Interpolate controls to eliminate zipper noise

[unfa]

I'm currently making a video about x42-dpl and I've found that one shouldn't automate the controls if there's signal coming though, or there'll be zipper noise (if you have loud bass, it'll be very noticeable).

Do you think it'd make sense to tackle that?

BTW, I think this is an excellent limiter - simple, sounds great and has a slick, clean UI.

I'm really thankfkul you've made this plug-in, @x42. I've only recently realized it's one of the very best FOSS limiter plug-ins out there. It saves user's time and provides excellent quality.

[x42]

The input-gain is filtered, however the threshold is not, default release-time applies to it though.

That is intentional: no sample must exceed the threshold, ever. If it was low-pass filtered there may be short times where the signal can exceed a given threshold.

I assume you've automated the threshold. What use-case is there for that?

[x42]

I see. The issue is sparse automation. Internally the de-zipper takes place over a very short time (sample-rate dependent; at 48kHz the fade take 64 samples), but Ardour only sends a new value every cycle, here 512 samples / 48kHz = 10ms ~ 1 horizontal gird in the scope:

So there's a short ramp (internal dezipper) and then a longer flat period.

[unfa]

I actually just changed it quickly by hand while playing loud bass though and noticed artifacting.
I would very rarely automate a limiter, but at times such option is useful if I for example want to remove dynamics on a drum part for section of a composition to then bring that back.

[x42]

Which parameter have you changed?

[unfa]

This is exactly what I've done:
https://user-images.githubusercontent.com/491704/125860451-8d8262ac-e4ec-4e67-8d06-145ef7ca38de.mp4

[x42]

git pull :)

Sadly just missed the quarterly release cycle by less than 24hours.

[x42]

now ramping up 30dB over the span of 1/2 second at 1024 / 48kHz looks like

One process cycle (new gain value) happens roughly every two horizontal grid units.

[unfa]

Alright, so the interpolation was just too fast? :D

I'll remove the mention of this in my video then to not confuse viewers.

BTW, would you like to watch my whole video before I publish it to make sure I'm not getting something completely wrong?
it should be about ~10m long total.

[x42]

yes, it was too fast. Now it's an exponential approach that reaches the 90% of the target value in ~10ms.

Still I'm not too worried if a rapid +/- 40dB control value increase introduces some audible artifacts. Going from min to max in a short time is borderline insane.. still thanks for bringing this to my attention.

sure, please email the video to me.

[x42]

Fixed in dpl-1 v0.5.3 -- which is part of the x42-plugins 20211012 release