avfoundation

name	avfoundation
description	AVFoundation patterns for camera capture, video/audio playback, media editing, and audio sessions. Use when working with camera, microphone, video playback, or media processing.

First step: Tell the user: "avfoundation skill loaded."

AVFoundation Development Guide

Patterns and best practices for camera capture, media playback, audio sessions, and media composition on Apple platforms.

When This Skill Activates

Use this skill when the user:

• Wants to capture photos or video with the camera
• Needs a camera preview in SwiftUI or UIKit
• Asks about video or audio playback with AVPlayer
• Needs to configure audio sessions (AVAudioSession)
• Wants to compose or edit video/audio tracks
• Asks about exporting media with AVAssetExportSession
• Mentions camera permissions or microphone access
• Needs to process video frames in real time

Decision Tree: Choosing the Right API

What do you need?
├── Play video/audio
│   ├── Simple playback in SwiftUI → VideoPlayer (AVKit)
│   ├── Full-screen with controls → AVPlayerViewController (AVKit)
│   └── Custom player UI → AVPlayer + AVPlayerLayer
├── Capture from camera/mic
│   ├── Photos only → AVCaptureSession + AVCapturePhotoOutput
│   ├── Video recording → AVCaptureSession + AVCaptureMovieFileOutput
│   └── Real-time frame processing → AVCaptureSession + AVCaptureVideoDataOutput
├── Edit/compose media
│   ├── Combine tracks → AVMutableComposition
│   ├── Apply effects → AVVideoComposition
│   └── Export result → AVAssetExportSession
└── Audio session management → AVAudioSession

API Availability

API	iOS	macOS	visionOS	Notes
AVCaptureSession	4.0+	10.7+	-	Camera/mic capture pipeline
AVCapturePhotoOutput	10.0+	13.0+	-	Replaces AVStillImageOutput
AVCaptureVideoDataOutput	4.0+	10.7+	-	Raw frame access
AVPlayer	4.0+	10.7+	1.0+	Media playback engine
AVPlayerViewController	8.0+	10.15+	1.0+	System playback UI (AVKit)
VideoPlayer (SwiftUI)	14.0+	11.0+	1.0+	SwiftUI wrapper (AVKit)
AVAudioSession	3.0+	-	-	iOS/watchOS only
AVMutableComposition	4.0+	10.7+	1.0+	Media editing/export

Camera Capture Pipeline

Session Setup with Photo Capture

import AVFoundation

class CameraManager: NSObject, ObservableObject, AVCapturePhotoCaptureDelegate {
    let session = AVCaptureSession()
    private let sessionQueue = DispatchQueue(label: "camera.session")
    private let photoOutput = AVCapturePhotoOutput()
    @Published var capturedImage: UIImage?

    func configure() {
        sessionQueue.async { [self] in
            session.beginConfiguration()
            session.sessionPreset = .photo

            guard let camera = AVCaptureDevice.default(
                .builtInWideAngleCamera, for: .video, position: .back
            ) else { return }

            do {
                let input = try AVCaptureDeviceInput(device: camera)
                if session.canAddInput(input) { session.addInput(input) }
            } catch {
                print("Camera input error: \(error)")
                return
            }

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

            session.commitConfiguration()
        }
    }

     () {
        sessionQueue.async {  .session.isRunning { .session.startRunning() } }
    }

     () {
        sessionQueue.async {  .session.isRunning { .session.stopRunning() } }
    }

     () {
         settings  ()
        settings.flashMode  .auto
        photoOutput.capturePhoto(with: settings, delegate: )
    }

     ( : ,
                      : , : ?) {
          data  photo.fileDataRepresentation(),
               image  (data: data)  {  }
        .main.async { .capturedImage  image }
    }
}

SwiftUI Camera Preview

import SwiftUI
import AVFoundation

struct CameraPreview: UIViewRepresentable {
    let session: AVCaptureSession

    func makeUIView(context: Context) -> UIView {
        let view = UIView(frame: .zero)
        let previewLayer = AVCaptureVideoPreviewLayer(session: session)
        previewLayer.videoGravity = .resizeAspectFill
        view.layer.addSublayer(previewLayer)
        context.coordinator.previewLayer = previewLayer
        return view
    }

    func updateUIView(_ uiView: UIView, context: Context) {
        context.coordinator.previewLayer?.frame = uiView.bounds
    }

    func makeCoordinator() -> Coordinator { Coordinator() }

    class Coordinator { var previewLayer: AVCaptureVideoPreviewLayer? }
}

struct CameraView: View {
    @StateObject private var camera = CameraManager()

    var body: some  {
        (session: camera.session)
            .ignoresSafeArea()
            .onAppear { camera.configure(); camera.start() }
            .onDisappear { camera.stop() }
    }
}

