Small test:aucdtect -m0 *.wav auCDtect: CD records authenticity detector, version 0.6 Copyright (c) 2004 Oleg Berngardt. All rights reserved. Copyright (c) 2004 Alexander Djourik. All rights reserved. ------------------------------------------------------------ Processing file: [MP3 - Dithered.wav] Data analysis: [100%] ------------------------------------------------------------ This track looks like a high-quality CD record Processing file: [MP3-No Dither.wav] Data analysis: [100%] ------------------------------------------------------------ This track looks like an MP3 decoded record Processing file: [MPC - Dithered.wav] Data analysis: [100%] ------------------------------------------------------------ Could not determine the source of this record Processing file: [MPC - No Dither.wav] Data analysis: [100%] ------------------------------------------------------------ This track looks like an MP3 decoded record Processing file: [Original.wav] Data analysis: [100%] ------------------------------------------------------------ This track looks like a high-quality CD record Processing file: [Vorbis - Dithered.wav] Data analysis: [100%] ------------------------------------------------------------ This track looks like a high-quality CD record Processing file: [Vorbis - No Dither.wav] Data analysis: [100%] ------------------------------------------------------------ This track looks like an MP3 decoded record The MP3 was --alt-preset standard. the mpc was --xtreme -xlevel and the vorbis version was GTune 3 beta 2 @ q8. All were encoded from Original.wav and decoded with foobar2000 with and without Strong ATH noise shaping. The problem could be that dithering adds noise in the high side of the spectrum, so the analisis of the lowpass is borked (specially since the lowpass in APS is 19Khz anyway).