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Silvia, Reading through your explanation, it seems to me the key issue is the division of labor around the rendering of the external file description text. I believe you have made the assumption that the AT will render this - at its own pace - while the general approach of accessibility APIs is that of exposing GUI/UI elements to AT. The issue of whether the description text is in the formal DOM or a "shadow DOM" is, I think, a red herring. The user agent has access to the text, and the user agent presents all of the media to the user/AT in some fashion. For example, a key facet of the accessibility API is exposing the bounding rectangle of all rendered text - something that is also not in the DOM but is known to the user agent. There is no reason why the user agent cannot likewise expose the description text in some for to the user/AT. But, returning to what I suspect is the crux of the matter... I think we shouldn't attempt to decide which approach is better before coding up a sample of each approach and examining them. I propose three explorations:
Regards, Peter On 6/16/2011 3:35 PM, Silvia Pfeiffer wrote: Hi Pete, Thanks for your review and questions on the video side of things. I'm hoping the combined expertise here will be able to define the best way to deal with video and the track specification of HTML5 [1]. I may, however, need to go into detail on how tracks and cues are handled in HTML5 before we can come to the right solution.[1] http://www.whatwg.org/specs/web-apps/current-work/multipage/the-iframe-element.html#the-track-element On Fri, Jun 17, 2011 at 5:36 AM, Pete Brunet <[email protected]> wrote:I've read through the discussion and have these comments and questions: What is the use case to justify an API (and associated synchronization complexity) for access to cues that is not solved by captions for those who can't hear the audio and audio descriptions of visual media for those who can't see the video?The <track> element in HTML5 allows association of external text files that provide lists of timed caption cues, subtitle cues, text description cues and chapter cues to audio and video elements. This is on top of what can come from within a audio or video file, which can contain captions and subtitles as text, as well as audio descriptions as audio and sign language as video. Why I approached Alexander was to find out how to deal with text descriptions. Text descriptions are something new that you may not have seen in traditional accessibility approaches for audio and video: they provide the text that is usually spoken in audio descriptions as actual timed text cues. The files are essentially the same as caption files with cues that have a start and an end time and some text. However, it is expected that these text descriptions are read out by a screen reader or handed to a braille device to be communicated to those who can't hear. In addition, it should probably be possible to also expose caption cues (and subtitle cues for that matter) to AT for those that can neither hear nor see and want to consume them through braille. This was, however, not my main use case. Note that none of the text cues are part of the DOM of the Web page but only live in the shadow DOM. Therefore, I guess, some method of exposure is required.Since it's early in the discussion of this issue I think this topic needs to be separated from the rest of the discussion. Alex can you move that to a separate section like you did for the Registry API? At least at this point I'm not in favor of the media control methods. Developers should provide accessible GUI controls. The developer would have to implement the access in any case and having access through the GUI would eliminate adding the code for these new methods on both sides of the interface. If the app developer does a correct implementation of the GUI there would be no extra coding required in ATs.I guess the idea here was that there may be situations where AT needs to overrule what is happening in the UI, for example when there are audio and video resources that start autoplaying on a newly opened page. However, I am not quite clear on this point either. The key problem that I saw with text descriptions and video controls is that we have quite a special case with text descriptions since the author of the text descriptions can identify the breaks in the video timeline into which a description cue needs to be fitted, and they can provide the text that needs to be spoken in this break, but they cannot know how long it will take to actually voice or braille this text. Therefore, AT in this case needs to control the video's playback timeline and possibly put it on hold when the end time of the cue is reached until AT has finished with the text of the cue. I would think that this may be one of the only cases where AT actually has to control the display of the Web page rather than just being a mere observer. Best Regards, Silvia. _______________________________________________ Accessibility-ia2 mailing list [email protected] https://lists.linux-foundation.org/mailman/listinfo/accessibility-ia2 --
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