'MPEG-4 Audio File' vs 'MPEG-4 Audio'?

Discussion in 'Digital Audio' started by KeithPratt, Sep 23, 2010.

  1. KeithPratt macrumors 6502a

    Mar 6, 2007
    I have an MP4 of a live performance and I want to put the audio from it on my Sony Walkman.

    I opened the MP4 in Quicktime Pro and deleted the video portion, leaving only the AAC audio, and saved it as a MOV. I then changed the extension from MOV to M4A in the Finder.

    I imported the file into iTunes, and it plays just as you'd expect, but when I dragged-and-dropped it onto my Walkman and attempted to play it I got a "cannot play, file is damaged" message.

    Despite the M4A extension, the document icon has remained the Quicktime one, and when I click Get Info it lists the kind as 'MPEG-4 Audio'. For an iTunes Store file or CD rip the M4A the icon is the iTunes one and the Get Info kind is 'MPEG-4 Audio File'.

    So my questions are, what's the difference and how can I take the audio portion of an H.264 video and turn it into a bona fide M4A (without recompressing it)?
  2. KeithPratt thread starter macrumors 6502a

    Mar 6, 2007
    Duh! I used MPEG Streamclip to rewrap the MOV to MP4 and all seems to be well in iTunes and on the Walkman. That was pretty obvious then.

    I did try re-extensioning the MP4 to M4A to see if it changed the icon to the iTunes one and the Get Info kind to MPEG-4 Audio File. It did neither, but it seems with no consequences. I want that iTunes icon though!

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