From d6b9eb15578f1f4eb08d67fb3a9f9f8dbd5c85b4 Mon Sep 17 00:00:00 2001
From: TiagoLr <prog4mr@gmail.com>
Date: Thu, 28 Dec 2023 14:50:54 +0000
Subject: [PATCH] Release JSAdditiv v1.3 (#359)

replace zdf with rbj filters
fix note clicking
fix volume knob clicking
---
 Synth/tilr_JSAdditiv.jsfx                    | 118 ++---
 Synth/tilr_JSAdditiv/add.gfxlib.jsfx-inc     |   1 -
 Synth/tilr_JSAdditiv/add.rbj_filter.jsfx-inc | 433 +++++++++++++++++++
 Synth/tilr_JSAdditiv/add.zdf_filter.jsfx-inc | 403 -----------------
 4 files changed, 476 insertions(+), 479 deletions(-)
 create mode 100644 Synth/tilr_JSAdditiv/add.rbj_filter.jsfx-inc
 delete mode 100644 Synth/tilr_JSAdditiv/add.zdf_filter.jsfx-inc

diff --git a/Synth/tilr_JSAdditiv.jsfx b/Synth/tilr_JSAdditiv.jsfx
index 57a07be..2e163ac 100644
--- a/Synth/tilr_JSAdditiv.jsfx
+++ b/Synth/tilr_JSAdditiv.jsfx
@@ -1,10 +1,10 @@
 desc: JSAdditiv
 author: tilr
-version: 1.2
+version: 1.3
 changelog:
-  Fix support large wave files
-  Fix import wave samplerate
-  Support file drag and drop
+  replace zdf with rbj filters
+  fix note clicking 
+  fix volume knob clicking
 provides:
   tilr_JSAdditiv/add.adsr.jsfx-inc
   tilr_JSAdditiv/add.array.jsfx-inc
@@ -12,7 +12,6 @@ provides:
   tilr_JSAdditiv/add.gfxlib.jsfx-inc
   tilr_JSAdditiv/add.mouselib.jsfx-inc
   tilr_JSAdditiv/add.wavetable.jsfx-inc
-  tilr_JSAdditiv/add.zdf_filter.jsfx-inc
   [data] tilr_JSAdditiv/Complex 1.wav
   [data] tilr_JSAdditiv/Complex 2.wav
   [data] tilr_JSAdditiv/Complex 3.wav
@@ -38,6 +37,7 @@ provides:
   [data] tilr_JSAdditiv/Square 2.wav
   [data] tilr_JSAdditiv/Stairs.wav
   [data] tilr_JSAdditiv/Triangle.wav
+  tilr_JSAdditiv/add.rbj_filter.jsfx-inc
 screenshot: https://raw.githubusercontent.com/tiagolr/JSAdditiv/master/doc/ss.png
 about:
   # JSAdditiv
@@ -84,7 +84,7 @@ slider26:pitch_rel=500<1, 5000, 1:log>-Pitch Release
 import add.wavetable.jsfx-inc
 import add.array.jsfx-inc
 import add.adsr.jsfx-inc
-import add.zdf_filter.jsfx-inc
+import add.rbj_filter.jsfx-inc
 import add.gfxlib.jsfx-inc
 import add.mouselib.jsfx-inc
 import add.fft_real_synth.jsfx-inc
@@ -120,6 +120,20 @@ function db2gain (db) local (val) (
 function normalize_vol_slider(val) ( val * 60 / 100 - 60 );
 function note2freq(n) ( 440 * pow(2, (n - 69) / 12); );
 
+function rc_set(rc)
+  instance(a) (
+    a = 1 / (rc * srate + 1);
+);
+function rc_lp(sample)
+  instance(lp, a) (
+    lp += a * (sample - lp);
+);
+function smooth()
+  instance (lp, smooth) (
+    lp = smooth;
+    smooth = this.rc_lp(this);
+);
+
 function normalize_wave(buf, len)
 local (_min, _max, i)
 (
@@ -189,7 +203,7 @@ function resynthesize() (
   semi_normalize_wave(wavebuf, four.size * 2); // correct signal strenght after summing frequencies
 );
 
-function read_file(filehandle) 
+function read_file(filehandle)
 local (len)
 (
   filehandle > 0 ? (
@@ -226,58 +240,12 @@ function read_file_string(str) (
   read_file(filehandle);
 );
 
