[vlc-devel] [PATCH] Merge VoD module into RTP stream output module
remi at remlab.net
Sat Oct 30 10:27:01 CEST 2010
Le samedi 30 octobre 2010 09:00:29 Pierre Ynard, vous avez écrit :
> > Why do you need to a specific PTS?
> The RTSP headers already give the initial RTP timestamps to the client,
> before the instance and the rtp sout are started. So I need to use a
> common reference, and I need to pass it somewhere.
Might as well create a value that can be recomputed from the infos that the
vod stream already has. The use of mdate() was purely arbitrary.
> > This is a silly problem. Payload types are scoped to the RTP session
> > / the SDP m-line. Since VLC never streams more than one payload
> > format per RTP stream, there is no risk of conflict. We might as well
> > hard-code value 96 for all dynamic payload types.
> We could also implement streaming several payload types in the same RTP
Yes, but that's rarely useful. First, the design of RTP implicitly limits this
to payload types with equal timestamp frequency. Otherwise delay jitter
computations and synchronization would go crazy. Second, I have to expect many
receivers will fail miserably, including current VLC.
In practice, I only know two uses of multiple payload types in a single
- journaling or error correction,
- switching codecs on the fly, typically to/from comfort noise.
SIP can also use many payload types per m-line in the INVITE message. But
typically only one codec will be selected and used in RTP. This is merely a
trick to negotiate the codecs between sender and receiver.
> that would provide an alternative to TS muxing in order to
> stream without needing SDP.
You are not supposed to multiplex concurrent streams on the same RTP session.
> I planned on thinking more about that later
> and flatten out this code then, that's why I didn't mind that it wasn't
> perfect for now.
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