axiom-camera-capture-ref

name	axiom-camera-capture-ref
description	Reference — AVCaptureSession, AVCapturePhotoSettings, AVCapturePhotoOutput, RotationCoordinator, photoQualityPrioritization, deferred processing, AVCaptureMovieFileOutput, session presets, capture device APIs
license	MIT
metadata	{"version":"1.0.0"}

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

Preset	Resolution	Use Case
.photo	Optimal for photos	Photo capture
.high	Highest device quality	Video recording
.medium	VGA quality	Preview, lower storage
.low	CIF quality	Minimal storage
.hd1280x720	720p	HD video
.hd1920x1080	1080p	Full HD video
.hd4K3840x2160	4K	Ultra HD video
.inputPriority	Use device format	Custom configuration

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

Reason	Value	Cause
.videoDeviceNotAvailableInBackground	1	App went to background
.audioDeviceInUseByAnotherClient	2	Another app using audio
.videoDeviceInUseByAnotherClient	3	Another app using camera
.videoDeviceNotAvailableWithMultipleForegroundApps	4	Split View (iPad)
.videoDeviceNotAvailableDueToSystemPressure	5	Thermal throttling

---

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

Type	Description
.builtInWideAngleCamera	Standard camera (1x)
.builtInUltraWideCamera	Ultra-wide camera (0.5x)
.builtInTelephotoCamera	Telephoto camera (2x, 3x)
.builtInDualCamera	Wide + telephoto
.builtInDualWideCamera	Wide + ultra-wide
.builtInTripleCamera	Wide + ultra-wide + telephoto
.builtInTrueDepthCamera	Front TrueDepth (Face ID)
.builtInLiDARDepthCamera	LiDAR depth

Device Configuration

do {
    try device.lockForConfiguration()
    defer { device.unlockForConfiguration() }

    // Focus
    if device.isFocusModeSupported(.continuousAutoFocus) {
        device.focusMode = .continuousAutoFocus
    }

    // Exposure
    if device.isExposureModeSupported(.continuousAutoExposure) {
        device.exposureMode = .continuousAutoExposure
    }

    // Torch (flashlight)
    if device.hasTorch && device.isTorchModeSupported(.on) {
        device.torchMode = .on
    }

    // Zoom
    device.videoZoomFactor = 2.0  // 2x zoom

} catch {
    print("Failed to configure device: \(error)")
}

Switching Cameras

// Switch between front and back during active session
func switchCamera() {
    sessionQueue.async { [self] in
        session.beginConfiguration()
        defer { session.commitConfiguration() }

        // Remove current camera input
        if let currentInput = session.inputs.first(where: { ($0 as? AVCaptureDeviceInput)?.device.hasMediaType(.video) == true }) as? AVCaptureDeviceInput {
            session.removeInput(currentInput)

            // Get opposite camera
            let newPosition: AVCaptureDevice.Position = currentInput.device.position == .back ? .front : .back
            guard let newDevice = AVCaptureDevice.default(.builtInWideAngleCamera, for: .video, position: newPosition),
                  let newInput = try? AVCaptureDeviceInput(device: newDevice) else { return }

            if session.canAddInput(newInput) {
                session.addInput(newInput)
            }
        }
    }
}

Important: Always switch on the session queue, within beginConfiguration/commitConfiguration.

Authorization

// Check status
let status = AVCaptureDevice.authorizationStatus(for: .video)

switch status {
case .authorized: break
case .notDetermined:
    await AVCaptureDevice.requestAccess(for: .video)
case .denied, .restricted:
    // Show settings prompt
@unknown default: break
}

---

AVCaptureDevice.RotationCoordinator (iOS 17+)

Automatically tracks device orientation and provides rotation angles.

