[Uploads] Allow for AV1 Webms to be uploaded by making mimetype "audio/webm" part of webm.

[Mocha3218]

Seems to work. If someone tries to upload an audio only WebM it gets caught.

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[liamwhite]

You'd probably want to use ffprobe to more thoroughly analyze the streams, since the WebM container can be stuffed with invalid codecs. In this way you would be properly rejecting uploads that the site can't process.

[ghost]

You'd probably want to use ffprobe to more thoroughly analyze the streams, since the WebM container can be stuffed with invalid codecs. In this way you would be properly rejecting uploads that the site can't process.

That is already done with video codecs and video containers in the code. The problem here is that only specific mime types are allowed regardless of file extension. vp9 has a mime type of video/webm, but av1 has a mime type of audio/webm.

[liamwhite]

It does not have a mime type of audio/webm, that is just some garbage output by libmagic. Its mime type is video/webm and should be corrected to such if you already verify streams.

[ghost]

Ok, I made a bad assumption that the browser was sending in the wrong mime type (audio/webm) and that the server was correct and was wrong.

The actual problem lies with Marcel: https://github.com/rails/marcel/issues/80

So this patch should be scrapped since it isn't a proper fix and Marcel should just be forked (temporarily) and patched to fix the av1 bug.

[Sindrake]

Closed in favor of #987.