"Y" the heck would you want to convert one "lossy" format to another? That means like taking a sack of beans, taking out half in order to convert it to mp3, then taking out more beans in order to convert it to mpeg4 (m4a/mp4.) I mean, why lose more beans (quality?) I'd hate to lose my beans. lol
IF your asking about iTunes/iPod then please specify & the reasons "Y"???