81

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.

0

6 Answers 6

108

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

where 0.01666 is 1/60 in decimal representation.

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  • 15
    While the playback speed seems to be changed for this, the video duration seems to be represented incorrectly; e.g., a 3 minute video sped up 3x will still show as being 3 minutes long. If you play it in a video player (e.g., VLC) the video will only take up the first minute and then freeze on a frame for the remaining 2 minutes.
    – jrh
    Nov 19, 2018 at 21:55
  • 1
    Does it have audio?
    – Gyan
    Nov 20, 2018 at 5:45
  • 11
    It does make sense that ffmpeg would leave the full length of the video because there was still audio data. Good catch, it turns out, it did have audio (my speakers were muted). With the -an parameter, the length of the video is set properly.
    – jrh
    Nov 20, 2018 at 18:12
  • 5
    Yes, video playback speed is governed by packet metadata. 60x is a very high speed up and players will usually choke. You'll see more expected results with, say, a 6x speed up. Players can't "skip" frames in a compressed video bitstream since almost all frames depend on one or more surrounding frames for decoding. So, you have to drop frames and re-encode i.e. a timelapse, e.g. ffmpeg -i input -vf framestep=60,setpts=N/30/TB -r 30 -an out.mp4
    – Gyan
    Feb 25, 2020 at 4:15
  • 2
    There's a large difference in these two methods in terms of file size, at least for my specific movie. The former outputs a video that's ~100x smaller, while the latter outputs a file that's the same size as the original. Mar 29, 2020 at 0:20
32

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

Docs: https://trac.ffmpeg.org/wiki/How%20to%20speed%20up%20/%20slow%20down%20a%20video

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
2
8

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.

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  • 1
    In "atempto=1.875", would atempto be atempo?
    – Harry
    Jan 4, 2021 at 23:02
  • @Harry You are absolutely correct. Thank you so much for finding that typo.
    – Jack G
    Jan 5, 2021 at 0:46
1

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
0

Only for video, like timelapses:

ffmpeg -i input.mp4 -map 0:v -c:v copy -bsf:v h264_mp4toannexb raw.h264

ffmpeg -fflags +genpts -r 30 -i raw.h264 -c:v copy output.mp4
0

This will only work on 4.4 and up:

ffmpeg -i input.mkv -bsf:v setts=TS/60 -af atempo=60 -c copy output.mkv
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