fix: 音视频同步——音频从 firstFrameTime 开始读取
之前音频用 player.currentTime() 作为起始时间，视频用 AVPlayerItemVideoOutput 的 firstFrameTime，两者可能不一致 导致音视频不同步。 改为: - prepareAudioCapture: 只预加载音频轨道，不立即开始读取 - captureVideoFrame: 第一帧时设置 firstFrameTime 后调用 beginAudioReading(startTime: firstFrameTime) - 音频和视频共用同一个时间基准，确保精确同步 - 移除 startRecording 的 startTime 参数
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@ -122,8 +122,7 @@ final class PlayerBridge: ObservableObject {
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}
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guard !queue.isEmpty else { return }
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let sourceURL = queue[currentIndex].url
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let startTime = player.currentTime()
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screenRecorder.startRecording(from: output, sourceURL: sourceURL, startTime: startTime)
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screenRecorder.startRecording(from: output, sourceURL: sourceURL)
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}
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#endif
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}
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@ -22,6 +22,10 @@ final class PlayerRecorder: NSObject {
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/// 音频线程读取 firstFrameTime 的镜像
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nonisolated(unsafe) private var audioFirstFrameTime: CMTime?
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// 音频预加载状态
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private var pendingAudioAsset: AVURLAsset?
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private var pendingAudioTrack: AVAssetTrack?
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@Published var isRecording = false
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@Published var durationText = "00:00"
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@ -38,7 +42,7 @@ final class PlayerRecorder: NSObject {
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}
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/// 开始录制
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func startRecording(from output: AVPlayerItemVideoOutput, sourceURL: URL, startTime: CMTime) {
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func startRecording(from output: AVPlayerItemVideoOutput, sourceURL: URL) {
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guard !isRecording else { return }
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weakOutput = output
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@ -97,8 +101,8 @@ final class PlayerRecorder: NSObject {
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startTimer()
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startCaptureLoop()
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// 启动音频读取（从源 URL）
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startAudioCapture(sourceURL: sourceURL, startTime: startTime, audioWriterInput: aInput)
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// 准备音频读取（等待 firstFrameTime 后才真正开始）
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prepareAudioCapture(sourceURL: sourceURL)
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}
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/// 停止录制
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@ -151,6 +155,8 @@ final class PlayerRecorder: NSObject {
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audioFirstFrameTime = itemTime // 同步给音频线程
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writer?.startSession(atSourceTime: itemTime)
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isRunning = true
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// 音频预加载完成后，用 firstFrameTime 作为起始时间开始读取
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beginAudioReading(startTime: itemTime)
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}
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// 相对时间戳
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@ -182,8 +188,12 @@ final class PlayerRecorder: NSObject {
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}
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// MARK: - 音频读取（从源 URL）
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private func startAudioCapture(sourceURL: URL, startTime: CMTime, audioWriterInput: AVAssetWriterInput) {
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/// 预加载音频轨道（异步），不立即开始读取
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private func prepareAudioCapture(sourceURL: URL) {
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let asset = AVURLAsset(url: sourceURL)
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pendingAudioAsset = asset
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pendingAudioTrack = nil
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Task {
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do {
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@ -192,43 +202,66 @@ final class PlayerRecorder: NSObject {
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print("[Recorder] No audio track in source")
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return
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}
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let reader = try AVAssetReader(asset: asset)
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let output = AVAssetReaderTrackOutput(track: audioTrack, outputSettings: [
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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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output.alwaysCopiesSampleData = false
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// 从播放位置开始读取
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reader.timeRange = CMTimeRange(start: startTime, duration: .positiveInfinity)
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if reader.canAdd(output) {
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reader.add(output)
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reader.startReading()
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self.audioReader = reader
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self.audioReaderOutput = output
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// 后台线程读取音频
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let queue = DispatchQueue(label: "recorder.audio.capture")
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self.audioCaptureQueue = queue
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queue.async { [weak self] in
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guard let self = self, let aInput = self.audioInput else { return }
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self.readAudioLoop(reader: reader, output: output, audioInput: aInput)
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}
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self.pendingAudioTrack = audioTrack
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// 如果 firstFrameTime 已经设置好了，立即开始读取
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if let fft = self.firstFrameTime {
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self.beginAudioReading(startTime: fft)
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}
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} catch {
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print("[Recorder] Audio capture setup failed: \(error)")
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print("[Recorder] Audio track load failed: \(error)")
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}
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}
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}
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/// 用 firstFrameTime 作为起始时间，创建 reader 并开始后台读取
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private func beginAudioReading(startTime: CMTime) {
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guard let asset = pendingAudioAsset, let audioTrack = pendingAudioTrack else {
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return // 轨道还没加载好，prepareAudioCapture 的回调会再次调用
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}
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guard let aInput = audioInput else { return }
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// 防止重复启动
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guard audioReader == nil else { return }
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do {
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let reader = try AVAssetReader(asset: asset)
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let output = AVAssetReaderTrackOutput(track: audioTrack, outputSettings: [
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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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output.alwaysCopiesSampleData = false
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// 从视频第一帧时间开始读取，确保音视频同步
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reader.timeRange = CMTimeRange(start: startTime, duration: .positiveInfinity)
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if reader.canAdd(output) {
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reader.add(output)
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reader.startReading()
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self.audioReader = reader
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self.audioReaderOutput = output
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// 后台线程读取音频
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let queue = DispatchQueue(label: "recorder.audio.capture")
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self.audioCaptureQueue = queue
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queue.async { [weak self] in
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guard let self = self else { return }
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self.readAudioLoop(reader: reader, output: output, audioInput: aInput)
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}
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}
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} catch {
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print("[Recorder] Audio capture setup failed: \(error)")
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}
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// 清理预加载状态
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pendingAudioAsset = nil
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pendingAudioTrack = nil
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}
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private nonisolated func readAudioLoop(reader: AVAssetReader, output: AVAssetReaderTrackOutput, audioInput: AVAssetWriterInput) {
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while !audioStopped && reader.status == .reading {
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guard let sampleBuffer = output.copyNextSampleBuffer() else {
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