8.
- Shift and Offset represent normalization constants. Since W_Max is set to 8 (2 ⁇ 3), the value of Shift may be set to 3 and the value of Offset may be set to 4.
- the current block is divided into a weighted sum region and a non-weighted sum region, and then different prediction sample derivation methods are set for each region.
- the prediction sample is derived by a weighted sum operation of the first prediction block and the second prediction block over the entire region of the current block, but the weight applied to each of the first prediction block and the second prediction block, FIG. 22
- the above-described division line may be used as an element for determining a weight assigned to each sample instead of dividing the current block into a weighted sum region and an unweighted sum region.
- an encoder may perform motion estimation. Also, as described above, when the template-based motion estimation method, the bidirectional matching method, or the unidirectional matching method is applied, the decoder may perform motion estimation in the same manner as the encoder.
- FIG. 23 is a flowchart of a method for adjusting a search range according to an embodiment of the present disclosure.
- the current picture may be divided into a plurality of regions (S2310).
- Each region may consist of one or more Coding Tree Units (CTUs).
- CTUs Coding Tree Units
- a plurality of CTUs, a plurality of CUs, or a plurality of PUs may be defined as one area.
- motion estimation may be performed on each of the divided regions (S2320). Through the motion estimation, motion information for each region may be determined.
- motion information of an area including the current block may be set as initial motion information of the current block (S2330).
- Initial motion information may be used when setting a search area for a current block.
- the search area may be set within a predetermined range from a position specified by a motion vector indicated by the initial motion information within a reference picture indicated by the initial motion information.
- FIG. 24 illustrates an example in which a current picture is divided into a plurality of regions.
- each region is composed of 64 CTUs.
- the CTU can be set to a size of 64x64, 128x128 or 256x256.
- the size of the CTU is 64x64
- each region shown in FIG. 24 has a size of 512x512.
- each area does not have to have a uniform size.
- each region is to be composed of 8x8 CTUs, there may be a case where less than 8 CTU columns or CTU rows remain in the region adjacent to the right boundary or the lower boundary of the current picture.
- an area adjacent to the right boundary or the bottom boundary of the current picture may have a size smaller than 8x8 (ie, 64 CTUs).
- slices, tiles, or subpictures may be set as one region.
- motion estimation for each region may be performed. Accordingly, a reference picture and a motion vector for each region may be determined.
- motion estimation may be performed on the reference picture in units of 512x512 areas.
- motion estimation of the corresponding area is forced in a specific direction.
- motion estimation for an area A adjacent to the top and left edges of the current picture can be performed only in the right and left directions, and cannot be performed in the left and top directions. Accordingly, a problem may occur in that motion information of a region does not properly reflect motion characteristics of blocks belonging to the corresponding region.
- N rows and/or M columns from a block bordering the current picture boundary or from the current picture boundary may be configured not to be classified as a specific region.
- FIG. 25 it is illustrated that remaining CTUs excluding one CTU line bordering the current picture are divided into a plurality of regions. Accordingly, motion estimation for area A may be performed not only in the right and bottom directions, but also in the left and top directions corresponding to the size of CTU.
- motion information of the region may be set as initial motion information of a block (eg, a coding unit or a prediction unit) belonging to the region.
- a block eg, a coding unit or a prediction unit
- motion information of a region to which the corresponding coding unit belongs may be set as initial motion information.
- a search range for a coding unit may be set around the reference position.
- 26 illustrates an example in which a search range is set around a reference point.
- a search range having a width of w0+w1 and a height of h0+h1 is set around the collocated position (x, y).
- the search range set around the reference point can be limited so as not to deviate from the search range shown in FIG. there is.
- the search range may have sizes of (w0-n), w1, (h0-m), and h1 centered on the reference point. there is.
- the width and/or height of the search range can be reduced by n and/or m.
- motion estimation may be performed only for the first CTU in the region (eg, the upper left CTU in the region).
