[Media] Enable AVIF support

[chrisdavidmills]

Acceptance criteria

1. • The listed features are documented sufficiently on MDN
2. • BCD is updated
3. • Interactive example and data repos are updated if appropriate
4. • The content has been reviewed as needed

Features to document

1. AVIF. We don't really record compat-data for image formats as such, but you can find details of this at:
   • https://developer.mozilla.org/en-US/docs/Web/Media/Formats/Image_types
   • https://developer.mozilla.org/en-US/docs/Learn/Performance/Multimedia
   • https://developer.mozilla.org/en-US/docs/Web/HTML/Element/img

So a few places to update information.

Related Gecko bugs

1. • Enable AVIF support by default

For folks helping with Firefox-related documentation features — make sure above AC have been done, but also:

• Set bugs to dev-doc-complete
• Add entry to Firefox release notes if feature is enabled in release
• Add entry to Firefox experimental features page if feature is not yet enabled in release

[hamishwillee]

Most of this got done when we thought it would go into FF83 - see mdn/sprints#3804 (comment)

Actions

• Update image formats docs to indicate correct versions: Fix image types doc - FF86 update and flaws #1871.
• Remove info about the preference from experimental section: Experimental features: Fix flaws and remove AVIF support #1872
• Nothing needs to be done for this in HTML/Element/img as it imports and links to the image formats docs. I have however done a flaw fix and tidy of the source in Fix flaws/notes in HTML.img element #1922
• Update Learn/Performance/Multimedia - to links to Image format docs and state that AVIF is also supported in Firefox.
• Responsive images clarify that avif no longer "spotty" support - just no historical depth: Responsive images: clarify avif support #1925
• HTTP > List of default Accept values - default change to include avif: HTTP Accept header with avif FF86 #1927
• Release notes - FF86 Release notes for AVIF addition #1929
• Set bugs to dev-doc-complete - comment on what work done here - simply refers to this post. Dev-doc-complete needs to be added by Chris.

[Rumyra]

Yes please feel free to carry on @hamishwillee :) I was only going through and assigning anything relevant to myself.

Let me know anyhoo - happy with whatever

[hamishwillee]

Thanks @Rumyra - I'll take this one then. FYI I've edited my original post to you to become the "status".

[hamishwillee]

@chrisdavidmills This should be more or less ready for review. I added comment for the dev team just then, so there might be further comments of course.

[chrisdavidmills]

DDC set, all work reviewed, outstanding PRs merged. This is an outstanding set of work; thanks @hamishwillee !

[chrisdavidmills]

@hamishwillee Hi Hamish, sorry to land this on you at the 11th hour, but AVIF support has been pulled from 86: https://bugzilla.mozilla.org/show_bug.cgi?id=1682995#c31

As a priority in your next working day, can you revert the changes in this bug as much makes sense? I.e. I don't think you need to revert everything, just explicit mentions of Fx version support in 86.

I'll remove it from the 86 rel notes and release blog post.

[chrisdavidmills]

OK, removed from rel notes: f4b1336

[hamishwillee]

Yoiks. OK

• Removal of the accept header avifs in FF86: Fix list of accept values for FF66/72/88 #2590
• Revert the experimental features and the image guide docs: Revert avif addition for FF86 #2601
  Think we're all "good" once those are merged.

[chrisdavidmills]

Yoiks. OK

* Removal of the accept header avifs in FF86: #2590

* Revert the experimental features and the image guide docs: #2601
  Think we're all "good" once those are merged.

Yup, agreed. All reviewed and merged. Thanks!

[hamishwillee]

Excellent. Closing this again then. Unless we're getting avif back in FF87 of course :-)

[chrisdavidmills]

I'd actually like to keep it open; we will definitely be getting it back at some point.

[hamishwillee]

Closing again. This was actually addressed back in FF92 :-).