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. > > 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.
I make no claims to being a digital engineer - or understanding everything transpired in this thread. What I do trust is that I hear real differences in sample rate converter algorithms. What has been perplexing me most about this thread is the comments made that integer sampling rate converstions -- say from 96Khz to 48Khz are easy and not challenging for any reasonable SRC algorthm to do -- simply remove bits on the fly -- and low-pass filter them to remove the extraneous high frequency. The comment directly above suggests this somewhat. However, even though most of my resampling tests are exactly that 96-->48 -- which should be easy to accomplish without major artifacts -- I still hear a substantial difference among the SRC choices...mostly related to high-frequency naturalness and harshness reduction (among the better filters). Perhaps artifacts are what I am hearing on some and not others -- to a greater or lesser extent -- even in the "easy" integer reduction ratio? -- jt25741 SB3->AR Masters Coax -> PS Audio DLIII -> Coincident CST IC XLR -> Sim Audio P5 -> Cardas Golden Reference XLR -> Sim Audio W5 -> PS Audio Xtreme Plus(Low) AQCV4(mid/hi)-> Magnepan 3.6R ------------------------------------------------------------------------ jt25741's Profile: http://forums.slimdevices.com/member.php?userid=8645 View this thread: http://forums.slimdevices.com/showthread.php?t=32958 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/lists/listinfo/audiophiles
