diff --git a/Sources/PlayerRecorder.swift b/Sources/PlayerRecorder.swift
index 0f9119b..3afceb2 100644
--- a/Sources/PlayerRecorder.swift
+++ b/Sources/PlayerRecorder.swift
@@ -1,50 +1,43 @@
 import AVFoundation
 import CoreMedia
-import MediaToolbox
 #if os(macOS)
 import AppKit
 
-// MARK: - 音频捕获上下文（通过 tapStorage 传给 C 回调）
+// MARK: - 音频捕获上下文
 class AudioCaptureContext {
     var writerInput: AVAssetWriterInput?
     nonisolated(unsafe) var isRunning: Bool = true
-    nonisolated(unsafe) var formatDescription: CMAudioFormatDescription?
     nonisolated(unsafe) var appendCount: Int = 0
+    nonisolated(unsafe) var formatDescription: CMAudioFormatDescription?
+    nonisolated(unsafe) var firstAppendLogged: Bool = false
 }
 
-// MARK: - MTAudioProcessingTap C 回调函数
-
-private func tapInit(_ tap: MTAudioProcessingTap,
-                     _ clientInfo: UnsafeMutableRawPointer?,
-                     _ tapStorageOut: UnsafeMutablePointer<UnsafeMutableRawPointer?>) {
-    // 将 clientInfo 存入 tapStorage
-    tapStorageOut.pointee = clientInfo
-}
-
-private func tapFinalize(_ tap: MTAudioProcessingTap) {
-    // 释放 context 的 Unmanaged 引用
-    guard let storage = Optional(MTAudioProcessingTapGetStorage(tap)),
-          let ctxPtr = storage.assumingMemoryBound(to: UnsafeMutableRawPointer?.self).pointee else { return }
-    Unmanaged<AudioCaptureContext>.fromOpaque(ctxPtr).release()
-}
+/// 全局引用，供 C 回调访问（单实例录制，线程安全由 isRunning 保护）
+private nonisolated(unsafe) var gAudioContext: AudioCaptureContext?
 
+// MARK: - MTAudioProcessingTap C 回调
 private func tapPrepare(_ tap: MTAudioProcessingTap,
-                        _ maxFrames: Int,
+                        _ maxFramesPerSlice: CMItemCount,
                         _ processingFormat: UnsafePointer<AudioStreamBasicDescription>) {
-    guard let storage = Optional(MTAudioProcessingTapGetStorage(tap)),
-          let ctxPtr = storage.assumingMemoryBound(to: UnsafeMutableRawPointer?.self).pointee else { return }
-    let ctx = Unmanaged<AudioCaptureContext>.fromOpaque(ctxPtr).takeUnretainedValue()
-    
+    print("[Recorder] tapPrepare called, maxFrames=\(maxFramesPerSlice)")
+    guard let ctx = gAudioContext else {
+        print("[Recorder] tapPrepare: gAudioContext is nil!")
+        return
+    }
     var asbd = processingFormat.pointee
-    var fmtDesc: CMAudioFormatDescription?
+    print("[Recorder] tapPrepare: sampleRate=\(asbd.mSampleRate), channels=\(asbd.mChannelsPerFrame)")
     CMAudioFormatDescriptionCreate(allocator: kCFAllocatorDefault,
                                     asbd: &asbd,
                                     layoutSize: 0, layout: nil,
                                     magicCookieSize: 0, magicCookie: nil,
                                     extensions: nil,
-                                    formatDescriptionOut: &fmtDesc)
-    ctx.formatDescription = fmtDesc
-    print("[Recorder] Audio tap prepared: \(asbd.mSampleRate)Hz, \(asbd.mChannelsPerFrame)ch, format=\(asbd.mFormatID)")
+                                    formatDescriptionOut: &ctx.formatDescription)
+}
+
+private func tapInit(_ tap: MTAudioProcessingTap,
+                     _ clientInfo: UnsafeMutableRawPointer?,
+                     _ tapStorageOut: UnsafeMutablePointer<UnsafeMutableRawPointer?>) {
+    // 初始化 tap
 }
 
 private func tapUnprepare(_ tap: MTAudioProcessingTap) {
@@ -52,7 +45,7 @@ private func tapUnprepare(_ tap: MTAudioProcessingTap) {
 }
 
