claude's first attempt
This commit is contained in:
Samuel Newman
@@ -0,0 +1,369 @@
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import AVFoundation
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class VideoCompressor {
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private let url: URL
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private let targetBitrate: Int
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private let maxSize: Int
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private let jobId: Int
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private let onProgress: (Int, Double) -> Void
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private var isCancelled = false
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init(
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url: URL,
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targetBitrate: Int,
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maxSize: Int,
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jobId: Int,
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onProgress: @escaping (Int, Double) -> Void
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) {
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self.url = url
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self.targetBitrate = targetBitrate
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self.maxSize = maxSize
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self.jobId = jobId
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self.onProgress = onProgress
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}
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func cancel() {
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isCancelled = true
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}
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func compress() async throws -> [String: Any] {
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let asset = AVURLAsset(url: url)
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let duration = try await asset.load(.duration)
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let totalSeconds = CMTimeGetSeconds(duration)
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guard totalSeconds > 0 else {
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throw NSError(
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domain: "ExpoVideoCompress",
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code: 2,
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userInfo: [NSLocalizedDescriptionKey: "Invalid video duration"]
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)
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}
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// Load video track
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let videoTracks = try await asset.loadTracks(withMediaType: .video)
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guard let videoTrack = videoTracks.first else {
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throw NSError(
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domain: "ExpoVideoCompress",
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code: 1,
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userInfo: [NSLocalizedDescriptionKey: "No video track found"]
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)
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}
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let naturalSize = try await videoTrack.load(.naturalSize)
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let preferredTransform = try await videoTrack.load(.preferredTransform)
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// Calculate output dimensions
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let outputSize = calculateOutputSize(
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naturalSize: naturalSize,
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transform: preferredTransform,
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maxSize: maxSize
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)
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// Load audio tracks
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let audioTracks = try await asset.loadTracks(withMediaType: .audio)
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let hasAudio = !audioTracks.isEmpty
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// Audio analysis for passthrough decision
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var shouldPassthroughAudio = false
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if hasAudio, let audioTrack = audioTracks.first {
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shouldPassthroughAudio = try await canPassthroughAudio(audioTrack)
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}
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// Create output file
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let outputURL = FileManager.default.temporaryDirectory
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.appendingPathComponent(UUID().uuidString)
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.appendingPathExtension("mp4")
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// Set up reader
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let reader = try AVAssetReader(asset: asset)
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let writer = try AVAssetWriter(outputURL: outputURL, fileType: .mp4)
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// Video reader output - request raw frames
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let videoReaderSettings: [String: Any] = [
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kCVPixelBufferPixelFormatTypeKey as String: kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange
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]
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let videoReaderOutput = AVAssetReaderTrackOutput(
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track: videoTrack,
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outputSettings: videoReaderSettings
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)
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videoReaderOutput.alwaysCopiesSampleData = false
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guard reader.canAdd(videoReaderOutput) else {
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throw NSError(
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domain: "ExpoVideoCompress",
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code: 3,
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userInfo: [NSLocalizedDescriptionKey: "Cannot read video track"]
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)
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}
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reader.add(videoReaderOutput)
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// Video writer input
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let videoWriterSettings: [String: Any] = [
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AVVideoCodecKey: AVVideoCodecType.h264,
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AVVideoWidthKey: outputSize.width,
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AVVideoHeightKey: outputSize.height,
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AVVideoCompressionPropertiesKey: [
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AVVideoAverageBitRateKey: targetBitrate,
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AVVideoProfileLevelKey: AVVideoProfileLevelH264HighAutoLevel,
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AVVideoMaxKeyFrameIntervalKey: 90, // ~3s at 30fps
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AVVideoExpectedSourceFrameRateKey: 30
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] as [String: Any]
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]
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let videoWriterInput = AVAssetWriterInput(
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mediaType: .video,
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outputSettings: videoWriterSettings
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)
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videoWriterInput.expectsMediaDataInRealTime = false
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// Apply transform for rotation
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videoWriterInput.transform = preferredTransform
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guard writer.canAdd(videoWriterInput) else {
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throw NSError(
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domain: "ExpoVideoCompress",
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code: 4,
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userInfo: [NSLocalizedDescriptionKey: "Cannot write video track"]
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)
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}
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writer.add(videoWriterInput)
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// Audio setup
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var audioReaderOutput: AVAssetReaderOutput?
