Transcoding AAC to MP3
  • Vote Up0Vote Down Roger WilcoRoger Wilco
    Posts: 784Banned
    Hey all! Anyone know of a quick and easy command/app to convert AAC(.M4A) files nestled within a couple levels of folders over to MP3 320kbps CBR or -V0 VBR?

    Ideally, the output would copy the original folder structure along with the transcoded files as well.
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  • Vote Up0Vote Down Martin KonecnyMartin Konecny
    Posts: 1,860Member
    You could try ffmpeg. An example:

    ffmpeg -i input.m4a -acodec mp3 -ac 2 -ab 128 output.mp3

    As for maintaining folder structure, you could try something similar to

    find /absolute/path/to/folder/ -iname "*.m4a" -exec ffmpeg -i {} -acodec mp3 -ac 2 -ab 128 {}.mp3 \;

    The {} braces expand to the current m4a file.
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  • Vote Up0Vote Down Roger WilcoRoger Wilco
    Posts: 784Banned
    Awesome! I'll give it a try here in a bit. Starting to think the "random" glitches/disconnects/etc I've experienced might have something to do with occasional spikes in the VBR AAC files encoded by QT/iTunes. First, I'll try 320 CBR MP3 since that's what Liquidsoap sends to Icecast anyway. After that, I'll give -V0 a shot to see if maybe VBR is more reliable overall on MP3 instead.

    Today I discovered 320kbps is the absolute max of an MP3 frame, even in VBR mode. AAC has the ability to jump much much higher, sometimes close to 500kbps. Alternatively, maybe quiet spots with really tiny frames trigger an "end of file" event? Or perhaps not. Just thinking out loud.

    Ideally speaking, it'd be great to see some traction on this, along with AAC support in exactly the same manner. Ah, to dream... :)

    Post edited by Roger Wilco at 2013-02-01 14:37:30
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