title: Android problems with MediaMetadataRetriever: return null value
body: <p>Trying to retrieve mp3 informations (Albumname,...) with MediaMetadataRetriever.
  In the emulator it worked fine. On my device most methods returns null.</p>
  
  <p>MediaMetadataRetriever mmr = new MediaMetadataRetriever();
  mmr.setDataSource(songPath);</p>
  
  <p>String albumName = mmr.extractMetadata(MediaMetadataRetriever.METADATA_KEY_ALBUM);</p>
  
  <p>String mp3Title = mmr.extractMetadata(MediaMetadataRetriever.METADATA_KEY_TITLE);</p>
  
  <p>String mimekey = mmr.extractMetadata(MediaMetadataRetriever.METADATA_KEY_MIMETYPE);</p>
  
  <p>The mp3 has definitly these informtion because in the emulator these information (the same file!) are shown. The file path is ok the mimekey is set and I got no exception.</p>
  
  <p>I'm using SdkVersion=14.
  I've checked 
  <a href="https://stackoverflow.com/questions/18164413/how-to-get-songs-from-album-artist-in-android-using-mediametadataretriever">How to get songs from album/Artist in android,using MediametadataRetriever?</a> and 
  <a href="https://stackoverflow.com/questions/12465915/android-mediametadataretriever-returns-null-values-from-most-keys">Android MediaMetadataRetriever returns null values from most keys</a>
  but it didn't help. Can't debug the MediaMetadataRetriever.extractMetadata because its native code.</p>
  
  <p>Any ideas?</p>