fix: 修复HLS流媒体录制无音频问题

- 存储tapPrepareCallback实际采样率，替代不可靠的timeRange.duration.timescale
- findAudioTrackID增加3路fallback: playerItem.tracks → asset.tracks → 非视频推断
- async load(.tracks)从单次尝试改为每3秒重试
- 增加muxed track fallback（HLS可能返回非标准mediaType）

Sources/PlayerRecorder.swift

@@ -15,6 +15,8 @@ class AudioCaptureContext {
     nonisolated(unsafe) var appendCount: Int = 0
     nonisolated(unsafe) var firstAppendLogged: Bool = false
     nonisolated(unsafe) var processCallCount: Int = 0
+    nonisolated(unsafe) var sampleRate: Double = 44100.0
+    nonisolated(unsafe) var channelsPerFrame: UInt32 = 2
 }
 
 // MARK: - MTAudioProcessingTap C 回调
@@ -39,6 +41,8 @@ private func tapPrepareCallback(
 ) {
     guard let ctx = gAudioContext else { return }
     var asbd = processingFormat.pointee
+    ctx.sampleRate = Double(asbd.mSampleRate)
+    ctx.channelsPerFrame = asbd.mChannelsPerFrame
     var fmtDesc: CMAudioFormatDescription?
     CMAudioFormatDescriptionCreate(
         allocator: kCFAllocatorDefault,
@@ -49,7 +53,7 @@ private func tapPrepareCallback(
         formatDescriptionOut: &fmtDesc
     )
     ctx.formatDescription = fmtDesc
-    NSLog("[Recorder] tapPrepare: %.1fHz, %uch", asbd.mSampleRate, asbd.mChannelsPerFrame)
+    NSLog("[Recorder] tapPrepare: %.1fHz, %uch, mFormatID=%u", asbd.mSampleRate, asbd.mChannelsPerFrame, asbd.mFormatID)
 }
 
 private func tapUnprepareCallback(_ tap: MTAudioProcessingTap) {
@@ -127,8 +131,7 @@ private func tapProcessCallback(
     }
     
     // PTS 基于累积帧数（与视频一样从0开始）
-    let sampleRate = Double(timeRange.duration.timescale) > 0
+    let sampleRate = ctx.sampleRate
-        ? Double(timeRange.duration.timescale) : 44100.0
     let ptsValue = Double(ctx.appendCount) / sampleRate
     let pts = CMTime(seconds: ptsValue, preferredTimescale: Int32(sampleRate))
     
@@ -408,12 +411,12 @@ final class PlayerRecorder: NSObject {
         }
         self.tracksObservation = observation
         
-        // 保底轮询：含 async asset.load(.tracks) 备选
+        // 保底轮询：含 async asset.load(.tracks) 多次重试
-        // 超时保护：30秒后放弃
+        // 超时保护：20秒后放弃
         Task {
             var attempts = 0
-            var didTryAsyncLoad = false
+            var lastAsyncAttempt = -100  // 确保首次就能尝试
-            while attempts < 300 && self.isRunning && self.audioTap == nil { // 30秒
+            while attempts < 200 && self.isRunning && self.audioTap == nil { // 20秒
                 try await Task.sleep(nanoseconds: 100_000_000) // 0.1秒
                 attempts += 1
                 
@@ -428,10 +431,10 @@ final class PlayerRecorder: NSObject {
                     return
                 }
                 
