The Joint Collaborative Team on Video Coding (jct-vc) of itu-t wp3/16 and iso/iec jtc 1/ sc 29/ wg 11 held its tenth meeting during 11-20 July 2012 at the City Conference Centre (ccc), a k. a

JCTVC-J0560 Cross-check report for JCTVC-J0408 [H. Sasai (Panasonic)] [late]
JCTVC-J0254 Position-based Context Derivation of coeff_abs_level_greater1_flag Coding [T. Ji, X. Yu, D. He, G. Martin-Cocher (RIM)]

This contribution proposes a position-based context derivation scheme for the syntax element coeff_abs_level_greater1_flag coding. In the current HM7.0 design, the context indices for coeff_abs_level_greater1_flag can only be derived in a sequential manner, since the context for one coeff_abs_level_greater1_flag is dependent on its immediately previous coeff_abs_level_greater1_flag . It is proposed here to derive contexts for coeff_abs_level_greater1_flag in a CG based on the position of the coeff_abs_level_greater1_flag in the scanning order. Thus, it completely removes the context dependency for coeff_abs_level_greater1_flag within a CG, and allows all context indices for coeff_abs_level_greater1_flag in one CG to be derived in parallel. The BD rate penalty is on average 0.1%.

Loss is largest in all-intra settings and particularly in class F.

Q: Is it really a benefit? The proposal does not remove the dependency between GT1 and GT2 flags

Even though this is one syntax element which could be frequently occurring (15% ), there is no consensus how critical this really is (may be depending on implementation platform).

Not evident that the advantage that is claimed justifies the loss in performance.

No action.