[FFmpeg-devel] [PATCH] sdp: Emit only one c= line for multiple streams, if they have the same destination

Martin Storsjö martin
Wed Oct 6 09:27:47 CEST 2010

On Wed, 6 Oct 2010, Luca Abeni wrote:

> On 10/05/2010 03:52 PM, Martin Storsj? wrote:
> > On Tue, 5 Oct 2010, Luca Abeni wrote:
> > 
> > > I'll have a look at this patch later (or tomorrow). Can you provide an
> > > ffmpeg command line generating an SDP that vlc cannot read?
> > > (I never managed to produce such SDPs, and I use ffmpeg to stream
> > > sessions with multiple streams almost dayly).
> > 
> > Hmm, yes, when storing the SDP to a file and playing it from there, it
> > seems to work ok.
> > 
> > In my case, I'm sending the SDP over SAP (RFC 2974), and in that case, VLC
> > refuses to play it unless there's only one c= line.
> Uhmm... Is this a vlc (or live555) issue/bug? Last time I played with SAP,
> I do not remember it adding any constraints to the SDP (so, every valid
> SDP should be accepted...).

Probably a live555 issue. I don't know of any additional constraints 

If sending multiple streams to vlc/live555 in the same SDP, they must also 
both be sent to the same port(!), but that's of easy to enable/disable 
with an option in the SAP muxer.

> Anyway, even if this is a vlc bug I am ok with adding a workaround. So,
> the patch is good in principle; the code also looks good. But I'd like
> to have a better look at it first... Give me 1 day or 2 :)

Ok, no problem.

> > I'm building an integrated SAP muxer - this was one of the cleanup commits
> > I had to do to prepare for it. Once I post that one, you should be able to
> > test it out as a whole :-)
> Nice! Having a SAP muxer would definitively be a good thing... Up to
> now, I always used a hacky SAP announcer as an external program.

Good that you're interested in having this functionality, too!

// Martin

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