Video encoder, video decoder, and corresponding method
A video encoder, a video decoder, and a corresponding method are provided. The method includes: parsing a bitstream to obtain an index, where the index indicates a target candidate motion vector group of a current coding block; determining the target candidate motion vector group in an affine candidate motion vector list based on the index, where the affine candidate motion vector list includes at least a first candidate motion vector group, the first candidate motion vector group is obtained based on a first group of control points of a first neighboring affine coding block, and the first group of control points is determined based on a CTU located relative to the current coding block, wherein the first neighboring affine coding block is located in the CTU; and predicting a predicted sample value of the current coding block based on the target candidate motion vector group.
1 . A decoding method, comprising:
in response to an affine inter mode for a current coding block,
parsing a bitstream to obtain an index, wherein the index is used to indicate a target candidate motion vector group of the current coding block;
determining the target candidate motion vector group in a candidate motion vector predictor list based on the index, wherein the target candidate motion vector group represents motion vector predictors of a group of control points of the current coding block, the affine candidate motion vector list comprises at least a first candidate motion vector group, the first candidate motion vector group is obtained based on a first group of control points of a first neighboring affine coding block of the current coding block, and the first group of control points of the first neighboring affine coding block are control points determined based on a relative location of a coding tree unit CTU with respect to the current coding block, wherein the first neighboring affine coding block is located in the CTU;
obtaining a new candidate motion vector group based on motion vector difference MVDs obtained from the bitstream through parsing and the target candidate motion vector group indicated by the index; and
obtaining the motion vectors of the one or more sub-blocks of the current coding block based on the new candidate motion vector group; and
predicting the predicted sample value of the current coding block based on the motion vectors of the one or more sub-blocks of the current coding block.
2 . The method according to claim 1 , further comprising:
generating the candidate motion vector predictor MVP list of the current coding block, wherein the candidate motion vector predictor MVP list comprises a plurality of candidate motion vector groups, and the candidate motion vector groups comprise the first candidate motion vector group and a third candidate motion vector group; the first neighboring affine coding block is a lowest coding block in the first CTU, and the current coding block is an uppermost coding block in the second decode tree unit CTU; the third candidate motion vector group is a candidate motion vector predictor of a group of control points of the current coding block obtained by combining candidate motion vectors of at least two control points of the current coding block.
3 . The method according to claim 1 , wherein the parameter model of the current coding block is a 4-parameter affine model, and the first group of control points of the first neighboring affine coding block is determined in the following manner:
if the first coding tree unit CTU and the second coding tree unit CTU are in a top-down relative position relationship, the first group of control points of the first neighboring affine coding block is a bottom-left control point and a bottom-right control point of the first neighboring affine coding block; and;
if the first coding tree unit CTU and the second coding tree unit CTU are not in a top-down relative position relationship, the first group of control points of the first neighboring affine coding block is a top-left control point and a top-right control point of the first neighboring affine coding block.
4 . The method according to claim 1 , wherein the parameter model of the current coding block is a 6-parameter affine model, and the first group of control points of the first neighboring affine coding block is determined in the following manner:
if the first coding tree unit CTU and the second coding tree unit CTU are in a top-down relative position relationship, the first group of control points of the first neighboring affine coding block is a bottom-left control point and a bottom-right control point of the first neighboring affine coding block; and;
if the first coding tree unit CTU and the second coding tree unit CTU are not in a top-down relative position relationship, the first group of control points of the first neighboring affine coding block is a top-left control point, a top-right control point, and a bottom-left control point of the first neighboring affine coding block.
5 . The method according to claim 1 , wherein the predicting a predicted sample value of the current coding block based on the motion vectors of the one or more sub-blocks of the current coding block comprises:
predicting the predicted sample value of the current coding block based on the motion vectors of the one or more sub-blocks of the current coding block and a reference frame index and a prediction direction that is indicated by the index.
6 . The method according to claim 3 , wherein both location coordinates (x 6 , y 6 ) of a bottom-left control point of the first neighboring affine coding block and location coordinates (x 7 , y 7 ) of a bottom-right control point of the first neighboring affine coding block are derived based on location coordinates (x 4 , y 4 ) of a top-left control point of the first neighboring affine coding block, the location coordinates (x 6 , y 6 ) of the bottom-left control point of the first neighboring affine coding block are represented by (x 4 , y 4 +cuH), and the location coordinates (x 7 , y 7 ) of the bottom-right control point of the first neighboring affine coding block are represented by (x 4 +cuW, y 4 +cuH), wherein cuW is a width of the first neighboring affine coding block, and cuH is a height of the first neighboring affine coding block.
