Learning Core Audio A Hands-On Guide to Audio Programming for Mac and iOS

by Adamson, Chris; Avila, Kevin

• ISBN13: 9780321636843
• ISBN10: 0321636848
• Edition: 1st
• Format: Paperback
• Copyright: 2012-03-30
• Publisher: Addison-Wesley Professional

Summary

The only guide to Apple's powerful Core Audio framework. Introduces the essential concepts of Mac and iOS audio programming. Task-based coverage explains everything from playing files to digital effects, with detailed sample code. Covers sophisticated techniques, including the creation of 3D sound output for desktop and iOS applications. Co-author Kevin Avila is one of the formeost authorities on Core Audio. Written by two of the world's leading audio programmers, this book is the definitive resource for understanding Apple's Core Audio framework. It fills an enormous gap in the marketplace, providing the practical and accessible learning materials that Core Audio developers have never had. The book begins with a complete introduction to generic digital audio concepts, written to be accessible to the vast majority of developers who've never programmed audio before. It takes high-level look at how Core Audio implements these concepts, presents common 'use cases' for Core Audio, and discusses crucial trade-offs between audio quality, performance, and file size. Next, the authors drill down to each specific task Core Audio developers are likely to perform; tasks such as recording and playing audio, controlling audio files, transcoding between formats, and adding digital effects. They thoroughly explain the relevant API, demonstrating each concept with usable sample code, and offer the insight and context needed to truly adapt that code to fit realworld projects. Building on the basics, the authors introduce several advanced audio development techniques, including programming 3D audio with OpenAL to deliver surround sound output in both Mac and iOS applications. The book also covers Core MIDI, a subset of the Core Audio framework, which can be used to control MIDI devices.

Author Biography

Chris Adamson is an independent writer, editor, and developer who specializes in iOS and Mac development. He is coauthor of iOS SDK Development and author of QuickTime for Java: A Developer's Notebook, Kevin Avila has more than 15 years experience developing for the Mac and, since its release, the iPhone. Kevin has been involved in every corner of the audio market, from being an engineer at Apple to configuring professional recording studios. He currently is a code-mercenary for various clients while sitting in his underwear at home, sipping coffee.