Setup

// Create with device and preview layer
let coordinator = AVCaptureDevice.RotationCoordinator(
    device: captureDevice,
    previewLayer: previewLayer
)

Properties

Property	Type	Description
videoRotationAngleForHorizonLevelPreview	CGFloat	Rotation for preview layer
videoRotationAngleForHorizonLevelCapture	CGFloat	Rotation for captured output

Observation

// KVO observation for preview updates
let observation = coordinator.observe(
    \.videoRotationAngleForHorizonLevelPreview,
    options: [.new]
) { [weak previewLayer] coordinator, _ in
    DispatchQueue.main.async {
        previewLayer?.connection?.videoRotationAngle = coordinator.videoRotationAngleForHorizonLevelPreview
    }
}

// Set initial value
previewLayer.connection?.videoRotationAngle = coordinator.videoRotationAngleForHorizonLevelPreview

Applying to Capture

func capturePhoto() {
    if let connection = photoOutput.connection(with: .video) {
        connection.videoRotationAngle = coordinator.videoRotationAngleForHorizonLevelCapture
    }
    photoOutput.capturePhoto(with: settings, delegate: self)
}

---

AVCapturePhotoOutput

Output for capturing still photos.

Configuration

let photoOutput = AVCapturePhotoOutput()

// High resolution
photoOutput.isHighResolutionCaptureEnabled = true

// Max quality prioritization
photoOutput.maxPhotoQualityPrioritization = .quality

// Deferred processing (iOS 17+)
photoOutput.isAutoDeferredPhotoDeliveryEnabled = true

// Live Photo
photoOutput.isLivePhotoCaptureEnabled = true

// Depth
photoOutput.isDepthDataDeliveryEnabled = true

// Portrait Effects Matte
photoOutput.isPortraitEffectsMatteDeliveryEnabled = true

Supported Features

// Check support before enabling
photoOutput.isHighResolutionCaptureEnabled && photoOutput.isHighResolutionCaptureSupported
photoOutput.isLivePhotoCaptureSupported
photoOutput.isDepthDataDeliverySupported
photoOutput.isPortraitEffectsMatteDeliverySupported
photoOutput.maxPhotoQualityPrioritization  // .speed, .balanced, .quality

Responsive Capture APIs (iOS 17+)

// Zero Shutter Lag - uses ring buffer for instant capture
photoOutput.isZeroShutterLagSupported
photoOutput.isZeroShutterLagEnabled  // true by default for iOS 17+ apps

// Responsive Capture - overlapping captures
photoOutput.isResponsiveCaptureSupported
photoOutput.isResponsiveCaptureEnabled

// Fast Capture Prioritization - adapts quality for burst-like capture
photoOutput.isFastCapturePrioritizationSupported
photoOutput.isFastCapturePrioritizationEnabled

// Deferred Processing - proxy + background processing
photoOutput.isAutoDeferredPhotoDeliverySupported
photoOutput.isAutoDeferredPhotoDeliveryEnabled

---

AVCapturePhotoOutputReadinessCoordinator (iOS 17+)

Provides synchronous shutter button state updates.

Setup

let coordinator = AVCapturePhotoOutputReadinessCoordinator(photoOutput: photoOutput)
coordinator.delegate = self

Tracking Captures

// Call BEFORE capturePhoto()
coordinator.startTrackingCaptureRequest(using: settings)
photoOutput.capturePhoto(with: settings, delegate: self)

Delegate

func readinessCoordinator(_ coordinator: AVCapturePhotoOutputReadinessCoordinator,
                          captureReadinessDidChange captureReadiness: AVCapturePhotoOutput.CaptureReadiness) {
    switch captureReadiness {
    case .ready:                         // Can capture immediately
    case .notReadyMomentarily:           // Brief delay, prevent double-tap
    case .notReadyWaitingForCapture:     // Flash firing, sensor reading
    case .notReadyWaitingForProcessing:  // Processing previous photo
    case .sessionNotRunning:             // Session stopped
    @unknown default: break
    }
}

---

AVCapturePhotoSettings

Configuration for a single photo capture.

Basic Settings

// Standard JPEG
var settings = AVCapturePhotoSettings()

// HEIF format
settings = AVCapturePhotoSettings(format: [AVVideoCodecKey: AVVideoCodecType.hevc])

// RAW
settings = AVCapturePhotoSettings(rawPixelFormatType: kCVPixelFormatType_14Bayer_BGGR)

// RAW + JPEG
settings = AVCapturePhotoSettings(
    rawPixelFormatType: kCVPixelFormatType_14Bayer_BGGR,
    processedFormat: [AVVideoCodecKey: AVVideoCodecType.jpeg]
)

