Decoder for coded pictures having regions with common motion models
A decoder includes circuitry configured to receive a bitstream; construct, for a current block, a motion vector candidate list including adding a single global motion vector candidate to the motion vector candidate list, the single global motion vector candidate selected based on a global motion model utilized by the current block; and reconstruct pixel data of the current block and using the motion vector candidate list. Related apparatus, systems, techniques and articles are also described.
1. A decoder configured to:
receive a bitstream, the bitstream comprising a sequence parameter set and a coded picture, the coded picture comprising a first contiguous region comprising a first plurality of coding blocks and a second contiguous region comprising a second plurality of coding blocks;
decode the first contiguous region of the coded picture by:
for each coding block of the first plurality of coding blocks in the first contiguous region, utilize a motion model, the motion model being the same for all of the first plurality of coding blocks in the first contiguous region, the motion model being one of translational motion, 4-parameter affine motion, and 6-parameter affine motion, the sequence parameter set containing information about the motion model;
when the motion model is translational motion, construct for each of the first plurality of coding blocks in the first contiguous region, a motion vector candidate list including a first candidate, wherein the first candidate is a motion vector of a nearest neighbor block in the coded picture, and decode each of the first plurality of coding blocks in the first contiguous region using the first candidate for translational motion compensation;
when the motion model is 4-parameter affine motion, construct for each of the first plurality of coding blocks in the first contiguous region, a motion vector candidate list including a second candidate comprising two control point motion vectors, wherein each of the two control point motion vectors is a motion vector of a nearest neighbor block in the coded picture, and decode each of the first plurality of coding blocks in first contiguous region using the second candidate for 4-parameter affine motion compensation;
when the motion model is 6-parameter affine motion, construct for each of the first plurality of coding blocks in the first contiguous region, a motion vector candidate list including a third candidate comprising three control point motion vectors, wherein each of the three control point motion vectors is a motion vector of a nearest neighbor block in the coded picture, and decode each of the first plurality of coding blocks in first contiguous region using the third candidate for 6-parameter affine motion compensation;
decode the second contiguous region of the coded picture by decoding each of the coding blocks in the second plurality using individual motion information contained in the bitstream for each of the second plurality of coding blocks, and
store the decoded picture in a decoded picture buffer.
2. The decoder of claim 1 wherein each of said blocks is part of a coding tree unit.
3. The decoder of claim 1 , wherein at least one block is a symmetric block.
4. The decoder of claim 2 wherein each of the blocks is N×N where N is one of 32, 64 or 128.