a quick comparison of these i did earlier out of boredom.
let me first off say, OGG takes the prize. Followed closely by AAC, unfortunately, WMA is at the bottom of the list, which i will explain why in a minute......
Firstly, i was doing an ABX comparison in foobar of AAC at 320kbps and kept failing miserably, probability i was guess got up to about 80%, and i can't disagree with that :P so i decided to find out which sounds better at lower bitrates. A common "low bitrate" is 128kbps, so that's what i used. First off i want to start by describing what i heard differently between the two (this was not a blind test, simply a back and forth between the two) what did i hear different between the FLAC file and the OGG file? a very VERY mild loss of what i would describe as "crispness" in the highs. That's it, nothing else, and it was truly mild enough i had to strain to hear it. AAC had basically the same effect, but it was worse and the highs were clearly rolled off after i would guess around 16-17khz.
Now for the loser and why i picked it as the loser......WMA, i officially hate this codec....
What i noticed with WMA was everything was nice and crispy like the FLAC file, but the stereo image was skewed....what does this mean you say? Well, to put it simply, a certain cymbal continued ending up in the center, and in the flac file it was glaringly obvious this cymbal was NOT in the center, but about 10% to the left of center. It seems to me they made it more "efficient" by averaging "close to center" sounds and placing them into the center image. My guess is this saves bitrate because anything in the center can in theory take up half the data as things off center because the data for the two channels is identical. This is similar to how the "joint stereo" mode in MP3 encoding works, although it does not average out the center image, the center remains intact like it should but takes up half the bitrate allocation. Just my theory. Anyways there you have it. OGG FTW 
it is truely almost transparent at 128.
Edited by yepimonfire - 4/25/11 at 9:11pm
