Markdown Version | Session Recording

Session Date/Time: 28 Feb 2023 20:00

CELLAR

Summary

The CELLAR WG meeting covered updates on the Matroska and FLAC drafts, discussed a critical clarification needed for Matroska's EBML lacing details, and reviewed the roadmap and recent FOSDEM presentation for FFV1. Previous meeting minutes were accepted, and next steps for document progression were outlined.

Key Discussion Points

• Administrative Matters

  • The Note Well was displayed.
  • Draft minutes from the previous meeting were accepted.
  • The next interim meeting date was confirmed as April 4th, as March 28th conflicted with an IETF meeting. A follow-up meeting in late April is also scheduled.

• Matroska (draft-ietf-cellar-matroska-15)

  • The draft is currently in IETF Last Call, which concludes today.
  • The next step is for the Internet Engineering Steering Group (IESG) to review comments, directorate reviews, and ballot for publication as a Proposed Standard.
  • EBML Lacing Details Clarification: A significant discussion revolved around the current text in the Matroska document regarding EBML lacing being incorrect.
    • The document states it uses a type of encoding similar to EBML signed integers, but the 20-year-old reference implementation code yields different results.
    • A participant, Martin, proposed text to describe the actual encoding used in Matroska lacing. This encoding, while perhaps not "nice," is widely implemented.
    • It was noted that Matroska's lacing encoding (often referred to as "signed file in") describes its own length, unlike standard EBML signed integers which would require separate length description.
    • The Matroska lacing encoding shows efficiency benefits for negative values, whereas EBML signed values might be more efficient for positive ones. For typical small lacing values (e.g., -20 to +20), the current implementation is generally fine.
    • The consensus was that the Matroska specification needs to accurately describe the currently implemented lacing logic. The proposed text will be reviewed against the reference code.

• FLAC (draft-ietf-cellar-flac-07)

  • The recent review of the FLAC draft was acknowledged and appreciated, particularly for providing a "bird's eye overview" after many smaller changes.
  • Specific feedback included removing or rephrasing BCP 14 (RFC 2119) terminology from non-normative sections (e.g., appendices, early overview sections).
  • The co-chair offered notes from a careful reading of the draft.
  • The document was generally praised for being well-written, including the appendices which were specifically designed as cross-references between informal and formal parts.

• FFV1 (FFV1 v4 wish list)

  • No changes were made to the V4 wish list due to time constraints from key developers.
  • A FOSDEM presentation on FFV1 earlier this month generated questions regarding comparison with JPEG XS and JPEG XL.
    • It was noted that JPEG XL drew some ideas from FFV1, making comparisons relevant.
    • Further discussion with JPEG XL developers is needed to explore potential ideas for FFV1 v4 (e.g., not compressing last bits).
    • Performance demonstrations comparing FFV1, FFV1 lossless, and JPEG XL are needed.
    • The FOSDEM presentation also covered the working group's approach to ecosystem building.
  • The lack of progress on the V4 wish list was discussed, and assistance was offered.

Decisions and Action Items

• Decision: Previous meeting minutes were accepted.
• Action Item: Michael/Chair to check the Data Tracker to ensure correct dates for upcoming interim meetings (April 4th and a subsequent April meeting).
• Action Item: Chair to add "Any Other Business" to the agenda for the next meeting.
• Action Item (Matroska): The proposed text clarifying EBML lacing details will be reviewed and incorporated into the Matroska draft before it is sent to the IESG.
• Action Item (FLAC): Comments and clarifications regarding the recent review feedback should be posted to the CELLAR mailing list. The document authors will incorporate feedback, particularly regarding BCP 14 terminology in non-normative sections.
• Action Item (FFV1): GitHub labels will be added to V4 issues to indicate priorities.
• Action Item (FFV1): Dave to send an email to the CELLAR mailing list summarizing the V4 issues and encouraging discussion and prioritization from the working group.

Next Steps

• Matroska: The draft, once updated with the EBML lacing clarification, will proceed to IESG balloting for publication as a Proposed Standard. Anticipate IETF Last Call comments to arrive in the next couple of weeks.
• FLAC: Incorporate review feedback and then send a revised Internet-Draft to the Area Director for AD evaluation.
• FFV1: Focus on defining and prioritizing the V4 wish list, with initial work spurred by the mailing list discussion and potential ideas from JPEG XL comparisons.