JVET-AL0119 AHG9: Support of low-delay DSC verification process [Y.-K. Wang, J. Xu (Bytedance), Y. Li, K. Yang, Y. Xu (SJTU)]
Currently, within a verification period (the period between two consecutive DSCI SEI messages), it is not allowed to have multiple DSCV SEI messages for a particular substream while between some of these DSCV SEI messages there are verification NAL units for the verification substream. It is asserted that this results in a delay issue, as the verification of any substream can only be performed at the end of a verification period.
This contribution proposes changes to allow verifying a subset of a substream while the verification NAL units are being received, before the reception of the entire substream.
The changes are summarized as follows:
- Within a verification period, it is allowed to have multiple DSCV SEI messages for a particular substream while between two consecutive DSCV SEI messages there are verification NAL units for the verification substream.
- It is specified that dscv_signature contains the digital signature for the current verification substream subset, which consists of only those verification NAL units for the verification substream present in the current PU or in PUs earlier in decoding order in the current verification period, and the derivation of the current and reference digests is updated accordingly.
The detailed proposed text changes to VSEI are provided in an attachment to this contribution. The VSEI changes are marked relative to the spec text provided in JVET-AL0103 plus the asserted bug fix proposed in JVET-AL0118 item 7. The spec text provided in JVET-AL0103 includes asserted purely editorial changes to the DSC SEI messages based on JVET-AK2006-v1.
In -v2 of this contribution, the basis text for detailed proposed text changes to VSEI has been updated for using the updated asserted bug fix for JVET-AL0118 item 7 in JVET-AL0118-v2. The actual changes proposed in the contribution itself have not been changed.
The proposal allows to send multiple DCSV SEI messages for a substream for the same DSCI SEI, without requiring repeating of the DSCI SEI.
It was noted that the existing design has alignment of verification of all substreams when a new DSCI is present, and was suggested that this proposal does not require alignment of verification of all substreams.
It was suggested to do a comparison of tradeoffs between shortening the verification period using the existing design vs. the proposed design with multiple DSCV SEI messages in a verification period, including understanding the practical amount of delay needed and understanding the implementation burden. It was suggested that sub 1 second delay may not be required.
It is noted that the DSCV SEI message is large compared to the DSCI SEI message.
No action was taken on this.