after converting mp3 to aac

why would anyone want to bother converting mp3s to aac?

The quality will only get lower as it will be compressing a compressed file.

Also aac is proprietary, I'd rather keep my music in an open (ok, I know mp3 isn't strictly open, but to all intents and purposes it is) format that can be read by pretty much every music program and on every modern computer.

Converting from mp3 to acc has no discernable benefits AND is lessens the audio quality!

Originally posted by HiRez
AAC is higher-quality at the same bitrate compared to MP3. The discernable benefit is a significant savings in disk space for the same quality, or higher quality for the same disk space. If you have high-quality MP3s (192+) you can convert them with little loss in quality, though reripping your CDs directly in AAC is preferable if it's an option (bassman is correct that you will not gain any quality by converting an MP3, but you can by re-encoding the original). As for it being proprietary, what is the big deal? The DRM is not an inherent part of AAC, if you rip your own you are free to do whatever you want with them. I guess I can see your point in keeping everything MP3, but personally I like AAC's audio quality and space-efficiency.

I would not recommend re-ripping your existing music collection to AAC even if our files are 192 kbps.
There is a loss in quality even at that level, although most likely less discernable than if you went from a 128 MP3 to a 128 AAC.

Stick with your MP3's, if you have the original CD and you are so inclined than re-encode the CD into AAC. But do yourself a favor and don't rip from one ?lossy? format to another. You aren't going to save enough disk space doing that for it to be worth it. And in the end chances are you will loss more in the way of quality than you will gain in disk space.