IIUC, the Accept spec no longer allows a codecs parameter:
Previous specifications allowed additional extension parameters to appear after the weight parameter. The accept extension grammar (accept-params, accept-ext) has been removed because it had a complicated definition, was not being used in practice, and is more easily deployed through new header fields. —RFC 9110: HTTP Semantics
Container formats increasingly don’t tell you enough about the codecs used inside of them (especially for video, but even for images [which are increasingly encoded using the keyframe bits of video codecs]). I have hoped for more codecs usage going forward, not less.
Media Capabilities is great if you are orchestrating loading via Javascript. What if you aren’t?
- How do existing browsers deal with
<picture type>and<video type>that containcodecs? How could/should future browsers/HTML solve this using markup? - I’d (also?) strongly support solving this problem with Client Hints, given its opt-in, privacy-preserving design.