Bits & Bytes

Posts Tagged ‘example’

Signal Processing Sound Data in Actionscript 3.0

This program demonstrates how to perform a signal processing operation on sound data and play it back. If you left-click the box above, you can hear the clip saying “” that I have been using in the other examples played at double speed. Note that if you want to hear the clip played a second time, you need to refresh the page.

The code is shown below. The first three lines output the “Click To Play” message. The next two lines create two Sound objects. The two lines after those set an event listener that is called when the file loads and then call load() to load the mp3 file.

The remaining code consists of three functions. The first function, FinishedLoading(), is called when the file is loaded since it was set as the callback. The FinishedLoading() function sets PlaySound() as a callback function for mouse clicks. Doing this prevents the PlaySound() from being called before the sound file is loaded.

The second function, PlaySound(), sets the DoubleSpeed() function as a callback when data is requested for the destination sound. Then it calls play(), which triggers a series of data requests as the sound plays.

The third function, DoubleSpeed(), calls the extract() function to retrieve data into the source byte array. Inside the while loop, each pair of source samples is averaged and then written into the destination array. Finally, the destination byte array is written back into the SampleDataEvent object.

// Output the initial instructions to user
var qInstructions:TextField = new TextField();
qInstructions.text = "Click To Play";

var qSrc:Sound		= new Sound();
var qDest:Sound		= new Sound();

qSrc.addEventListener(Event.COMPLETE, FinishedLoading);
qSrc.load(new URLRequest(""));

function FinishedLoading(e:Event):void {
	stage.addEventListener(MouseEvent.CLICK, PlaySound);

function PlaySound(e:Event):void {
	qDest.addEventListener(SampleDataEvent.SAMPLE_DATA, DoubleSpeed);;

function DoubleSpeed(e:SampleDataEvent) {
	var qSrcBytes:ByteArray = new ByteArray();
	qSrc.extract(qSrcBytes, 8192);
	var qDestBytes:ByteArray = new ByteArray();
	var dLeft:Number = 0;
	var dRight:Number = 0;
	qSrcBytes.position = 0;
	// Read and average two samples
	while (qSrcBytes.bytesAvailable > 0) {
		dLeft = qSrcBytes.readFloat();
		dRight = qSrcBytes.readFloat();
		if (qSrcBytes.bytesAvailable > 0) {
			dLeft = (dLeft + qSrcBytes.readFloat())/2.0;
			dRight = (dRight + qSrcBytes.readFloat())/2.0;

Graphing Sound Data Visualizations in Actionscript 3.0

This program demonstrates how to retrieve and graph a set of samples of sound data. To see the program run, left-click the box above.

The code begins with three lines to output the click instructions. The next three lines create a Sound object, load an mp3 file, and set a callback for when the sound finishes playing. Then we create a ByteArray to store the sound data and set the StartSound() function as a callback for left-clicks.

The rest of the code consists of functions. The StartSound() function begins playing the sound and sets the callback function StartFrame() to get called for every frame of the animation. The SoundFinished() function stops StartFrame() from receiving messages after the sound is finished playing.

The function StartFrame() retrieves the sound data and graphs it. It begins with a call to the static function computeSpectrum() that returns 512 sound samples, 256 for each channel, in the ByteArray qSignal. Next, it clears the old graphics and sets the line style to a green line of width 1 pixel, and calls DrawSignal() twice, once for each channel.

Finally, the DrawSignal() function graphs each of the 256 sound samples. The graph is centered at the y-value dCenterY and the amplitude is scaled by 50 pixels. The scaling means that the samples, which range between -1 and 1, are scaled to the range -50 to 50. We begin each graph with a call to moveTo() so that no line is written from the previous position.

// Output the initial instructions to user
var qInstructions:TextField = new TextField();
qInstructions.text = "Click To Play";

var qSound:Sound = new Sound(); 
qSound.load(new URLRequest(""));
qSound.addEventListener(Event.SOUND_COMPLETE, SoundFinished);

var qSignal:ByteArray = new ByteArray();

stage.addEventListener(MouseEvent.CLICK, StartSound);

function StartSound(e:Event):void {
	var qSoundChannel:SoundChannel =;
	addEventListener(Event.ENTER_FRAME, StartFrame);

function SoundFinished(e:Event):void { 
	removeEventListener(Event.ENTER_FRAME, StartFrame); 

function StartFrame(e:Event):void {
	// Get the data for the left and right channels
	SoundMixer.computeSpectrum(qSignal, false, 0);
	graphics.lineStyle(1, 0x00FF00);
	// Graph the left channel on the top
	// Graph the right channel on the bottom

function DrawSignal(dCenterY:Number):void {
	graphics.moveTo(0, dCenterY + 50*qSignal.readFloat());
	for (var i:int = 1; i < 256; i++) { 
		graphics.lineTo(i, dCenterY + 50*qSignal.readFloat()); 

Loading and Playing a Sound File in Actionscript 3.0

This program loads an mp3 file and plays it. The entire program is given below and the compiled SWF is shown above. To hear the file play, left-click the window above.

The code begins with three lines that tell the user to click the screen. Then we create a String for the URL, which could also be a local file. Next, we set our function as the callback for mouse clicks. Inside the function OnClick(), we create a Sound object, load the sound file, and then play it.

// Output the initial instructions to user
var qInstructions:TextField = new TextField();
qInstructions.text = "Click To Play";

const ksXoaXDotNet:String = "";

// Play the mp3 when the screen is clicked
stage.addEventListener(MouseEvent.CLICK, OnClick);

function OnClick(e:MouseEvent): void {
	var qSound:Sound = new Sound();
	qSound.load(new URLRequest(ksXoaXDotNet));;