Inside Macintosh: Sound /

Chapter 2 - Sound Manager

This chapter describes the Sound Manager, the part of the Macintosh system software that controls the production and manipulation of sounds on Macintosh computers. You can use the Sound Manager to create a wide variety of sounds and to manipulate sounds in many ways. The Sound Manager is also used by other parts of the Macintosh system software that produce sounds, such as the Speech Manager and QuickTime.

To use this chapter, you should already be familiar with the information in the chapter "Introduction to Sound on the Macintosh" earlier in this book, especially with the portions of that chapter that describe the Macintosh sound architecture and the routines related to sound output. That chapter shows how your application can play a sound resource or a sound file synchronously (that is, with other processing suspended while the sound plays).

You should read this chapter if you need a greater degree of control over sound output than the routines described in that introductory chapter provide. For example, if you want to play sounds asynchronously or to exercise very fine control over the process of sound production, this chapter contains information you need.

This chapter begins by describing the capabilities of the Sound Manager and the role of sound commands and sound channels in producing sound. Then it explains how you can use the Sound Manager to

• create and manage sound channels
• obtain information about available sound features and sound channels
• play notes and other sounds at various frequencies and volumes
• play one or more sounds asynchronously
• parse sound resources and sound files to obtain information about them
• compress and expand sound data
• use double buffers to bypass the normal play-from-disk routines

You're not likely to use all of these capabilities in a single application. In general, you should read the section "About the Sound Manager" and then turn to the parts of the section "Using the Sound Manager" that describe the features you want to use in your application. The section "Sound Storage Formats" beginning on page 2-73 explains in detail the format of sound resources and sound files. You can find a complete reference to the Sound Manager data structures and routines in the section "Sound Manager Reference" beginning on page 2-89.

IMPORTANT

This chapter describes the capabilities and programming interfaces of version 3.0 of the Sound Manager. See the chapter "Introduction to Sound on the Macintosh" for some information on how version 3.0 differs from earlier versions. The capabilities and performance of version 3.0 are significantly better than those of all previous Sound Manager versions, even though their programming interfaces are largely identical. This chapter occasionally warns you about techniques or routines that cannot be used in versions prior to 3.0, but it does not provide an exhaustive comparison of all available versions.

---

Chapter Contents

About the Sound Manager

Sound Data

Square-Wave Data

Wave-Table Data

Sampled-Sound Data

Sound Commands

Sound Channels

Sound Compression and Expansion

Using the Sound Manager

Managing Sound Channels

Allocating Sound Channels

Initializing Sound Channels

Releasing Sound Channels

Manipulating a Sound That Is Playing

Stopping Sound Channels

Pausing and Restarting Sound Channels

Synchronizing Sound Channels

Managing Sound Volumes

Obtaining Sound-Related Information

Obtaining Information About Available Sound Features

Obtaining Version Information

Testing for Multichannel Sound and Play-From-Disk Capabilities

Obtaining Information About a Single Sound Channel

Obtaining Information About All Sound Channels

Determining and Changing the Status of the System Alert Sound

Playing Notes

Installing Voices Into Channels

Looping a Sound Indefinitely

Playing Sounds Asynchronously

Using Callback Procedures

Synchronizing Sound With Other Actions

Managing an Asynchronous Play From Disk

Playing Selections

Managing Multiple Sound Channels

Parsing Sound Resources and Sound Files

Obtaining a Pointer to a Sound Header

Playing Sounds Using Low-Level Routines

Finding a Chunk in a Sound File

Compressing and Expanding Sounds

Using Double Buffers

Setting Up Double Buffers

Writing a Doubleback Procedure

Sound Storage Formats

Sound Resources

The Format 1 Sound Resource

The Format 2 Sound Resource

Sound Files

Chunk Organization and Data Types

The Form Chunk

The Format Version Chunk

The Common Chunk

The Sound Data Chunk

Format of Entire Sound Files

Sound Manager Reference

Constants

Gestalt Selector and Response Bits

Channel Initialization Parameters

Sound Command Numbers

Chunk IDs

Data Structures

Sound Command Records

Audio Selection Records

Sound Channel Status Records

Sound Manager Status Records

Sound Channel Records

Sound Header Records

Extended Sound Header Records

Compressed Sound Header Records

Sound Double Buffer Header Records

Sound Double Buffer Records

Chunk Headers

Form Chunks

Format Version Chunks

Common Chunks

Extended Common Chunks

Sound Data Chunks

Version Records

Leftover Blocks

State Blocks

Sound Manager Routines

Playing Sound Resources

Playing From Disk

Allocating and Releasing Sound Channels

Sending Commands to a Sound Channel

Obtaining Information

Controlling Volume Levels

Compressing and Expanding Audio Data

Managing Double Buffers

Performing Unsigned Fixed-Point Arithmetic

Linking Modifiers to Sound Channels

Application-Defined Routines

Completion Routines

Callback Procedures

Doubleback Procedures

Resources

The Sound Resource

Summary of the Sound Manager

Pascal Summary

Constants

Data Types

Sound Manager Routines

Application-Defined Routines

C Summary

Constants

Data Types

Sound Manager Routines

Application-Defined Routines

Assembly-Language Summary

Data Structures

Trap Macros

Result Codes