Clipper Oversampling Causing Artifacts on Export

[Myriad Rocker]

Searched around but didn't really find anything.  But I could be searching for the wrong terms.

I like to use a clipper on some songs (StandardClip to be specific).  When I'm exporting/bouncing, I'm getting some artifacts/pops when I increase the oversampling to 32x, which I believe is generally recommended when using a clipper.  Is there a way to force the host to take as much time as it needs to properly render the audio or is the bounce always real-time where CPU could get slammed by the oversampling?

[bitflipper]

Rendering is never real-time unless you expressly tell it to be by selecting the real-time bounce option. So normally, the CPU should have all the time in the world. I can't think of an explanation for your dropouts off the top of my head, but I can say that unless the clipper is extraordinarily poorly designed, 32x oversampling is overkill and unnecessary. Under most circumstances, 2x should be adequate. If it isn't, and you're hearing aliasing at 2x, try a different plugin.

[Myriad Rocker]

5 hours ago, bitflipper said:

Rendering is never real-time unless you expressly tell it to be by selecting the real-time bounce option. So normally, the CPU should have all the time in the world. I can't think of an explanation for your dropouts off the top of my head, but I can say that unless the clipper is extraordinarily poorly designed, 32x oversampling is overkill and unnecessary. Under most circumstances, 2x should be adequate. If it isn't, and you're hearing aliasing at 2x, try a different plugin.

Thanks for the info.  Where is the option to toggle on and off the real time bounce?  I've searched and I may just be missing it.

[bitflipper]

You probably missed it because you were looking for something labeled "real time bounce", and the option is called "fast bounce". You un-check the box to enable real-time rendering.

 

[Myriad Rocker]

I was staring directly at that option yesterday wondering if that was it.  That being said, I have that checked on every export I do.  It was the clipper set at 32x that was causing the chirps/artifacts, though, for sure.  When I lowered it back down to 4x, it was fine.  StandardClip is a fairly well regarded clipper, though.  So it's not junk.  If I had Fast Bounce enabled and StandardClip set to 32x (although perhaps unnecessary), it should have taken all the time it needed to render without the artifacts.

I'll stick with the 4x oversampling since that works for now.  But I may do some testing with higher oversampling and some of the other settings with Fast Bounce enabled.

I'll admit that my CPU is somewhat of a dinosaur by technology standards.  11 years old now. 

Edited August 23, 2021 by Myriad Rocker

[bitflipper]

It could just be a peculiarity of the plugin you're using.

The way to test if the oversampling is sufficient is to look for aliasing. If there is none, or it's very low (< -70 dB below the signal) then oversampling is working.

It's easiest to use a sine wave test tone for this, along with a spectrum analyzer such as Voxengo SPAN. As the amount of clipping distortion is raised, you'll start to see higher and higher levels of odd-order harmonics appear in SPAN's display (e.g. if your test tone is 100 Hz, you'll start to see 300, 500, 700, etc. Hz components appear). This is normal and is the  primary reason you use a clipper. 

However, if some of those manufactured frequencies exceed the Nyquist frequency (~ half the sample rate), you'll get aliasing - unpleasant frequencies that are not harmonics. They're pretty easy to spot with SPAN, but not necessarily a problem if they're low enough to be inaudible. Oversampling raises the Nyquist frequency, shifting the aliased components upward where they can be filtered out with a low-pass filter without altering the tone. Each time you double the sample rate you double the Nyquist frequency, thus doubling the highest "legal" frequency the plugin can handle before aliasing starts.

If the first aliased frequency is, say, 10 KHz but it's 96 dB below the main signal, you're good. If it's 1KHz and 12 dB below the main signal, then you need to increase the oversampling rate. This test will tell you how much oversampling you need for this specific plugin. It may end up being 2x or 4x, but probably not higher than that - unless the plugin is very badly designed. And you may get away with a lower rate if the plugin is followed by a low pass filter set to a high cutoff frequency.

[Xoo]

Try disabling 64 bit audio engine on export if you have been ticking it - a handful of plugins don't seem to like it being set.

[Will.]

23 hours ago, Myriad Rocker said:

Searched around but didn't really find anything.  But I could be searching for the wrong terms.

I like to use a clipper on some songs (StandardClip to be specific).  When I'm exporting/bouncing, I'm getting some artifacts/pops when I increase the oversampling to 32x, which I believe is generally recommended when using a clipper.  Is there a way to force the host to take as much time as it needs to properly render the audio or is the bounce always real-time where CPU could get slammed by the oversampling?

32x isn't really needed you know. An oversampling setting of 4x is pretty much all you need.