// Create shader
[Embed(source="mixer.pbj", mimeType="application/octet-stream")]
var MixerShader:Class;
var mixerShader:Shader = new Shader(new MixerShader());

// buffers will become shader inputs
var buffer:Vector.<ByteArray> = new Vector.<ByteArray>(15);
// volume control volume on each track, 1.0 is full volume
var volume:Vector.<Number> = new Vector.<Number>(15);

// initialize the shader inputs and volume values
for (var j:int = 0; j < 15; j++) {
  volume[j]=1.0;
  buffer[j] = new ByteArray();
  // set so shader will always work even we have not enough tracks
  buffer[j].length = BUFFER_SIZE*4*2; 
  mixerShader.data["track"+j]["width"] = 1024;
  mixerShader.data["track"+j]["height"] = BUFFER_SIZE/1024;
  mixerShader.data["track"+j]["input"] = buffer[j];
}

function onSoundData(e:SampleDataEvent) : void
{
  // extract the mp3 data into our shader inputs
  for (var i:int = 0; i < NUM_TRACKS; i++) {
    buffer[i].position = 0;
    sounds[i].extract(buffer[i], BUFFER_SIZE); 
    buffer[i].position = 0;
  }
  // update the volume value in the shader
  for (var k:int = 0; k < NUM_TRACKS; k++)  {
    mixerShader.data["volume"+k]["value"] = [ volume[k], volume[k] ];
  }
  // mix!
  var mixerJob:ShaderJob = new ShaderJob(mixerShader, e.data, 1024, BUFFER_SIZE/1024);
  mixerJob.start(true);
}