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 an encoded video bit stream;
context decoding a first bin string from the encoded video bit stream, the first bin string corresponding to a prefix of a delta quantization parameter syntax element represented by a truncated unary code with a maximum codeword length of five;
debinarizing the first bin string to determine a value of the prefix; and
in response to the value of the prefix being five:
bypass decoding a second bin string from the encoded video bit stream, wherein the second bin string corresponds to a suffix of the binarized value of the delta quantization parameter syntax element represented by a zeroth order exponential Golomb code; and
debinarizing the second bin string to determine a value of the suffix.
2. The method of claim 1 , further comprising determining a value for the delta quantization parameter using the value of the prefix and the value of the suffix, wherein the value of the prefix is five.
3. The method of claim 1 , wherein the second bin string comprises a single bin with a value of zero.
4. The method of claim 1 , further comprising bypass decoding a bin indicating a sign of the value, wherein the bin is in the encoded video bit stream immediately following the second bin string.
5. The method of claim 3 , wherein bypass decoding the bin indicating the sign of the value occurs only when the value of the delta quantization parameter syntax element is non-zero.
6. The method of claim 1 , wherein debinarizing the first bin string comprises debinarizing the first bin string using a truncated unary binarization process.
7. The method of claim 1 , wherein debinarizing the second bin string comprises debinarizing the first bin string using a zeroth order exponential Golomb binarization process.
8. A system comprising:
a receiver configured to receive an encoded video bit stream representing a sequence of pictures;
a decoder coupled to the receiver, the decoder configured to:
context decode a first bin string from the encoded video bit stream, the first bin string corresponding to a prefix of a binarized value of a delta quantization parameter syntax element represented by a truncated unary code with a maximum codeword length of five;
debinarize the first bin string to determine a value of the prefix; and
in response to the value of the prefix being five:
bypass decode a second bin string from the encoded video bit stream, wherein the second bin string corresponds to a suffix of the binarized value of the delta quantization parameter syntax element represented by a zeroth order exponential Golomb code; and
debinarize the second bin string to determine a value of the suffix; and
a display coupled to the decoder, the display configured to display the sequence of pictures.
9. The system of claim 8 , wherein the decoder is further configured to determine a value for the delta quantization parameter by using the value of the prefix and the value of the suffix, wherein the value of the prefix is five.
10. The system of claim 8 , wherein the second bin string comprises a single bin with a value of zero.
11. The system of claim 8 , wherein the decoder is further configured to bypass decode a bin indicating a sign of the value, wherein the bin is in the encoded video bit stream immediately following the second bin string.
12. The system of claim 11 , wherein bypass decoding the bin indicating the sign of the value occurs only when the value of the delta quantization parameter syntax element is non-zero.
13. The system of claim 8 , wherein debinarizing the first bin string comprises debinarizing the first bin string using a truncated unary binarization process.
14. The system of claim 8 , wherein debinarizing the second bin string comprises debinarizing the first bin string using a zeroth order exponential Golomb binarization process.
15. A system comprising:
a receiver configured to receive an encoded video bit stream; and
a decoder coupled to the receiver, the decoder configured to:
context decode a first bin string from the encoded video bit stream, the first bin string corresponding to a prefix of a binarized value of a delta quantization parameter syntax element represented by a truncated unary code with a maximum codeword length of five;
debinarize the first bin string to determine a value of the prefix; and
in response to the value of the prefix being five:
bypass decode a second bin string from the encoded video bit stream, wherein the second bin string corresponds to a suffix of the binarized value of the delta quantization parameter syntax element represented by a zeroth order exponential Golomb code; and
debinarize the second bin string to determine a value of the suffix.
16. The system of claim 15 , wherein the decoder is further configured to determine a value for the delta quantization parameter by combining the value of the prefix and the value of the suffix, wherein the value of the prefix is five.
17. The system of claim 15 , wherein the second bin string comprises a single bin with a value of zero.
18. The system of claim 15 , wherein the decoder is further configured to bypass decode a bin indicating a sign of the value, wherein the bin is in the encoded video bit stream immediately following the second bin string.
19. The system of claim 18 , wherein bypass decoding the bin indicating the sign of the value occurs only when the value of the delta quantization parameter syntax element is non-zero.
20. The system of claim 15 , wherein debinarizing the first bin string comprises debinarizing the first bin string using a truncated unary binarization process.
21. The system of claim 15 , wherein debinarizing the second bin string comprises debinarizing the first bin string using a zeroth order exponential Golomb binarization process.