AVFoundation Audio Reference

Comprehensive API reference for AVFoundation audio covering AVAudioSession, AVAudioEngine, bit-perfect USB DAC output, and iOS 26+ spatial audio features.

Overview

Complete guide to AVFoundation audio based on WWDC 2025 sessions 251 and 403, covering input device selection, AirPods high-quality recording, spatial audio capture with ASAF/APAC formats, and Audio Mix integration with the Cinematic framework.

What This Reference Covers

AVAudioSession

• Categories (playback, record, playAndRecord)
• Modes (default, voiceChat, videoRecording)
• Options (mixWithOthers, allowBluetooth, bluetoothHighQualityRecording)
• Route management and interruption handling

AVAudioEngine

• Node connections and pipelines
• Input/output taps for processing
• Format conversion and sample rates
• Real-time audio processing

Bit-Perfect Output (USB DAC)

• iOS automatic passthrough behavior
• Sample rate matching
• Format negotiation
• Hardware-native playback

iOS 26+ Features

• AVInputPickerInteraction for in-app input selection
• AirPods high-quality recording mode
• Spatial audio capture (First Order Ambisonics)
• ASAF (Apple Spatial Audio Format)
• APAC (Apple Positional Audio Codec)
• Audio Mix with Cinematic framework

When to Use This Reference

Use this reference when:

• Configuring audio session categories and modes
• Building AVAudioEngine processing pipelines
• Implementing USB DAC bit-perfect output
• Adding iOS 26+ input selection UI
• Recording spatial audio with AirPods
• Implementing Audio Mix effect control

Key Patterns

AVAudioSession Categories

let session = AVAudioSession.sharedInstance()

// Playback only (silences other apps)
try session.setCategory(.playback)

// Recording only
try session.setCategory(.record)

// Simultaneous play and record
try session.setCategory(.playAndRecord, options: [.defaultToSpeaker])

// Mix with other apps (background music)
try session.setCategory(.playback, options: [.mixWithOthers])

iOS 26+ Input Selection

import AVKit

let picker = AVInputPickerInteraction()
picker.delegate = self
myButton.addInteraction(picker)

// In button action:
picker.present()

AirPods High-Quality Recording

try AVAudioSession.sharedInstance().setCategory(
    .playAndRecord,
    options: [.bluetoothHighQualityRecording, .allowBluetoothA2DP]
)

Spatial Audio Capture

// Configure AVCaptureDeviceInput for spatial audio
deviceInput.multichannelAudioMode = .firstOrderAmbisonics

// Or configure AVCaptureSession directly
captureSession.supportsMultichannelAudioRecording = true

Audio Mix with Cinematic Framework

import Cinematic

let audioInfo = CNAssetSpatialAudioInfo(asset: asset)
audioInfo.effectIntensity = 0.7  // 0-1
audioInfo.renderingStyle = .cinematic  // or .studio, .inFrame

let audioMix = try audioInfo.audioMix()
playerItem.audioMix = audioMix

Complete Coverage

This reference includes:

• All AVAudioSession categories, modes, and options
• AVAudioEngine node types and connections
• iOS 26+ input picker implementation
• AirPods high-quality recording setup
• Spatial audio formats (FOA, ASAF, APAC)
• Audio Mix parameter control
• Bit-perfect USB DAC configuration
• Common anti-patterns and prevention

Anti-Patterns

Using Default Category

// ❌ Default category may not suit your needs
let session = AVAudioSession.sharedInstance()
// Missing category configuration

Ignoring Interruptions

// ❌ Not handling phone calls, alarms, Siri
// Your audio stops without graceful handling

Blocking Main Thread

// ❌ Processing audio on main thread
audioEngine.inputNode.installTap(...) { buffer, time in
    self.heavyProcessing(buffer)  // Blocks UI
}

Related Resources

• networking — Network.framework for streaming
• WWDC 2025/251 — Enhance audio capabilities
• WWDC 2025/403 — Apple Immersive Video and Spatial Audio

Documentation Scope

This is a reference skill — comprehensive API guide without mandatory workflows.

Reference includes

• Complete AVFoundation audio API documentation
• iOS 26+ spatial audio features
• Bit-perfect DAC output patterns
• WWDC 2025 code examples
• Anti-pattern prevention

Vs Diagnostic: Reference skills provide information. Diagnostic skills enforce workflows and handle pressure scenarios.