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RE: Discovery of track and named fragment names

From: Bailer, Werner <werner.bailer@joanneum.at>
Date: Tue, 24 Nov 2009 09:23:33 +0100
To: "Troncy, Raphael" <Raphael.Troncy@cwi.nl>, Davy Van Deursen <davy.vandeursen@ugent.be>, "public-media-annotation@w3.org" <public-media-annotation@w3.org>
CC: "'Silvia Pfeiffer'" <silviapfeiffer1@gmail.com>, "public-media-fragment@w3.org" <public-media-fragment@w3.org>
Message-ID: <CD9846F872C7874BB4E0FDF2A61EF09F3CDB149C63@RZJC1EX.jr1.local>
Dear RaphaŽl, 

> *Question:* Could the ma:fragments and ma:namedFragments properties be
> used to enable track and named fragments discovery?
> 
> > DOMString[] getTrackNames(MediaResource mr) {
> > 	Fragment[] fragments = mr.fragments();
> > 	DOMString[] tracknames;
> > 	for(Fragment f : fragments) {
> > 		If(f.role = "Track") {
> > 			tracknames.add(f.identifier);
> > 		}
> > 	}
> > 	return tracknames;
> > }
> >
> > Does this makes sense or am I completely misusing the fragments()
> function
> > here :-)?

It makes sense, although we have not thought about this use of ma:fragments :) 

The idea was to use ma:fragments for spatial and temporal fragments. We have ma:numTracks, which would allow you to iterate through the tracks by numerical index and get their identifiers. Of course this is one indirection more than in your example.

I think we need to discuss if we want to support the approach you are proposing (handling spatial, temporal and track fragments with ma:fragments). An alternative could be to replace ma:numTracks with ma:tracks which gives the list of track identifiers (the number of tracks is defined by the size of the array returned).

Best regards,
Werner

> -----Original Message-----
> From: public-media-fragment-request@w3.org [mailto:public-media-
> fragment-request@w3.org] On Behalf Of RaphaŽl Troncy
> Sent: Montag, 23. November 2009 22:45
> To: Davy Van Deursen; public-media-annotation@w3.org
> Cc: 'Silvia Pfeiffer'; public-media-fragment@w3.org
> Subject: Re: Discovery of track and named fragment names
> 
> Dear Davy, Media Annotations WG,
> 
> *Background:* the Media Fragments WG is interested at this stage in
> listing all the technologies that enable track and named fragments
> discovery, i.e., the UA has a way to know for example which tracks are
> available in a particular media file.
> 
> Davy has hacked a nice prototype using the ROE format [1]. Hence, the
> following HTTP request:
> 
> GET /DownloadServlet/fragf2f.ogv HTTP/1.1
> Host: schutz.elis.ugent.be:8080
> Accept: application/roe
> 
> returns a ROE description of the media file 'fragf2f.ogv'.
> This ROE description will look like:
> <ROE xmlns="http://www.xiph.org/roe1.0">
>    <body>
>      <track id="ogg_1" provides="video">
>        <mediaSource id="ogg_1_source" content-type="video/theora"
> src="http://schutz.elis.ugent.be:8080/DownloadServlet/fragf2f.ogv?track
> ='ogg_1'"
> />
>      </track>
>      <track id="ogg_2" provides="audio">
>        <mediaSource id="ogg_2_source" content-type="audio/vorbis"
> src="http://schutz.elis.ugent.be:8080/DownloadServlet/fragf2f.ogv?track
> ='ogg_2'"
> />
>      </track>
>    </body>
> </ROE>
> 
> So the UA can now request one of the two tracks available.
> 
> *Question:* Could the ma:fragments and ma:namedFragments properties be
> used to enable track and named fragments discovery?
> 
> > DOMString[] getTrackNames(MediaResource mr) {
> > 	Fragment[] fragments = mr.fragments();
> > 	DOMString[] tracknames;
> > 	for(Fragment f : fragments) {
> > 		If(f.role = "Track") {
> > 			tracknames.add(f.identifier);
> > 		}
> > 	}
> > 	return tracknames;
> > }
> >
> > Does this makes sense or am I completely misusing the fragments()
> function
> > here :-)?
> 
> Could we make such a use of the Media Ontology API for solving our
> problem?
> Best regards.
> 
>    RaphaŽl
> 
> [1] http://wiki.xiph.org/index.php/ROE
> 
> --
> 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.eurecom.fr/~troncy/
Received on Tuesday, 24 November 2009 08:24:20 GMT

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