[FFmpeg-devel] [PATCH] Implement an option in ffmpeg to make it print the output SDP and exit

[Michael Niedermayer]

On Wed, Jul 16, 2008 at 10:38:55AM +0200, Stefano Sabatini wrote:
> On date Wednesday 2008-07-16 08:38:54 +0200, Luca Abeni encoded:
> > Hi Stefano,
> > 
> > Stefano Sabatini wrote:
> > > Hi all,
> > > 
> > > this patch changes the current behavious of ffmpeg which currently
> > > print if needed the SDP of the output streams.
> > 
> > Michael is ffmpeg.c maintainer, but since I am the one who
> > implemented SDP output I have some comments.
> > 
> > First of all, thanks for the patch: I believe the "-sdp" option is
> > needed (and I've been lazy not implementing it :).
> > 
> > > This patch implements a behaviour which could result useful when
> > > scripting things like this:
> > > 
> > > ffmpeg  -i ~/test.avi -vn -sdp -f rtp rtp://localhost:5004 > test.sdp
> > > ffplay test.sdp
> > > ffmpeg  -i ~/test.avi -vn -f rtp rtp://localhost:5004 > test.sdp
> > > 
> > > Since I think this is the assumed use for the SDP output then I think
> > > this behaviour is preferable since it doesn't require the user to
> > > invoke a transcoding just to print out the SDP.
> > 
> > I generally use "-t 0.001" if I want to generate the SDP without actually
> > streaming anything.
> > 
> > 
> > > Note that this breaks compatibility with the previous behaviour, now
> > > when ffmpeg is invoked without -sdp it won't print the SDP anymore.
> > 
> > I think this is ok.
> > 
> > 
> > > Also the SDP printed won't be prefixed by "SDP:\n" as before.
> > 
> > I believe this is ok too.
> > 
> > 
> > > Comments/suggestions are welcome as always.
> > 
> > In my opinion, it would be more useful to have a "-sdp" option that
> > prints the SDP without exiting (if the user wants ffmpeg to exit
> > immediately after printing the SDP, he can use "-t 0.001").
> > But I have no strong opinions about this: if other people think that
> > "-sdp" should exit, I am ok with it.
> 
> What I want to achieve is to give the user the possibility to
> understand if the SDP has been written, if for example the output
> stream doesn't support an SDP (e.g. ffmpeg -i foo.mpeg -sdp foo.avi)
> then ffmpeg should exit with an error code.
> 
> This is achievable also without to exit, the only problem is for
> example when the outgoing stream *may* be described by an SDP but the
> transcoding occurred in the firtst 0.01 seconds is broken and ffmpeg
> exits with 1, in this case the user cannot distinguish the two cases.

What would -sdp output on stdout in case of an error? if nothing then
this should be enough to distinguish it.

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Concerning the gods, I have no means of knowing whether they exist or not
or of what sort they may be, because of the obscurity of the subject, and
the brevity of human life -- Protagoras
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 189 bytes
Desc: Digital signature
URL: <http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/attachments/20080716/a840819d/attachment.pgp>