[vlc] can't transcode and display

[Angus McMorland]

Hi all,

I'm trying to achieve something that I think should be relatively
simple: capturing from a webcam, transcoding to a compressed movie
file, and displaying on the screen. I can get the transcoding or the
display to work independently, but not together. I can also achieve
displaying and saving, without transcoding, into a .avi muxer.

I'm calling vlc with the following script:

SESSION=quack
SAVEDIR=/tmp
VIDEV=v4l2:///dev/video0

DST_DSP=display{noaudio}
#DST_MP4=transcode{vcodec=mp4v,scale=1,vb=2048,vt=80000,size=1920x1080,fps=25}:standard{mux=mp4,access=file,dst=${SAVEDIR}/${SESSION}.mp4,noaudio}
DST_MP4=transcode{vcodec=mp4v}:standard{mux=mp4,access=file,dst=${SAVEDIR}/${SESSION}.mp4,noaudio}
DST_AVI=std{mux=avi,access=file,dst=${SAVEDIR}/${SESSION}.avi}

#SOUT='#duplicate{dst="'${DST_AVI}'"}'  # config 1
#SOUT='#duplicate{dst="'${DST_MP4}'"}' # config 2
#SOUT='#duplicate{dst="'${DST_DSP}'",dst="'${DST_MP4}'"}' # config 3
SOUT='#duplicate{dst="'${DST_DSP}'",dst="'${DST_AVI}'"}' # config 4

vlc -vvv --one-instance ${VIDEV} --v4l-caching 1024 --sout=${SOUT}
--no-sout-audio &

where using the SOUT lines for configs 1, 2 and 4 work as expected,
but the one I want, config 3, doesn't. Instead, it creates the .mp4
file, but doesn't write into it, and error messages are printed to
stdout like:

[0x12a58a0] stream_out_transcode stream out debug: late picture skipped (1017)

I'm running a x86_64 quad core 2.7 GHz Intel machine with 8 GB of RAM,
so I guess I'll be surprised if the hardware just isn't up to it.
There's no appreciable CPU load when I'm trying any of these config
modes.

Please can anyone tell me what I'm doing wrong?

Thanks,

Angus
-- 
AJC McMorland
Post-doctoral research fellow
Neurobiology, University of Pittsburgh