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 second meeting during 21-28 July, 2010 at the itu-t premises in Geneva, ch

JCTVC-B074 [M. Karczewicz, H.-C. Chuang, P. Chen, R. Joshi, W.-J. Chien (Qualcomm)] Rounding controls for bidirectional averaging

Two modifications for increasing the precision of bi-directional prediction and DCT transform, when IBDI mode is not used, were proposed. The average BD rate reduction is 2.58% for IPPP configuration and 1.36% for hierarchical-B configuration. The results are obtained using TMuC 0.2.

Experiment performed in TMuC. Rounding approach same as in VCEG-AI020 and implemented in KTA, signaling the rounding direction for the case of bi-prediction. Report that gain due to IBDI is higher in TMuC than in JM (around 3.5 % than 2%). Experimented with additional change in DCT where the rounding in the fast algorithm is always going in one direction. If that is modified (similar to the 8 bit integer DCT in 23002-2), the gap between using IBDI and using it not becomes lower.

The contribution mentions a DCT rounding issue which is further discussed in the context of the TMuC environment.