Session Date/Time: 23 Aug 2022 19:00

CELLAR

Summary

The CELLAR Working Group discussed the status of the FLAC and FFV1 documents. Key discussions revolved around handling normative versus informative references for container encapsulation in the FLAC specification, the inclusion of historical development information, and strategies for documenting implementation compatibility. For FFV1, a plan was made to manage technical and formatting changes in separate document updates to facilitate review. The October interim meeting was confirmed to be co-located with the "No Time to Wait" conference, with remote participation supported.

Key Discussion Points

October Interim Meeting: The AD approved co-locating the October interim meeting with the "No Time to Wait" conference. Remote participation will be supported for those unable to attend in person.
FLAC Document Update (PR 158):
- Discussion on the inclusion of encapsulation specifications for Ogg (Org), Matroska, and MP4.
- Concern was raised regarding normative references to other drafts (e.g., Matroska codec part) that might not be published concurrently, as this is typically problematic for IETF RFCs.
- The sense of those present was that for clarity and independence, the FLAC document should contain the specific (short) encapsulation text for Ogg and Matroska directly within its own specification, rather than relying on normative references to external, un-published Matroska codec documents. If a Matroska codec document were to be published later, it could then informatively reference the FLAC RFC for FLAC encapsulation details.
- For MP4 encapsulation, which is significantly longer, referencing an external document (e.g., on GitHub) was deemed appropriate.
FLAC Development History:
- A proposal to add a non-normative section or appendix detailing past changes, specifically a 2007 FLAC specification change concerning a coded number, was discussed.
- This is relevant because some older, deployed software can still create files that are not compliant with the current spec. Given CELLAR's focus on archival usage, such information would be valuable for interpreting old files.
FLAC Implementation Compatibility:
- The group discussed adding information about FLAC features that are not well-supported by all hardware and software decoders, based on testing with the flac-test-files repository.
- Concern was raised that such compatibility information might age poorly if included directly in the normative document.
- A solution was discussed where this information could reside in a separate, updateable document (e.g., a Markdown file in GitHub or the existing WG wiki) that the main RFC could then informatively reference. This allows for dynamic updates to compatibility guidelines without requiring a new RFC publication.
FFV1 Version 4 Updates:
- The author for FFV1 v4 intends to merge two updates, one of which includes significant layout changes in addition to bug fixes (missing field descriptions).
- Concern was raised about large diffs due to formatting changes making technical review difficult.
- A strategy was proposed to split the updates into two distinct submissions: first, all technical changes, and then a subsequent update containing only formatting and layout adjustments. This allows reviewers to focus on technical content first.

Decisions and Action Items

Decisions:

The minutes from the previous meeting were approved without objection.
The October interim meeting will be co-located with the "No Time to Wait" conference. Remote participation will be available.
For FLAC, encapsulation text for Matroska and Ogg should be included directly in the FLAC specification. MP4 encapsulation should be referenced externally.
A non-normative appendix for FLAC detailing development history and past spec changes will be included.
FLAC implementation compatibility guidelines will be maintained in a separate, dynamically updateable document (e.g., GitHub wiki or a dedicated MD file), which the FLAC RFC will informatively reference.
FFV1 v4 updates will be split into two separate pull requests/document submissions: one for technical changes, and a subsequent one solely for formatting and layout changes.

Action Items:

(FLAC Author) Adjust FLAC PR 158 to incorporate Matroska and Ogg encapsulation text directly into the document and merge it.
(FLAC Author) Add a non-normative appendix to the FLAC document detailing development history and past specification changes.
(FLAC Author) Add FLAC implementation compatibility guidelines to the existing "implementation status" wiki or a new, separate Markdown file in the GitHub repository, and ensure the FLAC document includes an informative reference to it.
(FFV1 Author) Split the FFV1 v4 updates into two distinct submissions: one for technical changes, and a second for formatting-only changes.

Next Steps

The next CELLAR WG meeting will be held in September at the usual time and place.
The following meeting in October will be the co-located interim meeting with "No Time to Wait."
Authors are requested to proceed with their respective action items for FLAC and FFV1.