References:
http://www.renevolution.com/how-to-install-ffmpeg-on-mac-os-x/
http://sound.stackexchange.com/questions/26633/free-batch-conversion-from-flac-to-apple-lossless-alac

1. Install brew
2. Install ffmpeg

   user@box dir $ brew install ffmpeg --with-fdk-aac --with-ffplay --with-freetype --with-frei0r --with-libass --with-libvo-aacenc --with-libvorbis --with-libvpx --with-opencore-amr --with-openjpeg --with-opus --with-rtmpdump --with-schroedinger --with-speex --with-theora --with-tools
   

3. Convert all flac files

   for f in `find . -type f -name *.flac`; do ffmpeg -i "$f"  -vf "crop=((in_w/2)*2):((in_h/2)*2)" -c:a alac "${f%.flac}.m4a"; done