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Re: Liaison Statement to W3C (SC 29 N 13268)

From: Jean-Claude Dufourd <jean-claude.dufourd@telecom-paristech.fr>
Date: Thu, 21 Feb 2013 09:55:05 +0100
Message-ID: <5125E0E9.7050903@telecom-paristech.fr>
To: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
CC: Bob Lund <B.Lund@cablelabs.com>, "Mark Vickers @ Comcast" <mark_vickers@cable.comcast.com>, "<public-web-and-tv@w3.org>" <public-web-and-tv@w3.org>
Le 21/2/13 04:58 , Silvia Pfeiffer a écrit :
> On Thu, Feb 21, 2013 at 8:37 AM, Bob Lund <B.Lund@cablelabs.com 
> <mailto:B.Lund@cablelabs.com>> wrote:
>>         1.The ability to accurately time the playback of different
>>         media elements (for instance using wall clock time) in the
>>         document in a declarative manner, i.e. without reverting to
>>         scripting in a way similar to SMIL. MMT does not require a
>>         scripting engine. 
>         I'm not sure why scripting is optional in MMT. Can someone
>         familiar with SMIL describe what declarative form they're
>         looking for here?
> SMIL allows wallcock time synchronization through using wallclock 
> times in @begin and @end attributes [1] within <par> and <seq> markup. 
> It requires that the document "start" time has to be associated with a 
> wallclock time and thus allows the mapping.
JCD: Yes, that is what they mean when writing about SMIL.

> The closest effort to this at the W3C FAIK is the Web Animations work 
> [2] which is planning to introduce a document timeline [3]. It's still 
> in its early stages, so no browser implementation. Also, I don't know 
> if it will satisfy the "declarative markup" requirement, because it 
> only introduces a JS API for now. But it's probably well worth 
> pointing out this effort to MPEG.
> [1] 
> http://www.w3.org/TR/2005/REC-SMIL2-20050107/smil-timing.html#Timing-WallclockSyncValueSyntax
> [2] https://dvcs.w3.org/hg/FXTF/raw-file/default/web-anim/index.html
> [3] 
> https://dvcs.w3.org/hg/FXTF/raw-file/default/web-anim/index.html#the-document-timeline
> --
> Overall, I do wonder about what MMT has to do with these 
> application-level requirements. IIUC MMT is about delivering packed 
> media, so it's an enabler of applications. It should not need to look 
> at HTML & the JS APIs for defining its specifications.
JCD: We have told the MMT group over and over that they are mixing 
layers, that their MMT architecture is a mess, etc.
I have personally fought against this particular part of MMT, called 
Composition Information, for 2 years.
Most of the people involved in the design of DASH have said the same.
It seems the W3C liaison still did not help.
Thanks anyway.
Best regards

> HTH.
> Cheers,
> Silvia.

JC Dufourd
Directeur d'Etudes/Professor
Groupe Multimedia/Multimedia Group
Traitement du Signal et Images/Signal and Image Processing
Telecom ParisTech, 37-39 rue Dareau, 75014 Paris, France
Tel: +33145817733 - Mob: +33677843843 - Fax: +33145817144
Received on Thursday, 21 February 2013 08:55:36 UTC

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