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

At the HTML WG F2F meeting I was assigned Media TF ACTION-65:
http://www.w3.org/html/wg/media/track/actions/65

which refers to the point 3 in the email below:

>3. Sylvia and/or Hixie update the HTML specs to reflect the expected behavior for language & kind changes.

Have such bugs been filed and/or processed for HTML5?  If so could you give me pointers so that I can close out the ACTION item?

If not do you need any further information to open such bugs?

/paulc

Paul Cotton, Microsoft Canada
17 Eleanor Drive, Ottawa, Ontario K2E 6A3
Tel: (425) 705-9596 Fax: (425) 936-7329

From: Aaron Colwell [mailto:acolwell@google.com]
Sent: Monday, April 07, 2014 3:06 AM
To: <public-html-media@w3.org>
Subject: [MSE] Summary of "Resolving Bug 24370" thread and proposed next steps

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