I found this example
ffmpeg -i input.mkv -filter:v "setpts=0.5*PTS" output.mkv
but I have a video I want to speed up by 60 times, not just 2X.
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Simply multiply by the reciprocal of the speed factor.
ffmpeg -i input.mkv -filter:v "setpts=PTS/60" output.mkv
This does not affect the audio speed. Use
-an to not include audio in the output.
A faster method, but which can have unexpected results with audio (pauses or async):
ffmpeg -itsscale 0.01666 -i input.mkv -c copy output.mkv
1/60 in decimal representation.
If you also want to speed up the audio, you need to do this:
ffmpeg -i input.mkv -filter_complex "[0:v]setpts=0.5*PTS[v];[0:a]atempo=2[a]" -map "[v]" -map "[a]" output.mkv
The command above works if you want to multiply by 2 the speed. If you want to multiply by any
x (between 0 and 100), the parameters become:
ffmpeg -i input.mkv -filter_complex "[0:v]setpts=1/<x>*PTS[v];[0:a]atempo=<x>[a]" -map "[v]" -map "[a]" output.mkv
For instance, if you want to multiply by 1.15, the command is
ffmpeg -i input.mkv -filter_complex "[0:v]setpts=0.87*PTS[v];[0:a]atempo=1.15[a]" -map "[v]" -map "[a]" output.mkv
For a stop-motion project where I wanted to reduce the delay between frames (instead of dropping frames), I wanted to speed up the audio and video many times beyond 2x too. For 60x speed, do the following. It may be a bit verbose, but it works great. The problem is that atempo cannot be greater than two or less than 0.5, so we must repeat atempo many times to get the sound to the rate that we want it.
ffmpeg -i input.mkv -filter:v "setpts=PTS/60" -filter:a "atempo=2,atempo=2,atempo=2,atempo=2,atempo=2,atempo=1.875" output.mkv
Press Ctrl+Shift+I, and click the "console" tab. In the console, to start typing/pasting text, click in the whitespace just right of the blue horizontal chevron (double chevron in FireFox). In Firefox, type
allow pasting into the console to allow copy'n'paste, then Ctrl+A then backspace to remove that text. Then, copy and paste this code into the console and press Enter to run. The code also works with slowing down the video.
var speed=eval(prompt("Enter speed up or slowdown factor (>1 is speedup, " + "<1 is slowdown; can use 1/X for slowdown): ", "60")); var k=speed, audio=""; while (2 < k && k === k) k /= 2, audio+="atempo=2,"; while (k < 0.5 && k === k) k *= 2, audio+="atempo=0.5,"; audio += "atempo=" + k; prompt( "Copy the following commandline: ", 'ffmpeg -i input.mkv -filter:v "setpts=PTS/' + speed + '" -filter:a "' + audio + '" output.mkv' );
This code will prompt you to enter a value and present you with the result. Entering
60 yields a 60X speedup, entering
0.1 yields a 10X slowdown, and entering
1/30 yields a 30X slowdown. I hope this helps.
For me, using
setpts in conjunction with
atempo left the audio rate low (and with low pitch).
What finally worked for me is:
#!/bin/sh # Note: First use ffprobe to get the audio rate. # Adjust below if it's not 48000. # The example below increases the speed of audio and video # rate by a factor of 4 (adjust as needed). # Sources: # https://superuser.com/questions/1261678/how-do-i-speed-up-a-video-by-60x-in-ffmpeg # https://stackoverflow.com/questions/53374590/ffmpeg-change-tone-frequency-pitch-audio ffmpeg -i $1 -filter:v "setpts=PTS/4" -af "asetrate=48000*4,aresample=48000" out.mp4