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.
And linear interpolation to fill in the gaps after upsampling doesn't work properly either: it creates artifacts. The correct approach is sinc interpolation, but in an ideal sense that is infinitely expensive to compute. So it's all about tradeoffs: the ultra-easy computation produces really bad results sometimes, but an ultra-correct computation is really really slow. And different SRC applications take different approaches, with different degrees of success. -- inguz ------------------------------------------------------------------------ inguz's Profile: http://forums.slimdevices.com/member.php?userid=1139 View this thread: http://forums.slimdevices.com/showthread.php?t=32958 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/lists/listinfo/audiophiles
