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

5.11TE4: Variable length coding and other contributions on entropy coding

JCTVC-B070 [K. Sugimoto, S. Sekiguchi, Y. Isu, Y. Itani, A. Minezawa (Mitsubishi)] Proposal on improved entropy coding method for DCT coefficients

This contribution proposed an entropy coding method for DCT coefficients in large transform block. Adding a flag to signal the last position of existence of DCT coefficient greater than one improves coding efficiency especially for noisy video contents. In this contribution, we applied this idea on the JCTVC-A124 software[1], which is the base code for TMuC software. Simulation results show that the proposed approach improves the conventional AVC/H.264 method for A, B and SHV sequences.

It was reportedly found by statistical analysis that longer runs of "trailing ones" are occuring for larger transform block sizes. To address this, it was proposed t use a "last more significant" (LMS) flag to signal the position of the last coefficient with level larger than one. This reportedly saves bits on level encoding. The average gain reported on class B and larger is reported to be 0.5-0.6% bit rate reduction. The effect seems to be dominant for noisy sequences (e.g. Nebuta festival 4% reduction). The reported improvement was mainly for luma in P and B pictures.

If de-noising is performed as pre-processing, it was suggested that the gain would almost disappear.

The typical gain seems to be in the 0.1-0.2% BR reduction range. The technique adds complexity (one additional condition to be checked in transform coefficient decoding).

Conclusion: Further study was suggested.