Inside Macintosh: Sound /

Chapter 6 - Audio Components

This chapter describes audio components, which are code modules used by the Sound Manager to adjust volumes or other settings of a sound output device. In general, you need to write an audio component only if you are developing a sound output device with multiple output ports that can be independently controlled by software. If your sound output device has only one software-controllable output port, the sound output device component for that device manages the volume levels of the port.

IMPORTANT

The Sound Manager loads and manages audio components, which operate transparently to applications. The routines described in this chapter are intended for use exclusively by audio components.

To use this chapter, you should already be familiar with writing sound output device components, as described in the chapter "Sound Components" in this book. Because audio components are components, you also need to be familiar with the Component Manager, described in Inside Macintosh: More Macintosh Toolbox.

This chapter begins by describing what audio components are and the Sound Manager uses them. Then it provides instructions on how to write an audio component. The section "Audio Components Reference" beginning on page 6-8 describes the routines that your audio component might need to define.

Note

Pascal interfaces for audio components are not currently available. As a result, this chapter provides all source code examples and reference materials in C.

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Chapter Contents

About Audio Components

Writing an Audio Component

Creating an Audio Component

Dispatching to Audio Component-Defined Routines

Audio Components Reference

Data Structures

Audio Information Records

Audio Component-Defined Routines

Getting and Setting Volumes

Managing the Mute State

Resetting Audio Components

Getting Audio Component Information

Summary of Audio Components

C Summary

Constants

Data Types

Audio Component-Defined Routines

Assembly-Language Summary

Data Structures