Table of Contents

About the Authors	p. xiii
Foreword	p. xv
Introduction	p. 1
Audience for This Book	p. 2
What You Need to Know	p. 3
Looking Up Documentation	p. 3
How This Book Is Organized	p. 5
About the Sample Code	p. 9
Understanding Core Audio
Overview of Core Audio	p. 13
The Core Audio Frameworks	p. 14
Core Audio Conventions	p. 15
Your First Core Audio Application	p. 16
Running the Example	p. 19
Core Audio Properties	p. 22
Summary	p. 23
The Story of Sound	p. 25
Making Waves	p. 25
Digital Audio	p. 27
DIY Samples	p. 32
Buffers	p. 40
Audio Formats	p. 40
Summary	p. 41
Audio Processing with Core Audio	p. 43
Audio Data Formats	p. 43
Example: Figuring Out Formats	p. 46
Canonical Formats	p. 51
Processing Audio with Audio Units	p. 53
The Pull Model	p. 55
Summary	p. 55
Basic Audio
Recording	p. 59
All About Audio Queues	p. 59
Building a Recorder	p. 60
A CheckError() Function	p. 63
Creating and Using the Audio Queue	p. 64
Utility Functions for the Audio Queue	p. 71
The Recording Audio Queue Callback	p. 75
Summary	p. 78
Playback	p. 81
Defining the Playback Application	p. 81
Setting Up a File-Playing Audio Queue	p. 83
Setting Up the Playback Buffers	p. 85
Starting the Playback Queue	p. 88
Playback Utility Functions	p. 89
Handling the Magic Cookie	p. 89
Calculating Buffer Size and Expected Packet Count	p. 90
The Playback Audio Queue Callback	p. 91
Features and Limits of Queue-Based Playback	p. 94
Summary	p. 95
Conversion	p. 97
The afconvert Utility	p. 97
Using Audio Converter Services	p. 100
Setting Up Files for Conversion	p. 102
Calling Audio Converter Services	p. 105
Implementing the Converter Callback	p. 109
Converting with Extended Audio File Services	p. 112
Reading and Converting with Extended Audio Files	p. 116
Summary	p. 118
Advanced Audio
Audio Units: Generators, Effects, and Rendering	p. 123
Where the Magic Happens	p. 123
How Audio Units Work	p. 124
Sizing Up the Audio Units	p. 126
Your First Audio Units	p. 129
Building the main() Function	p. 131
Creating an Audio Unit Graph	p. 133
Setting Up the File Player Audio Unit	p. 137
Speech and Effects with Audio Units	p. 141
Building Blocks of the Speech Synthesis Graph	p. 142
Creating a Speech Synthesis AUGraph	p. 144
Setting Up a Speech Synthesizer	p. 146
Adding Effects	p. 147
Adding Your Code to the Audio Rendering Process	p. 150
The Audio Unit Render Cycle	p. 150
A Custom Rendering Example	p. 151
Creating and Connecting Audio Units	p. 154
The Render Callback Function	p. 155
Summary	p. 160
Audio Units: Input and Mixing	p. 161
Working with I/O Input	p. 161
Connecting Input and Output Units	p. 164
Creating an AUHAL Unit for Input	p. 168
Writing the Input Callback	p. 176
Building an AUGraph to Play Samples from a CARingBuffer	p. 178
Writing the Play-Through App's Render Callback	p. 181
Running the Play-Through Example	p. 182
Mixing	p. 183
Summary	p. 189
Positional Sound	p. 191
Sound in Space	p. 191
The OpenAL API	p. 193
Putting a Sound in Space	p. 196
Setting Up the Example	p. 197
Using OpenAL Objects	p. 200
Animating the Source's Position	p. 205
Loading Samples for an OpenAL Buffer	p. 206
Streaming Audio in OpenAL	p. 210
Setting Up the OpenAL Streaming Example	p. 210
Setting Up an ExtAudioFile for Streaming	p. 215
Refilling the OpenAL Buffers	p. 217
Summary	p. 220
Additional Topics
Core Audio on iOS	p. 223
Is That Core Audio in Your Pocket?	p. 223
Playing Nicely with Others: Audio Session Services	p. 224
An Audio Session Example	p. 227
Setting Up the App	p. 227
Initializing the Audio Session and Audio Queue	p. 231
The Tone Generator Method	p. 234
Handling iOS Interruptions	p. 236
Audio Units on iOS	p. 238
Building an Audio Pass-Through App with the iOS RemoteIO Unit	p. 239
Setting Up the Pass-Through Example	p. 241
Setting Up the RemoteIO Audio Unit for Capture and Play-Out	p. 244
The RemoteIO Render Callback	p. 249
Other iOS Audio Tricks	p. 253
Remote Control on iOS	p. 253
iOS Hardware Hazards	p. 254
Summary	p. 254
Core MIDI	p. 257
MIDI Concepts	p. 257
Core MIDI	p. 258
Core MIDI Architecture	p. 258
Core MIDI Terminology	p. 258
Core MIDI Properties	p. 260
MIDI Messages	p. 260
Instrument Units	p. 261
Building a Simple MIDI Synthesizer	p. 262
Connecting to MIDI	p. 265
Handling MIDI Notifications and Events	p. 267
Playing Your AUGraph	p. 269
Creating MIDI Events	p. 269
Setting Up the MIDIWifiSource Example	p. 269
Setting Up MIDI over Wi-Fi	p. 271
Sending MIDI Messages	p. 273
Setting Up Your Mac to Receive Wi-Fi MIDI Data	p. 275
Summary: MIDI Mastery … but Mobility?	p. 277
Coda	p. 279
Still More Core Audio	p. 279
Next Steps	p. 280
Digital Signal Processing	p. 280
Lion and iOS 5	p. 281
AUSampler	p. 281
Core Audio on iOS 5	p. 285
The Core Audio Community	p. 286
Summary: Sounds Good	p. 287
Index	p. 289
Table of Contents provided by Ingram. All Rights Reserved.