[foms] Proposal: adaptive streaming using open codecs

Mark Watson watsonm at netflix.com
Mon Nov 15 10:29:27 PST 2010


It depends what kind of sync issues you mean. Actually rendering audio and video out of sync can only happen if you are not paying correct attention to the sample timestamps. This is always a bug (IMO) and independent of the way the media was received.

The other kind of problem is that you may end up with sufficient data to render one component but not the other (and so you have to pause). This can be really well mitigated by just buffering the audio quite a lot further ahead in time than the video. This is low cost because the audio is so much lower bitrate than the video (generally). You might still run out of video and so have to stall for a while, but the impact of buffering further ahead with the audio on the frequency of such stalls is negligible.

In terms of download speed, having multiple parallel connections does make it slightly more complex - because you have to consider how to use the per-connection speed together with the aggregate speed. But separate audio and video files doesn't imply parallel connections (you can interleave requests for audio and video blocks onto a single connection if you want).


On Nov 15, 2010, at 9:49 AM, Steve Lhomme wrote:

> On Mon, Nov 15, 2010 at 6:48 PM, Steve Lhomme <slhomme at matroska.org> wrote:
>> Doesn't it lead to more sync issues when the files you received are
>> not interleaved ? The 2 streams may not load at the same speed (once
>> better cached than the other for example). It also makes it harder to
>> estimate the current download speed... That's an edge case, but
>> precisely the kind of odd network behaviour that "adaptative"
>> streaming is meant to handle.
>> One big pro for non interleaved is that switching between languages
>> (or regular/commentary track) is a lot easier and the only reasonable
>> way to handle it server side.
> PS: And also allows something not possible now: listen to music from
> video sites without having to load the video part. It's possible with
> RTP but the quality (on YouTube for ex) is just not there.
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