| JCTVC-M0442 Inter-Prediction Residual DPCM [M. Naccari, M. Mrak, A. Gabriellini (BBC), S. Blasi, E. Izquierdo (QMUL)] [late]
In this contribution, a DPCM scheme for inter-prediction of residuals is proposed and implemented in HM 10.0-RExt-2.0 for HEVC lossless coding. The scheme follows the residual DPCM scheme proposed for intra-prediction in JCTVC-M0079. The same set of DPCM modes as in intra case (no DPCM, vertical and horizontal DPCM) is used, where each mode is available for coding of inter residual prediction block. The choice is signalled in the bit-stream. To enable lower complexity of DPCM processing at the decoder side for larger blocks, the residual samples are divided into chunks of a fixed length of eight rows or columns reducing the maximal number of operations per sample from 63 to 7. It is reported that the overall bit-rate saving of applying intra and inter DPCM in random access and low-delay configurations is −9.7 % and −10.6 %, respectively, for screen content sequences.
The chunking aspect is a somewhat separate concept.
M0068 was noted to have some conceptual similarity (although using a different DPCM type).
The contributor suggested also considering variants of the scheme in terms of application at the CU level and TU level as well as application at the PU level.
As tested, two flags are sent for each component for each PU, where one flag indicates whether to invoke the mode or not, and the other indicates whether to apply it horizontally or vertically. No spatial context is used for coding the flags.
M0452 is a late cross check.
Further study in CE was planned.
JCTVC-M0452 Cross-check of inter-prediction residual DPCM (JCTVC-M0442) [J. Sole (Qualcomm)]
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