-// copy filter coeficients from buffer1 to buffer2
-function filter_copy_coefs(buf1, buf2) (
-  buf2[2] = buf1[2];
-  buf2[3] = buf1[3];
-  buf2[4] = buf1[4];
-);
-
-// wraps filter function using buffers
-function filter_setf(buf, freq, q) (
-  filter.zdf_setf(freq, q);
-  buf[2] = filter.g;
-  buf[3] = filter.r2;
-  buf[4] = filter.h;
-);
-
-// wraps filter function using buffers
-function filter_lp(buf, sample) local(lp) (
-  filter.s1 = buf[0];
-  filter.s2 = buf[1];
-  filter.g = buf[2];
-  filter.r2 = buf[3];
-  filter.h = buf[4];
-  lp = filter.zdf_svf_lp(sample);
-  buf[0] = filter.s1;
-  buf[1] = filter.s2;
-  lp;
-);
-
-// wraps filter function using buffers
-function filter_bp(buf, sample) local(bp) (
-  filter.s1 = buf[0];
-  filter.s2 = buf[1];
-  filter.g = buf[2];
-  filter.r2 = buf[3];
-  filter.h = buf[4];
-  bp = filter.zdf_svf_bp(sample);
-  buf[0] = filter.s1;
-  buf[1] = filter.s2;
-  bp;
-);
-
-// wraps filter function using buffers
-function filter_hp(buf, sample) local(hp) (
-  filter.s1 = buf[0];
-  filter.s2 = buf[1];
-  filter.g = buf[2];
-  filter.r2 = buf[3];
-  filter.h = buf[4];
-  hp = filter.zdf_svf_hp(sample);
-  buf[0] = filter.s1;
-  buf[1] = filter.s2;
-  hp;
+function copy_filter_coefs (f1, f2) (
+  f2[0] = f1[0]; // a1
+  f2[1] = f1[1]; // a2
+  f2[2] = f1[2]; // b0
+  f2[3] = f1[3]; // b1
+  f2[4] = f1[4]; // b2
 );
 
 function on_slider() (
@@ -296,6 +264,10 @@ function on_slider() (
 // FIX - read initial wave from string instead of slider
 read_file_string("tilr_JSAdditiv/Sine 1.wav");
 
+// Init smoothing
+gain.rc_set(0.0033);
+gain.smooth = db2gain(normalize_vol_slider(vol));
+
 @serialize
 file_var(0, osc_free);
 file_mem(0, wavebuf, wavelen + four.size * 4);
@@ -395,6 +367,7 @@ while (midirecv(offset, msg1, note, vel)) (
 );
 
 @sample
+gain.smooth();
 
 ptr = poly.array_first();
 while(ptr >= 0) ( // for each note/voice
@@ -430,34 +403,29 @@ while(ptr >= 0) ( // for each note/voice
   flt_shape != 0 ? (
     filterbuf = filter_env + ptr[0] * 7; // envelope buffer
     adsr_process(filterbuf);
-    filterbuf_l = filter_arr_l + ptr[0] * 11; // filter buffer left
-    filterbuf_r = filter_arr_r + ptr[0] * 11; // filter buffer right
     multiplier = pow(20000/flt_freq, filterbuf[0] * flt_amt / 100);
 
-    filter_setf(filterbuf_l, flt_freq * multiplier, flt_q);
-    filter_copy_coefs(filterbuf_l, filterbuf_r);
+    filterbuf_l = filter_arr_l + ptr[0] * 11; // filter buffer left
+    filterbuf_r = filter_arr_r + ptr[0] * 11; // filter buffer left
 
-  flt_shape == 1 ? (
-      outl = filter_lp(filterbuf_l, outl);
-      outr = filter_lp(filterbuf_r, outr);
+    flt_shape == 1 ? (
+      rbj_lp(filterbuf_l, flt_freq * multiplier, flt_q);
     ) : flt_shape == 2 ? (
-      outl = filter_bp(filterbuf_l, outl);
-      outr = filter_bp(filterbuf_r, outr);
+      rbj_bp(filterbuf_l, flt_freq * multiplier, flt_q);
     ) : (
-      outl = filter_hp(filterbuf_l, outl);
-      outr = filter_hp(filterbuf_r, outr);
+      rbj_hp(filterbuf_l, flt_freq * multiplier, flt_q);
     );
+    copy_filter_coefs(filterbuf_l, filterbuf_r);
+    outl = rbj_df1(filterbuf_l, outl);
+    outr = rbj_df1(filterbuf_r, outr);
   );
 
-  spl0 += outl * gain;
-  spl1 += outr * gain;
+  spl0 += outl * gain.smooth;
+  spl1 += outr * gain.smooth;
 
   ptr = poly.array_next(ptr);
 );
 