- motion information generated as a result of motion estimation of the first CTU in the region may be set as initial motion information of blocks (eg, coding units or prediction units) included in the region.
- n and/or m may be set differently between a case based on motion information generated based on a region and a case based on motion information generated based on a CTU.
- motion estimation is performed on blocks (eg, coding units or prediction units) belonging to a first CTU in a region
- blocks eg, coding units or prediction units
- at least one of an average value, a minimum value, a maximum value, or a median value of motion vectors of the blocks is determined. It can also be set as an initial motion vector.
- motion estimation for blocks belonging to the first CTU may be performed based on a search range to which variables w0, w1, h0, and h1 are applied, as in the example shown in FIG. 3 .
- the difference between the motion vector generated through motion estimation for the region and the motion vector generated through motion estimation for the first CTU in the region, or the motion vector generated through motion estimation for region y and the block belonging to the first CTU n and/or m may be determined based on a difference between an average value, a minimum value, a maximum value, or a median value of motion vectors of .
- motion estimation results for neighboring CTUs of the CTU to which the current block belongs may be set as initial motion information.
- the neighboring CTU may include at least one of a left or an upper CTU.
- one of a mean value, a minimum value, a maximum value, or a median value of motion vectors of coding units belonging to neighboring CTUs may be set as an initial motion vector of the current block.
- Initial motion information (eg, motion information of a region) may be explicitly encoded and signaled to a decoder.
- a search range may be set based on the initial motion information. For example, when setting a search range under the above-described template-based motion estimation method, bilateral matching method, or unidirectional matching method, the search range may be set based on initial motion information.
- initial motion information when initial motion information is derived based on a previously reconstructed region (eg, a neighboring CTU), encoding/decoding of the initial motion information may be omitted.
- the decoder may obtain initial motion information by performing motion estimation in the same way as the encoder.
- the complexity of the decoder can be reduced and loss in encoding efficiency can be minimized.
- the search range may be adjusted based on motion characteristics within a picture.
- Motion characteristics may be derived based on difference values between samples in the current picture and the reference picture.
- FIG. 27 illustrates an example of determining motion characteristics of a current picture.
- the current picture can be divided into areas with strong motion and areas with weak motion.
- the background area is an area with weak motion
- the area where the subject appears is an area with strong motion.
- the current picture and the reference picture may be divided into a plurality of regions.
- FIG. 28 illustrates an example of dividing a current picture and a reference picture into a plurality of regions.
- each region is illustrated as being in the form of a block having a size of NxN.
- One or a plurality of CTUs may be defined as one area.
- one or a plurality of coding units (or prediction units) may be defined as one region.
- information indicating the size of the region may be explicitly coded and signaled.
- information indicating N may be explicitly coded and signaled.
- motion characteristics may be determined in units of slices, tiles, or sub-pictures.
- differences between co-located samples in the region are derived. That is, a difference between a sample included in the current picture and a sample co-located with the sample in the reference picture may be derived.
- the standard deviation of the difference values may be derived in units of regions.
- the motion characteristics of the region may be determined by comparing the standard deviation derived for each region with a threshold value.
- the threshold may be a value predefined in the encoder and/or the decoder.
- the threshold value may be determined based on the bit depth of the current picture.
- information on the threshold value may be encoded and signaled to the decoder.
- the corresponding region may be classified as a region with weak motion. If the standard deviation is greater than or equal to the critical value, it means that there is significant motion within the region. In this case, the corresponding region may be classified as a region with strong motion.
- 27(b) shows an example in which the current picture is classified into a strong motion area and a weak motion area according to a comparison result of a standard deviation and a threshold value for each area.
- a black portion represents a strong motion region
- a white portion represents a weak movement region
- a search range for motion estimation may be determined by referring to motion characteristics of each region. Specifically, a search range for the current block may be determined based on whether the current block belongs to a region with strong motion or a region with weak motion.
- the size of the search area when the current block belongs to an area with strong motion may be larger than the size of the search area when the current block belongs to an area with weak motion.
