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-J0189 Cross check report of IDSQ (J0076) proposed by BBC [A Ichigaya (NHK)]
JCTVC-J0509 Cross-check: Subjective viewing on intensity dependent spatial quantisation (JCTVC-J0076) [K. Sugimoto, S. Sekiguchi (Mitsubishi)] [late]
JCTVC-J0318 Consideration on Chroma QP Range Extension for HEVC version 1 and 2 [J. Xu, A. Tabatabai, K. Sato (Sony)]

This did not need to be presented, as it is addressed by the decision on J0342.

JCTVC-J0342 Chroma QP range extension [G. J. Sullivan, S. Kanumuri, J. Xu, Y. Wu (Microsoft)]

This contribution proposes a way to extend the range of QP values used for chroma from [0, 39] to [0, 51]. The table used in the derivation of chroma QP values from luma QP is proposed to be modified to enable the extended range. In addition, the use of slice-level chroma QP offsets is discussed. The proposed scheme is asserted to have no significant impact on BD bit rate for common test conditions, as the modification mostly applies outside of the range of values that is tested in the common conditions. The results reportedly show a very small improvement for luma and a very small loss for chroma. Results are also reported for higher QP values than are used in the common conditions.

This contribution also proposes that offset range limits similar to those specified in AVC (ranging from −12 to +12) should be placed on the chroma QP offset values.

For the default case (offset 0), the ratio of luma versus chroma quant stepsize is suggested to be bouded to 2 (unlike 4 as it is currently).

The proposal has no effect on current common conditions (except one small change at QPluma=34 which is done for the purpose of simpler implementation of the table).

The current HEVC spec does not have a limit on the offset values (whereas the software has the limit +/- 12 as suggested here).

Decision: Adopt (all parts of the proposal).

It was later mentioned by one expert (in the session about deblocking filtering) that the inclusion of chroma QP offset values at the slice layer may make it necessary to store these for the operation of the deblocking filter (provided they would be used as suggested in J0091).