aac support bitrates higher than 320.. the average human ear will consider mp3 at vbr 192kbps and aac at 128kbps transparent.. if you're using really high end equipments and try to focus real hard you can differentiate between lossy and lossless at those bitrates but going mp3 cbr320 and aac 256 you can never hear any difference.. you would need an audio spectral frequency analyzer such as adobe audition to check and differentiate the original source lossless from the lossy format.Warchamp7 said:Ignoring the fact that that's insane and completely unnecessary.
MP3 only supports up to 320, and AAC being the successor, I assume is the same.