-spl0 += outl * gain;
-spl1 += outr * gain;
-
 @gfx 520 270
 
 gfx_clear = COLOR_BG;
diff --git a/Synth/tilr_JSAdditiv/add.gfxlib.jsfx-inc b/Synth/tilr_JSAdditiv/add.gfxlib.jsfx-inc
index ee89f28..df20794 100644
--- a/Synth/tilr_JSAdditiv/add.gfxlib.jsfx-inc
+++ b/Synth/tilr_JSAdditiv/add.gfxlib.jsfx-inc
@@ -202,7 +202,6 @@ local (harm_w, amp, i, mouse_active, hx, ph, yamp, phase, real, img, yphase)
       );
       phase_mode && mouse_active && mouse_in_rect(hx, y, harm_w, h) ? (
         yphase = mouse.control ? 0 : (mouse.y - y) / h * -2 - 1;
-        yphasee = yphase;
         amp = harmonic_amplitude(buf[i], buf[i+1]);
         buf[i+1] = amp * cos(yphase*$pi); // real
         buf[i] = amp * sin(yphase*$pi); // img
diff --git a/Synth/tilr_JSAdditiv/add.rbj_filter.jsfx-inc b/Synth/tilr_JSAdditiv/add.rbj_filter.jsfx-inc
new file mode 100644
index 0000000..981c874
--- /dev/null
+++ b/Synth/tilr_JSAdditiv/add.rbj_filter.jsfx-inc
@@ -0,0 +1,433 @@
+desc:2nd-order RBJ filter
+
+// Copyright (C) 2012-2022 Theo Niessink <theo@taletn.com>
+// This work is free. You can redistribute it and/or modify it under the
+// terms of the Do What The Fuck You Want To Public License, Version 2,
+// as published by Sam Hocevar. See http://www.wtfpl.net/ for more details.
+
+// Based on "Cookbook formulae for audio EQ biquad filter coefficients" by
+// Robert Bristow-Johnson.
+// http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt
+
+/* Example
+
+   desc:Low-pass filter
+
+   slider1:1000<20,20000,1>Cutoff (Hz)
+   slider2:0.5<0.01,4.0,0.01>Q
+
+   import Tale/rbj_filter.jsfx-inc
+
+   @slider
+   lp.rbj_lp(slider1, slider2);
+   lp.rbj_gain(0.5);
+
+   @sample
+   spl0 = spl1 = lp.rbj_df1(spl0 + spl1);
+
+   Setting Functions
+
+    * rbj_lp(freq, q)       -- Low-pass
+    * rbj_hp(freq, q)       -- High-pass
+    * rbj_bp(freq, q)       -- Band-pass (constant skirt gain)
+    * rbj_bp2(freq, q)      -- Band-pass (constant peak gain)
+    * rbj_bs(freq, q)       -- Band-stop
+    * rbj_ap(freq, q)       -- All-pass
+    * rbj_eq(freq, q, gain) -- Peaking EQ
+    * rbj_ls(freq, q, gain) -- Low-shelf
+    * rbj_hs(freq, q, gain) -- High-shelf
+      Example: lp.rbj_lp(1000, 0.5);
+      Sets up the filter for the specified cutoff frequency (in Hz), and Q
+      and gain factors, and returns the a0 coefficient.
+
+      (To convert from dB to gain: gain=10^(db/20).)
+
+    * rbj_gain(gain)
+    * rbj_dry_wet(dry, wet)
+      Example: lp.rbj_lp(1000, 0.5); lp.rbj_gain(-2.0);
+      Example: lp.rbj_lp(1000, 0.5); lp.rbj_dry_wet(0.1, 0.9);
+      Modifies the filter by applying the specified output gain or dry/wet
+      mix.
+
+      Note: You should always first setup the filter, and then modify it. If
+      you change the filter frequency/Q afterwards, then this will reset the
+      gain and dry/wet values, and so you will have to modify them again.
+
+   Filter Functions
+
+    * rbj_df1(sample)  -- Direct Form 1
+    * rbj_df2(sample)  -- Direct Form 2
+    * rbj_tdf2(sample) -- Transposed Direct Form 2
+      Example: output = lp.rbj_tdf2(input);
+      Sends a sample through the filter, and returns its output.
+
+   Miscellaneous Functions
+
+    * rbj_reset_df1([input])  -- Direct Form 1
+    * rbj_reset_df2([input])  -- Direct Form 2
+    * rbj_reset_tdf2([input]) -- Transposed Direct Form 2
