6 responses

  1. Glyn
    July 29, 2011

    Very helpful. Can you clarify a little further ?
    My aac encoder (Pystel built 2002) has both mp2 and mp4 encoding options (?), and I presume these result in very different AAC files that may or maynot be compatible with decoders / devices ?
    It also appears to offer 2 different header formats as well as no header. (and other options)
    Are these all valid variant AAC files ?
    Can I assume that M4A can only be the mp4 type of AAC encoded file (if that makes sense) ?

    I used this encoder to convert WAV to AAC, and it played in my mediaplayer fine, but my son’s Nintendo DSi did not recognise the .aac file.
    I’ve read elsewhere that it requires .m4a – so that might only mean renaming the extension (this article implies that is the case)
    OR it might mean that I have to be careful to use parameters for mp4 type AAC encode ?, for the right header ?, and stay within the bitrate that will be compatible.


    • Leon Pelletier
      August 17, 2013

      2 years later. I’ll make a travel in time. I might be wrong, but we need to remember that .mp4 and .mp2 are container, thus it encapsulated the actual, raw data in its own format, specification, version… Container are all holding, sorting, indexing the data in a different way.

      When AAC first arrived, I think it may have spread a bit inside MP2 container before getting their popularity inside MP4 container. If an encoder is name [Etc] 2002, then that could mean it is encapsulating songs in MP2 format. Most simple devices are only willing to read MP4 AAC song, and H.264 AVC video.

      Some simple devices are way too slow to use software codecs like we do in Windows or OSX, and they are instead using electronic “chips” which contain some very fast codecs, and a limited set of these codecs, generally H.263, H.264, proprietary codecs (ex: Windows Phone reads Windows Movie Video – WMV), and AAC, MP3, some voice compressor (AMR, uLaw, aLaw), then all these phones will just refuse to read what can’t be read by their electronic chips.


  2. Leon Pelletier
    August 17, 2013

    (Sorry, I’ve made several typos.)


  3. Thomas
    November 8, 2017

    Great article, explains everything in a sufficintly short way – go on so!!!


  4. Goatlips
    April 18, 2019

    Pro tip: A 192kbps VBR AAC rip of a music CD is more than enough definition for human hearing range to not detect imperfections or differences from the original – 162kbps is actually enough for most humans. So don’t bother with WAVs hogging disc space and not being user-friendly.


  5. Sven
    April 5, 2020

    Hi, I think many people including me, which are reading this article would be interested if AAC can include surround sound. By briefly looking into it, I don’t think so. Which might be interesting for people trying to pick the right file to download…


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