Question

Below is a snippet from the Adobe Live Docs SampleDataEvent class. It demonstrates how to create an audible sine wave by pushing samples into a ByteArray. The part that I am hung up on is why you need to push the same value into the writeFloat() method twice?

var mySound:Sound = new Sound();
function sineWaveGenerator(event:SampleDataEvent):void 
{
    for ( var c:int=0; c<8192; c++ ) {
        event.data.writeFloat( Math.sin((Number(c+event.position)/Math.PI/2))*0.25 );
        event.data.writeFloat( Math.sin((Number(c+event.position)/Math.PI/2))*0.25 );
    }
}

mySound.addEventListener(SampleDataEvent.SAMPLE_DATA,sineWaveGenerator);
mySound.play();

As a test, I removed one of the calls to writeFloat() and increased the buffer to 16384 samples ( twice the current ). This created an audible gap and click in the the audio, but didn’t enlighten me much as to why. Perhaps you can…

Thanks again 🙂

Answer 1

It takes two writes because it’s stereo. Each channel takes one sample. In this case, the value being written is the same, but if you wanted to pan the sound 100% to one side, for example, you could write the value with the first (or the second) writeFloat, and pass 0 to the other call.