- the search range can be adjusted based on the motion characteristics of the current picture.
- information representing motion characteristics of each region may be explicitly encoded and signaled.
- an L0 prediction block is generated based on the L0 motion information
- an L1 prediction block is generated based on the L1 motion information.
- a prediction block of the current block may be generated through a weighted sum of the L0 prediction block and the L1 prediction block.
- the weight applied to the L0 prediction block and the weight applied to the L1 prediction block may be derived based on a weight list. Specifically, when one of the plurality of weight candidates included in the weight list is selected, the weight applied to the L0 prediction block and the weight applied to the L1 prediction block may be determined based on the selected weight candidate.
- Equation 6 shows an example of generating a prediction block by a weighted sum operation of the L0 prediction block and the L1 prediction block.
- P0 means an L0 prediction block
- P1 means an L1 prediction block
- Pbi means a prediction block generated through a weighted sum of the L0 prediction block and the L1 prediction block.
- wf means a weight. The above weight wf may be set to one of a plurality of weight candidates included in the weight list. For example, in Equation 6, it is illustrated that a weight of wf is applied to the L1 prediction block and a weight of (1-wf) is applied to the L0 prediction block. Contrary to the above example, a weight of wf may be applied to the L0 prediction block and a weight of (1-wf) may be applied to the L1 prediction block.
- the weight wf may have a real value.
- Equation 6 in order to use integer arithmetic instead of real number arithmetic, Equation 6 may be modified and used as Equations 7 and 8 below.
- prec means a scale value for integer operation.
- prec is 3.
- a weight list may include a plurality of weight candidates.
- the size of the weight list indicates the number of weight candidates included in the weight list.
- the following shows an example of a weight list having a size of 5. ⁇ -2, 3, 4, 5, 10 ⁇
- the following shows an example of a weight list having a size of 3. ⁇ 3, 4, 5 ⁇
- weight candidates constituting the weight list is not limited to the above example. Also, a weight candidate having a value of 0 may be included in the weight list.
- the size of the weight list may be predefined in the encoder and decoder. Or, whether the POC of the current picture exists between the POC of the L0 reference picture and the POC of the L1 reference picture, whether the POC of the current picture is lower or higher than the POC of the L0 reference picture and/or the L1 reference picture, It may be determined based on at least one of a POC difference between L0 reference pictures and a POC difference between the current picture and the L1 reference picture.
- one of a plurality of weight lists may be selected.
- index information specifying one of a plurality of weight lists may be encoded and signaled.
- One of the plurality of weight lists may be adaptively selected based on at least one of the POC difference between L0 reference pictures and the POC difference between the current picture and the L1 reference picture.
- the encoder may explicitly encode and transmit index information indicating a weight candidate selected in the weight list to the decoder.
- one of the weight candidates may be selected according to at least one of the size of the current block, the POC of the current block, the POC of the L0 reference picture, or the POC of the L1 reference picture.
- Whether to determine the weight using the weight list is determined by at least one of the size of the current block, the number of samples included in the current block, the shape of the current block, the POC of the current block, the POC of the L0 reference picture, or the POC of the L1 reference picture. can be determined based on For example, a weight may be determined using a weight list only when the number of samples in the current block is greater than or equal to a threshold. That is, when the number of samples in the current block is smaller than the threshold value, the weight list may be set not to be used.
- the prediction block may be derived by averaging the L0 prediction block and the L1 prediction block. For example, when prec is 3, in Equation 7, M has a value of 8. Accordingly, when the weight list is not applied, in Equation 7, the weight w may be set to 4.
- signaling of index information indicating one of the weight candidates may be omitted, and the encoder and decoder may derive a prediction block by the same method (ie, average operation).
- the weight of the current block may be derived from the motion information merging candidate.
- the weight of the current block may be set to be the same as that of the motion information merging candidate.
- the motion information merging candidate may include not only information about motion vectors, reference picture indexes, and prediction directions, but also information about weights.
