Organisation internationale de normalisation

6AVC reference encoding methods

6.1.1.1.1JVT-AB031 (Ref soft 2.0/3.1) [W.-S. Kim, P. Pahalawatta, Z. Li, A. M. Tourapis (Dolby)] New Video Quality Metrics in JM reference software

The H.264/AVC JM reference software currently only provides encoder distortion information using Mean Square Error (MSE) based error metrics. The computation is also constrained by the color format of the source sequence. It is claimed that such metrics do not model the human visual system very accurately. In this contribution the reference software is extended to support additional distortion metrics in the encoder such as the Structural Similarity Index (SSIM), the Multi-scale SSIM (MS-SSIM), and distortion computation in different color spaces such as RGB. The introduced code is claimed to be very flexible and could be further extended in the future with additional distortion metrics and could also consider different color spaces if so desired.
It is implemented such that the user of the JM encoder provides in addition to PSNR an SSIM value as output per picture. Average SSIM and also MS-SSIM values are output for the entire video sequence.

ITU-R 601 is used for color conversion in case the measurement is done for RGB.

JVT decision: Adopt.

6.1.1.1.2JVT-AB032 (Ref soft 2.0/3.1) [P. Pahalawatta, A. M. Tourapis (Dolby)] Reorg of Error Resilient RDO in the ref software

This document describes several major problems in the existing implementation of error resilient rate distortion optimization (ER-RDO) in the H.264/AVC reference software. It is presented that the existing code had to be significantly revamped in order to provide useful results. The document describes the steps taken to remedy some of the issues and improve the usability of the code, and provides simulation results using the corrected implementation. The motivation for this work is that the ER-RDO is a very useful component for improving the error resiliency of compressed AVC content. Fixing the implementation and improving its usability will greatly enhance the ability to further study rate distortion optimization schemes under lossy conditions.
Current implementation does not support B slices, and color distortion measurement. Planned to be available in next release.
Results have been presented showing that at 0% packet loss rate, the result is identical to the normal RDO. For 1% packet loss rate, an improvement of 3dB is reported.
JVT decision: Adopt.
Question on ER-RDO for JSVM. Needs checking.

6.1.1.1.3JVT-AB033 (Ref soft 2.0/3.1) [A. Leontaris, A. M. Tourapis (Dolby)] Weighted Prediction Alternative to Adaptive Interpolation mechanisms

It is claimed that many proposals have been presented suggesting that H.264/AVC could be improved by the use of different interpolation mechanisms from the one currently supported in the reference software. In this contribution evidence is provided that one may consider simple tricks using the weighted prediction process, which is already supported by the standard, to emulate these mechanisms and achieve similar improvements.
Methods for use of the existing weighted prediction syntax are presented. Tried IPPP, IBBPBBP, and hier. B picture structures.
Results are reported in the IPPP setting for the case when the most recent reference picture is duplicated using RPLR syntax and assigned an offset of -1. Average bit-rate reductions are shown to be 4.65 for HD, 0.92% for CIF and 0.79% for QCIF.
Results are reported for the IBBP setting with list 0 unchanged and a similar modification was applied for list 1 as in IPPP. Average bit-rate reductions are shown to be 2.58% for HD, 0.68% for CIF and 0.87% for QCIF.
For hier. B pictures, the method is applied when coding reference P and reference B pictures. Average bit-rate reductions are shown to be 2.67% for HD, 1.06% for CIF and 1.38% for QCIF.
Contribution noted. Further work encouraged.

6.1.1.1.4JVT-AB034 (Ref soft 2.0/3.1) [E. Maani, L. Liu, A. M. Tourapis (Dolby)] JM Reference Software Enhancements

In this contribution several enhancements that have been introduced into the H.264/AVC JM reference software, are presented. The enhancements include proper support of Adaptive Rounding for the low complexity rate distortion optimized mode decision, and support of bi-predictive motion estimation for partitions smaller than 16x16, among others.

Contribution noted. Further work encouraged.