Mark Lanctot;187002 Wrote: > I'm also surprised no one's done this before. Still, I can't see why > this isn't accurate. You are comparing two waveforms, and by > subtracting one from the other, you get the difference between the two.
Actually this might be very very misleading. You're subtracting two signals in the time domain. The resulting signal is determined by all sorts of things which have nothing to do with audible differences. For example, suppose the signals are slightly mis-aligned in time. In that case the difference will be large even if the files were otherwise absolutely identical. If the mis-alignment is small, the difference will be almost all in the high-frequency domain, as you are seeing. I suspect MP3 functions by performing a Fourier transform, applying a filter, and then FTing back. That process almost certainly alters the phase of the frequency components. If the algorithm is properly designed the filter will be linear phase - in other words it will correspond to a time shift, and will therefore lead to a large difference between the two files (at least at high frequency), but that says nothing at all about audibility. -- opaqueice ------------------------------------------------------------------------ opaqueice's Profile: http://forums.slimdevices.com/member.php?userid=4234 View this thread: http://forums.slimdevices.com/showthread.php?t=32576 _______________________________________________ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