7 . The method according to claim 6 , wherein a motion vector of the bottom-left control point of the first neighboring affine coding block is a motion vector of a bottom-left sub-block of the first neighboring affine coding block, and a motion vector of the bottom-right control point of the first neighboring affine coding block is a motion vector of a bottom-right sub-block of the first neighboring affine coding block.
8 . The method according to claim 1 , wherein the first candidate motion vector group is candidate motion vector predictors of a group of control points of the current coding block obtained based on motion vectors of the first group of control points of the first neighboring affine coding block.
9 . A video data decoding device, comprising:
a memory, configured to store video data in a form of a bitstream; and
a video decoder, configured to:
in response to an affine inter mode for a current coding block, parse the bitstream to obtain an index, wherein the index is used to indicate a target candidate motion vector group of the current coding block;
determine the target candidate motion vector group in a candidate motion vector predictor list based on the index, wherein the target candidate motion vector group represents motion vector predictors of a group of control points of the current coding block, the affine candidate motion vector list comprises at least a first candidate motion vector group, the first candidate motion vector group is obtained based on a first group of control points of a first neighboring affine coding block of the current coding block, and the first group of control points of the first neighboring affine coding block are control points determined based on a relative location of a coding tree unit CTU with respect to the current coding block, wherein the first neighboring affine coding block is located in the CTU;
obtain a new candidate motion vector group based on motion vector difference MVDs obtained from the bitstream through parsing and the target candidate motion vector group indicated by the index; and
obtain the motion vectors of the one or more sub-blocks of the current coding block based on the new candidate motion vector group; and;
predict the predicted sample value of the current coding block based on the motion vectors of the one or more sub-blocks of the current coding block.
10 . The video data decoding device according to claim 9 , wherein the video decoder, is further configured to:
generate the candidate motion vector predictor MVP list of the current coding block, wherein the candidate motion vector predictor MVP list comprises a plurality of candidate motion vector groups, and the candidate motion vector groups comprise the first candidate motion vector group and a third candidate motion vector group; the first neighboring affine coding block is a lowest coding block in the first CTU, and the current coding block is an uppermost coding block in the second decode tree unit CTU; the third candidate motion vector group is a candidate motion vector predictor of a group of control points of the current coding block obtained by combining candidate motion vectors of at least two control points of the current coding block.
11 . The video data decoding device according to claim 9 , wherein the parameter model of the current coding block is a 4-parameter affine model, and the first group of control points of the first neighboring affine coding block is determined in the following manner:
if the first coding tree unit CTU and the second coding tree unit CTU are in a top-down relative position relationship, the first group of control points of the first neighboring affine coding block is a bottom-left control point and a bottom-right control point of the first neighboring affine coding block; and;
if the first coding tree unit CTU and the second coding tree unit CTU are not in a top-down relative position relationship, the first group of control points of the first neighboring affine coding block is a top-left control point and a top-right control point of the first neighboring affine coding block.
12 . The video data decoding device according to claim 9 , wherein the parameter model of the current coding block is a 6-parameter affine model, and the first group of control points of the first neighboring affine coding block is determined in the following manner:
if the first coding tree unit CTU and the second coding tree unit CTU are in a top-down relative position relationship, the first group of control points of the first neighboring affine coding block is a bottom-left control point and a bottom-right control point of the first neighboring affine coding block; and;
if the first coding tree unit CTU and the second coding tree unit CTU are not in a top-down relative position relationship, the first group of control points of the first neighboring affine coding block is a top-left control point, a top-right control point, and a bottom-left control point of the first neighboring affine coding block.
13 . The video data decoding device according to claim 9 , wherein the video decoder, is configured to:
predicting the predicted sample value of the current coding block based on the motion vectors of the one or more sub-blocks of the current coding block and a reference frame index and a prediction direction that is indicated by the index.
