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Re: [MSE] Summary of "Resolving Bug 24370" thread and proposed next steps

From: Cyril Concolato <cyril.concolato@telecom-paristech.fr>
Date: Wed, 09 Apr 2014 18:56:59 +0200
Message-ID: <53457BDB.20807@telecom-paristech.fr>
To: public-html-media@w3.org
CC: "dash@lists.uni-klu.ac.at" <dash@lists.uni-klu.ac.at>
Hi all,

As a data point for this discussion, Bob Lund and I submitted a 
contribution to the MPEG meeting, held last week in Valencia, to 
highlight the problem in the mapping of DASH Role to HTML5 kind. The 
contribution is available here: 
The MPEG group agreed to define 3 new role values ("description", "sign" 
and "metadata") as part of the amendment 2 of DASH.


Le 07/04/2014 09:05, Aaron Colwell a écrit :
> In the interest of trying to move forward on the MSE bug 24370, I'm 
> going to try to provide a high level summary of the "Resolving Bug 
>  24370" thread and propose a way forward. Please forgive me if I 
> accidentally misrepresent something.
> *Summary:*
> 1. Changes in languages are allowed during the course of a 
> presentation, but there is some debate about how these should be 
> represented in HTML5. The majority opinion in the thread appears to 
> prefer immutable language & kind attributes and track objects being 
> added & removed to reflect language changes.
> 2. Currently track kind can't be signalled in ISO-BMFF content. A new 
> box/atom needs to be defined 
> <http://lists.w3.org/Archives/Public/public-html-media/2014Apr/0018.html> 
> to signal this information.
> 3. No argument or example has been given that requires Javascript to 
> explicitly change the language or kind of a track. My interpretation 
> of Jim Ley's comment 
> <http://lists.w3.org/Archives/Public/public-html-media/2014Apr/0015.html> is 
> that the application only wants to be notified of changes in the media 
> and does not need to be able to change the values on the tracks.
> 4. Bob Lund and David Singer appear to explicitly support removing the 
> mutable attribute definitions. I believe Silvia Pfeiffer implicitly 
> supports their removal based on the arguments she has made in the 
> thread. I also support removal of the mutable attribute definitions.
> *Proposed Next Steps:*
> 1. Remove the mutable attribute definitions for language and kind. I'm 
> unclear about the process around this sort of change since this is not 
> an "at risk" feature. I'd hate to have to go through a long Last Call 
> process again for this.
> 2. Work with David Singer and other MPEG savy folks to define a new 
> box/atom for ISO-BMFF to carry track kind information. This definition 
> could initially live in the ISO-BMFF byte stream format spec 
> <https://dvcs.w3.org/hg/html-media/raw-file/default/media-source/isobmff-byte-stream-format.html> 
> while it is waiting to be officially standardized by MPEG.
> 3. Sylvia and/or Hixie update the HTML specs to reflect the expected 
> behavior for language & kind changes. I don't have concrete proposals 
> for this at the moment, but it seems like there has been confusion 
> around the intended behavior when track changes occur mid-playback and 
> whether or not the track attributes can change value during playback.
> *Please indicate your support or opposition to the summary and 
> proposed next steps.*
> Thank you,
> Aaron

Cyril Concolato
Multimedia Group / Telecom ParisTech
Received on Wednesday, 9 April 2014 16:57:22 UTC

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