inguz;182737 Wrote: > Simply dropping samples doesn't work properly. Take a 96kHz signal with > a loud sinewave at 46kHz. If you go to 48kHz sampling rate by throwing > away every other sample, you should ideally end up with silence (the > 46kHz signal can't be represented at that sampling rate) but instead > you'll get a very loud 2kHz whistle that wasn't present in the original > at all; it's an artifact of the downsampling. To get rid of the > artifacts you need to low-pass-filter (ideally a brickwall at 24kHz, in > this case) first.
Yeah, this is what cliveb was pointing out earlier. There must be a really nice way to think about this discrete sampling stuff. It's as if when you sample at some frequency f you wrap the signal around a circle in frequency space, with DC at one point and f/2 (the Nyquist frequency) at the antipode, and then f again at the DC point, (3/2)f at the Nyquist point, etc. I guess this follows from the fact that a discrete Fourier transform is like a normal FT on a circle. I'm sure this is obvious to someone that thinks about discrete signal analysis - anyone have a recommendation for a good technical reference? -- opaqueice ------------------------------------------------------------------------ opaqueice's Profile: http://forums.slimdevices.com/member.php?userid=4234 View this thread: http://forums.slimdevices.com/showthread.php?t=32958 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/lists/listinfo/audiophiles
