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-B051 [S. Matsuo, Y. Bandoh, S. Takamura, H. Jozawa (NTT)] Region-based adaptive interpolation filter

This document proposes enhancement of the adaptive interpolation filtering (AIF) scheme, relative to that in the KTA software. As characterized by the proponent, "conventional AIF" optimizes the filter coefficients on a frame-by-frame basis. When an original image has uniform texture or movement, conventional AIF was suggested to be adequate. However, the proponent asserted that when the image has multiple movement areas or when different regions of the image have different texture characteristics, the coding efficiency could be improved by using region-by-region interpolation filtering. The proposal was implemented in the KTA software to evaluate its performance.

With the anchor being KTA 2.6r1, the average BD-rate gain for P frames of the proposal, compared to SAIF, was reportedly about 0.6% (SAIF: 5.0%, proposal: 5.6%) for the HEVC CfP sequences. The maximum reported gain was about 2.3% (SAIF: 4.3%, proposal: 6.6%) for the sequence "Cactus".

Various schemes were considered regarding how to divide the image into regions for region-adaptivity purposes. The encoder was designed to choose between these various methods using a rate-distortion criterion.

However, only two frames were actually coded for the experiments. Any results from such a test should be considered very preliminary.

Further study on such techniques is encouraged (hopefully without excess complexity).

A participant remarked that other region classification methods may be better, such as detail structure of local region, prediction error energy.