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 method for decoding a motion vector predictor of a current block in a picture of a sequence of pictures, the method comprising:
accessing a current block in the picture;
identifying a first block and a second block that are each adjacent to the current block in the picture;
conditioned on determining that a motion vector of the first block is not equal to a motion vector of the second block, including, in a motion vector predictor candidate set for the current block, the motion vector of the first block and the motion vector of the second block;
conditioned on determining that the motion vector of the first block is equal to the motion vector of the second block, including, in the motion vector predictor candidate set for the current block, one of the motion vector of the first block or the motion vector of the second block;
receiving a flag from a bitstream, the flag indicating whether a temporally-located motion vector can be used as a motion vector predictor;
conditioned on determining that the flag indicates that a temporally-located motion vector can be used as a motion vector predictor, including a motion vector of a block in another picture in the motion vector predictor candidate set for the current block;
conditioned on determining that the flag indicates that a temporally-located motion vector cannot be used as a motion vector predictor, excluding, from the motion vector predictor candidate set for the current block, the motion vector of the block in the other picture;
selecting a motion vector from the motion vector predictor candidate set as the motion vector predictor of the current block;
deriving a motion vector for the current block based on the selected motion vector predictor and a motion vector differential; and
generating a residual block as a difference between the current block and a reference block identified by the motion vector for the current block.