ADOBE® FLEX® 3: PROGRAMMING ACTIONSCRIPT™ 3.0

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Chapter 21: Working with sound

ActionScript™ is made for immersive, interactive applications—and one often overlooked element of powerfully

immersive applications is sound. You can add sound effects to a video game, audio feedback to an application user

interface, or even make a program that analyzes mp3 files loaded over the Internet, with sound at the core of the

application.

In this chapter, you’ll learn about loading external audio files and working with audio that’s embedded in a SWF.

You’ll learn to control the audio, to create visual representations of the sound information, and to capture sound from

a user’s microphone.

Contents

Basics of working with sound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 424

Understanding the sound architecture. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 426

Loading external sound files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 427

Working with embedded sounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 429

Working with streaming sound files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 430

Playing sounds. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 431

Security considerations when loading and playing sounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 434

Controlling sound volume and panning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 435

Working with sound metadata . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 436

Accessing raw sound data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437

Capturing sound input. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 440

Example: Podcast Player . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 443

Basics of working with sound

Introduction to working with sound

Just as computers can encode images in a digital format, store them on a computer, and retrieve them to display on

the screen, computers can capture and encode digital audio—computer representation of sound information—and

can store it and retrieve it to play back over speakers connected to the computer. You can play back sound using either

Adobe® Flash® Player or Adobe® AIR™ and ActionScript.

When sound data is converted to digital form, it has various characteristics, such as the sound’s volume and whether

it is stereo or mono sound. When you play back a sound in ActionScript, you can adjust these characteristics as

well—make the sound louder, or make it seem to be coming from a certain direction, for instance.

Before you can control a sound in ActionScript, you need to have the sound information loaded into Flash Player or

AIR. There are four ways you can get audio data into Flash Player or AIR so that you can work with it using Action-

Script. You can load an external sound file such as an mp3 file into the SWF; you can embed the sound information

into the SWF file directly when it’s being created; you can get audio input using a microphone attached to a user’s

computer, and you can access sound data that’s streamed from a server.

When you load sound data from an external sound file, you can begin playing back the start of the sound file while

the rest of the sound data is still loading.