Audio can affect the human brain in the most powerful and profound ways. Using Apple’s Core Audio, you can leverage all that power in your own Mac and iOS software, implementing features ranging from audio capture to real-time effects, MP3 playback to virtual instruments, web radio to VoIP support. The most sophisticated audio programming system ever created, Core Audio is not simple. In Learning Core Audio, top Mac programming author Chris Adamson and legendary Core Audio expert Kevin Avila fully explain this challenging framework, enabling experienced Mac or iOS programmers to make the most of it. In plain language, Adamson and Avila explain what Core Audio can do, how it works, and how it builds on the natural phenomena of sound and the human language of audio. Next, using crystal-clear code examples, they guide you through recording, playback, format conversion, Audio Units, 3D audio MIDI connectivity, and overcoming unique challenges of Core Audio programming for iOS. Coverage includes: mastering Core Audio’s surprising style and conventions; recording and playback with Audio Queue; synthesizing audio; perform effects on audio streams; capturing from the mic; mixing multiple streams; managing file streams; converting formats; creating 3D positional audio; using Core MIDI on the Mac; leveraging your Cocoa and Objective-C expertise in Core Audio’s C-based environment, and much more. When you’ve mastered the “black arts” of Core Audio, you can do some serious magic. This book will transform you from an acolyte into a true Core Audio wizard.

Table of Contents:
About the Authors     xiii Foreword  by Mike Lee  xv Introduction     1    Audience for This Book     2    What You Need to Know     3    Looking Up Documentation     3    How This Book Is Organized     5    About the Sample Code     9   PART I: UNDERSTANDING CORE AUDIO Chapter 1  Overview of Core Audio     13 The Core Audio Frameworks     14 Core Audio Conventions     15 Your First Core Audio Application     16    Running the Example     19 Core Audio Properties     22 Summary     23   Chapter 2  The Story of Sound     25 Making Waves     25 Digital Audio     27 DIY Samples     32 Buffers     40 Audio Formats     40 Summary     41   Chapter 3  Audio Processing with Core Audio     43 Audio Data Formats     43    Example: Figuring Out Formats     46 Canonical Formats     51 Processing Audio with Audio Units     53 The Pull Model     55 Summary     55   PART II: BASIC AUDIO Chapter 4  Recording     59 All About Audio Queues     59 Building a Recorder     60 A CheckError() Function     63 Creating and Using the Audio Queue     64 Utility Functions for the Audio Queue     71    The Recording Audio Queue Callback     75 Summary     78   Chapter 5  Playback     81 Defining the Playback Application     81 Setting Up a File-Playing Audio Queue     83    Setting Up the Playback Buffers     85    Starting the Playback Queue     88 Playback Utility Functions     89    Handling the Magic Cookie     89    Calculating Buffer Size and Expected Packet Count     90 The Playback Audio Queue Callback     91 Features and Limits of Queue-Based Playback     94 Summary     95   Chapter 6  Conversion     97 The afconvert Utility     97 Using Audio Converter Services     100 Setting Up Files for Conversion     102    Calling Audio Converter Services     105    Implementing the Converter Callback     109 Converting with Extended Audio File Services     112    Reading and Converting with Extended Audio Files     116 Summary     118   PART III: ADVANCED AUDIO Chapter 7  Audio Units: Generators, Effects, and Rendering     123 Where the Magic Happens     123 How Audio Units Work     124 Sizing Up the Audio Units     126 Your First Audio Units     129    Building the main() Function     131    Creating an Audio Unit Graph     133    Setting Up the File Player Audio Unit     137 Speech and Effects with Audio Units     141    Building Blocks of the Speech Synthesis Graph     142    Creating a Speech Synthesis AUGraph     144    Setting Up a Speech Synthesizer     146    Adding Effects     147 Adding Your Code to the Audio Rendering Process     150    The Audio Unit Render Cycle     150    A Custom Rendering Example     151    Creating and Connecting Audio Units     154    The Render Callback Function     155 Summary     160   Chapter 8  Audio Units: Input and Mixing     161 Working with I/O Input     161    Connecting Input and Output Units     164    Creating an AUHAL Unit for Input     168    Writing the Input Callback     176    Building an AUGraph to Play Samples from a CARingBuffer     178    Writing the Play-Through App’s Render Callback     181    Running the Play-Through Example     182 Mixing     183 Summary     189   Chapter 9  Positional Sound     191 Sound in Space     191 The OpenAL API     193 Putting a Sound in Space     196    Setting Up the Example     197    Using OpenAL Objects     200    Animating the Source’s Position     205    Loading Samples for an OpenAL Buffer     206 Streaming Audio in OpenAL     210    Setting Up the OpenAL Streaming Example     210    Setting Up an ExtAudioFile for Streaming     215    Refilling the OpenAL Buffers     217 Summary     220   PART IV: ADDITIONAL TOPICS Chapter 10  Core Audio on iOS     223 Is That Core Audio in Your Pocket?     223 Playing Nicely with Others: Audio Session Services     224 An Audio Session Example     227    Setting Up the App     227    Initializing the Audio Session and Audio Queue     231    The Tone Generator Method     234     Handling iOS Interruptions     236 Audio Units on iOS     238    Building an Audio Pass-Through App with the iOS RemoteIO Unit     239    Setting Up the Pass-Through Example     241    Setting Up the RemoteIO Audio Unit for Capture and Play-Out     244    The RemoteIO Render Callback     249 Other iOS Audio Tricks     253    Remote Control on iOS     253    IOS Hardware Hazards     254 Summary     254   Chapter 11  Core MIDI     257 MIDI Concepts     257 Core MIDI     258    Core MIDI Architecture     258    Core MIDI Terminology     258    Core MIDI Properties     260    MIDI Messages     260 Instrument Units     261 Building a Simple MIDI Synthesizer     262    Connecting to MIDI     265 Handling MIDI Notifications and Events     267     Playing Your AUGraph     269 Creating MIDI Events     269    Setting Up the MIDIWifiSource Example     269    Setting Up MIDI over Wi-Fi     271    Sending MIDI Messages     273    Setting Up Your Mac to Receive Wi-Fi MIDI Data     275 Summary: MIDI Mastery … but Mobility?     277   Chapter 12  Coda     279 Still More Core Audio     279 Next Steps     280    Digital Signal Processing     280 Lion and iOS 5     281    AUSampler     281    Core Audio on iOS 5     285 The Core Audio Community     286 Summary: Sounds Good     287   Index     289