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I try to create video with gource. I succeed with the following command line:

gource $LOG_FILE --log-format custom --stop-at-end --caption-file ${FILENAME}_captions.log --caption-duration 3 --title $TITLE --seconds-per-day 0.7 --auto-skip-seconds 1 --date-format\
 "%d/%m/%y" --hide "mouse,progress" --user-scale 0.6 --caption-size 20 -1380x950 -o - | ffmpeg -y -r 60 -f image2pipe -vcodec ppm -i - -vcodec libx264 -preset ultrafast -pix_fmt yuv420\
p -crf 1 -threads 4 -bf 0 $FILENAME.mp4

But the video are too big, 9Go for 4 min. How can I reduce the size with ffmpeg?

I use Fedora.

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2
  • Others answers already addressed your -crf 1, but -bf 0 makes little sense. x264 only uses B frames when they will help overall quality. If you need compat with ancient hardware players, use -profile baseline. (One case where x264's b-frame decisions aren't optimal (or weren't in 2009?) is a series of not-very-similar still pictures, where lots of I macroblocks are needed: forum.doom9.org/showthread.php?t=145005)
    – Peter Cordes
    Feb 24, 2015 at 23:53
  • Also, x264 auto-detects how many threads to use. Only use -threads if you want it not to saturate all your CPUs. (like if gource needs significant CPU time?)
    – Peter Cordes
    Feb 24, 2015 at 23:55

2 Answers 2

Reset to default
6

-preset

Use the slowest preset that is fast enough that it does not drop frames. You can see if ffmpeg is dropping frames in the console output (if I recall correctly). Presets are: ultrafast, superfast, veryfast, faster, fast, medium, slow, slower, veryslow.

-crf

Use the highest -crf value that still provides an acceptable quality level. Range is 0-51. 0 is lossless, 18 is generally considered to be visually lossless or nearly so, 23 is default, and 51 is worst quality. Using a value of 1 will likely result in a huge file.

Also see:

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  • Thanks a lot for the same input file the initial size was 1.3Go and now only 39Mo.
    – La Chamelle
    Sep 6, 2014 at 8:28
  • ultrafast for anything but lossless is a bad idea. -preset superfast -x264-params cabac=0 is MUCH better quality per bitrate (RD), and almost as fast.
    – Peter Cordes
    Feb 24, 2015 at 23:45
3

You specify a preset and a quality value at the same time and by that overriding the preset. I would also recommend you don't encode with ffmpeg while capturing as this would be pretty slow on most PCs.

The "error" in your ffmpeg commandline is the option -crf 1. CRF is a quality setting of x264 and the lower the value the higher the bitrate of the video will be. Setting it to 1 will make the video pretty much lossless. Just leave that command out and maybe use a preset like medium or slow and not ultrafast like you have right now to get a decent quality.

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