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ffmpeg recipes

Here I save things I do with ffmpeg, in case I need it in the future.

Video speed

Speed up 4x using setpts filter

ffmpeg -i GH010117.MP4 -r 16 -filter:v "setpts=0.25*PTS" -an GH010117.4x.mp4
  • -an removes audio too.

Cut video

ffmpeg -ss 00:00:22.0 -i GH010112.MP4 -c copy -t 00:04:00.0 GH010112.cut.mp4
  • -ss starting time, 22 seconds.
  • -t run time, can be omitted to run until end of video.

Drawtext filter

This is not regarding subtitles, only for example to show how many times you've sped up a video by imposing a ''x4'' on it.

Find out if ffmpeg is compiled with support for drawtext

You should see three things colored by grep in this output.

ffmpeg -h 2>&1|grep --color -E '(libfreetype|fontconfig|libfribidi)'

Add simple text string

Here I just add the text x4 starting at pixel 300x300 in x/y axis.

ffmpeg -i GH010117.x4.mp4 -vf "drawtext=text='x4':x=300:y=300:fontsize=42:fontcolor=white" GH010117.x4.text.mp4

I tried combining this filter with another filter like setpts to slow down a video but the result was unexpected so I found it best to do it in two runs.

Position text relative to x axis

  • This uses a pre-defined variable called dar to determine the text position in the y axis, relative to the x axis.

    ffmpeg -i GH010122.cut1.mp4 -vf "drawtext=text='cleaning noises':x=240:y=x/dar:fontsize=42:fontcolor=white" GH010122.cut1.text.mp4

Fade in and out text at specific interval

ffmpeg -i GH010122.cut4.x4.mp4 -filter_complex "drawtext=text='x4 speed':x=240:y=x/dar:fontsize=42:fontcolor=white:enable='between(t,0,57)',fade=t=in:start_time=0:d=0.5:alpha=1,fade=t=out:start_time=56.5:d=0.5:alpha=1[fg];[0][fg]overlay=format=auto,format=yuv420p" GH010122.cut4.x4.text.mp4
  • This uses the standard parameter enable that is not part of drawtext but many filters support using it.
  • I stole this from Stackoverflow so it's over my head but take note of the seconds 0 and 57 that are start and stop times for the text.
  • Additionally 0.5 and 56.5 are start and stop interval for the fade in, and fade out, respectively.

See also

Last update: September 11, 2021