In the Advanced menu there is, typically, a 'convert to aac' option. Turns out what you see here is determined by your import preferences. Set your import to MP3, this will show MP3.
You can convert, export and delete your mp3. I just export the ones I want to convert, move them to a different user account, and convert there.
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Updated 7/14/06
It took a bit of work to figure out the Blacktree iTunes LAME Encoder. It's a GUI wrapped around a command line AAC to MP3 transcoder. By now there's probably something out that's easier to use, but I haven't looked. There's not much documentation.
My Palm Tungsten E plays MP3 files. My DVD player plays MP3 CDs. Great -- except my iTunes library, legally ripped from my personal CDs, is all AAC encoded. Nothing, yet, plays AAC except my iPod and iTunes.
I needed to be able to convert AAC to MP3. This requires software to:
1. convert AAC to AIFF (uncompressed)This process takes time, is tedious, etc. I wanted a utility that would automate this.
2. convert AIFF to MP3
iTunes LAME encoder does this. Note the UI is all about "Import" but in this case we're exporting from iTunes.
Installation:
1. Drag the app to Applications.Usage:
2. Drag the script to the iTunes script folder.
1. Set preferences: Destination to save to a local folder rather than iTunes library.
2. Click preferences: "Use Alternate Naming Convention" and delete all but %t (so a flat list of MP3 files is exported).
%a is the album
%l is the ?
%t is the tune or song
3. Change capture settings if desired
4. Create album for AAC files to export/convert and tunes to export there. Select all.
5. Click the LAME script from iTunes. Conversion takes quite a while.