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[dcollins]

Nika Aldrich wrote on Tue, 24 August 2004 05:45

No.  I've gotten signals to exceed full scale by more than 6dB (8 or 9, I believe) and TC Electronic claimed 15dB.  It's rather easy to calculate once you come up with your coefficients for your filter.  The higher the summed absolute value of the coefficients the higher you can exceed full scale.

OK, but those signals are digitally generated, and might require knowledge of the filter coefficients.  I use white noise as an example that's a little more like music.  How far will that overshoot?

Quote:

Is "Gibbs effect" really from bandlimiting? No, not necessarily.

There was a series of posts from JJ a while ago about Gibbs, and Iirc them term is widely misused.

DC

[Nika Aldrich]

dcollins wrote on Tue, 24 August 2004 22:57

Nika Aldrich wrote on Tue, 24 August 2004 05:45 No.  I've gotten signals to exceed full scale by more than 6dB (8 or 9, I believe) and TC Electronic claimed 15dB.  It's rather easy to calculate once you come up with your coefficients for your filter.  The higher the summed absolute value of the coefficients the higher you can exceed full scale. OK, but those signals are digitally generated, and might require knowledge of the filter coefficients.  I use white noise as an example that's a little more like music.  How far will that overshoot?

It's a matter of probability.  White noise, being a random signal, certainly has a change of being numerically identical at a given point in time to a specific test signal.  White noise will theoretically hit ALL possible peak values at some point.  White noise, played long enough, should theoretically hit the maximum values possible.  Ergo, you can indeed get 6dB, 8dB, or even 15dB over with white noise, pending the filter coefficients used.

If you plot, however, the overs present due to white noise played at max=FS, you will find that there is a determinable curve representing its peaks, and that curve has exponentially high weighting at very close to 0dBFS and a significantly decreasing quantity of peaks beyond a few tenths of a decibel.  The chance of hitting the maximum excursion allowed by the filter coefficients is something like 16*65536! or so - not very likely.  As you go higher and higher above FS you have exponentially lower chances of hitting those peaks.  Music, being like white noise (as you pointed out) does hold to the same probabilities.

Does that make sense?

Quote:

and iirc them term is widely misused.

Yes, and if I understand correctly, this is one of those situations.

Nika.

[Erik]

Nika Aldrich wrote on Tue, 24 August 2004 18:26

... pending the filter coefficients used.

Likewise many DSP operations can potentially generate similar artifacts, depending on the filter design and/or windowing function chosen.  But you don't see fancy metering on them.  You've got to use your ears.

You really can't even get a mix that hot without using a limiter.  The damage done by a limiter or compressor is so much worse than what we're talking about here... and that happens every time you cross threshold.

--Erik

[chrisj]

Buh, I picked a fine time to finally start overhauling my website. Now all that's there is an elaborate panoramic pic of my studio, and I spent all day working on scans of photos covering everything from the instruments shown to a series depicting the construction of the studio mains shown.
Anyone who's confused by Erik's references? Most likely he's referring to what USED to be there- a mini-autobiographical blurb going back more than ten years, which explains how I have the form of autism known as 'Asperger's Syndrome', became homeless, landed briefly in a psych ward (they called me depressed. No shit..) etc etc.
Etc. etc, includes writing several novels, coming up with a peculiar handicraft best described as prosthetic tails for weird animal people (don't laugh too loud, it's paid for a lot of moist gear), and most relevantly, making the slow and painful transition from an enthusiastic crank to a half decent scientist able to examine his own conjectures instead of issuing PR blasts about them first.
I'm going to ask this once, and then go back to ignoring ad hominem stuff:
Do you expect me to be ashamed of surviving and rising above all that crap?
No way. I stand or fall as exactly who I am. If that's not good enough for you, Erik, that's just too bad.
As for Arny, he's an interesting guy, and the ABX software I used is found on his website. I ported it to MacOS (8 or 9) for him. For free.

[Erik]

Whoa buddy... not at all what I was talking about.

I wasn't talking about your life story, nor was I talking about how you raised money for an 8 track digital studio by selling fetishwear.

To be perfectly blunt, this page is perhaps one of my favorites on the entire Internet:

http://www.airwindows.com/costuming/index.html

Aside from the obvious, the MBA in me is tempted by the obvious business opportunity.  Specifically, the five-tailed kitsune.  Since they're all 50 smackers, the five-tailed version is like getting four tails for free.

Methinks I could buy five of those, set up my own website, then sell 25 mono-tailed kitsunes (or fox) for a tidy profit.  Imagine what kind of digital studio I could slap together with that kinda dough.

--Erik

[Nika Aldrich]

Erik wrote on Wed, 25 August 2004 01:42

You really can't even get a mix that hot without using a limiter.

You can exceed FS and clip your D/As without a limiter.  You can do it with gain change, normalizing, or even without any alteration at all, straight off the A/D, though this would be rare.

Nika.

[chrisj]

Hmmm... I think with a properly designed ADC (note the caveat!), even if you distort it to hell, you'll still have a very tough time getting anything out of it that would reconstruct significantly ABOVE full scale. At full scale, yes- but above it?
Wouldn't it depend on how good the anti-aliasing filters are? If they're really good, you wouldn't have any illegal content. Just content that sits at FS because you're overloading the ADC.
I thought this was how some guys get such extremely treble-rich but ungrating masterings- go into analog, fry the treble up good, hit the ADC and it prevents anything excessive from getting into the data stream...

[PP]

[chrisj]

Hey now, credit where credit is due. You wouldn't have heard anything about this if Erik hadn't been good enough to, er, mention it. (still wouldn't have, except that I had been revising my website at the time)
Maybe I still have some learning to do, since I seem to like such highfalutin plaudits a little TOO much. All that, and if my stuff sounds crap, it STILL sounds crap no matter how heroically I may have arrived at it. 44.1K files and ABX tests don't care if you're brave or cowardly. Let me stick to those for the time being.
Can we go back to talking about Gibb effect now? (what effect DO really lame hairstyles have on a close-harmony singing group?)

[magicchord]

Yeah, let's hand it to Bombguy for pointing out the people who are "different".

If it weren't for the "different" folks, we'd all still be recording on rocks.






Patrick Bryant
MagicChord Music

[Nika Aldrich]

magicchord wrote on Thu, 26 August 2004 17:45

Yeah, let's hand it to Bombguy for pointing out the people who are "different". If it weren't for the "different" folks, we'd all still be recording on rocks.

"Bombguy" may be case in point.