| JCTVC-J0358 Chroma intra prediction based on residual luma samples in 4:2:2 chroma format [K. Kawamura, T. Yoshino, H. Kato, S. Naito (KDDI Corp.)]
This contribution presents an additional chroma intra mode based on inter-channel correlation of residual samples for the 4:2:2 chroma format. Predicted Cb/Cr values are sum of regular prediction (same as DM) and linear equation using reconstructed luma-residual values with a parameter alpha. The parameter alpha is derived and coded on the encoder side. Anchor method is a modified HM7.0 that supports the 4:2:2 chroma format described in JCTVC-J0358. Compared to the modified HM7.0, the average BD-bitrate gains are 0.7%, 3.4%, 2.2%, and 1.4% for all intra HE configuration respectively for Y, U, V, and YUV components.
The design is somewhat different – using residual rather than reconstruction – than our current LM chroma prediction scheme.
(Treated as an information document.
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JCTVC-J0233 Syntax and semantics of Dual-coder Mixed Chroma-sampling-rate (DMC) coding for 4:4:4 screen content [Tao Lin, Peijun Zhang, Shuhui Wang, Kailun Zhou, Xianyi Chen]
This contribution presents the syntax and semantics of dual-coder mixed chroma-sampling-rate (DMC) coding for full-chroma (YUV444) screen content. The proposed DMC coding adds a full-chroma dictionary-entropy coder to the existing chroma-subsampled (YUV420) HEVC coder. The existing YUV420 HEVC syntax and semantics can be used without alteration. Three new syntax elements (matching_string_distance, matching_string_length_minus2, unmatchable_sample_residual) are added to enable YUV444 dictionary-entropy coding.
Prior contributions included JCTVC-H0065, JCTVC-H0073, JCTVC-I0272.
The contributor indicated a plan to integrate the DMC scheme into the HM and provide experiment results in the future. Hard-edged graphics areas (such as text regions) seemed to use the dictionary coding technology.
JCTVC-J0352 BD-rate performance vs. dictionary size and hash-table memory size in Dual-coder Mixed Chroma-sampling-rate (DMC) coding for 4:4:4 screen content [Peijun Zhang, Tao Lin, Xianyi Chen, Shuhui Wang, Kailun Zhou] [late]
This contribution presents BD-rate performance comparison of dual-coder mixed chroma-sampling-rate (DMC) coding for full-chroma (YUV444) screen content using different dictionary (as part of DPB) sizes from 4 MB to 16 KB and hash-table memory size from 16 MB to 10.5 KB. Some comparisons of results for the scheme were provided relative to 4:2:0 coding with HEVC.
JCTVC-J0353 R-D cost based effectiveness analysis of Dual-coder Mixed Chroma-sampling-rate (DMC) coding for 4:4:4 screen content [Xianyi Chen, Tao Lin, Peijun Zhang, Shuhui Wang, Kailun Zhou] [late]
This contribution presents R-D cost based effectiveness analysis of dual-coder mixed chroma-sampling-rate (DMC) coding for full-chroma (YUV444) screen content. The DMC coding technique codes a CU using a dictionary-entropy coder and a hybrid coder simultaneously and calculating two R-D costs Jdict and Jhybrid. The coder with smaller R-D cost is selected as the optimal coder to code the CU. For a given screen picture, to look at and understand the overall coder selection distribution across all CUs in the picture, a ratio Jhybrid/Jdict map can be plotted to visualize the coder selection distribution and to evaluate how effective the two coders are. The ratio distribution maps reportedly reveal that the two coders are complementary and play very different roles to compress effectively different contents.
Further study is encouraged, particularly in relation to 4:4:4 extension of HEVC.
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