JVET-P0573 AHG17/Non-CE8: Support parallel decoding based on initialization for palette predictor at CTU row [H. Jang, N. Park, J. Nam, S. Kim, J. Lim (LGE)]
Discussed in BoG JVET-P0999.
The palette mode uses palette entry which is already signaled and used in previous CU in decoding order as predictor entry. In VTM 6, if one of following conditions is true, the predictor palette entry is initialized.
- The fist CTU in a brick
- entropy_coding_sync_enabled_flag is equal to 1 && CtbAddrInRs % PicWidthInCtbsY is equal to 0.
Since Palette predictor is initialized on every CTU row only when WPP is enabled, it could cause problem with implementation of parallel decoding processing on particular H/W decoder architecture. In real implementation decoder, the entropy decoding is applied in advance of the pixel reconstruction and the pixel reconstruction could be support parallel processing regardless of whether WPP is enabled in encoder side. Therefore, this contribution proposes the palette predictor initialization at first CU in CTU row as the HMVP buffer is initialized at the beginning of each CTU row regardless of WPP to support parallel decoding in real decoder implementation. The test result show as below dual-tree on and dual-tree off respectively.
- over VTM-6.0 DualITree=0 YUV444
All intra | 0.28% | -0.10% | -0.47% | 100% | 100% |
Random access | -0.13% | -0.51% | -0.73% | 100% | 101% |
Low delay | -0.38% | -0.34% | -0.82% | 100% | 100% |
- over VTM-6.0 DualITree=1 YUV444
All intra | 0.07% | 0.21% | -0.07% | 100% | 100% |
Random access | 0.04% | 0.15% | 0.12% | 100% | 102% |
Low delay | -0.14% | 0.06% | -0.03% | 101% | 101% |
This is identical to JVET-P0424, which was suggested to be studied in CE.
BoG recommendation: Study in a CE.