[whatwg] Timestamp from video source in order to sync (e.g. expose OGG timestamp to javascript)

David Singer singer at apple.com
Mon May 17 15:44:12 PDT 2010

On May 17, 2010, at 14:31 , Odin Omdal Hørthe wrote:

> Hello!
> I filed bugs at mozilla and in chromium because I want to sync real
> time data stream to live video. Some of them told me to send it here
> as well. :-)
> It's only possible to get relative playtime with html5 in javascript. I
> want absolute timestamp that's embeded in OGG.
> The spec only deals with relative times, and not getting out
> information from the
> Here's the deal:
> I stream conferences using Ogg Theora+Vorbis using Icecast2. I have built a
> site that shows the video and then automatically shows the slides (as PNG
> files) as well. I use orbited (COMET) to have the server PUSH my «next»
> presses on my keyboard.
> The problem is that icecast does heavy buffering, and also the client, so
> that while I switch the slides, the browser will go from slide 3 to 4 WAY
> too early (from 10 second to 1 minute).

Buffering should not make any difference to how far into a stream a time means.  If the transition from slide 3 to slide 4 happens at 10 minutes in, then as the presentation time ticks from 9:59 to 10:00 you should flip the slide.  It doesn't matter how much data is in any buffers, does it?

> If I could get the timestamp OR time-since-started-sending/recording from
> the ogg file in javascript, I'd be able to sync everything.
> There are multiple way to sync this, may even an stream with the slide-data
> INSIDE the ogg file, however, AFAIK there's also no way of getting out such
> arbitrary streams.
> (PS: I had some problems, so sorry if you get this email many times! :-S)
> --
> Beste helsing,
> Odin Hørthe Omdal <odin.omdal at gmail.com>
> http://velmont.no

David Singer
Multimedia and Software Standards, Apple Inc.

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