Binarization of DQP using separate absolute value and sign (SAVS) in CABAC
Video coding systems or apparatus utilizing context-based adaptive binary arithmetic coding (CABAC) during encoding and/or decoding, are configured according to the invention with an enhanced binarization of non-zero Delta-QP (dQP). During binarization the value of dQP and the sign are separately encoded using unary coding and then combined into a binary string which also contains the dQP non-zero flag. This invention capitalizes on the statistical symmetry of positive and negative values of dQP and results in saving bits and thus a higher coding efficiency.
1. An apparatus for performing video coding, comprising:
a computer configured for encoding and/or decoding of video; and programming configured for execution on said computer for:
performing inter-prediction and/or intra-prediction for reducing temporal and/or spatial redundancies;
performing a transform and quantization during encoding and/or inverse transform and inverse quantization during decoding;
performing context-based adaptive binary arithmetic coding (CABAC) during encoding and/or decoding;
determining that Delta-QP (dQP), obtained as the difference of the quantization parameter (QP) between the current coding unit (CU) and the predicted CU, is non-zero; and
performing binarization of a non-zero Delta-QP (dQP) by
(a) coding a flag bit indicating that dQP is non-zero;
(b) mapping absolute value of dQP using unary coding, and separately coding sign of dQP, or alternatively coding the sign for dQP prior to coding the absolute value of dQP; and
(c) combining binary strings for sign and absolute value;
wherein said binarization benefits from the value of dQP having similar probability of being positive or negative for a given absolute value, so that the same lengths are assigned to nonzero dQP with the same absolute values;
wherein said video coding apparatus utilizes a Coding Unit (CU) structure in which block sizes are not fixed, and in which the Largest Coding Unit (LCU) is separated into multiple CU each having its own QP which can differ from one CU to another.
2. The apparatus recited in claim 1 , wherein said video coding is performed according to the High Efficiency Video Coding (HEVC) standard.
3. The apparatus recited in claim 2 , wherein said video coding is performed in a high efficiency coding mode within the High Efficiency Video Coding (HEVC) standard.
4. The apparatus recited in claim 1 , wherein said apparatus comprises a coder/decoder (CODEC).
5. A method of performing video coding, comprising:
performing inter-prediction and/or intra-prediction for reducing temporal and/or spatial redundancies;
performing a transform and quantization during encoding and/or inverse transform and inverse quantization during decoding;
performing context-based adaptive binary arithmetic coding (CABAC) during encoding and/or decoding; and
determining that Delta-QP (dQP), obtained as the difference of the quantization parameter (QP) between the current coding unit (CU) and the predicted CU, is non-zero;
performing binarization of a non-zero Delta-QP (dQP) by
(a) coding a flag bit indicating that dQP is non-zero;
(b) mapping absolute value of dQP using unary coding, and separately coding sign of dQP, or alternatively coding the sign for dQP prior to coding the absolute value of dQP; and
(c) combining binary strings for sign and absolute value;
wherein said binarization benefits from the value of dQP having similar probability of being positive or negative for a given absolute value, so that the same lengths are assigned to nonzero dQP with the same absolute values;
wherein said video coding method utilizes a Coding Unit (CU) structure in which block sizes are not fixed, and in which the Largest Coding Unit (LCU) is separated into multiple CU each having its own QP which can differ from one CU to another.
6. The method recited in claim 5 , wherein said video coding is performed according to the High Efficiency Video Coding (HEVC) standard.
7. The method recited in claim 6 , wherein said video coding is performed in a high efficiency coding mode within the High Efficiency Video Coding (HEVC) standard.
8. The method recited in claim 5 , wherein said apparatus comprises a coder/decoder (CODEC).
9. The method recited in claim 5 , wherein a flag bit is coded indicating that dQP is non-zero prior to the coding of the non-zero dQP and its sign.
10. A non-transitory computer-readable media containing a computer program executable on a computer configured for performing video coding, comprising:
performing inter-prediction and/or intra-prediction for reducing temporal and/or spatial redundancies on a computer configured for performing video coding;
performing a transform and quantization during encoding and/or inverse transform and inverse quantization during decoding;
performing context-based adaptive binary arithmetic coding (CABAC) during encoding and/or decoding;
determining that Delta-QP (dQP), obtained as the difference of the quantization parameter (QP) between the current coding unit (CU) and the predicted CU, is non-zero; and
performing binarization of a non-zero Delta-QP (dQP) by,
(a) coding a flag bit indicating that dQP is non-zero;
(b) mapping absolute value of dQP using unary coding, and separately coding sign of dQP, or alternatively coding the sign for dQP prior to coding the absolute value of dQP; and
(c) combining binary strings for sign and absolute value;
wherein said binarization benefits from the value of dQP having similar probability of being positive or negative for a given absolute value, so that the same lengths are assigned to nonzero dQP with the same absolute values;
wherein said video coding apparatus utilizes a Coding Unit (CU) structure in which block sizes are not fixed, and in which the Largest Coding Unit (LCU) is separated into multiple CU each having its own QP which can differ from one CU to another.
11. The computer-readable media recited in claim 10 , wherein said video coding is performed in a high efficiency coding mode according to the High Efficiency Video Coding (HEVC) standard.