- motion information of the current block may be corrected in the same manner.
- the derived motion information can be corrected through a template-based motion estimation method, bilateral matching method, or unidirectional matching method.
- the L0 motion information and the L1 motion information may be corrected by applying a bilateral matching method or a unidirectional matching method.
- the motion information of the current block is derived through the motion information merge list
- the motion information may be corrected by applying a template-based motion estimation method, a bilateral matching method, or a unidirectional matching method.
- Information indicating whether motion information is corrected may be explicitly encoded and signaled.
- Predefined conditions include whether motion information is derived based on the motion information merging mode, whether bi-directional prediction is applied to the current block, whether the width and/or height of the current block is greater than or equal to a threshold value, and the number of samples in the current block. Whether the number is greater than or equal to the threshold, whether the weights applied to the L0 prediction block and the L1 prediction block are the same (i.e., whether an averaging operation was applied), or whether brightness compensation techniques (e.g., weight prediction) were not used. At least one may be used under a predefined condition.
- the motion information is corrected when at least one or all of the predefined conditions are satisfied.
- whether to correct motion information may be determined by comparing a cost between prediction blocks specified by motion information or a cost between a current template and a reference template with a threshold value. As an example, only when the cost between the L0 prediction block (ie, the L0 reference block) derived based on the L0 motion information and the L1 prediction block (ie, the L1 reference block) derived on the basis of the L1 motion information is greater than the threshold , the motion information can be corrected.
- motion information is corrected by comparing a cost between the current template and the reference template with a threshold value.
- a reference template may be determined based on motion information. For example, motion information may be corrected only when the cost between the current template and the reference template is greater than a threshold value.
- the threshold may be set based on the size of the current block or the number of samples in the current block.
- the number of samples (eg, width x height) in the current block may be set as the threshold, or N multiples of the number of samples may be set as the threshold.
- the number of samples in a sub-block or N multiples of the number of samples may be set as a threshold value.
- a threshold value may be predefined in an encoder and/or a decoder.
- the threshold may be adaptively determined based on at least one of a bit depth and a color component.
- the motion information may be corrected based on a template-based motion estimation method, a bilateral matching method, or a unidirectional matching method.
- a method used for correcting motion information may be previously defined in an encoder and a decoder.
- a template-based motion estimation method may be fixedly used for correcting motion information.
- information indicating one of a plurality of decoder-side motion estimation methods may be encoded and signaled.
- information eg, a flag
- information indicating one of the two methods may be encoded and signaled.
- information indicating whether motion information is corrected by the template-based motion estimation method and information indicating whether motion information is corrected by the bilateral matching method may be encoded and signaled.
- a method based on motion compensation may be selected based on at least one of the size of the current block, the shape of the current block, the POC of the current picture, the POC of the L0 reference picture, the POC of the L1 reference picture, or bi-directional prediction.
- the motion information derived based on the motion information merging candidate has unidirectional information (eg, L0 motion information or L1 motion information)
- the motion information may be corrected by applying a template-based motion estimation method.
- the motion information derived based on the motion information merging candidate has bidirectional information (ie, L0 motion information and L1 motion information)
- the motion information can be corrected by applying a bidirectional matching method or a unidirectional matching method. .
- motion correction may be performed on the coding unit or prediction unit.
- motion information may be corrected in units of subblocks having a size smaller than that of a coding unit or a prediction unit.
- Motion information before correction will be referred to as initial motion information.
- the current block may be divided into a plurality of sub-blocks.
- the size of a sub-block may be predefined in an encoder and a decoder.
- the current block may be divided into 4x4 or 8x8 sub-blocks.
- the size of the sub-block may be adaptively determined based on at least one of the size or shape of the current block.
- motion information may be corrected for each of the sub-blocks.
- 29 is a diagram for explaining an example in which motion information for each sub-block is corrected.
- the size of the current block is 8x8 and the size of the sub-block is 4x4.
- the initial motion information is derived based on the motion information merging list, and the initial motion vector is corrected by a bilateral matching method.
