[Ffmpeg-devel] how to make FFPlay echo its input to a file?

john Galloway jrg
Mon Apr 25 18:48:57 CEST 2005

   I'm posting this to both lists as maybe some bright user has
figured out how to do this, but I suspect a (hopeful small) bit-o
development is going to be needed.

   I have ffmpeg (from mid 2004) running on a tiny pc (my robot)
and grabbing 1394 data from the camera there and sending it over
802.11 to a much bigger/beefier PC where the video is displayed.
I'd also like to save this video stream, that is the problem at
hand (a jpeg2000 codec to replace mpeg would be good too, but that's
far later! :-).  I don't want to have ffmpeg do this since that
will add more work to the tiny box, I want this to happen on the
receiving end.  Currently they are linked by a pipe that is set up
by a little app that then exec's ffmpeg (or any program you tell it)
and gives this new program one end of the pipe.  That works fine.
But if I insert say the tee app in front of ffplay or ffmpeg itself,
the video becomes uneven (stops, starts, etc).  The 2nd app on the
receiving system adds too many more data copies I suspect.

   So since all (most?) of the I/O in ffmpeg happens in the libs and
ffplay uses those same libs, I assume it wouldn't be THAT hard to
add an -o output_file to ffplay.  but since its all in the libs it
also isn't going to be obvious.

   Is so, is there an existing way to have ffplay write out 
its input? (no format conversion is needed).  If not, perhaps someone
could give a few pointers on what lib functions do this (for ffmpeg) so
I can add some options to ffplay and then trigger this same action.  

   If anyone is thinking about wrting a sound input driver (ALSA?) for 
Apple iSight 1394 camera mic's I would really love that!

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