3999hz Sine at 8khz SR
Reply #28 –
Thanks, ktf and xnor, now I get it. I was thinking only about resampling for file storage (i.e. 8 to 48-ish kHz), not about D/A conversion (which, as I failed to realize, ideally represents resampling to an infinitely large sampling rate). So yes, both any D/A converter as well as Audition's interpolative waveform display use time-limited interpolation filters for reasons mentioned earlier.
What I find curious is that I see the beating in Adobe Audition where I had assumed it could display what the waveform would look like with perfect reconstruction. Clearly I don't understand how the program is going about connecting the dots.
That beating is just because its using linear or at most polynomial to generate the display. Its too slow to use high quality interpolation for display so almost nothing does.
I think - and recall reading this somewhere - that Audition is doing better than that, meaning it uses a time-windowed sinc filter. Here's what a Dirac (single-sample) impulse looks like in Audition 1.x:
[attachment=7615:dirac_audition.png]
Edit: zooming in vertically reveals that this smooth interpolation curve extends to the entire time-range visible in that screenshot.
Chris