capmorgan

Hello all, I'm trying to understand something about compression. I know that CD tracks are pretty big files and when they get imported into iTunes (with AAC compression) the tracks get "shrunk" to pretty small file sizes. From what I read, compression is achieved by eliminating "unnecessary" bits of an audio track. To my mind if certain portions of an audio track are eliminated they're gone forever .. right? However, when I create an audio CD using AAC tracks from iTunes, on the CD the tracks become full size files again. So, my question is if compression was achieved by eliminating portions of the audio track how come when the same audio track is burnt onto a CD, it becomes a full size file again? Do the eliminated bits somehow come back to life in the CD burning process? Isn't compression an irreversible action? Is all of the above specific to AAC and CDA or is that how compression works in general - ie unnecessary bits are not really eliminated, they're just kinda hidden? This brings me to another question - when an AAC track is played back - am I listening to the compressed version or the full version? I've read quite a few articles on compression but they are all so technical and talk about the algorithms of compression (whatever the heck that means) but I just can't seem to find an article that ties together in layman terms compression, playback and "uncompression" if you will. Any light shed on this will be greatly appreciated. Cheers!