JCTVC-J0545 Mental cross-check of JCTVC-J0234: Inter-RPS complexity reduction [TK Tan (NTT Docomo)] [late]
JCTVC-J0115 AHG13: Signalling of long-term reference pictures in the slice header [A. K. Ramasubramonian, Y.-K. Wang, R. L. Joshi, Y. Chen (Qualcomm)]
It was reported that there is a problem with the signalling of long-term reference pictures (LTRPs).
An error-resilience problem is reported for the current signalling and derivation of long-term reference pictures (LTRPs). It is stated that the root of problem was that the reference picture set (RPS) derivation depends on the status of the decoded picture buffer (DPB), which was the main reason for replacing the sliding-window and memory management control operation (MMCO) based reference picture buffer management mechanism in AVC with the RPS based mechanism. This document proposes to send the delta POC values, either between the current picture and the LTRP or between the LTRP and the previous random access point (RAP) picture in decoding order to solve the reported error resiliency issue, and to satisfy the RPS design principle that the RPS derivation is self-contained (i.e., not depending on the DPB status). The simulation results are in the attachment of the proposal document.
Two cross-checks planned (J0402 and J0530), but not yet submitted when reviewed. J0402 was not provided, and was therefore considered withdrawn.
The current syntax can (only) have some case of non-robust behaviour if the encoder chooses to put it in that mode (not sending MSB cycle difference) and re-uses the same POC LSBs for multiple LTRPs.
The proposal would require always sending the MSB cycle difference rather than allowing the encoder to make this choice, and offers a way to code that difference more efficiently if the LTRP is close in position to the preceding RAP. These two aspects can, in principle, be considered as two separate suggestions.
There was no consensus that the proposed changes were appropriate to do. No action taken.
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