Quality Prioritization

Value	Speed	Quality	Use Case
.speed	Fastest	Lower	Social sharing, rapid capture
.balanced	Medium	Good	General photography
.quality	Slowest	Best	Professional, documents

settings.photoQualityPrioritization = .speed

Flash

settings.flashMode = .auto  // .off, .on, .auto

Apple ProRAW and HDR

// Check ProRAW support
if photoOutput.isAppleProRAWSupported {
    photoOutput.isAppleProRAWEnabled = true

    // Capture ProRAW
    let query = photoOutput.isAppleProRAWEnabled
        ? AVCapturePhotoOutput.AppleProRAWQuery(photoOutput)
        : nil
    if let rawType = query?.availableRawPixelFormatTypes.first {
        let settings = AVCapturePhotoSettings(
            rawPixelFormatType: rawType,
            processedFormat: [AVVideoCodecKey: AVVideoCodecType.hevc]
        )
    }
}

// HDR configuration
settings.photoQualityPrioritization = .quality  // Enables computational photography/HDR
// HDR is automatic with .balanced or .quality — no separate toggle needed

Note: ProRAW requires iPhone 12 Pro or later. HDR is automatic with quality prioritization — Apple's Deep Fusion and Smart HDR are controlled by the system based on the quality setting.

Resolution

// High resolution still image
settings.isHighResolutionPhotoEnabled = true

// Max dimensions (limit resolution)
settings.maxPhotoDimensions = CMVideoDimensions(width: 4032, height: 3024)

Preview/Thumbnail

// Preview for immediate display
settings.previewPhotoFormat = [
    kCVPixelBufferPixelFormatTypeKey as String: kCVPixelFormatType_32BGRA
]

// Thumbnail
settings.embeddedThumbnailPhotoFormat = [
    AVVideoCodecKey: AVVideoCodecType.jpeg,
    AVVideoWidthKey: 160,
    AVVideoHeightKey: 120
]

Important Notes

// Settings cannot be reused
// Each capture needs a NEW settings instance
let settings1 = AVCapturePhotoSettings()  // Use once
let settings2 = AVCapturePhotoSettings()  // Use for second capture

// Copy settings for similar captures
let settings2 = AVCapturePhotoSettings(from: settings1)

---

AVCapturePhotoCaptureDelegate

Delegate for photo capture events.

extension CameraManager: AVCapturePhotoCaptureDelegate {

    // Photo capture will begin
    func photoOutput(_ output: AVCapturePhotoOutput,
                     willBeginCaptureFor resolvedSettings: AVCaptureResolvedPhotoSettings) {
        // Show shutter animation
    }

    // Photo capture finished
    func photoOutput(_ output: AVCapturePhotoOutput,
                     didFinishProcessingPhoto photo: AVCapturePhoto,
                     error: Error?) {
        guard error == nil else {
            print("Capture error: \(error!)")
            return
        }

        // Get JPEG data
        if let data = photo.fileDataRepresentation() {
            savePhoto(data)
        }

        // Or get raw pixel buffer
        if let pixelBuffer = photo.pixelBuffer {
            processBuffer(pixelBuffer)
        }
    }

    // Deferred processing proxy (iOS 17+)
    func photoOutput(_ output: AVCapturePhotoOutput,
                     didFinishCapturingDeferredPhotoProxy deferredPhotoProxy: AVCaptureDeferredPhotoProxy,
                     error: Error?) {
        guard error == nil, let data = deferredPhotoProxy.fileDataRepresentation() else { return }
        replaceThumbnailWithFinal(data)
    }
}

---

AVCaptureMovieFileOutput

Output for recording video to file.

Setup

let movieOutput = AVCaptureMovieFileOutput()

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

// Add audio input
if let microphone = AVCaptureDevice.default(for: .audio),
   let audioInput = try? AVCaptureDeviceInput(device: microphone),
   session.canAddInput(audioInput) {
    session.addInput(audioInput)
}

Recording

// Start recording
let outputURL = FileManager.default.temporaryDirectory
    .appendingPathComponent(UUID().uuidString)
    .appendingPathExtension("mov")

// Apply rotation
if let connection = movieOutput.connection(with: .video) {
    connection.videoRotationAngle = rotationCoordinator.videoRotationAngleForHorizonLevelCapture
}

movieOutput.startRecording(to: outputURL, recordingDelegate: self)

// Stop recording
movieOutput.stopRecording()

