title: Using exportAsynchronouslyWithCompletionHandler
body: <p>I try to export an audio file from the iPod-Library. I want to create with this iPod-Library file an new file. In the AV Foundation Programming Guide in chapter Reading and Writing Assets there is a little example. However this code doesn't work for me. 4 errors happens </p>
  
  <pre><code>Export Status 4 Error Domain=AVFoundationErrorDomain 
  Code=-11800 "The operation could not be completed" 
  UserInfo=0x1edfa0 {NSLocalizedFailureReason=An unknown error occurred (-12124), 
  NSUnderlyingError=0x1ebdc0 "The operation couldn’t be completed. (OSStatus error -12124.)", 
  NSLocalizedDescription=The operation could not be completed}
  </code></pre>
  
  <p>My code</p>
  
  <pre><code>AVURLAsset *objAvUrlAsset = [[AVURLAsset alloc] initWithURL:[tempArray objectAtIndex:0]  options:nil];
  
  NSLog(@"%s objAvUrlAsset %@", __FUNCTION__, objAvUrlAsset);
  
  NSArray *compatiblePresets = [AVAssetExportSession exportPresetsCompatibleWithAsset:objAvUrlAsset];
  
  NSLog(@"%s compatiblePresets %@", __FUNCTION__, compatiblePresets);
  
  if ([compatiblePresets containsObject:AVAssetExportPresetAppleM4A]) {
  
  
      AVAssetExportSession *exportSession = [[AVAssetExportSession alloc]
                                             initWithAsset:objAvUrlAsset presetName:AVAssetExportPresetAppleM4A];
  
      NSString * exportPath = [NSString stringWithFormat:@"testTrack1.M4A"];
      NSURL *exportURL = [NSURL fileURLWithPath:exportPath];
  
      exportSession.outputURL = exportURL;
      exportSession.outputFileType = AVFileTypeAppleM4A;
      exportSession.shouldOptimizeForNetworkUse = YES;
  
       NSLog(@"%s export Session %@",__FUNCTION__, exportSession);
  
      [exportSession exportAsynchronouslyWithCompletionHandler: ^(void) {
          // export completed
          NSLog(@"Export Status %d %@", exportSession.status, exportSession.error);
      }];
      [exportSession release];
  }
  </code></pre>
  
  <p>the nslog message </p>
  
  <pre><code>-[MyLocalMusicLibrary getAllTracks] objAvUrlAsset AVURLAsset: 0x1dd5a0, URL = ipod-library://item/item.mp3?id=-212958261728896866
  
   -[MyLocalMusicLibrary getAllTracks] compatiblePresets (
  AVAssetExportPresetAppleM4A,
  AVAssetExportPreset960x540,
  AVAssetExportPresetLowQuality,
  AVAssetExportPresetMediumQuality,
  AVAssetExportPreset640x480,
  AVAssetExportPresetHighestQuality,
  AVAssetExportPreset1280x720
  )
  
   -[MyLocalMusicLibrary getAllTracks] export Session AVAssetExportSession: 0x1e85c0, 
  asset = AVURLAsset: 0x1dd5a0, URL = ipod-library://item/item.mp3?id=-212958261728896866, 
  presetName = AVAssetExportPresetAppleM4A, outputFileType = com.apple.m4a-audio
  
   -[MyLocalMusicLibrary getAllTracks] Export Status 4 Error Domain=AVFoundationErrorDomain 
  Code=-11800 "The operation could not be completed" 
  UserInfo=0x1edfa0 {NSLocalizedFailureReason=An unknown error occurred (-12124), 
  NSUnderlyingError=0x1ebdc0 "The operation couldn’t be completed. (OSStatus error -12124.)", 
  NSLocalizedDescription=The operation could not be completed}
  </code></pre>
  
  <p>How can i fix this four errors. Do i need for this export the AVAssetReader and AVAssetWriter.</p>