to all of you that say not to do it i would have to say, your right on the fact that you may lose some quality, but its not enought to notice.
I have done this many times and can never tell the diffrence. However, when ever i do this i usually am going from a .mp3 (which is always between 128-192 or higher, i never go below 128) to AAC 128.
I thought it would be a bad idea if you are going form mp3 128 to aac 128, because during the recompression process the computer has to take that song and resample it in the diffrent format (acc). Thus, this would discard some of the song info. But, when you are going from a larger song file, with a greater bit rate (mp3 192) and go down to a AAC 128, it throws out the extra data that it doesn't need. The end result however, is the same song with the same quality, at a smaller size, in a diffrent format.
Put it this way, i have almost 7,500 songs (27.54 GB) in my library, but when they all were mp3's, before i converted them, my library was 37.74 GB. The biggest reason i converted them is because i was running out of space on my HD, and because they couldn't all fit on my 30GB iPod.
I would have to say that you should try it first, and see if you can tell the diffrence. Take a cd import the songs as mp3's at 192. Then after doing this, select your songs which are mp3's, right click or control click and go down to "convert to acc". After they have been copied as the AAC format, listen to the two diffrent versions (mp3 192 vs. AAC 128), and tell me what diffrences you can hear, if any. You may notice a little diffrence between the songs if they were imported as mp3 128, and the converted to AAC 128 but not much.
Let me know, or us, what you find out.
Ryan
