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16th Meeting: Geneva, October 2019 2019-10-03 09:01
CE7-3.3: Context reduction for sig_coeff_flag, par_level_flag, abs_level_gtx_flag
Abstract
This contribution reports the results of CE7-3.3 for reducing the number of context variables for entropy coding the syntax elements sig_coeff_flag, par_level_flag and abs_level_gtx_flag. In the proposed tests, which are the combinations between CE7-3.1 and CE7-3.2, 1) the numbers of the context variables of the context subsets for entropy coding sig_coeff_flag associated with dependent quantization states 2 and 3 are further reduced; 2) the usage of the local neighborhood for the context derivation for syntax elements par_level_flag and abs_level_gtx_flag in some regions of the chroma transform blocks (TB) is removed. In CE7-3.3a, the proposed method reportedly provides 0.01%, -0.01%, and -0.06% luma BD-rates for the AI, RA, and LDB settings with the CABAC initial values retraining, respectively, versus the VTM6.0 anchor under the common test conditions (CTCs) while achieving 36 contexts reduction. In CE7-3.3b, the proposed method reportedly provides 0.02%, 0.00%, and -0.01% luma BD-rates for the AI, RA, and LDB settings with the CABAC initial values retraining, respectively, versus the VTM6.0 anchor under the common test conditions (CTCs) while achieving 42 contexts reduction.
JVET-P0067 CE7-3.3: Context reduction for sig_coeff_flag, par_level_flag, abs_level_gtx_flag [Y. Chen, F. Le Léannec, T. Poirier, F. Galpin (Intedigital), S.-T. Hsiang, T.-D. Chuang, Y.-W. Huang, S.-M. Lei (MediaTek)]

This contribution reports the results of CE7-3.2 for simplifying the context modelling and reducing the number of context variables for entropy coding the syntax elements par_level_flag and abs_level_gtx_flag. In the proposed tests, the usage of the local neighborhood for the context derivation for syntax elements par_level_flag and abs_level_gtx_flag in some regions of the chroma transform blocks (TB) is removed. In CE7-3.2, the proposed method reportedly provides 0.00%, 0.01%, and -0.03% luma BD-rates for the AI, RA, and LDB settings with the CABAC initial values retraining, respectively, versus the VTM6.0 anchor under the common test conditions (CTCs) while achieving 24 context reduction.

Decisions
This contribution reports the results of CE7-3.2 for simplifying the context modelling and reducing the number of context variables for entropy coding the syntax elements par_level_flag and abs_level_gtx_flag. In the proposed tests, the usage of the local neighborhood for the context derivation for syntax elements par_level_flag and abs_level_gtx_flag in some regions of the chroma transform blocks (TB) is removed. In CE7-3.2, the proposed method reportedly provides 0.00%, 0.01%, and -0.03% luma BD-rates for the AI, RA, and LDB settings with the CABAC initial values retraining, respectively, versus the VTM6.0 anchor under the common test conditions (CTCs) while achieving 24 context reduction.
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