How to calculate the audio amplitude in real time (android)

Question

I am working on an Android app where I need to calculate the audio amplitude in real time. As of now I am using MediaPlayer to play the track. Is t

Answer 1

Your problem lies in the improper conversion of 16-bit samples to double precision. First you need to convert two adjacent bytes to an int and then do the conversion to double. For example

double amplitude = 0;
for (int i = 0; i < audioData.length/2; i++) {
    double y = (audioData[i*2] | audioData[i*2+1] << 8) / 32768.0
    // depending on your endianness:
    // double y = (audioData[i*2]<<8 | audioData[i*2+1]) / 32768.0
    amplitude += Math.abs(y);
}
amplitude = amplitude / audioData.length / 2;

Please note that your code and my answer are both assuming one channel of data. If you have more than one channel you'll need to be careful to separate the amplitudes as the data will be interleaved L,R,L,R (after the conversion to double).