AVMutableComposition刪除視頻音軌

我一直在嘗試使用AVMutableComposition將音頻（錄製）與視頻（.mp4）混合，這意味着我需要2個文件在混合後並行播放，這裏是代碼i使用： temporaryRecFile正在錄製的文件URL路徑 audiosURL是視頻文件的URL路徑AVMutableComposition刪除視頻音軌

NSURL *audiosURL =[[NSURL alloc] initFileURLWithPath:[[NSBundle mainBundle] pathForResource:[NSString stringWithFormat:@"dam3.mp4"] ofType:nil]]; 

     NSLog(@"SOMEDATA IS THERE "); 
     AVURLAsset* audioAsset = [[AVURLAsset alloc]initWithURL:temporaryRecFile options:nil]; 
     AVURLAsset* audio2Asset = [[AVURLAsset alloc]initWithURL:audiosURL options:nil]; 

     AVMutableComposition* mixComposition = [AVMutableComposition composition]; 

    AVMutableCompositionTrack *compositionCommentary2Track = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid]; 
    [compositionCommentary2Track insertTimeRange:CMTimeRangeMake(kCMTimeZero, audio2Asset.duration) ofTrack:[[audio2Asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] atTime:kCMTimeZero error:nil]; 

     NSLog(@"audio =%@",audioAsset); 
     AVMutableCompositionTrack *compositionCommentaryTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid]; 
     [compositionCommentaryTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, audioAsset.duration) ofTrack:[[audioAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0] atTime:kCMTimeZero error:nil]; 


     AVAssetExportSession* _assetExport = [[AVAssetExportSession alloc] initWithAsset:mixComposition presetName:AVAssetExportPresetPassthrough]; 

     NSString* videoName = @"export.mov"; 

     NSString *exportPath = [NSTemporaryDirectory() stringByAppendingPathComponent:videoName]; 
     NSURL *exportUrl = [NSURL fileURLWithPath:exportPath]; 

     if ([[NSFileManager defaultManager] fileExistsAtPath:exportPath]) 
     { 
      [[NSFileManager defaultManager] removeItemAtPath:exportPath error:nil]; 
     } 

    _assetExport.outputFileType = AVFileTypeQuickTimeMovie; 
    //@"com.apple.quicktime-movie"; 
     NSLog(@"file type %@",_assetExport.outputFileType); 
     _assetExport.outputURL = exportUrl; 
     _assetExport.shouldOptimizeForNetworkUse = YES; 



     [_assetExport exportAsynchronouslyWithCompletionHandler: 
     ^(void) 
     { 
      switch (_assetExport.status) 
      { 
       case AVAssetExportSessionStatusCompleted: 
        // export complete 

        NSLog(@"Export Complete"); 
        // From Here I want play movie using MPMoviePlayerController.<<<--------- 
        NSString *fileNamePath = @"sound_record.mov"; 
        NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES); 
        NSString *documentsDirectory = [paths objectAtIndex:0]; 
        NSString *oldappSettingsPath = [documentsDirectory stringByAppendingPathComponent:fileNamePath]; 


        if ([[NSFileManager defaultManager] fileExistsAtPath:oldappSettingsPath]) { 

         NSFileManager *fileManager = [NSFileManager defaultManager]; 
         [fileManager removeItemAtPath: oldappSettingsPath error:NULL]; 

        } 
        NSURL *documentDirectoryURL = [NSURL fileURLWithPath:oldappSettingsPath]; 
        [[NSFileManager defaultManager] copyItemAtURL:exportUrl toURL:documentDirectoryURL error:nil]; 
        [audioAsset release]; 
        [audio2Asset release]; 
        [_assetExport release]; 
        [self performSelectorOnMainThread:@selector(playVideo:) withObject:documentDirectoryURL waitUntilDone:NO]; 

        break; 
       case AVAssetExportSessionStatusFailed: 
        NSLog(@"Export Failed"); 
        NSLog(@"ExportSessionError: %@", [_assetExport.error localizedDescription]); 

        //    export error (see exportSession.error) 
        break; 
       case AVAssetExportSessionStatusCancelled: 
        NSLog(@"Export Failed"); 
        NSLog(@"ExportSessionError: %@", [_assetExport.error localizedDescription]); 

        //    export cancelled 
        break; 

      } 
     } 
     ];

其結果是，導出的視頻播放錄製的音頻與視頻成功，但視頻中的音軌是已刪除，因此導出的.mov正在播放帶有視頻圖像的錄製音頻文件而沒有其聲音，爲什麼會發生這種情況？

來源

2013-03-11 Hash.Techniq