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var audioWriterInput: AVAssetWriterInput?
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if hasAudio, let audioTrack = audioTracks.first {
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if shouldPassthroughAudio {
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// Passthrough - copy audio as-is
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let audioOutput = AVAssetReaderTrackOutput(
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track: audioTrack,
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outputSettings: nil
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)
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audioOutput.alwaysCopiesSampleData = false
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if reader.canAdd(audioOutput) {
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reader.add(audioOutput)
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audioReaderOutput = audioOutput
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let audioInput = AVAssetWriterInput(
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mediaType: .audio,
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outputSettings: nil
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)
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audioInput.expectsMediaDataInRealTime = false
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if writer.canAdd(audioInput) {
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writer.add(audioInput)
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audioWriterInput = audioInput
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}
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}
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} else {
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// Re-encode audio to AAC 128kbps
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let audioDecoderSettings: [String: Any] = [
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AVFormatIDKey: kAudioFormatLinearPCM,
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AVSampleRateKey: 44100,
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AVNumberOfChannelsKey: 2,
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AVLinearPCMBitDepthKey: 16,
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AVLinearPCMIsFloatKey: false,
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AVLinearPCMIsBigEndianKey: false,
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AVLinearPCMIsNonInterleaved: false
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]
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let audioOutput = AVAssetReaderTrackOutput(
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track: audioTrack,
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outputSettings: audioDecoderSettings
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)
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audioOutput.alwaysCopiesSampleData = false
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if reader.canAdd(audioOutput) {
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reader.add(audioOutput)
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audioReaderOutput = audioOutput
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let audioEncoderSettings: [String: Any] = [
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AVFormatIDKey: kAudioFormatMPEG4AAC,
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AVSampleRateKey: 44100,
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AVNumberOfChannelsKey: 2,
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AVEncoderBitRateKey: 128_000
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]
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let audioInput = AVAssetWriterInput(
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mediaType: .audio,
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outputSettings: audioEncoderSettings
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)
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audioInput.expectsMediaDataInRealTime = false
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if writer.canAdd(audioInput) {
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writer.add(audioInput)
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audioWriterInput = audioInput
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}
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}
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}
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}
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// Start reading/writing
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reader.startReading()
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writer.startWriting()
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writer.startSession(atSourceTime: .zero)
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// Process video and audio concurrently
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try await withThrowingTaskGroup(of: Void.self) { group in
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// Video processing
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group.addTask {
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try await self.processTrack(
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readerOutput: videoReaderOutput,
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writerInput: videoWriterInput,
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totalDuration: totalSeconds
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)
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}
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// Audio processing
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if let audioOutput = audioReaderOutput, let audioInput = audioWriterInput {
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group.addTask {
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try await self.processTrack(
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readerOutput: audioOutput,
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writerInput: audioInput,
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totalDuration: nil
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)
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}
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}
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try await group.waitForAll()
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}
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// Check for cancellation
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if isCancelled {
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writer.cancelWriting()
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try? FileManager.default.removeItem(at: outputURL)
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throw NSError(
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domain: "ExpoVideoCompress",
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code: 5,
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userInfo: [NSLocalizedDescriptionKey: "Compression cancelled"]
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)
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}
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// Check reader status
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if reader.status == .failed {
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let error = reader.error ?? NSError(
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domain: "ExpoVideoCompress",
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code: 6,
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userInfo: [NSLocalizedDescriptionKey: "Reader failed"]
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)
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writer.cancelWriting()
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try? FileManager.default.removeItem(at: outputURL)
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throw error
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}
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// Finish writing
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await writer.finishWriting()
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if writer.status == .failed {
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let error = writer.error ?? NSError(
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domain: "ExpoVideoCompress",
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code: 7,
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userInfo: [NSLocalizedDescriptionKey: "Writer failed"]
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)
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try? FileManager.default.removeItem(at: outputURL)
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throw error
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}
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// Get output file attributes
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let attributes = try FileManager.default.attributesOfItem(atPath: outputURL.path)
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let fileSize = attributes[.size] as? Int ?? 0
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return [
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"uri": outputURL.absoluteString,
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"size": fileSize,
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"mimeType": "video/mp4",
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"width": outputSize.width,
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"height": outputSize.height,
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"duration": totalSeconds
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]
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}
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private func processTrack(
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readerOutput: AVAssetReaderOutput,
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writerInput: AVAssetWriterInput,
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totalDuration: Double?