+      Example: lp.rbj_reset_tdf2();
+      Resets the filter state to the specified input value, or to zero if
+      the value is omitted.
+
+    * rbj_bwtoq(bw)
+    * rbj_qtobw(q)
+      Example: q = rbj_bwtoq(2.0);
+      Converts bandwidth (in octaves) to Q factor, or vice versa.
+
+   Instance Variables
+
+    * a1
+    * a2
+    * b0
+    * b1
+    * b2
+      Example: lp2.a1 = lp1.a1; lp2.a2 = lp1.a2; lp2.b0 = lp1.b0; lp2.b1 = lp1.b1; lp2.b2 = lp1.b2;
+      Filter coefficients.
+
+      Note: The first coefficient (a0) is not included here, because all
+      coefficients are scaled (i.e. divided) by a0, after which a0 itself
+      would always be 1. The setting functions return the original a0 value,
+      should you need it (e.g. to get the original, non-scaled
+      coefficients).
+
+    * x0
+    * x1
+    * y0
+    * y1
+      Example: current_input = lp.x0;
+      Example: previous_output = lp.y1;
+      Direct Form 1 inputs/outputs.
+
+    * w0
+    * w1
+      Example: lp2.w0 = lp1.w0; lp2.w1 = lp1.w1;
+      Direct Form 2 filter state.
+
+    * s0
+    * s1
+      Example: lp2.s0 = lp1.s0; lp2.s1 = lp1.s1;
+      Transposed Direct Form 2 filter state.
+
+*/
+
+/*
+    Modified lib to work with buffers
+
+    0  = a1
+    1  = a2
+    2  = b0
+    3  = b1
+    4  = b2
+    5  = x0
+    6  = x1
+    7  = y0
+    8  = y1
+    9  = w0
+    10 = w1
+*/
+
+@init
+
+function rbj_bwtoq(bw)
+  local(x)
+(
+  // q = 1/(2 * sinh(log(2) / 2 * bw))
+  x = exp(0.5*log(2) * bw);
+  x/(sqr(x) - 1);
+);
+
+function rbj_qtobw(q)
+  local(x)
+(
+  // bw = 2 * asinh(1/(2 * q)) / log(2)
+  x = 0.5 / q;
+  2/log(2) * log(x + sqrt(sqr(x) + 1));
+);
+
+// Low-pass
+
+function rbj_lp(buf, freq, q)
+  // global(srate)
+  //instance(a1, a2, b0, b1, b2)
+  local(w0, alpha, a0, scale)
+(
+  w0 = 2*$pi * min(freq / srate, 0.49);
+  alpha = sin(w0) / (2*q);
+
+  scale = 1/(a0 = 1 + alpha);
+  buf[0] = cos(w0) * -2 * scale;
+  buf[1] = (1 - alpha) * scale;
+
+  buf[4] = buf[2] = (1 + buf[0] + buf[1]) * 0.25;
+  buf[3] = buf[2] * 2;
+
+  a0;
+);
+
+// High-pass
+
+function rbj_hp(buf, freq, q)
+  // global(srate)
+  // instance(a1, a2, b0, b1, b2)
+  local(w0, alpha, a0, scale)
+(
+  w0 = 2*$pi * min(freq / srate, 0.49);
+  alpha = sin(w0) / (2*q);
+
+  scale = 1/(a0 = 1 + alpha);
+  buf[0] = cos(w0) * -2 * scale;
+  buf[1] = (1 - alpha) * scale;
+
+  buf[4] = buf[2] = (1 - buf[0]  + buf[1]) * 0.25;
+  buf[3] = buf[2] * -2;
+
+  a0;
+);
+
+// Band-pass (constant skirt gain, peak gain = Q)
+
+function rbj_bp(buf, freq, q)
+  // global(srate)
+  // instance(a1, a2, b0, b1, b2)
+  local(w0, alpha, a0, scale)
+(
+  w0 = 2*$pi * min(freq / srate, 0.49);
+  alpha = sin(w0) / (2*q);
+
+  scale = 1/(a0 = 1 + alpha);
+  buf[0] = cos(w0) * -2 * scale;
+  buf[1] = (1 - alpha) * scale;
+
+  buf[4] = -(buf[2] = (1 - buf[1]) * 0.5 * q);
+  buf[3] = 0;
+
+  a0;
+);
+
+// Band-pass (constant 0 dB peak gain)
+/*
+function rbj_bp2(freq, q)
+  // global(srate)
+  instance(a1, a2, b0, b1, b2)
+  local(w0, alpha, a0, scale)
+(
+  w0 = 2*$pi * min(freq / srate, 0.49);
+  alpha = sin(w0) / (2*q);
+
+  scale = 1/(a0 = 1 + alpha);
+  a1 = cos(w0) * -2 * scale;
+  a2 = (1 - alpha) * scale;
+
+  b2 = -(b0 = (1 - a2) * 0.5);
+  b1 = 0;
+
+  a0;
+);
+*/
+// Band-stop
+/*
+function rbj_bs(freq, q)
+  // global(srate)
+  instance(a1, a2, b0, b1, b2)
