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Old 01-14-2022, 12:59 AM   #1
Phazma
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Default Constant low level signal in most JSFX (even Cockos)

A licecap is worth a thousand words:



I find this behavior in most (but not all) JSFX. The Cockos metering JS are unaffected but metering JS by other developers (even without audio code) are affected.

Also other plugin types are not affected. So I guess this is some JS bug.
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Old 01-14-2022, 04:11 AM   #2
schwa
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It's anti-denormalization. See ext_nodenorm here:
https://www.reaper.fm/sdk/js/vars.php#js_specialvars
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Old 01-14-2022, 06:56 AM   #3
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Ok thanks adding ext_nodenorm=1 makes it go away.. I am wondering what anti-denormalization actually is and why it is there by default. For sure it has some benefits. But I guess a google search will answer that question.
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Old 01-14-2022, 08:26 AM   #4
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Found the option Preferences > Plug-Ins > Compatibility > "Reduce denormalization from plug-ins"

This is a good explanation. So it seems it is needed to avoid potential high CPU spikes.

Strangely this signal doesn't disappear if I disable the preference (even if I reload a plugin).

But I guess it is better to leave it on anyway. At least now I know what this is and that it's there on purpose.
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Old 01-14-2022, 08:35 AM   #5
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That general preference affects everything *but* jsfx. JSFX have anti-denorm enabled by default, unless the specific plugin includes ext_nodenorm in the @init section.
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Old 01-14-2022, 08:48 AM   #6
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Ok got it. Thanks for letting me know.
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Old 01-14-2022, 11:54 AM   #7
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OK but this issue comes from the discussion of the meter plugin, right?

https://forum.cockos.com/showthread.php?p=2516247

That code doesnít output any audio and it feels pretty unintuitive that it would change the audio at all. Does it have to?
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Old 01-14-2022, 12:25 PM   #8
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No plugin has to, the plugin author can add ext_nodenorm if they want to.

The purpose of anti-denormalization is to prevent the audio processing from entering a state that is more CPU intensive than necessary. It doesn't matter if the plugin is generating output, as long as it is doing any calculations using the signal input, then denormalization is relevant.

The benefit of anti-denormalization varies, but the cost, namely extra signal at -300dB, is extremely small.
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Old 01-14-2022, 01:27 PM   #9
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I guess there are things one can do in their code to avoid these CPU spikes? But of course we canít really assume that any given plugin has done any of that. In fact, I feel like we almost have to assume they havenít unless theyíve already added that line. So itís not really safe to just go sticking it in anywhere I feel like I want it. If itís just the way she goes, then thatís where weíre at.

I havenít actually looked into this at all, and Iím not in a place I can look, but does disconnecting the plugís output pins solve this issue. I would expect that to keep it from altering the audio stream at all, but...
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Old 01-15-2022, 12:28 PM   #10
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We could probably remove the anti-denormal noise in JSFX (the other mechanisms to avoid denormals have evolved since it was originally introduced), though doing so would be of little benefit anyway.

(and there might be plugins that have their performance get degraded by denormals in certain instances)

Last edited by Justin; 01-15-2022 at 12:33 PM.
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Old 01-16-2022, 02:45 PM   #11
Phazma
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Quote:
Originally Posted by Justin View Post
We could probably remove the anti-denormal noise in JSFX (the other mechanisms to avoid denormals have evolved since it was originally introduced), though doing so would be of little benefit anyway.

(and there might be plugins that have their performance get degraded by denormals in certain instances)
Hmm, how about extending "Preferences > Plug-Ins > Compatibility > Reduce denormalization from plug-ins" to affect also JSFX? The creator of a JSFX could override the preference by defining ext_nodenorm as either 0 or 1 and if undefined the user preference is used.
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