Agenda Topics for TPAC Video Breakout Session

Friday, 5 Nov 2009, 10am PST

irc.w3.org channel #video

Baseline Codecs

Tracker Issue and Action

• HTML WG ISSUE-7: video-codecs support and the <video> element
  • HTML WG ACTION-130: Review status of video codec positions

Discussion

• 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?

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

Accessibility

Tracker Issue and Bugs

• HTML WG ISSUE-9: Video - How accessibility works for <video> is unclear. (Issue is in the raised state.)
  • No Tracker Action exists
• HTML Bug 5758: Insufficient accessibility fallback for <audio> or <video>.
• HTML5 Bug 8187: Section 4.8.7 on video makes no reference to audio description.

Previous Meetings and Discussion

• Accessibility of Media Elements in HTML 5 Gathering, November 1, 2009
  • Minutes: Accessibility of Media Elements in HTML 5 Gathering
  • Spec Review from PFWG
  • Email Discussion Threads on public-html
• accessibility of video element - Aurélien Levy, 02 July 2007

Requirements

Existing Documents

• Multimedia Accessibility - a detailed history of the issue from 2007 to date. It includes Issue Description, Status, Advice Request to PFWG, Related Bugs, Proposed Solutions, Definitions of Media Assets, Meetings, Related References, and Email Discussion Threads.
• Video accessibility - WHATWG Wiki
• Accessibility/Video a11y Study08

Future Documents

Those attending the Media Elements in HTML 5 Gathering discussed the need to write another requirements document - possibly a summary of the above.

Change Proposals

According to the HTML Working Group Decision Policy, Open Tracker Issues are issues with someone working on a change proposal. If the change proposal is not done by the deadline, the issue will be closed without prejudice and deferred to the next version of HTML. The default deadline to complete a Change Proposal is one month from the time someone volunteers. The chairs may grant a longer deadline for complex issues on request."

• Writing a Change Proposal (Instructions)
• Change Proposal Template

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?

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?
  • SRT Subtitles Specifications
  • Timed Text (TT) Authoring Format 1.0 – Distribution Format Exchange Profile (DFXP)
  • SMIL 3.0 smilText

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?

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 people with browser set to en
• Captions on by default / by selection

Audio Description Support

• There is a need to provide support for audio descriptions
• Textual vs. audio versions?
• Tontent negotiation for multi-track video?
• Tontrol of playback rate changes?

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 element
• How should that be included?

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?