[FFmpeg-devel] Atempo limits

Pavel Koshevoy pkoshevoy at gmail.com
Tue Jun 5 03:00:20 EEST 2018

On 06/04/2018 12:09 PM, Ronak wrote:
> Hello,
> How are you all?
> We are looking to use the atempo filter for our audio files. However, the limit between 0.5 - 2x is too restrictive for us. We would like to expand the limit to 0.5x - 3x.
> I tried changing the range in atempo.c and the rest of the tempo filter just worked.

Going below 0.5 is likely not going to sound good. Going above 2.0 should be 
fine.  The reason for current [0.5, 2.0] range is mostly for symmetry. 
atempo=0.5 followed by atempo=2.0 should sound like original audio.  This should 
also point you to an alternative solution -- put 2 atempo filters one after 
another to achieve tempo greater than 2  (atempo=2.0,atempo=1.5), or like this:

ffmpeg -i /scratch/Music/02\ Feeling\ Good.mp3 -af 
'atempo=sqrt(3.0),atempo=sqrt(3.0)' -y /tmp/tempo-3x.wav


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