- a starting point within a reference picture can be designated for each subblock. Specifically, a position separated by an initial motion vector from the upper left position of a subblock in a reference picture indicated by an initial reference picture index may be designated as a starting point.
- the reference area may be set by extending the boundary of the sub-reference block by a predetermined value based on the sub-reference block whose starting point is the top-left position.
- the reference region is set by extending four boundaries of the sub reference block by w0, w1, h0, and h1, respectively.
- the reference region for the 4x4 subblock may have an 8x8 size.
- a reference region may be generated through interpolation.
- reference regions may be set for each of the L0 direction and the L1 direction.
- a combination of an L0 sub-reference block and an L1 sub-reference block having an optimal cost is selected by applying a bilateral matching method in the L0-direction reference region and the L1-direction reference region.
- the vector between the L0 sub-reference blocks i.e., the L0 difference vector
- the vector between the L1 reference picture and the L1 sub-reference block i.e., the L1 difference vector has a magnitude and a direction It could be the opposite.
- a motion vector may be corrected with the positions of the corresponding L0 sub-reference block and L1 sub-reference block.
- a corrected motion vector can be derived by adding a value between (-2, -2) and (2, 2) to the initial motion vector (x0, y0).
- the horizontal direction component (ie, x-axis component) and the vertical direction component (ie, y-axis component) of the motion vector are each an integer between -2 and 2. corrected Accordingly, the above correction may be referred to as integer position correction.
- fractional position correction may be additionally performed. Fractional position correction may be performed using a reference block composed of fractional position samples within a reference region.
- the position of the reference block determined to have the optimal cost in the integer position calibration process may be set as a starting point for fractional position calibration, and based on the starting point, fractional position reference samples may be generated in a predefined unit.
- the predefined unit may be 1/16, 1/8, 1/4 or 1/2.
- a combination of an L0 sub-reference block and an L1 sub-reference block having an optimal cost is selected from among the L0 sub-reference blocks and L1 sub-reference blocks composed of fractional position reference pixels.
- a motion vector may be corrected with the positions of the corresponding L0 sub-reference block and L1 sub-reference block.
- Whether or not to perform fractional position correction may be determined based on whether the sub-reference block selected according to the integer position correction is in contact with the boundary of the reference region. That is, based on whether the corrected motion vector points to the edge of the reference region, it is possible to determine whether to correct the fractional position. If the corrected motion vector points to the edge of the reference region, fractional position correction may not be performed. Otherwise, fractional position correction may be additionally performed.
- the edge of the reference region may represent one of a left boundary, an upper boundary, a lower boundary, or a right boundary.
- fractional positioning it is possible to determine whether fractional positioning is performed by comparing the minimum cost calculated in the integer positioning process with a threshold value. For example, fractional position correction may be performed only when a combination of the L0 sub-reference block and the L1 sub-reference block having the lowest cost is equal to or greater than the threshold value.
- whether to perform fractional position correction may be determined by considering whether the precision of the initial motion vector is an integer unit or a fraction unit.
- an initial motion vector is corrected in units of sub-blocks. Unlike the illustrated example, an initial motion vector may be corrected for a coding unit or a prediction unit.
- the initial motion vector may be corrected using a template-based motion estimation method instead of the bilateral matching method.
- correction of the initial motion vector may be performed based on the cost between the current template and the reference template.
- the corrected motion vector may be re-corrected in units of sub-blocks.
- the initial motion vector may be corrected for only one of the L0 direction and the L1 direction, and the initial motion vector may not be corrected for the other direction.
- an L0 prediction block may be derived using the corrected motion vector.
- the L1 prediction block can be derived using the initial motion vector without correcting the initial motion vector.
- motion vector correction for only one of the L0 direction and the L1 direction may be applied on a block level or sub-block basis.
