Phonegap mixing audio files

Question

I\'m building a karaoke app using Phonegap for Ios.

I have audio files in the www/assets folder that I am able to play using the media.play()function

This al

Answer 1

I would suggest to mix the PCM directly. If you initialize a buffer that overlaps the time frames of both tracks, then the formula is additive:

mix(a,b) = a+b - a*b/65535.

This formula depends on unsigned 16bit integers. Here's an example:

SInt16 *bufferA, SInt16 *bufferB;
NSInteger bufferLength;
SInt16 *outputBuffer;

for ( NSInteger i=0; i 0 && bufferB[i] > 0 ) {
    // If both samples are positive, mixed signal must have an amplitude between the greater of
    // A and B, and the maximum permissible positive amplitude
    outputBuffer[i] = (bufferA[i] + bufferB[i]) - ((bufferA[i] * bufferB[i])/INT16_MAX);
  } else {
    // If samples are on opposite sides of the 0-crossing, mixed signal should reflect 
    // that samples cancel each other out somewhat
    outputBuffer[i] = bufferA[i] + bufferB[i];
  }
}

This can be a very effective way to handle signed 16 bit audio. Go here for the source.