14 . The video data decoding device according to claim 11 , wherein both location coordinates (x 6 , y 6 ) of a bottom-left control point of the first neighboring affine coding block and location coordinates (x 7 , y 7 ) of a bottom-right control point of the first neighboring affine coding block are derived based on location coordinates (x 4 , y 4 ) of a top-left control point of the first neighboring affine coding block, the location coordinates (x 6 , y 6 ) of the bottom-left control point of the first neighboring affine coding block are represented by (x 4 , y 4 +cuH), and the location coordinates (x 7 , y 7 ) of the bottom-right control point of the first neighboring affine coding block are represented by (x 4 +cuW, y 4 +cuH), wherein cuW is a width of the first neighboring affine coding block, and cuH is a height of the first neighboring affine coding block.
15 . The video data decoding device according to claim 14 , wherein a motion vector of the bottom-left control point of the first neighboring affine coding block is a motion vector of a bottom-left sub-block of the first neighboring affine coding block, and a motion vector of the bottom-right control point of the first neighboring affine coding block is a motion vector of a bottom-right sub-block of the first neighboring affine coding block.
16 . The video data decoding device according to claim 9 , wherein the first candidate motion vector group is candidate motion vector predictors of a group of control points of the current coding block obtained based on motion vectors of the first group of control points of the first neighboring affine coding block.
17 . A non-transitory computer-readable media storing computer instructions, that when executed by one or more processors, cause the one or more processors to perform operations, the operations comprising:
in response to an affine inter mode for a current coding block,
parsing a bitstream to obtain an index, wherein the index is used to indicate a target candidate motion vector group of the current coding block;
determining the target candidate motion vector group in a candidate motion vector predictor list based on the index, wherein the target candidate motion vector group represents motion vector predictors of a group of control points of the current coding block, the affine candidate motion vector list comprises at least a first candidate motion vector group, the first candidate motion vector group is obtained based on a first group of control points of a first neighboring affine coding block of the current coding block, and the first group of control points of the first neighboring affine coding block are control points determined based on a relative location of a coding tree unit CTU with respect to the current coding block, wherein the first neighboring affine coding block is located in the CTU;
obtaining a new candidate motion vector group based on motion vector difference MVDs obtained from the bitstream through parsing and the target candidate motion vector group indicated by the index; and
obtaining the motion vectors of the one or more sub-blocks of the current coding block based on the new candidate motion vector group; and;
predicting the predicted sample value of the current coding block based on the motion vectors of the one or more sub-blocks of the current coding block.
18 . The non-transitory computer-readable media according to claim 17 , wherein the operations further comprise:
generating the candidate motion vector predictor MVP list of the current coding block, wherein the candidate motion vector predictor MVP list comprises a plurality of candidate motion vector groups, and the candidate motion vector groups comprise the first candidate motion vector group and a third candidate motion vector group; the first neighboring affine coding block is a lowest coding block in the first CTU, and the current coding block is an uppermost coding block in the second decode tree unit CTU; the third candidate motion vector group is a candidate motion vector predictor of a group of control points of the current coding block obtained by combining candidate motion vectors of at least two control points of the current coding block.
19 . The non-transitory computer-readable media according to claim 17 , wherein the parameter model of the current coding block is a 4-parameter affine model, and the first group of control points of the first neighboring affine coding block is determined in the following manner:
if the first coding tree unit CTU and the second coding tree unit CTU are in a top-down relative position relationship, the first group of control points of the first neighboring affine coding block is a bottom-left control point and a bottom-right control point of the first neighboring affine coding block; and;
if the first coding tree unit CTU and the second coding tree unit CTU are not in a top-down relative position relationship, the first group of control points of the first neighboring affine coding block is a top-left control point and a top-right control point of the first neighboring affine coding block.
20 . The method according to claim 17 , wherein the parameter model of the current coding block is a 6-parameter affine model, and the first group of control points of the first neighboring affine coding block is determined in the following manner:
if the first coding tree unit CTU and the second coding tree unit CTU are in a top-down relative position relationship, the first group of control points of the first neighboring affine coding block is a bottom-left control point and a bottom-right control point of the first neighboring affine coding block; and;
if the first coding tree unit CTU and the second coding tree unit CTU are not in a top-down relative position relationship, the first group of control points of the first neighboring affine coding block is a top-left control point, a top-right control point, and a bottom-left control point of the first neighboring affine coding block.