 private func tapProcess(_ tap: MTAudioProcessingTap,
-                         _ numberOfFrames: CMItemCount,
+                         _ numberFrames: CMItemCount,
                          _ flags: MTAudioProcessingTapFlags,
                          _ bufferListInOut: UnsafeMutablePointer<AudioBufferList>,
                          _ numberFramesOut: UnsafeMutablePointer<CMItemCount>,
@@ -62,18 +55,14 @@ private func tapProcess(_ tap: MTAudioProcessingTap,
     
     guard numberFrames > 0 else { return }
     
-    // 获取源音频数据 + 时间范围
+    // 先获取源音频数据
     var timeRange = CMTimeRange()
-    var srcFlags: UInt32 = 0
-    var actualFrames: Int = 0
+    var srcFlags: MTAudioProcessingTapFlags = 0
+    var actualFrames: CMItemCount = 0
     
     let status = MTAudioProcessingTapGetSourceAudio(
-        tap,
-        numberFrames,
-        bufferListInOut,
-        &srcFlags,
-        &timeRange,
-        &actualFrames
+        tap, numberFrames, bufferListInOut,
+        &srcFlags, &timeRange, &actualFrames
     )
     
     numberFramesOut.pointee = actualFrames
@@ -81,71 +70,71 @@ private func tapProcess(_ tap: MTAudioProcessingTap,
     
     guard status == noErr, actualFrames > 0 else { return }
     
-    // 获取 context
-    guard let storage = Optional(MTAudioProcessingTapGetStorage(tap)),
-          let ctxPtr = storage.assumingMemoryBound(to: UnsafeMutableRawPointer?.self).pointee else { return }
-    let ctx = Unmanaged<AudioCaptureContext>.fromOpaque(ctxPtr).takeUnretainedValue()
-    
-    guard ctx.isRunning, let writerInput = ctx.writerInput,
+    // 通过全局变量获取 context
+    guard let ctx = gAudioContext, ctx.isRunning,
+          let writerInput = ctx.writerInput,
           writerInput.isReadyForMoreMediaData else { return }
     
     let bufferList = bufferListInOut.pointee
     guard bufferList.mNumberBuffers > 0 else { return }
     
-    // 计算总字节数
-    var totalBytes: UInt32 = 0
-    for i in 0..<Int(bufferList.mNumberBuffers) {
-        let buf = bufferList.mBuffers // Note: only single buffer for interleaved
-        totalBytes = buf.mDataByteSize
-        break
-    }
-    guard totalBytes > 0, let srcData = bufferList.mBuffers.mData else { return }
+    let buf = bufferList.mBuffers
+    let dataSize = Int(buf.mDataByteSize)
+    guard dataSize > 0, let srcData = buf.mData else { return }
     
     // 创建 CMBlockBuffer
     var blockBuffer: CMBlockBuffer?
-    guard CMBlockBufferCreateWithMemoryBlock(
-        allocator: kCFAllocatorDefault,
-        memoryBlock: nil,
-        blockLength: Int(totalBytes),
-        blockAllocator: kCFAllocatorDefault,
-        customBlockSource: nil,
-        offsetToData: 0,
-        dataLength: Int(totalBytes),
+    let blockStatus = CMBlockBufferCreateWithMemoryBlock(
+        allocator: kCFAllocatorDefault, memoryBlock: nil,
+        blockLength: dataSize, blockAllocator: kCFAllocatorDefault,
+        customBlockSource: nil, offsetToData: 0,
+        dataLength: dataSize,
         flags: kCMBlockBufferAssureMemoryNowFlag,
         blockBufferOut: &blockBuffer
-    ) == kCMBlockBufferNoErr, let bb = blockBuffer else { return }
+    )
+    guard blockStatus == kCMBlockBufferNoErr, let bb = blockBuffer else { return }
     
-    // 复制音频数据
-    guard CMBlockBufferReplaceDataBytes(
-        with: srcData,
-        blockBuffer: bb,
-        offsetIntoDestination: 0,
-        dataLength: Int(totalBytes)
-    ) == kCMBlockBufferNoErr else { return }
+    let replaceStatus = CMBlockBufferReplaceDataBytes(
+        with: srcData, blockBuffer: bb,
+        offsetIntoDestination: 0, dataLength: dataSize
+    )
+    guard replaceStatus == kCMBlockBufferNoErr else { return }
     
