Camera Capture API Reference

Quick Reference

// SESSION SETUP
import AVFoundation

let session = AVCaptureSession()
let sessionQueue = DispatchQueue(label: "camera.session")

sessionQueue.async {
    session.beginConfiguration()
    session.sessionPreset = .photo

    guard let camera = AVCaptureDevice.default(.builtInWideAngleCamera, for: .video, position: .back),
          let input = try? AVCaptureDeviceInput(device: camera),
          session.canAddInput(input) else { return }
    session.addInput(input)

    let photoOutput = AVCapturePhotoOutput()
    if session.canAddOutput(photoOutput) {
        session.addOutput(photoOutput)
    }

    session.commitConfiguration()
    session.startRunning()
}

// CAPTURE PHOTO
var settings = AVCapturePhotoSettings()
settings.photoQualityPrioritization = .balanced
photoOutput.capturePhoto(with: settings, delegate: self)

// ROTATION (iOS 17+)
let coordinator = AVCaptureDevice.RotationCoordinator(device: camera, previewLayer: previewLayer)
previewLayer.connection?.videoRotationAngle = coordinator.videoRotationAngleForHorizonLevelPreview

AVCaptureSession

Central coordinator for capture data flow.

Session Presets

Session Configuration

// Batch configuration (atomic)
session.beginConfiguration()
defer { session.commitConfiguration() }

// Check preset support
if session.canSetSessionPreset(.hd4K3840x2160) {
    session.sessionPreset = .hd4K3840x2160
}

// Add input/output
if session.canAddInput(input) {
    session.addInput(input)
}

if session.canAddOutput(output) {
    session.addOutput(output)
}

Session Lifecycle

// Start (ALWAYS on background queue)
sessionQueue.async {
    session.startRunning()  // Blocking call
}

// Stop
sessionQueue.async {
    session.stopRunning()
}

// Check state
session.isRunning      // true/false
session.isInterrupted  // true during phone calls, etc.

Session Notifications

// Session started
NotificationCenter.default.addObserver(
    forName: .AVCaptureSessionDidStartRunning,
    object: session, queue: .main) { _ in }

// Session stopped
NotificationCenter.default.addObserver(
    forName: .AVCaptureSessionDidStopRunning,
    object: session, queue: .main) { _ in }

// Session interrupted (phone call, etc.)
NotificationCenter.default.addObserver(
    forName: .AVCaptureSessionWasInterrupted,
    object: session, queue: .main) { notification in
        let reason = notification.userInfo?[AVCaptureSessionInterruptionReasonKey] as? Int
    }

// Interruption ended
NotificationCenter.default.addObserver(
    forName: .AVCaptureSessionInterruptionEnded,
    object: session, queue: .main) { _ in }

// Runtime error
NotificationCenter.default.addObserver(
    forName: .AVCaptureSessionRuntimeError,
    object: session, queue: .main) { notification in
        let error = notification.userInfo?[AVCaptureSessionErrorKey] as? Error
    }

Interruption Reasons

AVCaptureDevice

Represents a physical capture device (camera, microphone).

Getting Devices

// Default back camera
AVCaptureDevice.default(.builtInWideAngleCamera, for: .video, position: .back)

// Default front camera
AVCaptureDevice.default(.builtInWideAngleCamera, for: .video, position: .front)

// Default microphone
AVCaptureDevice.default(for: .audio)

// Discovery session for all cameras
let discoverySession = AVCaptureDevice.DiscoverySession(
    deviceTypes: [.builtInWideAngleCamera, .builtInUltraWideCamera, .builtInTelephotoCamera],
    mediaType: .video,
    position: .unspecified
)
let cameras = discoverySession.devices

Device Types

Device Configuration

do {