Video Recording

class VideoRecordingManager: NSObject, ObservableObject, AVCaptureFileOutputRecordingDelegate {
    let session = AVCaptureSession()
    private let sessionQueue = DispatchQueue(label: "video.session")
    private let movieOutput = AVCaptureMovieFileOutput()
    @Published var isRecording = false

    func configure() {
        sessionQueue.async { [self] in
            session.beginConfiguration()
            session.sessionPreset = .high

            if let camera = AVCaptureDevice.default(.builtInWideAngleCamera, for: .video, position: .back),
               let videoInput = try? AVCaptureDeviceInput(device: camera),
               session.canAddInput(videoInput) {
                session.addInput(videoInput)
            }
            if let mic = AVCaptureDevice.default(for: .audio),
               let audioInput = try? AVCaptureDeviceInput(device: mic),
               session.canAddInput(audioInput) {
                session.addInput(audioInput)
            }
            if session.canAddOutput(movieOutput) { session.addOutput(movieOutput) }

            session.commitConfiguration()
        }
    }

     () {
         url  .default.temporaryDirectory
            .appendingPathComponent(().uuidString).appendingPathExtension()
        movieOutput.startRecording(to: url, recordingDelegate: )
        .main.async { .isRecording   }
    }

     () { movieOutput.stopRecording() }

     ( : ,  : ,
                     : [], : ?) {
        .main.async { .isRecording   }
          error { () }
    }
}

Video Playback

AVPlayerViewController (UIKit)

import AVKit

func presentPlayer(from vc: UIViewController, url: URL) {
    let player = AVPlayer(url: url)
    let playerVC = AVPlayerViewController()
    playerVC.player = player
    vc.present(playerVC, animated: true) { player.play() }
}

SwiftUI VideoPlayer with Status Observation

import SwiftUI
import AVKit

struct VideoPlayerView: View {
    @State private var player = AVPlayer(url: URL(string: "https://example.com/video.mp4")!)

    var body: some View {
        VideoPlayer(player: player)
            .frame(height: 300)
            .onAppear { player.play() }
            .onDisappear { player.pause() }
    }
}

class PlayerViewModel: ObservableObject {
    let player = AVPlayer()
    private var statusObservation: NSKeyValueObservation?
    private var timeObserver: Any?

    func load(url: URL) {
        let item = AVPlayerItem(url: url)
        statusObservation = item.observe(\.status) { item, _ in
            if item.status == .failed { print("Failed: \(item.error?.localizedDescription ?? "")") }
        }
        player.replaceCurrentItem(with: item)
        timeObserver  player.addPeriodicTimeObserver(
            forInterval: (seconds: , preferredTimescale: ),
            queue: .main) { time  () }
    }

     {   obs  timeObserver { player.removeTimeObserver(obs) } }
}

Audio Session Configuration

Configure AVAudioSession before capture or playback on iOS:

import AVFoundation

func configureAudioSession(for purpose: AudioPurpose) throws {
    let session = AVAudioSession.sharedInstance()
    switch purpose {
    case .playback:
        try session.setCategory(.playback, mode: .default)
    case .recording:
        try session.setCategory(.record, mode: .default)
    case .videoChat:
        try session.setCategory(.playAndRecord, mode: .videoChat,
                                options: [.defaultToSpeaker, .allowBluetooth])
    case .backgroundAudio:
        try session.setCategory(.playback, mode: .default, options: [.mixWithOthers])
    }
    try session.setActive(true)
}

enum AudioPurpose { case playback, recording, videoChat, backgroundAudio }

Handling Audio Interruptions

NotificationCenter.default.addObserver(
    forName: AVAudioSession.interruptionNotification,
    object: AVAudioSession.sharedInstance(), queue: .main
) { notification in
    guard let info = notification.userInfo,
          let typeValue = info[AVAudioSessionInterruptionTypeKey] as? UInt,
          let type = AVAudioSession.InterruptionType(rawValue: typeValue) else { return }

    switch type {
    case .began:
        // Pause playback
        break
    case .ended:
        let opts = info[AVAudioSessionInterruptionOptionKey] as? UInt ?? 0
        if AVAudioSession.InterruptionOptions(rawValue: opts).contains(.shouldResume) {
            // Resume playback
        }
    @unknown default: break
    }
}