-    // 获取格式描述
-    guard let fmtDesc = ctx.formatDescription else { return }
+    // 获取 format description
+    guard let fd = ctx.formatDescription else { return }
+    
+    // 用累积帧数计算 PTS
+    let sampleRate = Double(timeRange.duration.timescale) > 0
+        ? Double(timeRange.duration.timescale) : 44100.0
+    let ptsValue = Double(ctx.appendCount) / sampleRate
+    let pts = CMTime(seconds: ptsValue, preferredTimescale: Int32(sampleRate))
     
-    // 创建 CMSampleBuffer（使用 timeRange 的 start 作为 PTS）
     var sampleBuffer: CMSampleBuffer?
     let createStatus = CMAudioSampleBufferCreateReadyWithPacketDescriptions(
         allocator: kCFAllocatorDefault,
         dataBuffer: bb,
-        formatDescription: fmtDesc,
+        formatDescription: fd,
         sampleCount: actualFrames,
-        presentationTimeStamp: timeRange.start,
+        presentationTimeStamp: pts,
         packetDescriptions: nil,
         sampleBufferOut: &sampleBuffer
     )
-    
     guard createStatus == noErr, let sb = sampleBuffer else { return }
     
     if writerInput.append(sb) {
         ctx.appendCount += actualFrames
+        if !ctx.firstAppendLogged {
+            ctx.firstAppendLogged = true
+            print("[Recorder] ✓ First audio frame appended! pts=\(pts.seconds)s, frames=\(actualFrames)")
+        }
     }
 }
 
-/// 视频源录制器：AVPlayerItemVideoOutput 抓帧 + MTAudioProcessingTap 捕获音频
+// 空的 init/finalize 回调
+private func tapInit(_ tap: MTAudioProcessingTap) {}
+private func tapFinalize(_ tap: MTAudioProcessingTap) {}
+
+/// 视频源录制器：从 AVPlayerItemVideoOutput 抓帧 + MTAudioProcessingTap 捕获音频，写入 mp4
 @MainActor
 final class PlayerRecorder: NSObject {
     
@@ -157,12 +146,13 @@ final class PlayerRecorder: NSObject {
     private var weakOutput: AVPlayerItemVideoOutput?
     nonisolated(unsafe) private var isRunning = false
     
-    // 视频：缓存上一帧
+    // 视频：缓存上一帧，确保静态场景也能持续写入
     private var lastPixelBuffer: CVPixelBuffer?
     private var captureFrameCount: Int = 0
     
     // 音频 (MTAudioProcessingTap)
     private var audioTap: MTAudioProcessingTap?
+    private var audioContext: AudioCaptureContext?
     private weak var currentPlayerItem: AVPlayerItem?
     
     nonisolated(unsafe) private var recordStartTime: CMTime = .zero
@@ -236,14 +226,15 @@ final class PlayerRecorder: NSObject {
             audioInput = aInput
         }
         
-        guard writer.startWriting() else {
+        let success = writer.startWriting()
+        if !success {
             print("[Recorder] startWriting failed: \(writer.error?.localizedDescription ?? "unknown")")
             onError?("Cannot start writer: \(writer.error?.localizedDescription ?? "unknown")")
             return
         }
         
         writer.startSession(atSourceTime: .zero)
-        print("[Recorder] Writer started")
+        print("[Recorder] Writer started, session at .zero")
         
         // 启动视频抓帧
         isRecording = true
@@ -251,7 +242,7 @@ final class PlayerRecorder: NSObject {
         startTimer()
         startCaptureLoop()
         
-        // 启动音频捕获
+        // 启动音频捕获（MTAudioProcessingTap）
         setupAudioTap(playerItem: playerItem, audioWriterInput: aInput)
     }
     
@@ -265,9 +256,16 @@ final class PlayerRecorder: NSObject {
         stopTimer()
         
         // 停止音频 tap
+        audioContext?.isRunning = false
+        
+        // 移除 audioMix（移除 tap）
         currentPlayerItem?.audioMix = nil
         currentPlayerItem = nil
+        
+        // 释放 tap 和 context
         audioTap = nil
+        audioContext = nil
+        gAudioContext = nil
         