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) async throws {
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var lastProgressTime: CFAbsoluteTime = 0
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await withCheckedContinuation { (continuation: CheckedContinuation<Void, Never>) in
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writerInput.requestMediaDataWhenReady(on: DispatchQueue(label: "com.bluesky.videocompress")) {
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while writerInput.isReadyForMoreMediaData {
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if self.isCancelled {
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writerInput.markAsFinished()
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continuation.resume()
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return
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}
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guard let sampleBuffer = readerOutput.copyNextSampleBuffer() else {
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writerInput.markAsFinished()
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continuation.resume()
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return
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}
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// Send progress events (throttled to ~10/sec) for video track only
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if let totalDuration = totalDuration {
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let now = CFAbsoluteTimeGetCurrent()
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if now - lastProgressTime >= 0.1 {
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lastProgressTime = now
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let pts = CMSampleBufferGetPresentationTimeStamp(sampleBuffer)
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let progress = min(CMTimeGetSeconds(pts) / totalDuration, 1.0)
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self.onProgress(self.jobId, progress)
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}
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}
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writerInput.append(sampleBuffer)
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}
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}
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}
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}
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private func calculateOutputSize(
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naturalSize: CGSize,
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transform: CGAffineTransform,
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maxSize: Int
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) -> (width: Int, height: Int) {
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// Apply transform to get actual display dimensions
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let isRotated = abs(transform.b) == 1.0 && abs(transform.c) == 1.0
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let sourceWidth = isRotated ? naturalSize.height : naturalSize.width
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let sourceHeight = isRotated ? naturalSize.width : naturalSize.height
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let maxDimension = CGFloat(maxSize)
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// If already within bounds, keep original size (rounded to even)
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if sourceWidth <= maxDimension && sourceHeight <= maxDimension {
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return (
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width: roundToEven(Int(sourceWidth)),
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height: roundToEven(Int(sourceHeight))
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)
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}
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// Scale down maintaining aspect ratio
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let scale: CGFloat
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if sourceWidth > sourceHeight {
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scale = maxDimension / sourceWidth
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} else {
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scale = maxDimension / sourceHeight
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}
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return (
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width: roundToEven(Int(sourceWidth * scale)),
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height: roundToEven(Int(sourceHeight * scale))
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)
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}
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private func roundToEven(_ value: Int) -> Int {
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return value % 2 == 0 ? value : value - 1
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}
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private func canPassthroughAudio(_ audioTrack: AVAssetTrack) async throws -> Bool {
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let formatDescriptions = try await audioTrack.load(.formatDescriptions)
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guard let formatDesc = formatDescriptions.first else {
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return false
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}
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let mediaSubType = CMFormatDescriptionGetMediaSubType(formatDesc)
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// Only passthrough AAC audio
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guard mediaSubType == kAudioFormatMPEG4AAC else {
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return false
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}
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// Check bitrate - passthrough if <= 128kbps
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let estimatedDataRate = try await audioTrack.load(.estimatedDataRate)
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return estimatedDataRate <= 128_000
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}
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}
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