+  local(w0, alpha, a0, scale)
+(
+  w0 = 2*$pi * min(freq / srate, 0.49);
+  alpha = sin(w0) / (2*q);
+
+  scale = 1/(a0 = 1 + alpha);
+  a1 = cos(w0) * -2 * scale;
+  a2 = (1 - alpha) * scale;
+
+  b2 = b0 = scale;
+  b1 = a1;
+
+  a0;
+);
+*/
+// All-pass
+/*
+function rbj_ap(freq, q)
+  // global(srate)
+  instance(a1, a2, b0, b1, b2)
+  local(w0, alpha, a0, scale)
+(
+  w0 = 2*$pi * min(freq / srate, 0.49);
+  alpha = sin(w0) / (2*q);
+
+  scale = 1/(a0 = 1 + alpha);
+  b1 = a1 = cos(w0) * -2 * scale;
+  b0 = a2 = (1 - alpha) * scale;
+
+  b2 = 1;
+
+  a0;
+);
+*/
+// Peaking EQ
+/*
+function rbj_eq(freq, q, gain)
+  // global(srate)
+  instance(a1, a2, b0, b1, b2)
+  local(w0, alpha, a, tmp, a0, scale)
+(
+  w0 = 2*$pi * min(freq / srate, 0.49);
+  alpha = sin(w0) / (2*q);
+  a = sqrt(gain);
+
+  tmp = alpha / a;
+
+  scale = 1/(a0 = 1 + tmp);
+  b1 = a1 = cos(w0) * -2 * scale;
+  a2 = (1 - tmp) * scale;
+
+  tmp = alpha * a * scale;
+
+  b0 = scale + tmp;
+  b2 = scale - tmp;
+
+  a0;
+);
+*/
+// Low-shelf
+/*
+function rbj_ls(freq, q, gain)
+  // global(srate)
+  instance(a1, a2, b0, b1, b2)
+  local(w0, cos_w0, a, tmp0, tmp1, tmp2, a0, scale)
+(
+  w0 = 2*$pi * min(freq / srate, 0.49);
+  cos_w0 = cos(w0);
+  a = sqrt(gain);
+
+  tmp0 = (a - 1) * cos_w0 + a + 1;
+  tmp1 = sqrt(a) * sin(w0) / q;
+  tmp2 = (a + 1) * cos_w0;
+
+  scale = 1/(a0 = tmp0 + tmp1);
+  a1 = (1 - a - tmp2) * 2 * scale;
+  a2 = (tmp0 - tmp1) * scale;
+
+  tmp0 = (1 - a) * cos_w0 + a + 1;
+  scale *= a;
+
+  b0 = (tmp0 + tmp1) * scale;
+  b1 = (a - 1 - tmp2) * 2 * scale;
+  b2 = (tmp0 - tmp1) * scale;
+
+  a0;
+);
+*/
+// High-shelf
+/*
+function rbj_hs(freq, q, gain)
+  // global(srate)
+  instance(a1, a2, b0, b1, b2)
+  local(w0, cos_w0, a, tmp0, tmp1, tmp2, a0, scale)
+(
+  w0 = 2*$pi * min(freq / srate, 0.49);
+  cos_w0 = cos(w0);
+  a = sqrt(gain);
+
+  tmp0 = (1 - a) * cos_w0 + a + 1;
+  tmp1 = sqrt(a) * sin(w0) / q;
+  tmp2 = (a + 1) * cos_w0;
+
+  scale = 1/(a0 = tmp0 + tmp1);
+  a1 = (a - 1 - tmp2) * 2 * scale;
+  a2 = (tmp0 - tmp1) * scale;
+
+  tmp0 = (a - 1) * cos_w0 + a + 1;
+  scale *= a;
+
+  b0 = (tmp0 + tmp1) * scale;
+  b1 = (1 - a - tmp2) * 2 * scale;
+  b2 = (tmp0 - tmp1) * scale;
+
+  a0;
+);
+*/
+/*
+function rbj_gain(gain)
+  instance(b0, b1, b2)
+(
+  b0 *= gain;
+  b1 *= gain;
+  b2 *= gain;
+);
+*/
+/*
+function rbj_dry_wet(dry, wet)
+  instance(a1, a2, b0, b1, b2)
+(
+  b0 = b0 * wet + dry;
+  b1 = b1 * wet + a1 * dry;
+  b2 = b2 * wet + a2 * dry;
+);
+*/
+// Direct Form 1
+
+function rbj_df1(buf, sample)
+  //instance(a1, a2, b0, b1, b2, x0, x1, y0, y1)
+  local(x2, y2)
+(
+  x2 = buf[6];
+  buf[6] = buf[5];
+  buf[5] = sample;
+
+  y2 = buf[8];
+  buf[8] = buf[7];
+  buf[7] = buf[2]*buf[5] + buf[3]*buf[6] + buf[4]*x2 - buf[0]*buf[8] - buf[1]*y2;
+);
+
+/*
+function rbj_reset_df1(input)
+  instance(a1, a2, b0, b1, b2, x0, x1, y0, y1)
+(
+  x0 = x1 = input;
+  y0 = y1 = input / (1 + a1 + a2) * (b0 + b1 + b2);
+);
+*/
+
+// Direct Form 2
+function rbj_df2(buf, sample)
+  // instance(a1, a2, b0, b1, b2, w0, w1)
+  local(w2)
+(
+  w2 = buf[10];
+  buf[10] = buf[9];
+  buf[9] = sample - buf[0]*buf[10] - buf[1]*w2;
+
+  buf[2]*buf[9] + buf[3]*buf[10] + buf[4]*w2;
+);
+
+/*
+function rbj_reset_df2(input)
+  instance(a1, a2, w0, w1)
+(
+  w0 = w1 = input / (1 + a1 + a2);
+);
+*/
+// Transposed Direct Form 2
