[FFmpeg-user] x11grab

Phil Troy phil at philtroy.com
Sun Sep 1 07:52:23 CEST 2013


I am trying to capture screens containing a libreoffice impress presentation using x11grab.  I will post the command used below. The issue I am having is that there are slight artifacts in the screen grab that are not there in the original presentation, even when I request perfect quality.  I am guessing that this might have to do with the fact that I am not using bit mapped fonts (Libreoffice does not use them); when I went from Times Roman to arial the artifacts decreased (but are still visible).

I am wondering if anyone has a suggestion for addressing this.

Here is the ffmpeg code I used:

fmpeg -f x11grab -r 2 -s 1024x768 -i :0.0 -f alsa -ac 1 -i pulse -vcodec libx264 -pix_fmt rgb24  -preset ultrafast -qp 0 output.avi

I am running Lubuntu 13.04 with a new version of LibreOffice (not that that should matter) on a samsung series 9 with an i7 processor with 8gb ram and a solid state drive.  The processor is not being stressed (when it is the fan turns on and the fan was not on).  I picked a low frames per second rate because the slides are static for several seconds at a time.  I also tried not using -pix_fmt and to also use the yuv420 pix_fmt; same thing happens.  I am capturing output from a viewsonic monitor with 1920x1080 native resolution set to 1024 x 768 resolution using arandr; the display from LibreOffice is perfectly sharp whereas this is not.  Also, I just installed ffmpeg using the script file which I am attaching within the last 48 hours.

I am not posting the second request to ffmpef because if the perfect quality does not work (as well as I would like it to) then the compressed version cannot be expected to work properly.

I would appreciate any suggestions.

Thanks . . .

Phil Troy

Philip M. Troy, Ph.D.

Process & Quantitative Decision Support/Systems Analyst
Les Entreprises TROYWARE
Phil at PhilTroy.com

Adjunct Professor of Surgery
McGill University
philip.troy at mcgill.ca

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