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Re: ACTION-76 : Question if MPEG-21 Part 17 got registered on IANA as a media mime type for fragments

From: Cyril Concolato <cyril.concolato@enst.fr>
Date: Thu, 16 Jul 2009 10:47:55 +0200
Message-ID: <4A5EE93B.6030903@enst.fr>
To: Media Fragment <public-media-fragment@w3.org>
Dear Media Fragment WG members,

I would like to add my 2 cents to this discussion but let me first introduce myself. My name is Cyril Concolato, I'm associate professor at Telecom ParisTech, a French engineering school in Paris. I have been involved in MPEG standardization for MPEG-4 and MPEG-21 and in W3C for SVG Tiny 1.2. I'm also one of the leader of the GPAC project (http://gpac.sf.net).

Michael Hausenblas a écrit :
> David,
> 
>> mpeg-4 and mpeg-21 chose to take the route that the mime registration
>> was merely a registration, a pointer from the code point (the mime
>> type) to the spec.  Is that a problem?
> 
> Honestly, I'm not in the position to tell if this is a problem, however,
> when I did my review [1] I implicitly was working under this assumption,
> yes.
> 
> Anyway, I think we are on the safe side, as the original question was about
> frag IDs in audio/*, image/*, and video/*' and we learned that MPEG21 has
> not registered anything there (but only in their own application/mp21).
You have to make the distinction between the MPEG-21 Part 9 (File Format) and the MPEG-21 Part 17 (Fragment Identification of MPEG Resources).

Part 9 defines a file format based on the ISO Base Media File Format. Its main purpose is to wrap media data with a XML description conformant to MPEG-21 Part 2 (Digital Item Declaration). Therefore it is registered as application/mp21. However due to the compatibility with the ISO BMFF, the same file, if it contains media data and conforms to other specifications, may be served as audio/mp4, video/mp4 ... I think looking at the MPEG-21 FF to find the answer to the question on your Wiki is not the right approach.

On the other hands, Part 17 clearly indicates that it "specifies a normative syntax for URI Fragment Identifiers to be used for addressing parts of any resource whose Internet Media Type is one of:
- audio/mpeg [RFC3003];
- video/mpeg [RFC2045, RFC2046];
- video/mp4 [RFC4337];
- audio/mp4 [RFC4337];
- application/mp4 [RFC4337]".

Now, I don't know if the process was right, or if such fragment identifier scheme should appear in the registration forms of those media types but it seems to me that the important questions are more technical: is this scheme good or not, is it too complex to implement or not, should it be profiled or not, extended or not ...

Regards,

Cyril
-- 
Cyril Concolato
Maître de Conférences/Associate Professor
Groupe Mutimedia/Multimedia Group
Département Traitement du Signal et Images
/Dept. Signal and Image Processing
Ecole Nationale Supérieure des Télécommunications
46 rue Barrault
75 013 Paris, France
http://tsi.enst.fr/~concolat 
Received on Thursday, 16 July 2009 08:48:29 GMT

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