JCTVC-M0419 Cross-check of JCTVC-M0091 (Non SCE1-Combined Intra Prediction with low-pass filter) [J. Lainema (Nokia)] [late]
JCTVC-M0115 Non-SCE1: Simplification of remaining modes coding in SHVC [E. François, S. Shi, C. Gisquet, G. Laroche, P. Onno (Canon)]
This contribution proposes a simplification of the intra mode coding for the EL, by reducing the number of remaining modes to a limited set of M=2 or 4 modes instead of 32 as in the current SHM design. Using this modes number reduction, the number of modes to be checked is significantly reduced. The change can be normative (remaining modes are coded using less bits) or non-normative. The reported results for the All-Intra configurations are as follows: 1) non-normative change, with M=2, encoding time reduction of 19% with an average BDBR-Y variation of 0.1% in luma; 2) non-normative change, with M=4, encoding time reduction of 13% with an average BDR-Y variation of 0.1% in luma; 3) normative change, with M=2, encoding time reduction of 19% with an average BDBR-Y variation of −0.1% in luma; 4) normative change, with M=4, encoding time reduction of 13% with an average BDR-Y variation of −0.10% in luma. The impact for chroma and in inter configurations is reportedly negligible.
Approximately no impact was reported for inter coding cases.
The primary motivation of the proposal is the reduction of encoding time, which can basically be achieved with the non-normative approach.
It was remarked that the performance would depend on the BL mode selection strategy.
The change was estimated to be around 25 lines of code, and applicable to both the TextureRL and RefIdx approaches.
It was remarked that the reference here is not exhaustive testing of all modes, but a test of a different (but larger) reduced set of modes, and thus that adopting the normative approach may be undesirable.
Decision (SW): Adopt N-N approach with M=2, not high priority, disabled by default (may be enabled for CEs not expected to be affected by it).
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