I had about 2000 mp3 files all in different bitrate (mostly 320 kbs), and I use to select the option to convert them to 128 aac for iPhone sync, and saved me good amount of space. I then decided to convert them all to 128 aac as I can't notice the difference much. Now that my whole library is 128 kbps aac, I still get an option to convert to 128 kbps arc for iPhone sync, when I put a check in it, my music size on the iPhone goes from 10gb down to 4.5gb, how is it possible that iTunes is offering me that option when all of my music is already 128 kbps aac. am i missing something, is the music on the iPhone compressed even farther that I don't know about. If someone can shine a light on this for me....I already did a search for it on the forums and google as well, didn't help. I have a iPhone 4s 32gb on 5.0....and my point in asking all this was, I would love to save much space as possible on the iPhone for movies n photos.... thank you all in advance...I am a new iPhone convert, always had palm then droid, but have used mac for a long long time.