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

5Contributions on specific technical features

5.1Parallel entropy coding

JCTVC-B034 [G. Korodi, D. He (RIM)] Source selection for V2V entropy coding in HEVC

A class of binary entropy coders processes the input sequence by encoding each binary symbol with a known probability from a discrete, finite set. The compression efficiency of such a system is affected by the magnitude of the set, and the accuracy by which its values approximate the empirical probabilities. This contribution provides a method for dynamically mapping the probability set to one of its subsets, with the objective of increasing compression efficiency. By coupling this method with parallel V2V coding, it becomes possible to achieve the desired throughput while at the same time provide competitive compression efficiency against CABAC as specified in ITU T Rec. H.264 | ISO/IEC 14496-10.

"Dynamic source selection" tries to model the probability distribution of a binary source better than the usual empirical approaches. Basic idea is partitioning of encoder states, where the best partition is selected to best match the source statistics.

Dynamic mapping is an iterative approach for determination of best state partition and corresponding code tree.

Best partition is encoded for each slice (40 bits per slice). Finding that for cases where the number of bits becomes large (>500000) the adaptive code can have slight reduction of bits compared to CABAC.

CABAC is used to estimate the probabilities. In principle this is a two-pass encoding method with side information. The multipass requirement for processing in the scheme was noted.

It was asked how much gain was produced for having the adaptive selection.

It was noted that CABAC has 2-bit context initialization (cabac_init_idc).

CABAC could also be initialised by such a an approach, potentially the advantage would disappear.

It was remarked that although the V2V schemes may address issues in the core of the binary coding, we still have a bottleneck in the binarization and context model aspects.

It was suggested to establish a related TE (RIM, TI, LG expressed interest)