+
+/*
+function rbj_tdf2(sample)
+  instance(a1, a2, b0, b1, b2, s0, s1)
+  local(y)
+(
+  y = b0 * sample + s0;
+
+  s0 = b1 * sample - a1*y + s1;
+  s1 = b2 * sample - a2*y;
+
+  y;
+);
+*/
+/*
+function rbj_reset_tdf2(input)
+  instance(a1, a2, b0, b1, b2, s0, s1)
+(
+  s0 = ((b0 + b1 + b2) / (1 + a1 + a2) - b0) * input;
+  s1 = b2 * input - a2 * (b0 * input + s0);
+);
+*/
diff --git a/Synth/tilr_JSAdditiv/add.zdf_filter.jsfx-inc b/Synth/tilr_JSAdditiv/add.zdf_filter.jsfx-inc
deleted file mode 100644
index 48c4b58..0000000
--- a/Synth/tilr_JSAdditiv/add.zdf_filter.jsfx-inc
+++ /dev/null
@@ -1,403 +0,0 @@
-desc:2nd-order zero-delay feedback state variable filter
-
-// Copyright (C) 2013-2021 Theo Niessink <theo@taletn.com>
-// This work is free. You can redistribute it and/or modify it under the
-// terms of the Do What The Fuck You Want To Public License, Version 2,
-// as published by Sam Hocevar. See http://www.wtfpl.net/ for more details.
-
-// Initially based on the rsStateVariableFilter C++ class by Robin Schmidt,
-// as posted (in the public domain) on the KVR forum.
-// http://www.kvraudio.com/forum/viewtopic.php?p=5243733#p5243733
-
-/* Example
-
-   desc:Low-pass filter
-
-   slider1:1000<20,20000,1>Cutoff (Hz)
-   slider2:0.5<0.01,4.0,0.01>Q
-
-   import Tale/zdf_filter.jsfx-inc
-
-   @slider
-   lp.zdf_lp(slider1, slider2);
-   lp.zdf_gain(0.5);
-
-   @sample
-   spl0 = spl1 = lp.zdf_svf(spl0 + spl1);
-
-   Setting Functions
-
-    * zdf_lp(freq, q)       -- Low-pass
-    * zdf_hp(freq, q)       -- High-pass
-    * zdf_bp(freq, q)       -- Band-pass (constant skirt gain)
-    * zdf_bp2(freq, q)      -- Band-pass (constant peak gain)
-    * zdf_bs(freq, q)       -- Band-stop
-    * zdf_ap(freq, q)       -- All-pass
-    * zdf_eq(freq, q, gain) -- Peaking EQ
-    * zdf_ls(freq, q, gain) -- Low-shelf
-    * zdf_hs(freq, q, gain) -- High-shelf
-      Example: lp.zdf_lp(1000, 0.7);
-      Sets up the filter for the specified cutoff frequency (in Hz), and Q
-      and gain factors, and returns the feedback precomputation factor (h).
-
-      (To convert from dB to gain: gain=10^(db/20).)
-
-      Note: In v20151024 the behavior of zdf_bp2() and zdf_ap() has been
-      changed in such a way that these functions are not backward
-      compatible. To convert code relying on the old behavior, replace
-      zdf_bp2(freq, bw) with zdf_bp(freq, zdf_bwtoq(bw)), and
-      zdf_ap(freq, bw) with zdf_ap(freq, zdf_bwtoq(bw)).
-
-    * zdf_gain(gain)
-      Example: lp.zdf_lp(1000, 0.5); lp.zdf_gain(2.0);
-      Modifies the filter by applying the specified output gain.
-
-      Note: You should always first setup the filter, and then modify it. If
-      you change the filter frequency/Q afterwards, then this will reset the
-      gain to 1.0, and so you will have to modify it again.
-
-    * zdf_setf(freq, q)
-      Example: lp.zdf_setf(1000, 0.7);
-      Sets up the specialized low-pass, high-pass, or band-pass filter.
-
-      Note: This works only with zdf_svf_lp(), zdf_svf_hp(), or zdf_svf_bp().
-
-   Filter Functions
-
-    * zdf_svf(sample)
-      Example: output = lp.zdf_svf(input);
-      Sends a sample through the filter, and returns its output.
-
-    * zdf_svf_multi(sample)
-      Example: output = lp.zdf_svf_multi(input);
-      Sends a sample through the filter, returns its output, and also stores
