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. An encoder device for encoding a motion vector predictor of a current block in a picture, the encoder device configured to perform operations comprising:
identifying a first block that is adjacent to the current block;
identifying a second block that is adjacent to the current block;
determining a motion vector of the first block and a motion vector of the second block;
comparing the motion vector of the first block to the motion vector of the second block;
in response to the comparison, generating a motion vector predictor candidate set, wherein when the motion vector of the first block is not equal to the motion vector of the second block, the 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, and when the motion vector of the first block is equal to the motion vector of the second block, the motion vector of the second block is trimmed from the motion vector predictor candidate set to eliminate duplicate motion vectors;
determining whether a temporally-located motion vector can be used as a motion vector predictor of the current block;
upon a determination that a temporally-located motion vector can be used as a motion vector predictor of the current block, (i) including a motion vector of a block in another picture in the motion vector predictor candidate set, and (ii) generating a flag indicating that a temporally-located motion vector is used as a motion vector predictor, such that 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 temporally-located motion vector and one of the motion vector of the first block or the motion vector of the second block; and
selecting a motion vector from the motion vector predictor candidate set as the motion vector predictor of the current block.
2. The encoder device of claim 1 , wherein comparing the motion vector of the first block to the motion vector of the second block and generating the motion vector predictor candidate set comprises:
determining that the motion vector of the first block is not equal to the motion vector of the second block; and
in response to the determination, adding both motion vectors of the first and the second blocks to the motion vector predictor candidate set.
3. The encoder device of claim 1 , wherein comparing the motion vector of the first block to the motion vector of the second block and generating the motion vector predictor candidate set comprises:
determining that the motion vector of the first block is equal to the motion vector of the second block; and
in response to the determination, adding one of the motion vector of the first block or the motion vector of the second block to the motion vector predictor candidate set.
4. The encoder device of claim 1 , wherein the operations further comprise:
upon a determination that a temporally-located motion vector cannot be used as a motion vector predictor of the current block, excluding the motion vector of the block in another picture from the motion vector predictor candidate set.
5. The encoder device of claim 1 , wherein the operations further comprise:
generating a motion vector differential of the current block based on the selected motion vector predictor of the current block.
6. A bitstream storing one or more encoded pictures in a sequence of pictures, the bitstream comprising:
a first block adjacent to a current block in a picture of the one or more encoded pictures;
a second block adjacent to the current block in the picture; 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, and
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 temporally-located motion vector and one of the motion vector of the first block or the motion vector of the second block.
7. The bitstream of claim 6 , further comprising:
a motion vector differential,
wherein a motion vector for the current block is based on a motion vector predictor selected from the motion vector predictor candidate set for the current block and the motion vector differential.