I have managed to play audio files using ffmpeg and AudioTrack class in my android project. I can change the speed of audio using AudioTrack class setRate method. But it also change the pitch of audio, I want to change only Tempo of audio but I found no solution on net.
anyone can please help me on this as there is no support for this.
Solution : I tried SoundTouch library. I compiled it successfully for android but then I failed to use its function because I don't know how to use this library to load audio.
But after that I tried library called Sonic. Its basically for Speech as it use PSOLA algo to change pitch and tempo. But its ok.
You can use the atempo filter in ffmpeg 1.0 and later:
ffmpeg -i input.wav -f:a atempo=1.25 output.wav
atempo only accepts values between 0.5 and 2.0, but you can bypass the limitation by chaining multiple filters:
ffmpeg -i input.wav -f:a atempo=2,atempo=1.5 output.wav
Pitch and tempo are very strongly linked. What you're trying to do is called "time stretching", and is a somewhat complicated algorithm. You can find information online about it, and a java library for it can be found here, along with a paper describing the process.
来源：https://stackoverflow.com/questions/11260043/how-to-change-audio-tempo-and-pitch-individuality-using-ffmpeg