Reducing context coded and bypass coded bins to improve context adaptive binary arithmetic coding (CABAC) throughput
Techniques for context-adaptive binary arithmetic coding (CABAC) coding with a reduced number of context coded and/or bypass coded bins are provided. Rather than using only truncated unary binarization for the syntax element representing the delta quantization parameter and context coding all of the resulting bins as in the prior art, a different binarization is used and only part of the resulting bins are context coded, thus reducing the worst case number of context coded bins for this syntax element. Further, binarization techniques for the syntax element representing the remaining actual value of a transform coefficient are provided that restrict the maximum codeword length of this syntax element to 32 bits or less, thus reducing the number of bypass coded bins for this syntax element over the prior art.
1. A method comprising:
receiving, by an encoder, a syntax element associated with a remaining value of a transform coefficient;
binarizing, by the encoder, the syntax element to generate one or more bins using a variable length code (VLC) that includes a maximum codeword length of 32 bits or less; and
bypass coding, by the encoder, the one or more bins.
2. The method of claim 1 ,
wherein the VLC is a code that adapts based on a value of a parameter R,
wherein codewords for values less than 4×2 R have a fixed length suffix of R bits,
wherein prefixes of codewords are unary coded,
wherein suffix length of codewords increases by 1 bit for each 1 bit increase in prefix length, and
wherein the maximum codeword length is 32 bits.
3. The method of claim 2 , wherein the value of R is one selected from a group consisting of 0, 1, 2, 3, and 4.
4. The method of claim 1 ,
wherein the VLC is a code that adapts based on a value of a parameter R,
wherein codewords for values less than 4×2 R have a fixed length suffix of R bits,
wherein prefixes of codewords are truncated unary coded,
wherein suffix length of codewords increases by 1 bit for each 1 bit increase in prefix length, and
wherein the maximum codeword length is 31 bits.
5. The method of claim 1 ,
wherein the VLC is a code that adapts based on a value of a parameter R,
wherein codewords for values less than 5×2 R have a fixed length suffix of R bits,
wherein prefixes of codewords are truncated unary coded,
wherein suffix length of codewords increases by 1 bit for each 1 bit increase in prefix length, and
wherein the maximum codeword length is 32 bits.
6. The method of claim 1 ,
wherein the VLC is a code that adapts based on a value of a parameter R,
wherein codewords for values less than 8×2 R have a fixed length suffix of R bits,
wherein prefixes of codewords are unary coded,
wherein suffix length of codewords increases by 1 bit for each 1 bit increase in prefix length for syntax element values less than 263×2 R ,
wherein suffix length of codewords for syntax element values greater than or equal to 263×2 R is 15 bits, and
wherein the maximum codeword length is 32 bits.
7. The method of claim 1 ,
wherein the VLC is a code that adapts based on a value of a parameter R,
wherein codewords for values less than 8×2 R have a fixed length suffix of R bits,
wherein prefixes of codewords are unary coded,
wherein suffix length of codewords increases by 2 bits for each 1 bit increase in prefix length, and
wherein the maximum codeword length is 32 bits.
8. The method of claim 1 ,
wherein the VLC is a code that adapts based on a value of a parameter R,
wherein codewords for values less than 6×2 R have a fixed length suffix of R bits,
wherein prefixes of codewords are unary coded,
wherein suffix length of codewords increases by 2 bits for each 1 bit increase in prefix length, and
wherein the maximum codeword length is 30 bits.
9. The method of claim 1 ,
wherein the VLC is a code that adapts based on a value of a parameter R,
wherein codewords for values less than 6×2 R have a fixed length suffix of R bits,
wherein prefixes of codewords are unary coded,
wherein suffix length of codewords increases by 2 bits for each 1 bit increase in prefix length, and
wherein the maximum codeword length is 29 bits.
10. A method comprising:
receiving, by a decoder, one or more bins;
bypass decoding, by the decoder, the one or more bins, wherein each of the one or more bins includes a prefix and a suffix of a binarized value of a syntax element for a remaining value of a transform coefficient; and
debinarizing, by the decoder, the one or more bins using a variable length code (VLC) to determine one or more syntax elements, wherein the VLC includes a maximum codeword length of 32 bits or less.
11. The method of claim 10 ,
wherein the VLC is a code that adapts based on a value of a parameter R,
wherein codewords for values less than 4×2 R have a fixed length suffix of R bits,
wherein prefixes of codewords are unary coded,
wherein suffix length of codewords increases by 1 bit for each 1 bit increase in prefix length, and
wherein the maximum codeword length is 32 bits.
12. The method of claim 11 , wherein the value of R is one selected from a group consisting of 0, 1, 2, 3, and 4.