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39th Meeting: Daejeon, KR, March 2025 2025-04-01 06:25
AHG9: On association of NAL units to DSC verification substreams
Authors: Ye-Kui Wang ByteDance Jizheng Xu ByteDance Yun Li SJTU K. Yang SJTU Y. Xu SJTU
Abstract
This document contains the draft text for changes to the Versatile Video Coding (VVC) standard (Rec. ITU-T H.266 | ISO/IEC 23090-3). The changes include the support of 15 new SEI messages, namely 1) SEI processing order, 2) processing order nesting, 3) encoder optimization information, 4) source picture timing information, 5) object mask information, 6) modality information, 7) text description information, 8) digitally signed content initialization, 9) digitally signed content selection, 10) digitally signed content verification, 11) generative face video, 12) generative face video enhancement, 13) AI usage restrictions, 14) packed regions information, and 15) image format metadata, through referencing the Versatile Supplemental Enhancement Information (VSEI) standard (Rec. ITU-T H.274 | ISO/IEC 23002-7). The changes also include updates to the interface text for support of the two neural-network post-filter (NNPF) SEI messages as well as some corrections to the previous version of the VVC standard.
Meeting Notes
JVET-AL0117 AHG9: On association of NAL units to DSC verification substreams [Y.-K. Wang, J. Xu (Bytedance), Y. Li, K. Yang, Y. Xu (SJTU)]

Currently, relevant NAL units are associated to a verification substream either explicitly by signalling the verification substream ID in a DSCS SEI message present in a PU, or implicitly by inferring the verification substream ID equal to 0. Therefore, for bitstream with multiple layers and/or multiple temporal sublayers where each operation point corresponds to one verification substream, for each PU in a non-base layer or non-base sublayer, a DSCS SEI message needs to be included in the PU. However, when each operation point corresponds to one verification substream, which is asserted to be a typical case, the verification substream ID values can be inferred thus avoid sending lots of DSCS SEI messages.

This contribution proposes changes that supports such an implicit association of relevant NAL units to verification substreams.changes are summarized as follows:

  1. Add three interface variables (LayerId, SubLrId, and MaxNumSubLrs), in both the SEI message semantics and the VVC interface text, for layer ID, sublayer ID, and the maximum number of sublayers.
  2. Add a flag dsci_vss_implicit_association_mode_flag to the DSCI SEI message to indicate whether the inference of verification substream ID is according to the values of MaxNumSubLrs, LayerId, and SubLrId, or is simply inferred to be equal to 0.
  3. In the DSCS SEI message semantics, specify that, if dsci_vss_implicit_association_mode_flag is equal to 1, the verification substream ID value is inferred to be equal to MaxNumSubLrs * LayerId + SubLrId, and otherwise inferred to be equal to 0.

The detailed proposed text changes to VSEI and to VVC are separately provided in two attachments to this contribution. The VSEI changes are marked relative to the spec text provided in JVET-AL0103, which includes asserted purely editorial changes to the DSC SEI messages based on JVET-AK2006-v1. The VVC changes are marked relative to JVET-AK2005-v2.

Interface text for AVC is not provided, and will likely require some changes vs. the VVC interface.

It is noted that the temporal ID of non-VCL NAL units may not be known until VCL NAL units are available, so may require a change in decoder operation.

A single flag is added to the syntax, and additional changes to the inference semantics of the DSCS SEI.

This approach could not easily be added later as an extension.

The proposal has bitrate savings for every PU when multiple substreams are present, which may be substantial.

Decision: Adopt to VSEI v4

Text provided in -v2 version reviewed on 1 April 2025 and was agreed.

It was noted that the number of substreams is coded in DSCI SEI is restricted to be less than or equal to 255, and may want to check if a constraint is needed on the derived substream ID when the DSCS SEI is not present. Further study encouraged on this issue.

JVET-AL0117 AHG9: On association of NAL units to DSC verification substreams

ARCHIVE :
JVET-AL0117-v2.docx JVET-AL0117-v2_avcSpecText.docx JVET-AL0117-v2_hevcSpecText.docx JVET-AL0117-v2_vseiSpecText.docx JVET-AL0117-v2_vvcSpecText.docx
Decisions
adopted
Adopt to VSEI v4
JVET-AL0117 AHG9: On association of NAL units to DSC verification substreams
Citation