How to build SNEX Playground?

[Christoph Hart]

@d-healey the SNEX playground is still functional but the main use case for it is me making unit tests for testing specific SNEX language features.

[Casmat]

@Christoph-Hart @d-healey Nice! I found this code on musicdsp.org:

x < a:
  f(x) = x
x > a:
  f(x) = a + (x-a)/(1+((x-a)/(1-a))^2)
x > 1:
  f(x) = (a+1)/2

How would I turn this into something snex can understand? Wouldn't it use if statements and how should X and A be swapped? It's supposed to make a soft saturation

Thanks!

[d.healey]

@Christoph-Hart Oh I think I was thinking of the SNEX workbench.

[ustk]

@Casmat said in How to build SNEX Playground?:

x < a:
f(x) = x
x > a:
f(x) = a + (x-a)/(1+((x-a)/(1-a))^2)
x > 1:
f(x) = (a+1)/2

This translates to something like:

float out = 0.0;

if (x < a)
   out = x;
else if (x > a)
   out = a + (x - a) / (1.0 + Math.sqr((x - a) / (1.0 - a)));
else if (x > 1)
   out = (a + 1.0) / 2.0;

Although it can probably be optimised depending on the use case...

[Casmat]

@ustk I was trying to write it out and got this:

	float getSample(float input, float a)
	{
		if(input < a)
		{
			return input;
		}
		else if(input > 1)
		{
			return (a + 1) / 2;
		}
		else
		{
			return a + (input - a) / (1 + ((input - a) / (1 - a))**2);
		}
	}

definitely wrong in all sorts of cases, I haven't ventured into dsp code, and this is by far the deepest, so thanks for helping! Have one more request, how in the world do I put this into the snex code editor? I tried reading the docs on snex, but was a bit stumped. I'm trying to build a saturation in a snex shaper node with one "Saturation" control. How do I continue?

Thanks a ton!

[ustk]

@Casmat The implementation of your function looks like this:

	float getSample(float s)
	{
		//return your stuff here
	}
	
	
	template <typename ProcessDataType> void process(ProcessDataType& data)
	{
		auto f = data.toFrameData();
		
		while (f.next())
		{
			for (auto& s: f)
				s = getSample(s);
		}
	}
	
	
	template <int C> void processFrame(span<float, C>& data)
	{
		for(auto& s: data)
			s = getSample(s);
	}

[ustk]

@Casmat And as I wrote above, the constants should be float if you don't want to get casting errors

[ustk]

@Casmat And one other thing, have you tried to plot your formula to see what you get out from it? Because it's going over the -1/+1 gain factor so you either need to scale the output or rework the formula...

[Casmat]

@ustk thanks for the info! I don’t think ive done anything with the formula, i found it on music dsp and I was clueless from the start on how to get it to be a simple saturator, is the gain factor related to the gain matching on a saturator?

Edit: so the gain factor is x?

[ustk]

@Casmat So I imagine a is your gain, right?
What do you get as a result? Is it at least sounding "something"?
Does the level need to be tamed a bit perhaps?

[Casmat]

@ustk as far as I know when looking at it, I thought that x was the input signal and a was the saturation amount

[ustk]

@Casmat said in How to build SNEX Playground?:

Edit: so the gain factor is x?

f(x) means the it's the output, so a should be the gain

[Casmat]

@ustk ohh yeah! Polynomials (or maybe not)!

[ustk]

@Casmat At first, does it look the way you want?


EDIT @Christoph-Hart @Dominik-Mayer Apparently there's still this Imgur over capacity issue that prevents us to see images...

[Casmat]

@ustk why was there an float s in the arguments? And I should be declaring a as a variable, right? I put the code you gave

if (x < a)
   out = x;
else if (x > a)
   out = a + (x - a) / (1.0 + Math.sqr((x - a) / (1.0 - a)));
else if (x > 1)
   out = (a + 1.0) / 2.0;

In the get sample func?

Edit: didn’t see your post yet, the img seems broken

[Casmat]

@ustk try using imgbb.com

[Christoph Hart]

@Casmat if imgur is over capacity then there‘s nothing we can do except for stop uploading images :)

[ustk]

@Christoph-Hart Yeah I though it was somehow related to the forum... Or use another provider

[ustk]

@Casmat

[ustk]

@Casmat You definitely need to declare a
At first, make it 0.0
Then add a parameter to control it