[FFmpeg-user] FFMPeg reading from Logitech C920 generating H264 source produces empty output file

William C Bonner wimbonner at gmail.com
Sat Aug 31 20:10:31 CEST 2013

I finally came up with a way of getting FFMPEG to read h.264 directly from
my Logitech C920 webcam and stream it over RTP. The parameter required
was -copyinkf (copy initial non-keyframes)

I'm not sure why this suddenly made it able to create a non-zero file when
saving to a local file, or create a working stream when pushing to another
machine, but it did.

Here's the command line that I'm currently using in my testing.

ffmpeg -s 1920x1080 -f v4l2 -vcodec h264 -i /dev/video0 -copyinkf -vcodec
copy -f rtp rtp://

On Mon, Jul 22, 2013 at 2:59 PM, William C Bonner <wimbonner at gmail.com>wrote:

> Can I attach text files to this list?
> I just was hoping to try since the output of the report is really wide,
> and breaking it into standard email format makes it that much harder to
> read. I'm attaching both the version with the -vcodec copy and without
> because while both have lines starting "demuxer -> " and "demuxer+ffmpeg
> ->" the second also has lines "decoder ->", "encoder ->", and "muxer <-".
> Wim.
> On Mon, Jul 22, 2013 at 2:47 PM, William C Bonner <wimbonner at gmail.com>wrote:
>> I tried adding the -debug_ts as the first option, and it spit lots of
>> information back at me that I don't really understand, so I also added a
>> -report option, and here's that output.
>> I wasn't sure where in the command line to try -use_wallclock_as_timestamps
>> 1 so I added it right before the -y test.mp4 but didn't notice any change,
>> so it's not in this output.
>> On Mon, Jul 22, 2013 at 1:51 AM, Carl Eugen Hoyos <cehoyos at ag.or.at>wrote:
>>> William C Bonner <wimbonner <at> gmail.com> writes:
>>> > frame=    0 fps=0.0 q=-1.0 Lsize=       0kB time=00:00:00.00
>>> bitrate=N/A
>>> > video:0kB audio:0kB subtitle:0 global headers:0kB muxing overhead inf%
>>> > Output file is empty, nothing was encoded
>>> > (check -ss / -t / -frames parameters if used)
>>> Use -debug_ts to show the timestamps of the incoming stream,
>>> and please try -use_wallclock_as_timestamps 1 which may
>>> help.
>>> Carl Eugen
>>> _______________________________________________
>>> ffmpeg-user mailing list
>>> ffmpeg-user at ffmpeg.org
>>> http://ffmpeg.org/mailman/listinfo/ffmpeg-user

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