Anyone here who has not already seen Xiph's Digital Show and Tell ( http://xiph.org/video/vid2.shtml ) should do themselves a favor and sit down for a watch. It makes sense of a lot of mysteries and misconceptions around digital audio.
So I watched, and I'm confused.
How exactly does DAC recreate a band limited signal without having an infinite lookahead?
Honest question. Any pointers?
"The Whittaker–Shannon interpolation formula or sinc interpolation is a method to construct a continuous-time bandlimited function from a sequence of real numbers."
http://en.wikipedia.org/wiki/Reconstruction_filter has a less mathematical explanation, but, as Monty mentions in the video, be wary of the sentence "in practice, the output of a DAC is more typically a zero-order hold series of stairsteps". This really only applies to some (mostly low-end) DACs. There are many DACs that will use anti-aliasing / interpolation and probably many other methods to recreate the signal.
Thanks, exactly what I was searching for. Quoting from "Reconstruction filter" page:
Practical filters have non-flat frequency or phase
response in the pass band and incomplete suppression
of the signal elsewhere. The ideal sinc waveform [..]
would require infinite delay.
So it's all good in theory, and it depends in practice.
Any idea what is the highest frequency "recomended" in a typical audio that will not cause trouble for consumer grade DACs?
That is, if I'm mastering, say, for 44.1kHz, what is the recomended antialiasing filter?