How to set audio speed to 0.3 in Ffmpeg?

Question

I am using ffmpeg to set the audio and video speed to 0.3x. I can set the video speed but can't set the audio speed to 0.3x. Here is the command

ffmpeg -y -i video.mp4 -vf "setpts=PTS/0.3" -r 50 -c:v mpeg4 -b:v 1500k -af "atempo=0.3" output.mp4

It says:

Value 0.300000 for parameter 'tempo' out of range [0.5 - 100]

Is there a workaround? Any help will be appreciated. Regards.

score 6 · Accepted Answer · answered Sep 15 '20 at 18:15

Use atempo + atempo:

ffmpeg -y -i video.mp4 -vf "setpts=PTS/0.3" -r 50 -c:v mpeg4 -b:v 1500k -af "atempo=0.6,atempo=0.5" output.mp4

Or use the rubberband filter for a better sounding output.

Or use the standalone rubberband tool:

rubberband -t 3 input.wav output.wav

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