This conflicts with https://gitlab.winehq.org/wine/wine/-/merge_requests/5055 and I would like to have that other one merged first.
I don't think that has any bearing on whether or when this patch is accepted.
I don't think we want to match parsers that output to *any* caps, but only those which are parsing to the same media type, and then we also don't need to query possibly missing pad.
What parser are you imagining would violate this?
Also I don't see why restricting this to H264 while at the same time querying a parser in a generic fashion, IMO adding an optional parser before any decoder is better.
The point is to not depend on a specific parser name.
We probably should be adding a parser regardless of the codec, and I even originally had it that way when developing, but it broke MPEG-1 video. I do intend to look into that, but in the meantime I think it's reasonable to deal with one codec at a time.