- a weight may be applied when calculating a cost between two reference blocks. That is, instead of calculating the cost based on the difference between the L0 reference block and the L1 reference block, the cost may be calculated based on the difference between the L0 reference block to which the first weight is applied and the L1 reference block to which the second weight is applied.
- weights to be applied to the L0 reference block and the L1 reference block may be determined based on weights derived from the motion information merging candidate.
- the cost can be calculated. That is, the cost can be calculated based on the difference between (5 x L0_Pred) and (3 x L1_Pred).
- L0_Pred represents the L0 reference block
- L1_Pred represents the L1 reference block.
- weights used for the L0 reference block and the L1 reference block may be determined based on the weight list.
- the weight list for bi-directional prediction can be equally used.
- a list that is simpler than the weight list for bi-directional prediction can be used.
- the simplified list means that a smaller number of weight candidates are included than the weight list for bi-directional prediction.
- a weight list separate from the weight list for bi-directional prediction may be set.
- Each of the weight candidates included in the weight list may be applied to the L0 reference block and the L1 reference block.
- the motion vector of the current block may be corrected by selecting one of combinations of the weight candidate, the L0 reference block, and the L1 reference block having the optimal cost.
- Only some of the weight candidates included in the weight list may be set to be usable.
- Weights can be used not only in the bilateral matching method, but also in the case of correcting motion vectors by the template-based motion estimation method.
- the first weight applied to the L0 reference block and the second weight applied to the L1 reference block may be applied to the reference template and the current template, respectively.
- each of the components (eg, units, modules, etc.) constituting the block diagram in the above disclosure may be implemented as a hardware device or software, and a plurality of components may be combined to be implemented as a single hardware device or software. It could be.
- the above disclosure may be implemented in the form of program instructions that can be executed through various computer components and recorded in a computer readable recording medium.
- the computer readable recording medium may include program instructions, data files, data structures, etc. alone or in combination.
- Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks and magnetic tapes, optical recording media such as CD-ROMs and DVDs, and magneto-optical media such as floptical disks. media), and hardware devices specially configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like.
- the hardware device may be configured to act as one or more software modules to perform processing according to the present disclosure and vice versa.
- This disclosure can be applied to computing or electronic devices capable of encoding/decoding video signals.
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Abstract
Description
Claims (15)
- 제1 인터 예측 모드에 기초하여, 현재 블록에 대한 제1 예측 블록을 획득하는 단계;제2 인터 예측 모드에 기초하여, 상기 현재 블록에 대한 제2 예측 블록을 획득하는 단계; 및상기 제1 예측 블록 및 상기 제2 예측 블록에 기초하여, 상기 현재 블록에 대한 최종 예측 블록을 획득하는 단계를 포함하는, 영상 복호화 방법.
- 제1 항에 있어서,상기 제1 인터 예측 모드 및 상기 제2 인터 예측 모드 중 적어도 하나는 기 복원된 참조 픽처를 이용하여, 복호화기가 부호화기와 동일한 방식으로 움직임 추정을 수행하는 복호화기 측 움직임 추정 모드인 것인 것을 특징으로 하는, 영상 복호화 방법.
- 제2 항에 있어서,상기 움직임 추정은, 상기 현재 블록 주변 기 복원된 영역으로 구성된 현재 템플릿과 상기 참조 픽처 내 상기 현재 템플릿과 동일한 크기의 참조 템플릿의 조합들 중 최적의 비용을 갖는 조합을 탐색하는 과정을 포함하는 것을 특징으로 하는, 영상 복호화 방법.
- 제3 항에 있어서,상기 움직임 추정은, 참조 픽처 리스트 내 참조 픽처 인덱스가 문턱값보다 작은 참조 픽처들 각각에 대해 수행되는 것을 특징으로 하는, 영상 복호화 방법.
- 제3 항에 있어서,상기 움직임 추정은, 참조 픽처 리스트 내 현재 픽처와의 출력 순서 차분이 문턱값 이하인 참조 픽처들 각각에 대해 수행되는 것을 특징으로 하는, 영상 복호화 방법.