-                // 方式2: 5秒后尝试 async load asset tracks（HLS 可能通过这个路径加载）
+                // 方式2: 每3秒重试一次 async load asset tracks（HLS 关键路径）
-                if !didTryAsyncLoad && attempts >= 50 {
+                if attempts - lastAsyncAttempt >= 30 {
-                    didTryAsyncLoad = true
+                    lastAsyncAttempt = attempts
-                    NSLog("[Recorder] Trying async asset.load(.tracks)...")
+                    NSLog("[Recorder] Trying async asset.load(.tracks) (attempt at %d)...", attempts)
                     do {
                         let assetTracks = try await playerItem.asset.load(.tracks)
                         NSLog("[Recorder] async load returned %d tracks", assetTracks.count)
@@ -439,6 +442,7 @@ final class PlayerRecorder: NSObject {
                             NSLog("[Recorder]   assetTrack[%d]: mediaType=%@, trackID=%d",
                                   i, t.mediaType.rawValue as NSString, t.trackID)
                         }
+                        // 找音频 track
                         if let audioAssetTrack = assetTracks.first(where: { $0.mediaType == .audio }) {
                             let trackID = audioAssetTrack.trackID
                             NSLog("[Recorder] ✓ Audio track via async load: trackID=%d", trackID)
@@ -449,6 +453,17 @@ final class PlayerRecorder: NSObject {
                             self.tracksObservation = nil
                             return
                         }
+                        // 没找到音频，尝试非视频非音频 track（muxed）
+                        if let muxedTrack = assetTracks.first(where: { $0.mediaType != .video && $0.mediaType != .audio }) {
+                            let trackID = muxedTrack.trackID
+                            NSLog("[Recorder] ✓ Muxed track via async load: trackID=%d, trying as audio", trackID)
+                            await MainActor.run {
+                                guard self.isRunning, self.audioTap == nil else { return }
+                                self.installTap(on: playerItem, trackID: trackID, audioWriterInput: audioWriterInput)
+                            }
+                            self.tracksObservation = nil
+                            return
+                        }
                     } catch {
                         NSLog("[Recorder] async load failed: %@", error.localizedDescription)
                     }
@@ -462,29 +477,43 @@ final class PlayerRecorder: NSObject {
                 }
             }
             if self.audioTap == nil {
-                NSLog("[Recorder] ❌ No audio track found after %d polling attempts (30s timeout)", attempts)
+                NSLog("[Recorder] ❌ No audio track found after %d polling attempts (20s timeout)", attempts)
                 self.tracksObservation = nil
             }
         }
     }
     
     /// 从 playerItem.tracks 查找音频 trackID
-    /// 对 HLS 流，assetTrack 可能延迟加载或始终为 nil
+    /// 对 HLS 流，多路 fallback：playerItem.tracks → asset.tracks → 非视频推断
     private func findAudioTrackID(in playerItem: AVPlayerItem) -> CMPersistentTrackID? {
+        // 方式1: playerItem.tracks + assetTrack（本地文件 / 已加载的HLS）
         let itemTracks = playerItem.tracks
-        guard !itemTracks.isEmpty else { return nil }
+        for track in itemTracks {
-        
+            if let assetTrack = track.assetTrack, assetTrack.mediaType == .audio {
-        for (i, track) in itemTracks.enumerated() {
+                NSLog("[Recorder]   findTrack: audio via playerItem.tracks, trackID=%d", assetTrack.trackID)
-            guard let assetTrack = track.assetTrack else {
-                NSLog("[Recorder]   findTrack: track[%d] assetTrack=nil (not loaded)", i)
-                continue
-            }
-            NSLog("[Recorder]   findTrack: track[%d] mediaType=%@, trackID=%d, enabled=%d",
-                  i, assetTrack.mediaType.rawValue as NSString, assetTrack.trackID, track.isEnabled)
-            if assetTrack.mediaType == .audio {
                 return assetTrack.trackID
             }
         }
+        
+        // 方式2: asset.tracks（HLS 流可能通过这个路径能拿到）
+        let assetTracks = playerItem.asset.tracks
+        for track in assetTracks {
+            if track.mediaType == .audio {
+                NSLog("[Recorder]   findTrack: audio via asset.tracks, trackID=%d", track.trackID)
+                return track.trackID
+            }
+        }
+        
+        // 方式3: 如果有 track 但不是音频，找非视频的 track（可能是 muxed 或音频）
+        for track in itemTracks {
+            if let assetTrack = track.assetTrack,
+               assetTrack.mediaType != .video, assetTrack.mediaType != .audio {
+                NSLog("[Recorder]   findTrack: non-video track (mediaType=%@, trackID=%d), trying as audio",
+                      assetTrack.mediaType.rawValue as NSString, assetTrack.trackID)
+                return assetTrack.trackID
+            }
+        }
+        
         return nil
     }