Methods and devices for enhancing block adaptive weighted prediction with block vector
This disclosure relates generally to video coding/decoding and particularly for enhancing block adaptive weighted prediction (BAWP) with a block vector. One method includes receiving a coded video bitstream; identifying, from the coded video bitstream, a block vector corresponding to a reference block associated with the current block of the current frame; determining a scaling factor based on a syntax explicitly signaled in the coded video bitstream; generating a predicted block based on the reference block according to a linear equation associated with the scaling factor; and reconstructing, by the device, the current block based on the predicted block.
1 . A method for decoding a current block of a current frame in a coded video bitstream, the method comprising:
obtaining, by a device comprising a memory storing instructions and a processor in communication with the memory, the coded video bitstream;
identifying, by the device from the coded video bitstream, a block vector corresponding to a reference block associated with the current block of the current frame;
extracting, by the device from the coded video bitstream, a flag indicating whether an explicit signaling is for the current block;
in response to the flag indicating that the explicit signaling is for the current block, determining, by the device, a scaling factor based on a syntax explicitly signaled in the coded video bitstream;
generating, by the device, a predicted block based on the reference block according to a linear equation associated with the scaling factor; and
reconstructing, by the device, the current block based on the predicted block.
2 . The method according to claim 1 , wherein:
the reference block is pointed by the block vector relative to the current block within the current frame.
3 . The method according to claim 1 , wherein the determining the scaling factor comprises:
determining the scaling factor based on a predefined lookup table, wherein the predefined lookup table for the reference block being within the current frame as the current block is different from a second lookup table for the reference block being at a different frame as the current block.
4 . The method according to claim 3 , wherein:
the predefined lookup table is different from the second lookup table with respect to at least one of the following:
the predefined lookup table having a larger size than the second lookup table, or
the predefined lookup table having a higher precision than the second lookup table.
5 . The method according to claim 1 , wherein the determining the scaling factor comprises:
determining the scaling factor based on a predefined lookup table, wherein the predefined lookup table for the reference block being within the current frame as the current block is same as a third lookup table for an inter prediction mode.
6 . The method according to claim 1 , wherein:
the current block has a first prediction mode, wherein a best prediction block is copied from a reconstructed part of the current frame, and a template of the best prediction block matches to a template of the current block.
7 . The method according to claim 1 , wherein:
the current block has a second prediction mode, wherein the block vector is used to indicate a prediction block from a previously decoded area of the current frame.
8 . The method according to claim 1 , wherein:
the flag indicates whether an explicit signaling of a block level weighted prediction for the current block, wherein a context for signaling the flag is based on whether the current block is coded with the block vector.
9 . The method according to claim 1 , wherein:
the current block has a plurality of linear models associated with a plurality of scaling factors; and
at least one scaling factor of the plurality of scaling factors is explicitly signaled in the coded video bitstream.
10 . The method according to claim 1 , wherein:
the flag indicates whether an explicit signaling of a block level weighted prediction for the current block, wherein a context for signaling the flag is based on whether one or more neighboring block of the current block is coded by explicit signaling of a block level weighted prediction for the one or more neighboring block.
11 . The method according to claim 1 , further comprising:
in response to the scaling factor being explicitly signed for the current block with the block vector, determining an adjacent reference line based on a second syntax explicitly signaled in the coded video bitstream, the adjacent reference line being used to derive an offset value for the current block.
12 . The method according to claim 1 , further comprising:
in response to the scaling factor being explicitly signed for the current block with the block vector, determining neighboring samples in a plurality of adjacent reference lines for deriving an offset value for the current block.
13 . The method according to claim 1 , further comprising:
in response to the scaling factor being explicitly signed for the current block with the block vector, determining an offset value for the current block as a predefined value.
14 . The method according to claim 1 , wherein:
in response to the scaling factor being explicitly signed for the current block with the block vector, the scaling factor is for a predefined component of the current block.
15 . The method according to claim 1 , further comprising:
extracting, from the coded video bitstream, a high-level syntax indicating whether an explicit signaling of a block level weighted prediction for the current block, wherein the high-level syntax comprises one of the following: a sequence-level flag, a picture-level flag, a slice-level flag, a subpicture-level flag, or a tile-level flag.
16 . An apparatus for encoding a current block of a current frame into a coded video bitstream, the apparatus comprising:
a memory storing instructions; and
a processor in communication with the memory, wherein, when the processor executes the instructions, the processor is configured to cause the apparatus to:
obtain video data;
determine, from the video data, a block vector corresponding to a reference block associated with the current block of the current frame;
encoding a flag into the coded video bitstream, the flag indicating whether an explicit signaling is for the current block;
in response to the flag indicating that the explicit signaling is for the current block, determine a scaling factor and encoding a syntax for the scaling factor into the coded video bitstream;
generate a predicted block based on the reference block according to a linear equation associated with the scaling factor; and
encoding the current block based on the predicted block into the coded video bitstream.
17 . The apparatus according to claim 16 , wherein
the reference block is pointed by the block vector relative to the current block within the current frame.
18 . A non-transitory computer readable storage medium storing a video bitstream that is generated by a video encoding method, the video encoding method comprising:
determine a block vector corresponding to a reference block associated with a current block of a current frame in video data;
encoding a flag into the video bitstream, the flag indicating whether an explicit signaling is for the current block;
in response to the flag indicating that the explicit signaling is for the current block, signaling a syntax explicitly in the video bitstream, wherein a scaling factor is determined based on the syntax;
generate a predicted block based on the reference block according to a linear equation associated with the scaling factor; and
encoding the current block based on the predicted block into the video bitstream.
19 . The non-transitory computer readable storage medium according to claim 18 , wherein
the reference block is pointed by the block vector relative to the current block within the current frame.