[vorbis] bitrate peeling

[Akos Maroy]

Jack Moffitt wrote:
> SureStream stores multiple encoded copies in the file.  RealServer just
> has some smarts to swap between them.  This is really no different than
> what icecast 1.x had, which allowed you to mark related streams, and
> would then move the client around (only moving down was support, iirc)
> based on various criteria.

I didn't know of this feature of icecast 1.x, but RealAudio does more 
then just move the client arount. It recieves quality information from 
the client, and tries to send the approprietly wide stream the client 
can handle (with a ceiling of course, usually being the width of the 
original stream selected by the client). The effect is, that if there 
are some network problems, the client gets a downscaled stream. If the 
problems go away, the client gets the wider stream again. All done 
transparently, the client doesn't notice anything (except the change in 
quality, of course).

This, coupled with UDP transport if possible (RTSP based on UDP), gives 
quite reliable streaming (e.g. the stream doen's block even if there are 
fluctuations in the quality of network connection).

This is of course theory, in reality nothing is perfect. :)

Don't get me wrong, I'm not trying to advocate RealAudio. What I want to 
point out is, that we're using a protocol (HTTP) for streaming that is 
quite simply not for streaming. And there are problems arising from 
this, mainly the problem of stream stability when the network connection 
between server and client is far from perfect.

BTW, has anyone tried MPEG4IP, with the Ogg Vorbis support? That uses 
RTSP. What clients support this?

<p>Akos

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