I used GarageBand to record the audio. I thought I could simply save it as an MP3 file but that would be too simple, wouldn't it? GarageBand only creates AAC encoded audio in M4A files. Unbelievable! Eventually I got a solution.
I read some tips about exporting the M4A to iTunes and then using iTunes to create MP3 files. That seemed cumbersome. I decided to used FAAD2 to convert the M4A file into a WAV file. Then I could re-encode the WAV to MP3 using LAME.
I didn't have LAME or FAAD2 yet, but luckily, I'd already gone through the pain of installing DarwinPorts for OSX. A simple 'sudo port install lame' had no trouble installing LAME. However, sudo port install faad2 failed with some kind of error about 'lrintf already defined'. A bit more research lead me to edit /usr/include/architecture/i386/math.h. I found extern long int lrint ( double ); and extern long int lrintf ( float ); on lines 377 and 378. I commented out those lines (put // in front of them) and tried installing FAAD2 again.
DarwinPorts got into some kind of funky mode where the Mac thought FAAD was installed even though it wasn't. Everytime I tried sudo port install faad2 it just kept ending with cleaning faad2. I went several rounds trying to uninstall FAAD. I didn't keep careful notes (sorry) but eventually I coerced DarwinPorts to re-install FAAD.
With FAAD and LAME properly installed, I went back to GarageBand. I changed the settings to export 192 kbps AAC files and selected Export Podcast to Disk (I started with a Podcast project since I was converting a lecture). I figured the 192 kbps file would be sufficiently high enough quality to survive re-encoding.
This is what I ended up doing:
- GarageBand export to file.m4a
- faad file.m4a -o file.wav
- lame -a --preset voice file.wav file.mp3