[FFmpeg-user] Question for using blackdetect video filter

Wu-bin Zhen vvubin at gmail.com
Sat Jan 26 06:58:21 CET 2013

On Fri, Jan 25, 2013 at 9:58 PM, Carl Eugen Hoyos <cehoyos at ag.or.at> wrote:

> Wu-bin Zhen <vvubin <at> gmail.com> writes:
> > Thanks for the quick reply. I am using live http streaming,
> > so it won't stop transferring data as long as the
> > connection is alive.
> The following produces identical output here
> for the http stream and a local file:
> $ ffmpeg -loglevel info -i
> http://samples.ffmpeg.org/V-codecs/SVQ3/Vertical400kbit.sorenson3.mov -vf
> blackdetect=d=0.1 -f null -t 10 -
> Please do not top-post here, it is considered rude.
> Carl Eugen
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> ffmpeg-user at ffmpeg.org
> http://ffmpeg.org/mailman/listinfo/ffmpeg-user

Thank you for the reminder. Now I learned this netiquette for English
speakers and I will keep it in mind here.

So after comparing with your sample, I think the blackdetect filter is not
working with the non-stop streaming urls. My temporary solution is:
> ./ffmpeg -i http://<non-stop-streaming-server>/live.flv -vcodec copy -an
-t 5 ./blackvideo.flv
> ./ffmpeg -v info -i ./blackvideo.flv -vf blackdetect=d=2 -f null -

This works, but it has two issues: (1) causing more I/O access, (2) time
delay for the black video detection.
So I am trying hard to detect the black video without creating small files.
Any suggestion will be appreciated.

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