[whatwg] Give guidance about RFC 4281 codecs parameter

[Kevin Marks]

On 4/11/07, Dave Singer <singer at apple.com> wrote:
>
> We had to settle on one type that was valid for all files, to deal
> with the (common) case where the server was not willing to do
> introspection to find the correct type.  We decided that "audio/"
> promises that there isn't video, whereas "video/" indicates that
> there may be.  It's not optimal, agreed.

I agree that video/xxx and audio/xxx are useful distinctions. Another
point is that as IE ignores MIME types in favour of extensions, in
practice we end up with multiple extensionss pointing to the same
filetype, to give a cue for differentiation:
.wmv vs .wma
.m4v vs .m4a (also .m4p for DRM'd and .m4b for audiobooks, no?)

That these distinctions keep being made, despite neutral formats with
extensions like .mov, .avi, .mp4 and .ogg implies that there is some
utility there.