On Thu, 1 Nov 2018 11:06:31 +1300 Robert Jeffares <jeffares.rob...@gmail.com> wrote:
> In digital audio, overshoots cause lots of instant distortion. Almost right. "Overshoot" has a specific technical meaning, ( involving bass ) and isn't as intuitive as one might think, but I think I know what you mean. In analog audio, when a peak "bangs the rail" you get a clip. In other words, if the absolute peak voltage of the audio wave form tries to exceed the power supply voltage ( the "rail" ) the voltage rise will just stop at the rail voltage and stay there until the slope of the wave form on the declining side drops below the rail. That flat topped portion has what it should have been clipped off, and is therefore called a clip. In analog, you may, or may not hear it depending on how deep the clip is in what should have been, and how often it happens. If you "normalize" as we did in the analog days around -26 or so, then you have 26 db above 0VU before bad things *might* happen. In the digital world, 0FS is the point where the digital representation of the waveform become all 1's. We call it a "digital clip" but it's not what that implies. "Digital clip" is a catastrophic total system failure. Since *ALL* of the 1's are used, there is no moderation, and no recovery. There is no slope. It's a sudden, and very harsh cut off, like the point of impact when a body falling from a tall building contacts the concrete street. This is why we need headroom ! Several 1's that we hope to never, ever use. True "overshoot" in the digital world is a case where 1+1=3. ( simplified ) Therefore, it is entirely possible to "over shoot" the 1+1=2 that was intended, go into digital clip, and the resulting catastrophic system failure. If there were 4 headroom, then the 1+1=3 distortion would still exist, but would be within the capability of the system, so the system doesn't fail at all. *THIS* is why 12 db or more of headroom is a good idea. Personally, I would not have chosen 13, because I prefer even numbers, but any "reasonable" number should be fine. -- Cowboy _______________________________________________ Rivendell-dev mailing list Rivendell-dev@lists.rivendellaudio.org http://caspian.paravelsystems.com/mailman/listinfo/rivendell-dev
