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desc:O____ROTARENEG_ESION_TEWLEW_NAISUAG____O____GAUSIAN_WELWET_NOISE_GENERATOR____O
//tags: analysis generator synthesis
//author: SCHWA

// Generator choices are listed in rough order of fanciness and cost.

slider1:-16<-120,6,0.1>Noise dB (RMS)
slider2:0.5<0,1,0.01>Wet Mix
slider3:1<0,3,1{Central Limit Approximation,Box-Muller,Ziggurat (not implemented yet),Inverse Transform}>Gaussian Generator
slider4:0<-1,1>Noise Mean (should be ~0)
slider5:0<0,2>Noise Standard Deviation (should be ~1)

in_pin:left input
in_pin:right input
out_pin:left output
out_pin:right output

@init

AMP_DB = 20.0 / log(10);

CENTRAL_LIMIT = 0;
BOX_MULLER = 1;
ZIGGURAT = 2;
INV_TRANSFORM = 3;

@slider

noise_level = exp(slider1 / AMP_DB);

(slider3 == CENTRAL_LIMIT) ? (
  N_DEV = 12;
)
:
(slider3 == INV_TRANSFORM) ? (
   A1 = -39.69683028665376;
   A2 =  220.9460984245205;
   A3 = -275.9285104469687;
   A4 =  138.3577518672690;
   A5 = -30.66479806614716;
   A6 =  2.506628277459239;

   B1 = -54.47609879822406;
   B2 =  161.5858368580409;
   B3 = -155.6989798598866;
   B4 =  66.80131188771972;
   B5 = -13.28068155288572;

   C1 = -0.007784894002430293;
   C2 = -0.3223964580411365;
   C3 = -2.400758277161838;
   C4 = -2.549732539343734;
   C5 =  4.374664141464968;
   C6 =  2.938163982698783;

   D1 =  0.007784695709041462;
   D2 =  0.3224671290700398;
   D3 =  2.445134137142996;
   D4 =  3.754408661907416;

   P_LO = 0.02425;
   P_HI = 1.0 - P_LO;
);

i = sum = sum2 = 0;

@sample

z0 = z1 = 0;

(slider3 == CENTRAL_LIMIT) ? (

  // Quick & dirty.  
  loop (N_DEV, 
    z0 += rand(1);
    z1 += rand(1);
  );
  z0 -= N_DEV / 2.0;
  z1 -= N_DEV / 2.0;
)
:
(slider3 == BOX_MULLER) ? (

  // Conveniently a stereo twofer.
  w = 0;
  while (
    z0 = 2.0 * rand(1) - 1.0;
    z1 = 2.0 * rand(1) - 1.0;
    w = z0 * z0 + z1 * z1;
    w >= 1.0;
  );
  w = sqrt(-2.0 * log(w) / w);
  z0 *= w;
  z1 *= w;
)
:
(slider3 == INV_TRANSFORM) ? (

   r0 = rand(1);
   r1 = rand(1);

   (r0 < P_LO) ? (
     q = sqrt(-2.0 * log(r0));
     z0 = ((((C1 * q + C2) * q + C3) * q + C4) * q + C5) * q + C6;
     z0 /= (((D1 * q + D2) * q + D3) * q + D4) * q + 1.0;
   )
   :
   (r0 < P_HI) ? (
     q = r0 - 0.5;
     r = q * q;
     z0 = (((((A1 * r + A2) * r + A3) * r + A4) * r + A5) * r + A6) * q;
     z0 /= ((((B1 * r + B2) * r + B3) * r + B4) * r + B5) * r + 1.0;
   )
   :
   (
     q = sqrt(-2.0 * log(1.0 - r0));
     z0 = -(((((C1 * q + C2) * q + C3) * q + C4) * q + C5) * q + C6);
     z0 /= (((D1 * q + D2) * q + D3) * q + D4) * q + 1.0;
   );

   (r1 < P_LO) ? (
     q = sqrt(-2.0 * log(r1));
     z1 = ((((C1 * q + C2) * q + C3) * q + C4) * q + C5) * q + C6;
     z1 /= (((D1 * q + D2) * q + D3) * q + D4) * q + 1.0;
   )
   :
   (r1 < P_HI) ? (
     q = r1 - 0.5;
     r = q * q;
     z1 = (((((A1 * r + A2) * r + A3) * r + A4) * r + A5) * r + A6) * q;
     z1 /= ((((B1 * r + B2) * r + B3) * r + B4) * r + B5) * r + 1.0;
   )
   :
   (
     q = sqrt(-2.0 * log(1.0 - r0));
     z1 = -(((((C1 * q + C2) * q + C3) * q + C4) * q + C5) * q + C6);
     z1 /= (((D1 * q + D2) * q + D3) * q + D4) * q + 1.0;
   );
);

spl0 = ((FLOOR(spl0 * (1.0 - slider2) + z0 * noise_level * slider2))+.5)/6;
spl1 = ((FLOOR(spl1 * (1.0 - slider2) + z1 * noise_level * slider2))+.5)/6;
//spl0 = spl0 * (1.0 - slider2) + z0 * noise_level * slider2;
//spl1 = spl1 * (1.0 - slider2) + z1 * noise_level * slider2;

sum += z0;
sum2 += z0 * z0;

i += 1;
(i == srate) ? (
  mean = sum / srate;
  stdev = sqrt(sum2 / srate - mean * mean);
  slider4 = mean;
  slider5 = stdev;
  sliderchange(2^4 + 2^5);
  i = sum = sum2 = 0;
);