How to change audio frequency?

audio ffmpeg bitrate resampling

25,714

Solution 1

With ffmpeg:

ffmpeg -i <input> -af 'asetrate=44100*1/2,atempo=2/1' <output>

Here, 1/2 is the pitch factor. See the other answer for more details.

If you need a GUI, use Audacity, it's a free, open source, cross platform audio editing tool.

Features: Change the pitch without altering the tempo, or vice-versa.

As an alternative, try sox. Something like that:

sox <infile> <outfile> pitch <shift>

where gives the pitch shift as positive or negative ‘cents’ (i.e. 100ths of a semitone). There are 12 semitones to an octave, so that would mean ±1200 as a parameter.

Solution 2

Find input audio rate beforehand thus:

ffmpeg -i input.mp4

Assuming input audio rate 44,100 Hz, this command will do the job:

ffmpeg -i input.mp4 -af asetrate=44100*3/4,atempo=4/3 output.mp4

The factor of 3/4 will change most female and “skinny” (chipmunk) voices into male and “fat” voices. Use 4/3 for the opposite:

ffmpeg -i input.mp4 -af atempo=3/4,asetrate=44100*4/3 output.mp4

Notice reversed filter order to prevent signal degradation. Whenever possible, lossless operation should come before lossy operation. I’m not 100% sure whether I’m not making some mistake here from misunderstanding FFmpeg filters.

FFmpeg filter asetrate should have a variable named ir for input audio rate, in analogy to iw×ih in some video filters, but I couldn’t find any mention of it in the documentation.

For factors greater than 2 (such as 4/1 or 1/4), you must use multiple atempo filters (1/4 = 1/2 * 1/2 or 4/1 = 2/1 * 2/1):

ffmpeg -i input.mp4 -af asetrate=44100*4,atempo=1/2,atempo=1/2 output.mp4

I don’t know how to obtain “skinny” male voice and “fat” female voice.

Instead of -af, you can write -filter:audio or -filter:a.

References

25,714

Lord Tesla

Updated on September 18, 2022

Comments

Lord Tesla over 1 year

I want to change the frequency of an audio file. Meaning: the whole file should sound (say) one octave higher or lower. How to do it? Using ffmpeg or other command line open source tool would be preferable.
Lord Tesla almost 13 years

awesome... sox is just what i need!
mrgloom almost 5 years

Does method using ffmpeg change the duration of the audio?
slhck almost 5 years

@mrgloom No, it should not.
mrgloom almost 5 years

After using ffmpeg -i man.wav -af asetrate=48000*0.75,aresample=48000 man_pitch_down.wav I see by ffmpeg -i original wav Duration: 00:00:01.95, bitrate: 3080 kb/s and modified wav Duration: 00:00:02.60, bitrate: 1536 kb/s. As I understand Duration is length in seconds.
mrgloom almost 5 years

I have tried this solution (superuser.com/a/1076762/213959) and it produce audios with same length (looking at Duration from ffmpeg -i output)
F. Vosnim almost 4 years

@slhck you are wrong. As mrgloom said your ffmpeg line also changes duration af the audio.
F. Vosnim almost 4 years

@slhck It's 100% your example: ffmpeg -i <input> -af asetrate=44100*0.5,aresample=44100 <output> where asetrate changes sample rate to 22050 AND increases the duration by 2. Then aresample upsamples it to 44100 keeping increased duration the same. The asetrate documentation clearly says This will result in a change of speed and pitch.
slhck almost 4 years

@F.Vosnim You're right. This must have changed (note that my answer was posted in 2011) in the meantime. Fixed the post.
Xel Naga almost 3 years

Doesn't work...
JRichardsz almost 3 years

thank you so much!! worked at first attempt!!
parsecer about 2 years

Is speed changed as well? The speed of speech? Is there a way to increase voice pitch without increasing speech speed?