Many people said iTunes can do this job. That's a tale of a tub.
iTunes does not support FLAC as the input format. How can iTunes convert FLAC to AAC?
From
Apple Discussion, I found out
an excellent solution of converting FLAC to AAC:
1. The solution will help you convert FLAC to AAC, MP3, WAV, M4A, ALAC, WMA, CAF, DTS, AIFF, etc;
2. It also allows you to optimize the output file;
3. If you want to extract audio file from videos and movies, it also can give you a hand.