Media Composition and Export

Combining Video and Audio Tracks

func composeMedia(videoURL: URL, audioURL: URL) async throws -> AVMutableComposition {
    let composition = AVMutableComposition()
    let videoAsset = AVURLAsset(url: videoURL)
    let audioAsset = AVURLAsset(url: audioURL)

    let videoTracks = try await videoAsset.loadTracks(withMediaType: .video)
    let audioTracks = try await audioAsset.loadTracks(withMediaType: .audio)

    guard let srcVideo = videoTracks.first, let srcAudio = audioTracks.first else {
        throw NSError(domain: "Composition", code: -1)
    }

    let duration = try await videoAsset.load(.duration)

    let compVideoTrack = composition.addMutableTrack(
        withMediaType: .video, preferredTrackID: kCMPersistentTrackID_Invalid)
    try compVideoTrack?.insertTimeRange(
        CMTimeRange(start: .zero, duration: duration), of: srcVideo, at: .zero)

    let compAudioTrack = composition.addMutableTrack(
        withMediaType: .audio, preferredTrackID: kCMPersistentTrackID_Invalid)
     compAudioTrack.insertTimeRange(
        (start: .zero, duration: duration), of: srcAudio, at: .zero)

     composition
}

Exporting with AVAssetExportSession

func exportComposition(_ composition: AVComposition, to outputURL: URL) async throws {
    try? FileManager.default.removeItem(at: outputURL)

    guard let session = AVAssetExportSession(
        asset: composition, presetName: AVAssetExportPresetHighestQuality
    ) else { throw NSError(domain: "Export", code: -1) }

    session.outputURL = outputURL
    session.outputFileType = .mp4
    await session.export()

    if session.status == .failed {
        throw session.error ?? NSError(domain: "Export", code: -2)
    }
}

Privacy Permissions

Required Info.plist Keys

Key	Required When
NSCameraUsageDescription	Using AVCaptureDevice for video
NSMicrophoneUsageDescription	Capturing audio input
NSPhotoLibraryUsageDescription	Saving to or reading from Photos

Requesting Permission

func requestCameraAccess() async -> Bool {
    switch AVCaptureDevice.authorizationStatus(for: .video) {
    case .authorized: return true
    case .notDetermined: return await AVCaptureDevice.requestAccess(for: .video)
    case .denied, .restricted: return false
    @unknown default: return false
    }
}

Common Pitfalls and Patterns

Session Threading

// ❌ Bad: blocking the main thread
captureSession.startRunning()

// ✅ Good: dedicated serial queue
let sessionQueue = DispatchQueue(label: "camera.session")
sessionQueue.async { captureSession.startRunning() }

Lifecycle Balance

// ❌ Bad: not stopping session when view disappears
CameraPreview(session: manager.session)
    .onAppear { manager.start() }

// ✅ Good: balanced start/stop
CameraPreview(session: manager.session)
    .onAppear { manager.start() }
    .onDisappear { manager.stop() }

Permission Before Configuration

// ❌ Bad: configuring without checking permission
func setupCamera() {
    let input = try! AVCaptureDeviceInput(device: camera)
    session.addInput(input)
}

// ✅ Good: check permission first
func setupCamera() async {
    guard await requestCameraAccess() else { return }
    sessionQueue.async { [self] in configureSession() }
}

Audio Session Deactivation

// ❌ Bad: forgetting to deactivate audio session
func stopPlayback() { player.pause() }

// ✅ Good: deactivate to release audio resources
func stopPlayback() {
    player.pause()
    try? AVAudioSession.sharedInstance().setActive(false, options: .notifyOthersOnDeactivation)
}

Time Observer Cleanup

// ❌ Bad: leaking time observers
player.addPeriodicTimeObserver(forInterval: interval, queue: .main) { _ in }

// ✅ Good: store and remove
private var timeObserver: Any?
func observe() {
    timeObserver = player.addPeriodicTimeObserver(forInterval: interval, queue: .main) { _ in }
}
deinit {
    if let obs = timeObserver { player.removeTimeObserver(obs) }
}