Is it possible to speed up video with audio using ffmpeg, without changing audio pitch?

Question

Is there a relatively simple way to speed up a video (mp4, with aac encoded audio), by say "x1.25" or "x1.3" while keeping the original audio-video sync, but also retaining the original pitch of the audio ?

I've read some discussions about extracting audio track into separate file, then use rubberband to lower the pitch by the requisite value, and then merge the audio video tracks using ffmpeg with speed-up, which raises the pitch of the audio back again to original. However, it appears that this is a bit of hit-n-miss, because rubberband appears to use number of octaves as the parameter to raise or lower pitch, and this may not always align perfectly with the video, as musical notes / octaves have specific ratios. Also, this is cumbersome.

So, is there any simpler ways using ffmpeg alone ?

rubberband offers a tempo option which takes in a decimal number. — Gyan, May 21 '18 at 06:03
Thanks @Gyan. Sounds like a valid answer, even if it is not as simple as I'd hope it to be, but removes the issue of rubberband being (wrongly presumed to be) limited to pitch change based on number of notes (of a chromatic scale). — bdutta74, May 21 '18 at 06:20
rubberband can be compiled as a ffmpeg filter, so no need to extract audio. — Gyan, May 21 '18 at 06:42

score 44 · Accepted Answer · edited Feb 25 '22 at 11:04

44

It can be done with ffmpgeg using a complex filter:

  ffmpeg -i input.mkv -filter_complex "[0:v]setpts=0.5*PTS[v];[0:a]atempo=2.0[a]" -map "[v]" -map "[a]" output.mkv

Documentation: 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>, 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

edited Feb 25 '22 at 11:04

cssyphus

1,172

answered Jan 15 '19 at 22:08

Weidenrinde

606

if i want to slow my video and audio down by exactly half, would atempo=0.5 and setpts=1.5 ?? – nomaam Sep 12 '21 at 02:59
2

For half speed: atempo=0.5 and setpts=2 – Weidenrinde Sep 13 '21 at 07:20
@Weidenrinde Why doesn't this work: [0:a]asetpts=PTS*0.5[a] ??? – Ricardo Bohner Jun 10 '22 at 22:34
@RicardoBohner If I try that, I don´t receive any audio. Does it work for you? – Weidenrinde Jun 13 '22 at 17:31
@Weidenrinde No it doesn't but in my head it's the equivalent of [0:v]setpts=PTS*0.5[v] what works to speed up the vídeo I wonder why it doesn't work for audio the same way. – Ricardo Bohner Jun 13 '22 at 18:15
With ffmpeg version 4.4 I got the audio sped up to 1.25 but the video stayed the same length. The answer by @sagunms did both. – Bill McGonigle Jun 24 '22 at 11:54

sagunms · Answer 2 · 2021-09-16T03:03:02.330

You can speed up video by 2.5X for example by doing this:

ffmpeg -i "input_video.mp4" -vf "setpts=(PTS-STARTPTS)/2.5" -af atempo=2.5 "input_video_2.5X.mp4"

Here is a bash script you can use for convenience (say convert_video.sh):

#!/bin/bash
Arguments
FILE_RAW=$1
SPEED_FACTOR=${2:-1.0} # Default is 1.0 X speed
Prepare variables
BASE_PATH=$(dirname $(readlink -f $FILE_RAW))
FILENAME_EXT="$(basename "${FILE_RAW}")"
FILENAME_ONLY="${FILENAME_EXT%.}"
EXT_ONLY="${FILENAME_EXT#.}"
FILENAME_ONLY_PATH="${BASE_PATH}/${FILENAME_ONLY}"
Speed up/slow down video
ffmpeg -i "${FILENAME_ONLY_PATH}.${EXT_ONLY}" -vf "setpts=(PTS-STARTPTS)/${SPEED_FACTOR}" -af atempo=$SPEED_FACTOR "${FILENAME_ONLY_PATH}_${SPEED_FACTOR}X.${EXT_ONLY}"

Note: Make script executable: chmod +x convert_video.sh

Usage (Output File: <PATH_TO_INPUT_VIDEO>_<OPTIONAL_SPEED>X.mp4)

. <PATH_TO_THIS_SCRIPT>/convert_video.sh <PATH_TO_INPUT_VIDEO> <OPTIONAL_SPEED>

Example 1: Speed up video to 2.5X (Output: ~/Videos/input_video_2.5X.mp4)

. ~/convert_video.sh ~/Videos/input_video.mp4 2.5

Example 2: Slow down video to 0.5X (Output: ~/Videos/input_video_0.5X.mp4)

. ~/convert_video.sh ~/Videos/input_video.mp4 0.5

Hope it helps.

WFM with ffmpeg version 4.4 . Thanks. – Bill McGonigle Jul 06 '22 at 17:45 — Bill McGonigle, Jul 06 '22 at 17:45

score 2 · Answer 3 · answered Oct 11 '22 at 16:45

2

The code I used.

speed_change(){
    input=$1
    output=$2
    a_speed=$3
    v_speed=$(awk -v a_speed=$a_speed 'BEGIN{print 1/a_speed}')
    echo -e "\nSpeed up ${a_speed}X, para to atempo is ${a_speed}, para to setpts is ${v_speed}.\n"
    ffmpeg -i $input -c:v hevc_videotoolbox -vf "setpts=$v_speed*PTS" -af atempo=$a_speed $output
}

answered Oct 11 '22 at 16:45

HuoJnx

21

1

Code without any explanation is useless. Can you elaborate on this a little more? – Toto Oct 11 '22 at 17:07

Is it possible to speed up video with audio using ffmpeg, without changing audio pitch?

3 Answers3

Arguments

Prepare variables

Speed up/slow down video

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