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Topics for "Video" Breakout Group

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Thu, 5 Nov 2009 17:01:18 -0800
Message-ID: <2c0e02830911051701n2456b8a2n256c31981c8e339d@mail.gmail.com>
To: public-html <public-html@w3.org>
Hi all,

This is a list of issues that I have gathered about video from
Sunday's workshop and would like to see discussed in the HTML WG
"Video" breakout group on Friday, 10am at TPAC.

If somebody wants to put this in a wiki, I'd be happy for it, but
since I'm not an editor, this is probably the best way to start the
list. Please reply to the email with anything I have missed in your

1. baseline codecs (http://www.w3.org/html/wg/tracker/issues/7,
* the consumer need for a common baseline codec is being voiced widely
* what are the options towards getting to an agreement on a common
baseline codec

2. Cue Ranges
* there seems to be a need for cue ranges, e.g. activate slide
changes, pause and display ad, captions for live video, others??
* why is timeupdate not sufficient?
* why was previous specification not acceptable?
* revisit Apple proposal:

3. Media element accessibility (http://www.w3.org/html/wg/tracker/issues/9)
* brief summary of Sunday workshop: http://www.w3.org/2009/11/01-media-minutes
* feedback from PFWG: http://www.w3.org/2009/08/html5-spec-review
* current status:

3.1. Requirements
* existing documents:
* existing bugs:
http://www.w3.org/Bugs/Public/show_bug.cgi?id=5758 (general accessibility)
http://www.w3.org/Bugs/Public/show_bug.cgi?id=8187 (audio descriptions)
* Sunday workshop stated need to write another requirements document -
possibly a summary of the above

3.2. Caption/Subtitle support
* there seems to be a need for declarative syntax for external caption
files - all inside the DOM or through javascript integrated?
* there seems to be a need to find out what content tracks are
available in a binary media file - a javascript query or a descriptive
block or a link to a file, SMIL-style?
* there seems to be a need to provide user interface controls for
captions (both, internal and external) and/or a standard API that
would allow a UA to query if media ".hasCaptions"
* there seems to be a need to provide a javascript API to get access
to the individual captions (both, internal and external)
* how would a user relate a caption file to a video inside the browser
on the fly?

3.3. What format to support for captions/subtitles?
* there seems to be a need for a baseline caption/subtitle codec
* srt vs DFXP vs. smilText? others?

3.4. Security issues with external caption files
* there seems to be a need to deal with XSS issues for external
caption/subtitle files
* is CORS the answer? http://www.w3.org/TR/access-control/

3.5. Display activation issues with captions/subtitles
* there seems to be a need to specify display mechanisms for captions
* automated activation based on a browser preference? e.g. subtitles = on/off
* automated language selection based on browser setting? e.g. en for
ppl with browser set to en
* captions on by default / by selection

3.6. Audio description support
* there is a need to provide support for audio descriptions
* textual vs. audio versions?
* content negotiation for multi-track video?
* control of playback rate changes?

4. Hierarchical navigation through audio/video elements
* there seems to be a need to mark up media elements with a
hierarchical structure that can be used for browsing through the
* how should that be included?

5. Multi-track video
* there are many more alternative information tracks for videos, such as
- sign language,
- music/background sound track,
- alternate video angles,
- dubbed audio tracks,
- ticker text
- active regions (timed)
- annotations
- timed metadata
- timed transcript
- karaoke
- lyrics
- linguistic markup
* how to deal with such a collection of additional materials?

Looking forward to an interesting and productive discussion tomorrow!

Best Regards,
Received on Friday, 6 November 2009 01:02:11 UTC

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