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Anyone here who has not already seen Xiph's Digital Show and Tell ( http://xiph.org/video/vid2.shtml http://xiph.org/video/vid2.shtml ) should do themselves a f

Anyone here who has not already seen Xiph's Digital Show and Tell ( http://xiph.org/video/vid2.shtml 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.

masklinn 12y ago
Starting with the first video of the series is probably a good idea, it's aptly named "a digital media primer for geeks" http://xiph.org/video/ http://xiph.org/video/ for the series.
- hackcasual 12y ago
  Though vid2 was specifically made to address misunderstandings from this article.
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 ago
  Have 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 ago
    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?
tim333 12y ago
Cool video, ta.

masklinn 12y ago

Starting with the first video of the series is probably a good idea, it's aptly named "a digital media primer for geeks" http://xiph.org/video/ http://xiph.org/video/ for the series.

hackcasual 12y ago
Though vid2 was specifically made to address misunderstandings from this article.

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 ago
Have 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 ago
  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?

tim333 12y ago

Cool video, ta.