JVET-H0002 JVET AHG report: JEM algorithm description editing (AHG2) [J. Chen, E. Alshina, J. Boyce]

This document reports the work of the JVET ad hoc group on JEM algorithm description editing (AHG2) between the 7^th JVET meeting at Torino, IT (July 13–21, 2017) and the 8^th meeting at Macao, CN (October 18–24, 2017).

Currently the document contains the algorithm description as well as encoding logic description for all new coding features in JEM6.0 beyond HEVC.

During the editing period, on top of JVET-F1001 Algorithm Description of Joint Exploration Test Model 6, the editors worked on the following two aspects to produce the final version of the JVET-G1001 Algorithm Description of Joint Exploration Test Model 7:

1. Integrate the following adoptions, which change the encoding or decoding process, at the 7th JVET meeting
   • JVET-G0104: Removal of ARSS; PDPC always applied to planar mode and no PDPC for all other modes; MDIS is applied for a block with non-zero NSST index; and strong intra smoothing is disabled
   • JVET-G0082: Block-based design for Bi-directional optical flow (BIO)
2. Editorial improvements by editors and solving of mismatch between text and software
   • Sub-block size derivation in affine motion compensation process
   • Miscellaneous editorial improvements

At the 7th JVET meeting, the intra prediction of the JEM was significantly simplified. With the removal of ARSS, and PDPC applied only for planar mode, the encoder running time of the JEM for all-intra configurations is greatly reduced. BIO is modified in a way that the motion vector offset is derived for a group of 4x4 luma samples instead of each luma sample, and it is not applied during the OBMC process.

The AHG recommended to:

• Continue to edit the Algorithm Description of Joint Exploration Test Model document to ensure that all agreed elements of JEM are described
• Continue to improve the editorial quality of the Algorithm Description of Joint Exploration Test Model document and address issues relating to mismatches between software and text.
• Identify and improve algorithm description for critically important parts of JEM design for better understanding of complexity.