[Bug 14104] <track> Live captioning

https://www.w3.org/Bugs/Public/show_bug.cgi?id=14104

--- Comment #37 from Silvia Pfeiffer <silviapfeiffer1@gmail.com> 2012-04-20 01:26:51 UTC ---
I'd actually prefer if we didn't get side tracked in this bug with introducing
markup for editing cues. I don't actually think there is a big requirement for
editing on the Web, since for live captioning & streaming we can delay the
transmission to make sure the captioner has finished fixing their transcript.

What I was trying to focus on in this bug was not the WebVTT markup, but the
problem that WebVTT files may get changed while the video is playing back and
that this is a legal use case for live streaming and that in this case the
browser needs to reload the WebVTT file frequently.

The problems that Philip lists can be addressed:

#1 would make use of the startDate together with the currentTime to know when
to display cues

#2 every time the WebVTT file has been loaded, the browser returns to
HAVE_METADATA - it doesn't need to wait

In fact, the server could be clever and provide to newly connected clients just
the cues that relate to the part of the video that they are currently looking
at. Though in this case it's almost identical to loading the captions via JS.

What the browser still doesn't know is when it has to reload the WebVTT file.
That's why I suggested a @live attribute which would cause the browser to
frequently reload the WebVTT file.

I can see three different ways to trigger a reload:
* whenever the browser runs out of cues for a video (in fact, this could likely
be useful in general)
* when a startDate is given on the video and the browser runs out of cues
* when a @live attribute is given on the video and the browser runs out of cues

Also, we'd need to limit the number of reload tries if there are no changes to
the WebVTT file.

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Received on Friday, 20 April 2012 01:26:55 UTC