[whatwg] Video : Slow motion, fast forward effects

Ralph Giles giles at xiph.org
Thu Aug 7 11:53:56 PDT 2008

On Thu, Aug 7, 2008 at 1:57 AM, Philip Jägenstedt <philipj at opera.com> wrote:

> I suggest that the spec allows raising the NOT_SUPPORTED_ERR exception
> in response to any playback rate which it cannot provide for the current
> configuration.

That sounds reasonable. It is a special effect.

> With a netcast you couldn't support any playback rate
> except 1.0 without first buffering all the data you want to play at a
> faster rate, so changing the playback rate doesn't make sense.

Well, it would be better to implement the requested playback rate (and
direction) as long as you can and then rebuffer when necessary. Doing
that well requires extra sophistication in the buffering code, but the
client might just be trying to scrub a bit, which would fit within a
normal seek buffer. Even with live streams, if you try to pull faster
than realtime you'll just buffer-wait, and if you're going slower
you'll fill whatever space you have, then have to drop and restart.

If all you have is a jitter buffer, then sure.


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