Got black screen when recording screen from xvfb by ffmpeg x11grab device

Posted by shawnzhu on Super User See other posts from Super User or by shawnzhu
Published on 2014-03-11T02:20:11Z Indexed on 2014/06/07 15:28 UTC
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ffmpeg

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xvfb

I'm trying to record video from a firefox run by xvfb-run but it always output nothing in the video file except black screen.

Here's what I did:

start a firefox, open google.com:

$ xvfb-run firefox https://google.com

Then it will use the default display server number 99. I can see the display information by command xdpyinfo -display :99.

A screenshot works very well by command:

$ xwd -root -silent -display :99.0 | xwdtopnm |pnmtojpeg > screen.jpg

Start using ffmpeg to record a video:

$ ffmpeg -f x11grab -i :99.0 out.mpg

When I play the video file out.mpg, there's black screen all the time.

Is there any parameter I missed?

Updates

I made progress that the video works instead of black screen only by this command:

$ ffmpeg -y -r 30 -g 300 -f x11grab -s 1024x768 -i :99 -vcodec qtrle out.mov

Notice it requires the screen resolution matches by specify more options to xvfb-run:

$ xvfb-run -s "-screen 0 1224x768x16" -a firefox http://google.com

But I still want to get more feedbacks and answers here.

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