title: Convert mp3 to AAC with mpeg-2 container (FFMPEG)
body: <p>I'm trying to convert an mp3 audio file to an AAC file with FFMPEG, and I need the audio to be wrapped in an MPEG-2 container.
  The resulting AAC file needs to be AAC-LC (Low Complexity), 1-channel, CBR mode, 44100 sample rate, and 48kb/s bitrate, so I use this command:</p>
  
  <pre><code>ffmpeg -y -i input.mp3 -ar 44100 -ab 48k -acodec libfdk_aac -ac 1 output.aac
  </code></pre>
  
  <p>But when I examine the ADTS headers, the audio file is always being wrapped in an MPEG-4 container. I have tried all the codecs listed here but I still end up with an mpeg-4 container wrapped around the audio: <a href="http://trac.ffmpeg.org/wiki/AACEncodingGuide" rel="nofollow">http://trac.ffmpeg.org/wiki/AACEncodingGuide</a>.</p>
  
  <p>Here are the headers I get when examining the AAC output file:</p>
  
  <p>mpeg_type: 'MPEG4',
    profile: 2,
    profile_name: 'AAC LC',
    sample_freq: 44100,
    channel_config: 1,
    channels: 1,
    frame_length: 139,
    buffer_fullness: 157,
    number_of_frames: 1,
    frames_per_sec: 43.06640625</p>
  
  <p>Any ideas as to why ffmpeg wraps an mp4 container around the audio? Can I get around this somehow? Are there any other encoders I can try aside from FFMPEG? I was giving FAAC encoder a shot and it gives me the proper encoding and ADTS headers, but alas it does not support mp3, only WAV. </p>