[vlc] can't transcode and display

[Angus McMorland]

On 27 June 2011 09:02, Angus McMorland <amcmorl at gmail.com> wrote:
> On 25 June 2011 14:50, gonzague <gonzagueddr at gmail.com> wrote:
>> Hi, It is happening sometime that ffmpeg is not fully effective.
>> To know the muxers you can use, type "ffpmeg -formats" , and check the 1rst
>> letters ( E=encode, D=decode, A=audio, V=video)
>> Same things to know the codecs you can use , typing "ffpmeg -codecs".
>
> I don't think the muxer itself is the problem, since the transcoding
> does work on its own. It only doesn't work when I also display the
> output. In any case, the page you suggest, shows that transcoding
> should work with linux, and the mp4/mp4v combination should be
> compatible.
>
> Can anyone suggest how I debug this?

Someone else has suggested trying a different muxer (mpeg-ts) as a
workaround to get display and transcoding working simultaneously
(thanks for that suggestion).

I've now tried this, and theora/ogg as well, and in each case I get no
usable transcoded file and the 'late picture skipped' error.

Does anyone know how to fix this?

Thanks,

Angus

>> On 24/06/2011 23:08, Angus McMorland wrote:
>>> 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}: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
>>
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-- 
AJC McMorland
Post-doctoral research fellow
Neurobiology, University of Pittsburgh