axiom-avfoundation-ref

# AVFoundation Audio Reference

## Quick Reference

```swift
// AUDIO SESSION SETUP
import AVFoundation

try AVAudioSession.sharedInstance().setCategory(
    .playback,                              // or .playAndRecord, .ambient
    mode: .default,                         // or .voiceChat, .measurement
    options: [.mixWithOthers, .allowBluetooth]
)
try AVAudioSession.sharedInstance().setActive(true)

// AUDIO ENGINE PIPELINE
let engine = AVAudioEngine()
let player = AVAudioPlayerNode()
engine.attach(player)
engine.connect(player, to: engine.mainMixerNode, format: nil)
try engine.start()
player.scheduleFile(audioFile, at: nil)
player.play()

// INPUT PICKER (iOS 26+)
import AVKit
let picker = AVInputPickerInteraction()
picker.delegate = self
myButton.addInteraction(picker)
// In button action: picker.present()

// AIRPODS HIGH QUALITY (iOS 26+)
try AVAudioSession.sharedInstance().setCategory(
    .playAndRecord,
    options: [.bluetoothHighQualityRecording, .allowBluetoothA2DP]
)
```

---

## AVAudioSession

### Categories

| Category | Use Case | Silent Switch | Background |
|----------|----------|---------------|------------|
| `.ambient` | Game sounds, not primary | Silences | No |
| `.soloAmbient` | Default, interrupts others | Silences | No |
| `.playback` | Music player, podcast | Ignores | Yes |
| `.record` | Voice recorder | — | Yes |
| `.playAndRecord` | VoIP, voice chat | Ignores | Yes |
| `.multiRoute` | DJ apps, multiple outputs | Ignores | Yes |

### Modes

| Mode | Use Case |
|------|----------|
| `.default` | General audio |
| `.voiceChat` | VoIP, reduces echo |
| `.videoChat` | FaceTime-style |
| `.gameChat` | Voice chat in games |
| `.videoRecording` | Camera recording |
| `.measurement` | Flat response, no processing |
| `.moviePlayback` | Video playback |
| `.spokenAudio` | Podcasts, audiobooks |

### Options

```swift
// Mixing
.mixWithOthers          // Play with other apps
.duckOthers             // Lower other audio while playing
.interruptSp