320kbps or not?

Question

I found I have two versions of a song, one I ripped in iTunes AGES ago, and one I ripped only a few years ago.
One is 128kbps, and the other is 320kbps, but the waveform in Audacity doesn't look right. (I am no expert in this stuff, it's my first time analyzing my library.)
Here's the 128kbps song:
And here it is at 320kbps:
Is that a genuine 320kbps?
Not sure what I've done here. I used to think that ripping between these was not a problem. Perhaps the 320 used to be a 256?
Trying to learn how to use this properly to clean up my iTunes library

Answer 1

Rudolfensis wrote:
I want to know if the 320kbps song is a true 320kbps song, or something that I converted into 320kbps from a lower bitrate — 128, 256 or whatever.
If both are the same songs, you can make the assumption that the second should have a better quality since it will reproduce high frequency information that was missing in the first file.
However, you cannot assess if was encoded from the original of if it is a conversion from a previously encoded 128kbps files.  In the first case, your high frequencies signal would have been encoded from existing data while in the second case, it would have been statistically interpolated from an already compressed signal.  In both case you will see high frequency signal but the first one would definitively sound better... or closer to the uncompress file.  Therefore, looking at the frequency spectrum will not allow you to conclude what was the original signal.  In fact, I don't know if there is only other ways that earing the file...
To verify if what I'm saying is true or not (I may be wrong) you can actually make the test of converting your 128kbps file to 320 and look if it ends up adding information above 12kHz.