title: AVAssetExportSession export mp3 while keeping metadata
body: <p>How do I export a mp3 using <code>AVAssetExportSession</code> while keeping the id3 tags?  Is it possible to edit the id3 tags before exporting them?</p>
  
  <p>This code does write the <code>AVAsset</code> (myMp3Asset) to file but the there are no id3 tag in the resulting mp3.</p>
  
  <pre><code>// myMp3Asset is an AVAsset
  AVAssetExportSession *exportS = [[AVAssetExportSession alloc]
                                   initWithAsset:myMp3Asset presetName:AVAssetExportPresetPassthrough];
  exportS.outputFileType = @"com.apple.quicktime-movie";
  
  NSString *path = [NSHomeDirectory() stringByAppendingFormat:@"/Documents/%@", @"song"];
  
  exportS.outputURL = [NSURL fileURLWithPath:path];;
  [exportS exportAsynchronouslyWithCompletionHandler:^{
      if (exportS.status == AVAssetExportSessionStatusCompleted)
      {
          //then rename mov format to the original format.
          NSFileManager *manage = [NSFileManager defaultManager];
          NSString *mp3Path = [NSHomeDirectory() stringByAppendingFormat:@"/Documents/%@.%@", @"song", @".mp3"];
  
          NSError *error = nil;
          [manage moveItemAtPath:path toPath:mp3Path error:&amp;error];
      }
  }];
  </code></pre>