[ogg-dev] Re: [theora-dev] Re: [Advocacy] Re: [Vorbis-dev] Proposal: An extension to rules all others

Ralph Giles giles at xiph.org
Sun Apr 29 13:57:57 PDT 2007

On Sun, Apr 29, 2007 at 10:01:58PM +1000, Silvia Pfeiffer wrote:

> http://wiki.xiph.org/index.php/MIME_Types_and_File_Extensions

Thanks for putting that together. A few opinions:

> it is required that random multitrack files contain a skeleton 
> track to identify all containing logical bitstreams 

I think this should be a best-practices recommendation, not a 
requirement (SHOULD, not MUST) in accord with the general design
principle of making it hard to make non-compliant streams. There is
a lot of software out there producing Ogg Theora streams without a 
Skeleton, for example. Likewise, RFC 3533 doesn't mention skeleton
as a requirement.

In practice the behaviour is the same: in the presense of unrecognized 
stream types, if there is no skeleton a muxer must throw up its hands,
but playback is largely unaffected. I think it's better to be explicit 
about this than to say skeleton's required and leave it to the 
implementation to decide how hard it should try with streams which 
violate this.

> is audio/flac currently being used for flac in native container?

audio/flac isn't registered, but presumedly should be. Ogg FLAC wraps
native flac, so it will probably work to define audio/flac as a
native flac stream, but still use it for "unencapsulated flac." However, 
that's not quite accurate with the Ogg embedding since there's an 
additional header at the front. I don't know if anyone's tried to do 
RTP streaming of flac.

My /etc/mime.types has application/x-flac for flac, so I guess that's
current practice. Google suggests that at least some people are using 
audio/x-flac, and that Josh supports this.


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