MyApp/CameraCaptureService.swift

1import AVFoundation2import UIKit3import CoreImage4 5/// The actor and AVFoundation delegates share one serial executor. No unchecked6/// Sendable conformance or asynchronous transfer of mutable sample buffers is used.7actor CameraCaptureService {8    nonisolated let queue = DispatchSerialQueue(label: "party.capture", qos: .userInitiated)9    nonisolated var unownedExecutor: UnownedSerialExecutor { queue.asUnownedSerialExecutor() }10    private let session = AVCaptureSession()11    private let video = AVCaptureVideoDataOutput()12    private let audio = AVCaptureAudioDataOutput()13    private let context = CIContext()14    private var writer: AVAssetWriter?15    private var videoInput: AVAssetWriterInput?16    private var audioInput: AVAssetWriterInput?17    private var origin: CMTime?18    private var videoTime: Double = 019    private var audioTime: Double = 020    private var hasVideo = false21    private var hasAudio = false22    private var lastPreview: Double = 023    private var recordingURL: URL?24    private var captureError: String?25    private var onFrame: (@MainActor @Sendable (UIImage) -> Void)?26    private lazy var delegate = SampleDelegate { [weak self] output, buffer in27        self?.assumeIsolated { isolatedSelf in28            isolatedSelf.receive(output: output, sampleBuffer: buffer)29        }30    }31 32    func setFrameHandler(_ handler: @escaping @MainActor @Sendable (UIImage) -> Void) { onFrame = handler }33 34    func configure(cameraID: String, rotationAngle: Double) throws {35        guard writer == nil else { throw PartyError.message("Stop recording before changing cameras.") }36        session.stopRunning()37        session.beginConfiguration()38        do {39            session.inputs.forEach { session.removeInput($0) }40            session.outputs.forEach { session.removeOutput($0) }41            session.automaticallyConfiguresApplicationAudioSession = false42            session.sessionPreset = session.canSetSessionPreset(.hd1920x1080) ? .hd1920x1080 : .high43            guard let camera = AVCaptureDevice(uniqueID: cameraID),44                  let mic = AVCaptureDevice.default(for: .audio) else {45                throw PartyError.message("Camera or microphone unavailable. Use nonrecording mode.")46            }47            for device in [camera, mic] {48                let input = try AVCaptureDeviceInput(device: device)49                guard session.canAddInput(input) else { throw PartyError.message("Capture input unavailable.") }50                session.addInput(input)51            }52            for output in [video as AVCaptureOutput, audio as AVCaptureOutput] {53                guard session.canAddOutput(output) else { throw PartyError.message("Capture output unavailable.") }54                session.addOutput(output)55            }56            video.alwaysDiscardsLateVideoFrames = true57            video.setSampleBufferDelegate(delegate, queue: queue)58            audio.setSampleBufferDelegate(delegate, queue: queue)59            if let connection = video.connection(with: .video), connection.isVideoRotationAngleSupported(rotationAngle) {60                connection.videoRotationAngle = rotationAngle61            }62            if camera.activeFormat.videoSupportedFrameRateRanges.contains(where: { $0.minFrameRate <= 30 && $0.maxFrameRate >= 30 }) {63                try camera.lockForConfiguration()64                camera.activeVideoMinFrameDuration = CMTime(value: 1, timescale: 30)65                camera.activeVideoMaxFrameDuration = CMTime(value: 1, timescale: 30)66                camera.unlockForConfiguration()67            }68            session.commitConfiguration()69        } catch {70            session.commitConfiguration()71            throw error72        }73        session.startRunning()74    }75 76    func start(url: URL) throws {77        guard session.isRunning, writer == nil else { throw PartyError.message("Camera is not ready.") }78        guard let videoSettings = video.recommendedVideoSettingsForAssetWriter(writingTo: .mov),79              let audioSettings = audio.recommendedAudioSettingsForAssetWriter(writingTo: .mov) else {80            throw PartyError.message("Recording settings unavailable.")81        }82        let writer = try AVAssetWriter(outputURL: url, fileType: .mov)83        let v = AVAssetWriterInput(mediaType: .video, outputSettings: videoSettings)84        let a = AVAssetWriterInput(mediaType: .audio, outputSettings: audioSettings)85        v.expectsMediaDataInRealTime = true86        a.expectsMediaDataInRealTime = true87        guard writer.canAdd(v), writer.canAdd(a) else { throw PartyError.message("Unsupported recording format.") }88        writer.add(v); writer.add(a)89        guard writer.startWriting() else { throw writer.error ?? PartyError.message("Recording could not start.") }90        self.writer = writer; videoInput = v; audioInput = a91        origin = nil; hasVideo = false; hasAudio = false92        videoTime = 0; audioTime = 0; captureError = nil93        recordingURL = url94    }95 96    func timeline() throws -> Double {97        if let captureError { throw PartyError.message(captureError) }98        guard writer?.status == .writing else { throw PartyError.message("Recording stopped unexpectedly.") }99        return hasVideo && hasAudio ? min(videoTime, audioTime) : 0100    }101 102    func finish() async throws -> URL {103        guard let writer, let url = recordingURL else { throw PartyError.message("No recording to finish.") }104        let valid = hasVideo && hasAudio && captureError == nil105        self.writer = nil106        videoInput?.markAsFinished(); audioInput?.markAsFinished()107        await writer.finishWriting()108        guard writer.status == .completed && valid else {109            throw writer.error ?? PartyError.message("Incomplete capture; attempt voided.")110        }111        return url112    }113 114    func stop() {115        writer?.cancelWriting(); writer = nil116        session.stopRunning()117    }118 119    private func receive(output: AVCaptureOutput, sampleBuffer: CMSampleBuffer) {120        let pts = CMSampleBufferGetPresentationTimeStamp(sampleBuffer)121        let isVideo = output === video122        // Recording gets first priority. Preview is deliberately throttled to 10 fps.123        if let writer, writer.status == .writing {124            if origin == nil, isVideo { origin = pts; writer.startSession(atSourceTime: pts) }125            if let origin, pts >= origin {126                let elapsed = (pts - origin).seconds127                if elapsed >= 20 { captureError = "20-second recording limit reached."; writer.cancelWriting(); return }128                let input = isVideo ? videoInput : audioInput129                if let input, input.isReadyForMoreMediaData, input.append(sampleBuffer) {130                    if isVideo { videoTime = elapsed; hasVideo = true }131                    else { audioTime = elapsed; hasAudio = true }132                } else { captureError = "Recording could not keep up. Please retry." }133            }134        }135        if isVideo, pts.seconds - lastPreview > 0.10, let buffer = CMSampleBufferGetImageBuffer(sampleBuffer) {136            lastPreview = pts.seconds137            let source = CIImage(cvPixelBuffer: buffer)138            let scaled = source.transformed(by: CGAffineTransform(scaleX: 0.45, y: 0.45))139            if let cg = context.createCGImage(scaled, from: scaled.extent) {140                let image = UIImage(cgImage: cg)141                let callback = onFrame142                Task { @MainActor in callback?(image) }143            }144        }145    }146}147 148private final class SampleDelegate: NSObject, AVCaptureVideoDataOutputSampleBufferDelegate, AVCaptureAudioDataOutputSampleBufferDelegate {149    let handler: @Sendable (AVCaptureOutput, CMSampleBuffer) -> Void150    init(handler: @escaping @Sendable (AVCaptureOutput, CMSampleBuffer) -> Void) { self.handler = handler }151    func captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) {152        handler(output, sampleBuffer)153    }154}