         videoInput?.markAsFinished()
         audioInput?.markAsFinished()
@@ -275,8 +273,8 @@ final class PlayerRecorder: NSObject {
         writer?.finishWriting { [weak self] in
             Task { @MainActor in
                 guard let self = self, let w = self.writer else { return }
-                let vFrames = self.captureFrameCount
-                print("[Recorder] finishWriting status: \(w.status.rawValue), error: \(w.error?.localizedDescription ?? "none"), video frames: \(vFrames)")
+                let count = self.captureFrameCount
+                print("[Recorder] finishWriting status: \(w.status.rawValue), error: \(w.error?.localizedDescription ?? "none"), video frames: \(count)")
                 if w.status == .completed, let url = self.tempURL {
                     self.showSaveDialog(tempURL: url)
                 } else {
@@ -299,22 +297,29 @@ final class PlayerRecorder: NSObject {
             do {
                 let audioTracks = try await asset.loadTracks(withMediaType: .audio)
                 guard let audioTrack = audioTracks.first else {
-                    print("[Recorder] No audio track for tap")
+                    print("[Recorder] ❌ No audio track for tap")
+                    return
+                }
+                guard self.isRunning else {
+                    print("[Recorder] ❌ isRunning=false, aborting audio tap setup")
                     return
                 }
-                guard self.isRunning else { return }
                 
-                // 创建 context，用 Unmanaged 传递给 C 回调
+                print("[Recorder] Audio track found: \(audioTrack.trackID), setting up tap...")
+                
+                // 创建音频捕获上下文
                 let context = AudioCaptureContext()
                 context.writerInput = audioWriterInput
                 context.isRunning = true
+                self.audioContext = context
                 
-                let contextPtr = Unmanaged.passRetained(context).toOpaque()
+                // ★ 设置全局引用，供 C 回调访问
+                gAudioContext = context
                 
-                // 创建回调结构体
+                // 创建 MTAudioProcessingTap
                 var callbacks = MTAudioProcessingTapCallbacks(
                     version: kMTAudioProcessingTapCallbacksVersion_0,
-                    clientInfo: contextPtr,
+                    clientInfo: nil,
                     init: tapInit,
                     finalize: tapFinalize,
                     prepare: tapPrepare,
@@ -323,33 +328,31 @@ final class PlayerRecorder: NSObject {
                 )
                 
                 var tap: MTAudioProcessingTap?
-                let status = withUnsafePointer(to: &callbacks) { cbPtr in
-                    MTAudioProcessingTapCreate(
-                        kCFAllocatorDefault,
-                        cbPtr,
-                        kMTAudioProcessingTapCreationFlag_PostEffects,
-                        &tap
-                    )
-                }
+                let status = MTAudioProcessingTapCreate(
+                    kCFAllocatorDefault,
+                    &callbacks,
+                    kMTAudioProcessingTapCreationFlag_PostEffects,
+                    &tap
+                )
                 
                 guard status == noErr, let audioTap = tap else {
-                    print("[Recorder] MTAudioProcessingTapCreate failed: \(status)")
-                    Unmanaged<AudioCaptureContext>.fromOpaque(contextPtr).release()
+                    print("[Recorder] ❌ MTAudioProcessingTapCreate failed: \(status)")
+                    gAudioContext = nil
                     return
                 }
                 
                 self.audioTap = audioTap
                 
-                // 创建 audioMix
+                // 创建 audioMix 并挂上 tap
                 let params = AVMutableAudioMixInputParameters(track: audioTrack)
                 params.audioTapProcessor = audioTap
                 let audioMix = AVMutableAudioMix()
                 audioMix.inputParameters = [params]
                 
                 playerItem.audioMix = audioMix
-                print("[Recorder] Audio tap installed")
+                print("[Recorder] ✓ Audio tap installed on player item")
             } catch {
-                print("[Recorder] Audio tap setup failed: \(error)")
+                print("[Recorder] ❌ Audio tap setup failed: \(error)")
             }
         }
     }
@@ -372,12 +375,14 @@ final class PlayerRecorder: NSObject {
         let hostTime = CACurrentMediaTime()
         let itemTime = output.itemTime(forHostTime: hostTime)
         
+        // 尝试获取新帧，否则复用上一帧
         if let pb = output.copyPixelBuffer(forItemTime: itemTime, itemTimeForDisplay: nil) {
             lastPixelBuffer = pb
         }
         
         guard let pb = lastPixelBuffer else { return }
         
+        // 相对时间戳
         let relativeTime = CMTimeSubtract(itemTime, recordStartTime)
         guard relativeTime.seconds >= 0 else { return }
         
@@ -405,7 +410,7 @@ final class PlayerRecorder: NSObject {
         return sampleBuffer
     }
     
-    // MARK: - Timer
+    // MARK: - Timer (显示录制时长)
     private func startTimer() {
         startDate = Date()
         durationText = "00:00"