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Re: fragment or sub-resources

From: RaphaŽl Troncy <Raphael.Troncy@cwi.nl>
Date: Mon, 07 Sep 2009 15:34:56 +0200
Message-ID: <4AA50C00.4080305@cwi.nl>
To: Yves Lafon <ylafon@w3.org>
CC: public-media-fragment@w3.org
Hi Yves,

I believe this is related to your ACTION-104 ;-)

> During the last two teleconferences, we discussed a bit the issue of # 
> vs ? (ie: fragment vs sub-resources).
> It seems that when we are not in the trivial case of just getting a part 
> of the compressed resource, ie: when transcoding is needed, that a 
> sub-resource might be a better match, it may have a Link: header 
> pointing to the original resource, but would be a resource on its own.

Indeed, the idea of dividing the cases where we mandate to use a # or a
? to request a "segment/portion" of multimedia content depending on
whether a transcoding operation is needed or not ... is appealing! In
this line of thought, we would often have Media Fragment URIs like:
   - http://www.example.com/video.ogg#t=30,90 (temporal fragment)
   - http://www.example.com/video.ogg?xywh=20,20,100,120 (spatial
segment) ... since extracting spatial segments generally require
transcoding.

However, as Davy rightly pointed out, although most of
current coding formats does not support spatial segment extraction
without transcoding, we should not assume that there will be no such
coding formats developed in the future ...

Furthermore, how the end-user should know which scheme to use? What's 
happen if one scheme is used but only the other one is supported by the 
server?

> Now, as you can't know in advance if the server support a specific 
> syntax for getting sub-resources of a specific resource, we might want 
> to signal this using a URI template [1], as in that case it really sets 
> expectations for the client (note that it is an example on how to 
> advertise that a server would use our syntax for sub-resource).
> Comments?
> 
> [1] http://tools.ietf.org/html/draft-gregorio-uritemplate-03

I still have trouble to understand how concretely that would work. Could
you give us a *detailed* example of how the use of Gregorio's
uritemplate will work in practice?
Cheers.

   RaphaŽl

-- 
RaphaŽl Troncy
EURECOM, Multimedia Communications Department
2229, route des CrÍtes, 06560 Sophia Antipolis, France.
e-mail: raphael.troncy@eurecom.fr & raphael.troncy@gmail.com
Tel: +33 (0)4 - 9300 8242
Fax: +33 (0)4 - 9000 8200
Web: http://www.cwi.nl/~troncy/
Received on Monday, 7 September 2009 13:46:19 GMT

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