Method and apparatus for video coding
Aspects of the disclosure provide methods and apparatuses for video encoding/decoding. In some examples, an apparatus for video decoding includes receiving circuitry and processing circuitry. The processing circuitry decodes prediction information of a current block in a current picture from a coded video bitstream. The prediction information is indicative of an affine model in a merge mode. The processing circuitry obtains, from a buffer, motion information of bottom locations in a neighboring block that is adjacent of the current block in the current picture, and determines parameters of the affine model that is used to transform between the block and a reference block in a reference picture based on the motion information of the bottom locations in the neighboring block. Further, the processing circuitry reconstructs samples of the current block based on the affine model.
1. A method for video decoding in a decoder, comprising:
decoding prediction information of a current block in a first coding tree unit (CTU) of a current picture from a coded video bitstream, the prediction information being indicative of an affine model in a merge mode;
obtaining, from a line buffer, one or more motion vectors of blocks located at bottom locations in a CTU row of a second CTU above the current block, wherein the line buffer only stores motion vectors of minimum-size blocks located at the bottom locations in the CTU row of the second CTU above the current block and the line buffer does not store (i) a block width or block height of the minimum-size blocks, (ii) affine control point information, and (iii) an affine flag;
deriving, based on the obtained one or more motion vectors, motion vectors of control points of the current block using the affine merge model; and
reconstructing at least a sample of the current block based on the affine merge model.
2. The method of claim 1 , wherein the line buffer is configured not to buffer motion vectors of non-bottom minimum-size blocks in the CTU row above the current block.
3. The method of claim 1 , wherein the line buffer is configured not to buffer motion information of control points of affine coded blocks.
4. The method of claim 1 , wherein the affine model is a 4-parameter affine model.
5. The method of claim 1 , wherein
the one or more obtained motion vectors consist of a pair of the minimum-size blocks that are affine coded, and
the affine model is a four-parameter affine model.
6. The method of claim 5 , wherein
the pair of the minimum-size blocks that are affine coded are consecutive minimum-size blocks.
7. The method of claim 1 , wherein
the one or more obtained motion vectors consist of a pair of the minimum-size blocks that are affine coded, and
the derived motion vectors of the control points consist of motion vectors of the top left corner and the top right corner of the current block.
8. The method of claim 1 , further comprising:
disabling an affine merge mode when none of left neighboring blocks of the current block is available as an affine coded block.
9. A video decoder for video decoding, comprising:
processing circuitry configured to:
decode prediction information of a current block in a first coding tree unit (CTU) of a current picture from a coded video bitstream, the prediction information being indicative of an affine model in a merge mode,
obtain, from a line buffer, one or more motion vectors of blocks located at bottom locations in a CTU row of a second CTU above the current block, wherein the line buffer only stores motion vectors of minimum-size blocks located at the bottom locations in the CTU row of the second CTU above the current block and the line buffer does not store (i) a block width or block height of the minimum-size blocks, (ii) affine control point information, and (iii) an affine flag,
derive, based on the obtained one or more motion vectors, motion vectors of control points of the current block using the affine merge model, and
reconstructing at least a sample of the current block based on the affine merge model.
10. The video decoder of claim 9 , wherein the line buffer is configured not to buffer motion vectors of non-bottom minimum-size blocks in the CTU row above the current block.
11. The video decoder of claim 9 , wherein the line buffer is configured not to buffer motion information of control points of affine coded blocks.
12. The video decoder of claim 9 , wherein the affine model is a 4-parameter affine model.
13. The video decoder of claim 9 ,
wherein the one or more obtained motion vectors consist of a pair of the minimum-size blocks that are affine coded, and
the affine model is a four-parameter affine model.
14. A non-transitory computer readable medium having instructions stored therein, which when executed by processor in a video decoder cause the processor to execute a method comprising:
decoding prediction information of a current block in a first coding tree unit (CTU) of a current picture from a coded video bitstream, the prediction information being indicative of an affine model in a merge mode;
obtaining, from a line buffer, one or more motion vectors of blocks located at bottom locations in a CTU row of a second CTU above the current block, wherein the line buffer only stores motion vectors of minimum-size blocks located at the bottom locations in the CTU row of the second CTU above the current block and the line buffer does not store (i) a block width or block height of the minimum-size blocks, (ii) affine control point information, and (iii) an affine flag;
deriving, based on the obtained one or more motion vectors, motion vectors of control points of the current block using the affine merge model; and
reconstructing at least a sample of the current block based on the affine merge model.