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-B092 [R. Cohen, A. Vetro, H. Sun (Mitsubishi)] Performance of direction-adaptive residual transforms

The primary purpose of this contribution is to summarize the coding performance of a direction-adaptive residual transform, using software and test conditions proposed by the Ad Hoc Group on Alternative Transforms. JM KTA 2.6r1 is used as an experimental platform, with an alternative 8x8 transform that performs 1 D DCTs along aligned directional paths within prediction residual blocks. A rate-distortion optimized decision process is used to select among the conventional 2 D transform and several directional transforms for 8x8 blocks. These alternative transforms are available for transforming both Inter and Intra prediction residuals. Experimental results are given for Hierarchical-B, IPP and all-Intra configurations. Subjective differences in visual quality are discussed as well.

Directional transforms in addition to 2D DCT both in cases of intra and inter

Conventional transforms without training, usage of existing quantizers

Simulation in KTA, directional transform in 8x8 mode

Gain is roughly 0.3-0.4 % for Hier. B and IPPP, and 0.7-0.8% for Intra only (compared to KTA with MDDT off).

Slight visual improvement is claimed in the case of using more directions.

Roughly 30% runtime increase in case of inter. Hardly justified by the small gain.

Benefit or disadvantage compared to MDDT not clear from the results that are presented.