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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?
by yyyy-mm-dd 12y ago
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?
- Intermernet 12y agoHave a look at http://en.wikipedia.org/wiki/Whittaker%E2%80%93Shannon_interpolation_formula http://en.wikipedia.org/wiki/Whittaker%E2%80%93Shannon_inter... . "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 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.
- yyyy-mm-dd 12y agoThanks, 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?