[FFmpeg-devel] [RFC] SDP Generation

Michael Niedermayer michaelni
Mon Jun 11 10:34:09 CEST 2007


On Mon, Jun 11, 2007 at 09:06:54AM +0200, Luca Abeni wrote:
> Hi Michael,
> Michael Niedermayer wrote:
> [...]
> >> Well, the problem is that every single media stream can have a different 
> >> destination address. If the "filename" field in AVFormatContext is used 
> >> for indicating the destination address, then I need an AVFormatContext 
> >> per media stream.
> > 
> > in what cases are different destination addresses needed/wanted?
> The classical example is video streamed to a multicast group, and audio 
> streamed to a different multicast group. If an application wants to 
> receive both audio and video, it joins both the two groups; if an 
> application wants to receive audio only, it only joins the audio group. 
> In this way, if multicast is routed in a smart way it is possible to 
> reduce the network traffic.
> > and why do we need them in a single SDP thingy?
> Because both audio and video streams are part of the same session.

so our choices are either supporting both multi stream AVFormatContext
and several AVFormatContext or doing something so we can store an address
per AVStream

multi stream AVFormatContext + several AVFormatContext seems more correct
as a different address = different file more or less

> > i can also put each stream into a different file, this though does not
> > prevent me from putting them in the same file ...
> Do you mean, each stream described in a different SDP file? In this 
> case, how can a receiving application understand that the streams are 
> part of the same session? Or did I misunderstand you here?

i dont know sdp too well ive just meant the general non sdp case
as comparission


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

When you are offended at any man's fault, turn to yourself and study your
own failings. Then you will forget your anger. -- Epictetus
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