Recreate Bitcrusher Module in Scriptnode

Casey Kolb

Hi all! I'm sure I'm missing something simple here, but is there a good way to recreate the bitcrusher sample rate knob in scriptnode? There's the bitcrush node, but I'm not sure how to do the sample rate. Thanks!

Casey Kolb

I think I may have just found it. The sampleandhold node seems to do something similar.

Christoph Hart

@Casey-Kolb yup, this is more or less what it does (however the sample and hold doesn't support sub-sample reducing).

Casey Kolb

@Christoph-Hart said in Recreate Bitcrusher Module in Scriptnode:

@Casey-Kolb yup, this is more or less what it does (however the sample and hold doesn't support sub-sample reducing).

Got it! I'm not sure what sub-sample reducing is, but it sounds like I can use the sampleandhold node interchangeably with the "Sample Rate" from the Degrade module?

Christoph Hart

@Casey-Kolb The sample and hold will hold a value for the given samples. So if it's set to 2, it will effectively reduce the sample rate from 44.1kHz to 22kHz (if it's set to 4 it will be 11kHz and so on). However the hold duration is an integer value so you can't reduce to any arbitrary sample rate.

For LoFi effects it should be good enough though.

Casey Kolb

@Christoph-Hart Sounds good! We don't need precision with the reduction, so it seems perfect for lofi effects, and we can modulate it now which is awesome!

Casey Kolb

@Christoph-Hart Running into a slightly weird issue with the custom bitcrusher scriptnode module within CUBE. For some reason the bit rate will create a perpetual fuzzy signal even after the sound has finished.

Here's an example:
https://www.dropbox.com/s/n3ehwtbvx18syii/Scriptnode Bitcrusher generating noise even without input.mov?dl=0

Christoph Hart

@Casey-Kolb If you're modulating the bit crusher it will create varying DC offsets at low bit values. What's in the modulation chain?

Casey Kolb

@Christoph-Hart Just a global modulator LFO.

Casey Kolb

@Christoph-Hart Even without modulation, the bitcrusher node it scriptnode leaves a signal active perpetually if the bit rate is anything below 16. The meters will show signal.

JL.LV

@Casey-Kolb I think thats DC offset, you would need to find a way to supress that. I think you would need something to stop th signal from going below -1 and above +1. I tried doing this with the clip node (by modifying the min/max) but it didnt work

Christoph Hart

@JL-LV No you don't get rid of DC offset by clipping to -1...1. What you need is a high pass filter (DC offset is a signal with the frequency 0Hz, so even a simple one pole high pass set to 20Hz will get rid of this).

Casey Kolb

@Christoph-Hart Great! That works for removing the phantom signal from the meter, but I'm still experiencing this weird static noise in my CUBE project: https://www.dropbox.com/s/n3ehwtbvx18syii/Scriptnode Bitcrusher generating noise even without input.mov?dl=0

Christoph Hart

@Casey-Kolb Hmm, the problem is still the DC offset that the bit crusher introduces.

I've made another bitcrusher as snex_shape node which behaves better when modulating (and there's no DC offset introduced).

The snippet export doesn't work with SNEX nodes yet, so you have to do it manually:

Add a snex_shaper node.
Make sure you have a "SNEX code editor" floating tile somewhere (best place would be a tab in the scripting editor tabs).
Create a new file (call it bitcrush2). Click on the SNEX button. Then you should see the shaper class in the SNEX editor.
Enter the code below and press compile.
Add a parameter and set its range to 4-16 (or whatever bit range you want to support
Use and compile the node like any other.

template <int NumVoices> struct bitcrush2
{
	SNEX_NODE(bitcrush2);
	
	// Implement the Waveshaper here...
	
	float getSample(float input)
	{
		const float invStepSize = Math.pow(2.0f, bitDepth);
		const float stepSize = 1.0f / invStepSize;
			
		if(input > 0.0f)
			return (stepSize * Math.floor(input * invStepSize));
		else
			return (stepSize * Math.ceil(input * invStepSize));
	}
	// These functions are the glue code that call the function above
	template <typename T> void process(T& data)
	{
		for(auto ch: data)
		{
			for(auto& s: data.toChannelData(ch))
			{
				s = getSample(s);
			}
		}
	}
	template <typename T> void processFrame(T& data)
	{
		for(auto& s: data)
			s = getSample(s);
	}
	void reset()
	{
		
	}
	void prepare(PrepareSpecs ps)
	{
		
	}
	
	void setExternalData(const ExternalData& d, int index)
	{
	}
	
	float bitDepth = 16.0f;
	
	template <int P> void setParameter(double v)
	{
		bitDepth = v;

	}
};

Christoph Hart

@Christoph-Hart NVM, I've added this as additional mode to the bit crusher node. You can now choose between DC and Bipolar. I couldn't just change the bit crusher algorithm because it sounds very different, but when you want to modulate the bit depth, the new Bipolar mode is much better because it doesn't create a DC offset that is dependent on the bit depth parameter.

(If you load an existing network, it will complain about a wrong parameter structure, but this is OK in this case).

Casey Kolb

@Christoph-Hart Amazing! Will give this a spin :) Thank you

Casey Kolb

@Christoph-Hart @langermarc19 We're hitting a snag here with the bitcrusher in scriptnode. In the compiled VST plugin, it will output only the left channel when the bitcrusher is active, regardless of the mode, DC or Bipolar, and regardless of the bitrate. It seems to happen in most DAWs, but not in standalone.

We're going to take a look at the node code for the bitcrusher, but any immediate thoughts?

Matt_SF

@Casey-Kolb I won't be of much help, but I built a simple bitcrusher here and it works fine (I recall I'm using the bipolar mode)

blezzbeats

Kinda related: Is there any way to access the in-between sample rates of the bitcrusher effect with an integer or float? To get at the rates between 22-44khZ for example, and not just jump that big notch.

Christoph Hart

@blezzbeats Do you mean the sample and hold module? The bitcrusher allows float bit rates.

Recreate Bitcrusher Module in Scriptnode

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