- From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
- Date: Mon, 1 Nov 2010 12:14:25 +1100
- To: Philip Jägenstedt <philipj@opera.com>
- Cc: public-html-a11y@w3.org
On Fri, Oct 29, 2010 at 2:08 AM, Philip Jägenstedt <philipj@opera.com> wrote: > On Thu, 28 Oct 2010 14:46:32 +0200, Geoff Freed <geoff_freed@wgbh.org> > wrote: > >> On Thu, 28 Oct 2010 13:05:57 +0200, Philip Jägenstedt <philipj@opera.com> >> wrote: >>> >>> It's >>> beyond this most basic case I'd like to understand the actual use cases. >>> To clarify, option 2 would allow things like this, borrowing SMIL syntax >>> as seen in SVG: >>> >>> <video id="v" src="video.webm"></video> >>> <video begin="v.begin+10s" src="video2.webm"></video> >>> <!-- video and video2 should be synchronized with a 10s offset --> >>> >>> or >>> >>> <video id="v" src="video.webm"></video> >>> <video begin="v.end" src="video2.webm"></video> >>> <!-- video and video2 should play gapless back-to-back --> >>> >>> Are there compelling reasons to complicate things to this extent? The >>> last example could be abused to achieve gapless playback between chunks in a >>> HTTP live streaming setup, but I'm not a fan of the solution myself. >> >> I think there are compelling cases which are likely to occur in production >> environment because they are more efficient than the example I outlined >> above. For example, an author could store the same three descriptions >> discretely, rather than in a single audio file, and then fire each one at >> the appropriate point in the timeline, in a manner similar to the one you've >> noted above: >> >> <video id="v" src="video.webm"></video> >> <audio sync="v.begin+15s" src="description1.webm"></audio> >> <audio sync="v.begin+30s" src="description2.webm"></audio> >> <audio sync="v.begin+45s" src="description3.webm"></audio> > > Rights, it's easy to see how it could be used. If the implementation cost is > worth what you get, I expect that similar implementations already exist in > desktop applications. Are there any implementations of such a system in > widespread use and does it actually get the sync right down to the sample? Jeroen from JWPlayer/Longtail Video has implemented something for audio descriptions, where audio descriptions come in separate files and are synchronized through markup - I believe the synchronization is done in the JWplayer in Flash, see http://www.longtailvideo.com/support/addons/audio-description/15136/audio-description-reference-guide . AFAIK this is the most used platform for providing audio descriptions on the Web at this point in time - I've seen it use in government Websites around the globe. If it can be done in Flash in an acceptable quality, I would think browsers should be able to do it. I can ask Jeroen for more implementation details if necessary - AFAIK he said there was frequent re-synchronization of the secondary resource to the main resource, which continues playback at its existing speed. Cheers, Silvia.
Received on Monday, 1 November 2010 01:15:19 UTC