title: shows incorrect file format
body: <p>by using above code i am able to generate mp3 file but when i try to validate its format it shows not a mp3</p>
  
  <pre><code>mr = new MediaRecorder();
  mr.setAudioSource(MediaRecorder.AudioSource.VOICE_DOWNLINK);
  mr.setOutputFormat(MediaRecorder.OutputFormat.MPEG_4); 
  mr.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
  mr.setOutputFile(Environment.getExternalStorageDirectory()+File.separator+"aa1.mp3");`
  </code></pre>
  
  <p>How to generate valid mp3 in android                                                                                            </p>