“Flac”:http://flac.sourceforge.net is an format that is lossless, so you get the original quality of the recording. I almost never see it, but if you do, use “xACT”:http://www.versiontracker.com/dyn/moreinfo/macosx/21952 to convert it to AIFF, the Apple lossless format or to MP3 with Lame, the best encoder.