-      the individual low-pass, band-pass, and high-pass outputs.
-
-    * zdf_svf_lp(sample) -- Low-pass
-    * zdf_svf_hp(sample) -- High-pass
-    * zdf_svf_bp(sample) -- Band-pass
-      Example: output = lp.zdf_svf_lp(input);
-      Specialized versions of zdf_svf(), each optimized for a specific
-      filter type.
-
-   Miscellaneous Functions
-
-    * zdf_reset([input])
-      Example: lp.zdf_reset();
-      Resets the filter state to the specified input value, or to zero if
-      the value is omitted.
-
-    * zdf_bwtoq(bw)
-    * zdf_qtobw(q)
-      Example: q = zdf_bwtoq(2.0);
-      Converts bandwidth (in octaves) to Q factor, or vice versa.
-
-   Instance Variables
-
-    * g  -- Embedded integrator gain
-    * r2 -- Damping (1/Q)
-    * h  -- Feedback precomputation factor
-      Example: lp2.g = lp1.g; lp2.r2 = lp1.r2; lp2.h = lp1.h;
-      Filter coefficients.
-
-    * cl -- Low-pass mix
-    * cb -- Band-pass mix
-    * ch -- High-pass mix
-      Example: lp2.cl = lp1.cl; lp2.cb = lp1.cb; lp2.ch = lp1.ch;
-      Filter mode output mix.
-
-    * s1
-    * s2
-      Example: lp2.s1 = lp1.s1; lp2.s2 = lp1.s2;
-      Filter state.
-
-    * yl -- Low-pass output
-    * yb -- Band-pass output
-    * yh -- High-pass output
-      Example: hp = lp.yh;
-      Multi-mode filter outputs.
-
-*/
-
-@init
-
-function zdf_bwtoq(bw)
-  local(x)
-(
-  // q = 1/(2 * sinh(log(2) / 2 * bw))
-  x = exp(0.5*log(2) * bw);
-  x/(sqr(x) - 1);
-);
-
-function zdf_qtobw(q)
-  local(x)
-(
-  // bw = 2 * asinh(1/(2 * q)) / log(2)
-  x = 0.5 / q;
-  2/log(2) * log(x + sqrt(sqr(x) + 1));
-);
-
-function _zdf_seth()
-  instance(g, r2, h)
-(
-  h = 1/((r2 + g)*g + 1);
-);
-
-// Low-pass
-
-function zdf_lp(freq, q)
-  // global(srate)
-  instance(g, r2, cl, cb, ch)
-(
-  g = tan($pi * min(freq / srate, 0.49));
-
-  r2 = 1/q;
-  cl = 1;
-  cb = 0;
-  ch = 0;
-
-  this._zdf_seth();
-);
-
-// High-pass
-
-function zdf_hp(freq, q)
-  // global(srate)
-  instance(g, r2, cl, cb, ch)
-(
-  g = tan($pi * min(freq / srate, 0.49));
-
-  r2 = 1/q;
-  cl = 0;
-  cb = 0;
-  ch = 1;
-
-  this._zdf_seth();
-);
-
-// Band-pass (constant skirt gain, peak gain = Q)
-
-function zdf_bp(freq, q)
-  // global(srate)
-  instance(g, r2, cl, cb, ch)
-(
-  g = tan($pi * min(freq / srate, 0.49));
-
-  r2 = 1/q;
-  cl = 0;
-  cb = 1;
-  ch = 0;
-
-  this._zdf_seth();
-);
-
-// Band-pass (constant 0 dB peak gain)
-
-function zdf_bp2(freq, q)
-  // global(srate)
-  instance(g, r2, cl, cb, ch)
-(
-  g = tan($pi * min(freq / srate, 0.49));
-
-  cl = 0;
-  cb = r2 = 1/q;
-  ch = 0;
-
-  this._zdf_seth();
-);
-
-// Band-stop
-
-function zdf_bs(freq, q)
-  // global(srate)
-  instance(g, r2, cl, cb, ch)
-(
-  g = tan($pi * min(freq / srate, 0.49));
-
-  r2 = 1/q;
-  cl = 1;
-  cb = 0;
-  ch = 1;
-
-  this._zdf_seth();
-);
-
-// All-pass
-
-function zdf_ap(freq, q)
-  // global(srate)
-  instance(g, r2, cl, cb, ch)
-(
-  g = tan($pi * min(freq / srate, 0.49));
-
-  r2 = 1/q;
-  cl = 1;
-  cb = -r2;
-  ch = 1;
-
-  this._zdf_seth();
-);
-
-// Peaking EQ
-
-function zdf_eq(freq, q, gain)
-  // global(srate)
-  instance(g, r2, cl, cb, ch)
-(
-  g = tan($pi * min(freq / srate, 0.49));
-
-  r2 = 1/(q * sqrt(gain));
-  cl = 1;
-  cb = r2 * gain;
-  ch = 1;
-
-  this._zdf_seth();
-);
-
-// Low-shelf
-
-function zdf_ls(freq, q, gain)
