I am developing a sound related application. I am trying to change the audio sound in to completely different like robot sound or make the audio echo. I tried with soundpool , but no any idea, anyone knows how to achieve that? i need only a basic idea to achieve this, please help. many thanks.
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Pitch and echo are 2 different things.
Pitch:
You can alter the pitch by modifing the playback rate. You can do it in 2 ways, with audioTrack and setPlayBackRate or with SoundPool and setRate. Depends on your needs, AudioTrack allow a larger range of pitch (from 1hz to x2) on large files and SoundPool for sound effects and picth can vary between x0.5 and x2.
Echo/reverb:
You can archive this with AudioEffect since API lvl 9 by attaching it to an AudioTrack or MediaPlayer instance.
Damien Praca
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For a robot effect you want to set a constant pitch for the audio. I.e. do a FFT, move everything into a single frequency bin, and then do an inverse FFT to get back into the time domain.
For an echo effect you could keep a separate buffer which is as long as your desired echo delay. And for every sample do something like the following (pseudo-code):
output = mix(currentSample, echoBuffer[echoPos]*echoVolume)
echoBuffer[echoPos] = mix(currentSample, echoBuffer[echoPos]*echofeedback)
echoPos += 1
Michael
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Im working on a similar project and i can say that you need to look into DSP (digital signal processing), PCM 16 format and preferably fourier transforms.
It is possible to loopback audio with the AudioRecord class (running a thread constantly filling the buffer on a AudioTrack)
But the delay might be too big for what you are trying to accomplish.
Best of luck in your endevours!
Some really good pointers: Android AudioRecord class - process live mic audio quickly, set up callback function
