[foms] WebM Manifest

Steve Lhomme slhomme at matroska.org
Thu Mar 17 15:56:20 PDT 2011

On Thu, Mar 17, 2011 at 10:53 PM, Timothy B. Terriberry
<tterribe at xiph.org> wrote:
>> life of the encoder (and likely the rate control process) easier. And
>> on the playback side there's hardly any drawback. But that means
>> players have to handle the case they want to switch but the next
>> keyframe is not available in the variant it wants to switch to.
> This also assumes this is even expressible in the manifest. I don't know
> DASH well enough yet to say if it is. And it leaves you with the
> possibility of switching to a rate and not being able to switch out of
> it for a long time. Imagine a relatively still scene with only forced
> keyframes at periodic intervals: if these are misaligned at the start,
> it could be many tens of seconds before there is another opportunity to
> switch. This sort of thing is not as uncommon as you think.

It would not be expressed in the manifest (just no forced duration
set). I agree it may not happen all the time, but the possibility
should not be ruled out because it cannot be used 100% of the time.

In the case you describe the only drawback is that playback is not as
perfect as it can theoretically be. But that's expected when using
adaptive streaming anyway.

Steve Lhomme
Matroska association Chairman

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