title: ffmpeg flac or mp3 to m4a - exactly the same length possible?
body: <p>I'm converting .flac and .mp3 audio files to .m4a using ffmpeg with libfdk_aac (Fraunhofer AAC encoder) like this:</p>
  <p><code>ffmpeg -i &quot;001.flac&quot; -c:a libfdk_aac &quot;001.m4a&quot;</code></p>
  <p>This works fine, but in case of .flac the resulting .m4a files include ~0.046 seconds of silence at the start and sometimes a few extra milliseconds at the end. Though, I need the .m4a files to be of exactly(!) the same length without any extra silence. Is there a way to achieve this?</p>
  <p>EDIT: At the moment I'm using an additional step, i.e. cutting the resulting .m4a file works at least in the beginning of the track, but there are still some (varying) extra ms in the end:</p>
  <p><code>ffmpeg -i 001.m4a -ss 0.047 -c:a libfdk_aac 001cut.m4a</code></p>