// Check state
movieOutput.isRecording
movieOutput.recordedDuration
movieOutput.recordedFileSize

Delegate

extension CameraManager: AVCaptureFileOutputRecordingDelegate {

    func fileOutput(_ output: AVCaptureFileOutput,
                    didStartRecordingTo fileURL: URL,
                    from connections: [AVCaptureConnection]) {
        // Recording started
    }

    func fileOutput(_ output: AVCaptureFileOutput,
                    didFinishRecordingTo outputFileURL: URL,
                    from connections: [AVCaptureConnection],
                    error: Error?) {
        if let error = error {
            print("Recording failed: \(error)")
            return
        }

        // Video saved to outputFileURL
        saveToPhotoLibrary(outputFileURL)
    }
}

---

AVCaptureVideoPreviewLayer

Layer for displaying camera preview.

Setup

let previewLayer = AVCaptureVideoPreviewLayer(session: session)
previewLayer.videoGravity = .resizeAspectFill
previewLayer.frame = view.bounds
view.layer.addSublayer(previewLayer)

Video Gravity

Value	Behavior
.resizeAspect	Fit entire image, may letterbox
.resizeAspectFill	Fill layer, may crop edges
.resize	Stretch to fill (distorts)

SwiftUI Integration

struct CameraPreview: UIViewRepresentable {
    let session: AVCaptureSession

    func makeUIView(context: Context) -> PreviewView {
        let view = PreviewView()
        view.previewLayer.session = session
        view.previewLayer.videoGravity = .resizeAspectFill
        return view
    }

    func updateUIView(_ uiView: PreviewView, context: Context) {}

    class PreviewView: UIView {
        override class var layerClass: AnyClass { AVCaptureVideoPreviewLayer.self }
        var previewLayer: AVCaptureVideoPreviewLayer { layer as! AVCaptureVideoPreviewLayer }
    }
}

---

Common Code Patterns

Complete Camera Manager

import AVFoundation

@MainActor
class CameraManager: NSObject, ObservableObject {
    let session = AVCaptureSession()
    let photoOutput = AVCapturePhotoOutput()
    private let sessionQueue = DispatchQueue(label: "camera.session")
    private var rotationCoordinator: AVCaptureDevice.RotationCoordinator?
    private var rotationObservation: NSKeyValueObservation?

    @Published var isSessionRunning = false

    func setup() async -> Bool {
        guard await AVCaptureDevice.requestAccess(for: .video) else { return false }

        return await withCheckedContinuation { continuation in
            sessionQueue.async { [self] in
                session.beginConfiguration()
                defer { session.commitConfiguration() }

                session.sessionPreset = .photo

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

                guard session.canAddOutput(photoOutput) else {
                    continuation.resume(returning: false)
                    return
                }
                session.addOutput(photoOutput)
                photoOutput.maxPhotoQualityPrioritization = .quality

                continuation.resume(returning: true)
            }
        }
    }

    func start() {
        sessionQueue.async { [self] in
            session.startRunning()
            DispatchQueue.main.async {
                self.isSessionRunning = self.session.isRunning
            }
        }
    }

    func stop() {
        sessionQueue.async { [self] in
            session.stopRunning()
            DispatchQueue.main.async {
                self.isSessionRunning = false
            }
        }
    }

    func capturePhoto() {
        var settings = AVCapturePhotoSettings()
        settings.photoQualityPrioritization = .balanced

        if let connection = photoOutput.connection(with: .video),
           let angle = rotationCoordinator?.videoRotationAngleForHorizonLevelCapture {
            connection.videoRotationAngle = angle
        }

        photoOutput.capturePhoto(with: settings, delegate: self)
    }
}

extension CameraManager: AVCapturePhotoCaptureDelegate {
    nonisolated func photoOutput(_ output: AVCapturePhotoOutput,
                                  didFinishProcessingPhoto photo: AVCapturePhoto,
                                  error: Error?) {
        guard let data = photo.fileDataRepresentation() else { return }
        // Handle photo data
    }
}

---

Resources

Docs: /avfoundation/avcapturesession, /avfoundation/avcapturedevice, /avfoundation/avcapturephotosettings, /avfoundation/avcapturedevice/rotationcoordinator

Skills: axiom-camera-capture, axiom-camera-capture-diag