Re: A tool to extract part of a video

On Sat, 18 Aug 2007, David Bolt wrote:-

On Fri, 17 Aug 2007, Hatto von Aquitanien wrote:-

<Snip>

Any ideas?

Well, you could try:

ffmpeg -ss 00:28:30.000 -t 00:06:45.000 -vcodec mpeg4 -vtag xvid -i
V08546-22.flv V08546-22.avi

which should do the job.

Should, but doesn't. The video stream is correctly cropped out, but the
audio stream isn't. However, using these commands will work:

ffmpeg -i V08546-22.flv -vn -f s16le -acodec pcm_s16le -ac 2 -ar 22050 -ss 00:28:30.000 -t 00:06:45.000 - >audio
ffmpeg -i V08546-22.flv -an -f yuv4mpegpipe -ss 00:28:30.000 -t 00:06:45.000 - >video
ffmpeg -f s16le -acodec libmp3lame -ac 2 -ar 22050 -i audio -f yuv4mpegpipe -vcodec mpeg4 -vtag xvid -sameq -y V08546-22.avi
rm audio video

You will need a large space for the video file as it's the raw video
and, in my tests, ended up close to 1.4GB.

Alternatively, you can use a couple of named pipes and three consoles to
do the job[0] and not need a large amount of free drive space. To do
this, these steps should do nicely:

1, open up three separate consoles and change directory to that
containing V08546-22.flv ;

2, in one of the console windows type the commands "mkfifo audio" and
"mkfifo video" ;

3, using the first console, enter the following command:

ffmpeg -i V08546-22.flv -vn -f s16le -acodec pcm_s16le -ac 2 -ar 22050 -ss 00:28:30.000 -t 00:06:45.000 - >audio

4, using the second console, enter the following command:

ffmpeg -i V08546-22.flv -an -f yuv4mpegpipe -ss 00:28:30.000 -t 00:06:45.000 - >video

5, using the third console, enter the following command:

ffmpeg -f s16le -acodec libmp3lame -ac 2 -ar 22050 -i audio -f yuv4mpegpipe -vcodec mpeg4 -vtag xvid -sameq -y V08546-22.avi

6, once the AVI is built, delete the pipes "audio" and "video", unless
you're going to use them for other transcoding.


[0] According to an example given in the ffmpeg FAQ, it's possible to do
this with only one console, however all that happened when I tried is
the two jobs sent into the background stopped and waited for me to bring
them into the foreground.

Regards,
David Bolt

--
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