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Originally Posted by anazgnos

I think you've posted a couple times about false positives in audiochecker, and it can only lead me to conclude that audiochecker is entirely unreliable about guessing whether a track is actually lossy. Better to check this stuff out yourself with a spectral analyzer.

Of course pitch correction will "alter" the audio in a file but there's no reason why it should cause it to "lose" any high frequency information.

The lossy data compression has nothing to do with high frequencies. Some algorithms for making MP3s, etc, also apply a low-pass roll-off, but not all. iTunes, for example, has a fantastic MP3 encoding process, when set correctly, that doesn't roll off (well, maybe a hair below 20k).. you can still tell it is lossy by the abrupt chunks missing from the spectrum. That is still the best way to tell and I've never seen an automatic method that is fool-proof for that.