Nested entropy encoding
Methods and systems for improving coding decoding efficiency of video by providing a syntax modeler, a buffer, and a decoder. The syntax modeler may associate a first sequence of symbols with syntax elements. The buffer may store tables, each represented by a symbol in the first sequence, and each used to associate a respective symbol in a second sequence of symbols with encoded data. The decoder decodes the data into a bitstream using the second sequence retrieved from a table.
1. A non-transitory computer-readable medium storing encoded image data, the encoded image data comprising:
a first block to the left of a current block in a picture;
a second block above the current block in the picture;
a motion vector differential;
a residual block of the current block; and
a flag indicating whether a temporally-located motion vector can be used as a motion vector predictor,
wherein when a motion vector of the first block is not equal to a motion vector of the second block, a motion vector predictor candidate set for the current block includes the motion vector of the first block and the motion vector of the second block,
when the motion vector of the first block is equal to the motion vector of the second block and the flag indicates that a temporally-located motion vector can be used as a motion vector predictor, the motion vector predictor candidate set for the current block includes the motion vector of the first block and the temporally-located motion vector,
when the flag indicates that a temporally-located motion vector cannot be used as a motion vector predictor, the motion vector of the block in another picture is excluded from the motion vector predictor candidate set,
wherein a motion vector from the motion vector predictor candidate set is selected as a motion vector predictor of the current block;
wherein a motion vector for the current block is based on the selected motion vector predictor and the motion vector differential, and
wherein the residual block is a difference between the current block and a reference block identified by the motion vector for the current block.
2. An apparatus comprising:
a non-transitory computer-readable medium storing encoded image data, the encoded image data comprising:
a first block to the left of a current block in a picture;
a second block above the current block in the picture;
a motion vector differential;
a residual block of the current block; and
a flag indicating whether a temporally-located motion vector can be used as a motion vector predictor,
wherein when a motion vector of the first block is not equal to a motion vector of the second block, a motion vector predictor candidate set for the current block includes the motion vector of the first block and the motion vector of the second block,
when the motion vector of the first block is equal to the motion vector of the second block and the flag indicates that a temporally-located motion vector can be used as a motion vector predictor, the motion vector predictor candidate set for the current block includes the motion vector of the first block and the temporally-located motion vector,
when the flag indicates that a temporally-located motion vector cannot be used as a motion vector predictor, the motion vector of the block in another picture is excluded from the motion vector predictor candidate set,
wherein a motion vector from the motion vector predictor candidate set is selected as a motion vector predictor of the current block;
wherein a motion vector for the current block is based on the selected motion vector predictor and the motion vector differential, and
wherein the residual block is a difference between the current block and a reference block identified by the motion vector for the current block; and
a processing unit for signaling a bitstream including the encoded image data to a decoder.