FLAC is now formally specified in RFC 9639

2024-12-19 05:38:38

RFC9639 has been published, specifying the Free Lossless Audio Codec (FLAC) format.

Although FLAC has had a specification document since 2000 and a open-source reference implementation filling in the details, this document should formally specify the format, such that implementers don't have to look at the reference source code or browse the mailing list archives for details.

This publication doesn't change the FLAC format except explicitly adding support for 32-bit audio and adding restrictions to accommodate, see here for details.

The main benefit this publications brings is that it should make writing a new FLAC decoder implementation from scratch much easier. It also provides assurance for archives wanting to use the FLAC format that their files remain decodable in the far future, in case FLAC ever becomes obsolete and its implementations unusable.

I'd like to thank all the users of this board that participated in making this document better.

Re: FLAC is now formally specified in RFC 9639

Reply #1 – 2024-12-24 10:07:40

Well done going through the process, from my vantage point it looked like a real ball ache.

Re: FLAC is now formally specified in RFC 9639

Reply #2 – 2024-12-26 19:27:44

The processing was very 'sparse':  a few weeks with lots and lots of comments, and then months of utter silence. I hadn't anticipated that it would take this long.

- The charter to formalize the FLAC spec was approved in November of 2015.
- The old format document was converted to markdown in October of 2017.
- From September 2021 to May 2022, the document was restructured, expanded and had existing part rewritten.
- In October 2022, the document was considered finished and we had working group last call.
- The feedback we got from there resulted in a lot of improvements, which were considered ready in November 2022
- The shepherd review was addressed in April 2023.
- The area director review was addressed in September 2023, which resulted in a Last Call
- The document was first on the IESG agenda in October 2023, where further changed were requested.
- Those changes were approved by the IESG in Febuary of 2024
- The document was processed by the RFC Editor in October 2024, but once again, quite a few questions popped up.
- Final publication was just last week, December 2024.

So, it took 6 years before somebody showed up to fix the document up. The fixing up lasted about 9 months, and then 2 years of review after review took place.

All in all, I think the IESG is a little understaffed at the moment