[vlc-devel] [PATCH] RTP output: no need to track dynamic payload types

Rémi Denis-Courmont rem at videolan.org
Sat Sep 27 11:52:51 CEST 2008

Le dimanche 21 septembre 2008 20:19:12 Marian Ďurkovič, vous avez écrit :
> On Sun, Sep 21, 2008 at 06:58:07PM +0300, Rémi Denis-Courmont wrote:
> > RTP payload types distinguishes formats within a unique stream.
> > VLC only ever uses one format per (elementary) stream. As such, there
> > can be no payload format collision ever. We can use number 96 for all
> > dynamic payload types, and skip book-keeping. We already do this for
> > static payload formats (i.e. re-use the same value if there are
> > multiple streams).
> Although the above looks to be fine with RFC,

It *is* compliant. Payload types are scoped to their RTP stream, a.k.a. their 
SDP media. This is clearly supported by the SDP syntax: a=rtpmap and a=fmtp 
are media-only attributes, and cannot be used at the session level.

> there's no single SAP on the global multicast network which will reuse 96
> within the same SDP for different payload types. I.e. when MPEG4-video uses
> 96, MPEG4-audio always uses 97.

That does not really tell me whether it works. If not, then we'll need to keep 
the hard limit of 32 elementary streams for #rtp.

Rémi Denis-Courmont

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