- 제3 항에 있어서,상기 참조 픽처에 설정된 탐색 범위 내에서, 상기 참조 템플릿이 탐색되고,상기 탐색 범위는, 상기 현재 블록의 초기 움직임 정보를 기초로 설정되는 것을 특징으로 하는, 영상 복호화 방법.
- 제6 항에 있어서,상기 초기 움직임 정보는, 상기 현재 블록보다 큰 크기의 영역에 대한 움직임 정보인 것을 특징으로 하는, 영상 복호화 방법.
- 제3 항에 있어서,상기 참조 픽처에 설정된 탐색 범위 내에서, 상기 참조 템플릿이 탐색되고,상기 탐색 범위는, 상기 현재 블록이 포함된 영역의 움직임 특성을 기초로 결정되고,상기 영역의 상기 움직임 특성은, 움직임이 강한 영역 및 움직임이 강한 영역 중 하나로 설정되는 것을 특징으로 하는, 영상 복호화 방법.
- 제2 항에 있어서,상기 움직임 추정은, L0 참조 픽처에 포함된 L0 참조 블록과, L1 참조 픽처에 포함된 L1 참조 블록의 조합들 중 최적의 비용을 갖는 조합을 탐색하는 과정을 포함하는 것을 특징으로 하는, 영상 복호화 방법.
- 제9 항에 있어서,상기 현재 픽처의 출력 순서는, 상기 L0 참조 픽처의 출력 순서 및 상기 L1 참조 픽처의 출력 순서 사이에 위치하는 것을 특징으로 하는, 영상 복호화 방법.
- 제1 항에 있어서,상기 제1 인터 예측 모드는, 상기 현재 블록의 L0 방향 예측에 이용되고,상기 제2 인터 예측 모드는, 상기 현재 블록의 L1 방향 예측에 이용되는 것을 특징으로 하는, 영상 복호화 방법.
- 제1 항에 있어서,상기 최종 예측 블록은, 상기 제1 예측 블록 및 상기 제2 예측 블록의 가중합 연산을 기초로 유도되고,상기 가중합 연산시, 상기 제1 예측 블록에 부여되는 제1 가중치 및 상기 제2 예측 블록에 부여되는 제2 가중치는, 상기 제1 인터 예측 모드 또는 상기 제2 예측 모드의 종류에 따라, 적응적으로 결정되는 것을 특징으로 하는, 영상 복호화 방법.
- 제12 항에 있어서,상기 제1 인터 예측 모드가 복호화기 측 움직임 추정 모드이고, 상기 제2 인터 예측 모드가 움직임 정보 시그날링 모드인 경우, 상기 제1 가중치가 상기 제2 가중치보다 큰 값을 갖는 것을 특징으로 하는, 영상 복호화 방법.
- 제1 인터 예측 모드에 기초하여, 현재 블록에 대한 제1 예측 블록을 획득하는 단계;제2 인터 예측 모드에 기초하여, 상기 현재 블록에 대한 제2 예측 블록을 획득하는 단계; 및상기 제1 예측 블록 및 상기 제2 예측 블록에 기초하여, 상기 현재 블록에 대한 최종 예측 블록을 획득하는 단계를 포함하는, 영상 부호화 방법.
- 제1 인터 예측 모드에 기초하여, 현재 블록에 대한 제1 예측 블록을 획득하는 단계;제2 인터 예측 모드에 기초하여, 상기 현재 블록에 대한 제2 예측 블록을 획득하는 단계; 및상기 제1 예측 블록 및 상기 제2 예측 블록에 기초하여, 상기 현재 블록에 대한 최종 예측 블록을 획득하는 단계를 포함하는, 영상 부호화 방법에 의해 생성된 비트스트림을 기록한 컴퓨터로 판독 가능한 기록 매체.
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CN202280062043.5A CN117941356A (zh) | 2021-09-15 | 2022-09-15 | 视频信号编码/解码方法以及存储有比特流的记录介质 |
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