[FFmpeg-devel] [RFC] Add a demuxer directly handling rtp:// URLs by inspecting their content

Martin Storsjö martin
Sat Oct 16 11:25:14 CEST 2010

On Mon, 11 Oct 2010, Martin Storsj? wrote:

> On Mon, 11 Oct 2010, Luca Abeni wrote:
> > On 10/10/2010 08:23 PM, Ronald S. Bultje wrote:
> > > Hi,
> > > 
> > > On Sun, Oct 10, 2010 at 12:37 PM, Luca Abeni<lucabe72 at email.it>  wrote:
> > > > I now see a bug on roundup asking for this, but... Is this really a good
> > > > idea? AFAIK, "rtp://..." URLs are not standardised in any way, and the
> > > > only
> > > > standard way to identify an RTP session is an SDP. I think that something
> > > > like this patch can work in some cases, but will fail in some other cases
> > > > (I
> > > > believe there are a lot of them - basically, the only case in which this
> > > > can
> > > > work reliably is TS over RTP...) and will end up confusing the users even
> > > > more...
> > > 
> > > J-B, how does VLC deal with this? VLC accepts rtp:// URIs afaics.
> I'm not sure if VLC has code of its own for that, or if all of that is 
> handled within Live555.
> > I might be wrong, but I think it only works with TS in RTP...
> > Double thinking about it, this might be a reasonable solution (see my
> > previous email).
> Hmm, what about all the static payload types, e.g. audio? Or is the sample 
> rate freely choosable for them, even if they're using a static payload 
> type?

I did some tests with VLC, and it was able to play back mulaw pcm with 
only a rtp:// url. The weird thing was that VLC/Live555 seemed to guess it 
as 4 kHz, not 8 kHz which would be the obvious guess.

> On the other hand, with something like this in place, it's quite easy to 
> add an error message telling the user that the input is ambiguous and an 
> explicit SDP description is needed, for all the cases that we don't want 
> to handle this way.

Updated patch attached, with more verbose warning messages. For 
mpegts/rtp, no warning is issued, for audio/video that is guessed, we give 
a warning saying that we're not sure about the content and may need an 
SDP. For other payloads not recognized, we say explicitly that we need an 
SDP file.

// Martin
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