-  // global(srate)
-  instance(g, r2, cl, cb, ch)
-  local(a)
-(
-  a = sqrt(gain);
-  g = tan($pi * min(freq / srate, 0.49)) / sqrt(a);
-
-  r2 = 1/q;
-  cl = gain;
-  cb = r2 * a;
-  ch = 1;
-
-  this._zdf_seth();
-);
-
-// High-shelf
-
-function zdf_hs(freq, q, gain)
-  // global(srate)
-  instance(g, r2, cl, cb, ch)
-  local(a)
-(
-  a = sqrt(gain);
-  g = tan($pi * min(freq / srate, 0.49)) * sqrt(a);
-
-  r2 = 1/q;
-  cl = 1;
-  cb = r2 * a;
-  ch = gain;
-
-  this._zdf_seth();
-);
-
-function zdf_gain(gain)
-  instance(cl, cb, ch)
-(
-  cl *= gain;
-  cb *= gain;
-  ch *= gain;
-);
-
-function zdf_svf(sample)
-  instance(s1, s2, g, r2, h, cl, cb, ch)
-  local(yl, yb, yh)
-(
-  // High-pass
-  yh = (sample - (r2 + g) * s1 - s2) * h;
-
-  // Band-pass
-  yb = g*yh + s1;
-  s1 = g*yh + yb;
-
-  // Zero denormals
-  abs(s1) < 0.00000000000000006 ? s1 = 0;
-
-  // Low-pass
-  yl = g*yb + s2;
-  s2 = g*yb + yl;
-
-  abs(s2) < 0.00000000000000006 ? s2 = 0;
-
-  cl*yl + cb*yb + ch*yh;
-);
-
-function zdf_svf_multi(sample)
-  instance(s1, s2, g, r2, h, cl, cb, ch, yl, yb, yh)
-(
-  yh = (sample - (r2 + g) * s1 - s2) * h;
-  yb = g*yh + s1;
-  s1 = g*yh + yb;
-  abs(s1) < 0.00000000000000006 ? s1 = 0;
-  yl = g*yb + s2;
-  s2 = g*yb + yl;
-  abs(s2) < 0.00000000000000006 ? s2 = 0;
-  cl*yl + cb*yb + ch*yh;
-);
-
-// Optimized versions of zdf_svf() returning only 1 of the 3 outputs.
-
-function zdf_setf(freq, q)
-  // global(srate)
-  instance(g, r2)
-(
-  g = tan($pi * min(freq / srate, 0.49));
-  r2 = 1/q;
-  this._zdf_seth();
-);
-
-function zdf_svf_lp(sample)
-  instance(s1, s2, g, r2, h)
-  local(yl, yb, yh)
-(
-  yh = (sample - (r2 + g) * s1 - s2) * h;
-  yb = g*yh + s1; s1 = g*yh + yb;
-  abs(s1) < 0.00000000000000006 ? s1 = 0;
-  yl = g*yb + s2; s2 = g*yb + yl;
-  abs(s2) < 0.00000000000000006 ? s2 = 0;
-  yl;
-);
-
-function zdf_svf_hp(sample)
-  instance(s1, s2, g, r2, h)
-  local(yl, yb, yh)
-(
-  yh = (sample - (r2 + g) * s1 - s2) * h;
-  yb = g*yh + s1; s1 = g*yh + yb;
-  abs(s1) < 0.00000000000000006 ? s1 = 0;
-  yl = g*yb + s2; s2 = g*yb + yl;
-  abs(s2) < 0.00000000000000006 ? s2 = 0;
-  yh;
-);
-
-function zdf_svf_bp(sample)
-  instance(s1, s2, g, r2, h)
-  local(yl, yb, yh)
-(
-  yh = (sample - (r2 + g) * s1 - s2) * h;
-  yb = g*yh + s1; s1 = g*yh + yb;
-  abs(s1) < 0.00000000000000006 ? s1 = 0;
-  yl = g*yb + s2; s2 = g*yb + yl;
-  abs(s2) < 0.00000000000000006 ? s2 = 0;
-  yb;
-);
-
-// Reset SVF state.
-
-function zdf_reset(input)
-  instance(s1, s2)
-(
-  s1 = 0;
-  s2 = input;
-);
-
-// Legacy
-
-// function zdf_bp2(freq, bw) ( this.zdf_bp(freq, zdf_bwtoq(bw)) );
-// function zdf_ap(freq, bw) ( this.zdf_ap(freq, zdf_bwtoq(bw)) );
-function zdf_notch(freq, bw) ( this.zdf_bs(freq, zdf_bwtoq(bw)) );
-function zdf_peak(freq, gain, bw) local(fc) ( fc = $pi * min(freq / srate, 0.49); this.zdf_eq(freq, zdf_bwtoq(bw) * fc / tan(fc), gain); );
-function zdf_low_shelf(freq, gain, bw) ( this.zdf_ls(freq, zdf_bwtoq(bw), gain) );
-function zdf_high_shelf(freq, gain, bw) ( this.zdf_hs(freq, zdf_bwtoq(bw), gain) );
-function zdf_mute() instance(g, r2, cl, cb, ch) ( g = tan(0.49*$pi); r2 = 1; cl = cb = ch = 0; this._zdf_seth(); );
-function zdf_bypass() instance(g, r2, cl, cb, ch) ( g = tan(0.49*$pi); r2 = cl = cb = ch = 1; this._zdf_seth(); );
-function zdf_bypass(freq, q) ( this.zdf_bypass() );