Merge pull request #1103 from daslyfe/ladder_filter

Add analog-style ladder filter

packages/core/controls.mjs

@@ -430,6 +430,17 @@ export const { crush } = registerControl('crush');
  */
 export const { coarse } = registerControl('coarse');
 
+/**
+ * filter overdrive for supported filter types
+ *
+ * @name drive
+ * @param {number | Pattern} amount
+ * @example
+ * note("{f g g c d a a#}%16".sub(17)).s("supersaw").lpenv(8).lpf(150).lpq(.8).ftype('ladder').drive("<.5 4>")
+ *
+ */
+export const { drive } = registerControl('drive');
+
 /**
  * Allows you to set the output channels on the interface
  *
@@ -742,15 +753,17 @@ export const { hprelease, hpr } = registerControl('hprelease', 'hpr');
  */
 export const { bprelease, bpr } = registerControl('bprelease', 'bpr');
 /**
- * Sets the filter type. The 24db filter is more aggressive. More types might be added in the future.
+ * Sets the filter type. The ladder filter is more aggressive. More types might be added in the future.
  * @name ftype
- * @param {number | Pattern} type 12db (default) or 24db
+ * @param {number | Pattern} type 12db (0), ladder (1), or 24db (2)
  * @example
- * note("c2 e2 f2 g2")
+ * note("{f g g c d a a#}%8").s("sawtooth").lpenv(4).lpf(500).ftype("<0 1 2>").lpq(1)
+ * @example
+ * note("c f g g a c d4").fast(2)
  * .sound('sawtooth')
- * .lpf(500)
- * .bpenv(4)
- * .ftype("12db 24db")
+ * .lpf(200).fanchor(0)
+ * .lpenv(3).lpq(1)
+ * .ftype("<ladder 12db 24db>")
  */
 export const { ftype } = registerControl('ftype');
 export const { fanchor } = registerControl('fanchor');

packages/superdough/helpers.mjs

@@ -14,6 +14,15 @@ const getSlope = (y1, y2, x1, x2) => {
   }
   return (y2 - y1) / (x2 - x1);
 };
+
+export function getWorklet(ac, processor, params, config) {
+  const node = new AudioWorkletNode(ac, processor, config);
+  Object.entries(params).forEach(([key, value]) => {
+    node.parameters.get(key).value = value;
+  });
+  return node;
+}
+
 export const getParamADSR = (
   param,
   attack,
@@ -103,14 +112,22 @@ export const getADSRValues = (params, curve = 'linear', defaultValues) => {
   return [Math.max(a ?? 0, envmin), Math.max(d ?? 0, envmin), Math.min(sustain, envmax), Math.max(r ?? 0, releaseMin)];
 };
 
-export function createFilter(context, type, frequency, Q, att, dec, sus, rel, fenv, start, end, fanchor) {
+export function createFilter(context, type, frequency, Q, att, dec, sus, rel, fenv, start, end, fanchor, model, drive) {
   const curve = 'exponential';
   const [attack, decay, sustain, release] = getADSRValues([att, dec, sus, rel], curve, [0.005, 0.14, 0, 0.1]);
-  const filter = context.createBiquadFilter();
+  let filter;
+  let frequencyParam;
+  if (model === 'ladder') {
+    filter = getWorklet(context, 'ladder-processor', { frequency, q: Q, drive });
+    frequencyParam = filter.parameters.get('frequency');
+  } else {
+    filter = context.createBiquadFilter();
+    filter.type = type;
+    filter.Q.value = Q;
+    filter.frequency.value = frequency;
+    frequencyParam = filter.frequency;
+  }
 
-  filter.type = type;
-  filter.Q.value = Q;
-  filter.frequency.value = frequency;
   // envelope is active when any of these values is set
   const hasEnvelope = att ?? dec ?? sus ?? rel ?? fenv;
   // Apply ADSR to filter frequency
@@ -122,7 +139,7 @@ export function createFilter(context, type, frequency, Q, att, dec, sus, rel, fe
     let min = clamp(2 ** -offset * frequency, 0, 20000);
     let max = clamp(2 ** (fenvAbs - offset) * frequency, 0, 20000);
     if (fenv < 0) [min, max] = [max, min];
-    getParamADSR(filter.frequency, attack, decay, sustain, release, min, max, start, end, curve);
+    getParamADSR(frequencyParam, attack, decay, sustain, release, min, max, start, end, curve);
     return filter;
   }
   return filter;

packages/superdough/superdough.mjs

@@ -7,9 +7,9 @@ This program is free software: you can redistribute it and/or modify it under th
 import './feedbackdelay.mjs';
 import './reverb.mjs';
 import './vowel.mjs';
-import { clamp, nanFallback } from './util.mjs';
+import { clamp, nanFallback, _mod } from './util.mjs';
 import workletsUrl from './worklets.mjs?url';
-import { createFilter, gainNode, getCompressor } from './helpers.mjs';
+import { createFilter, gainNode, getCompressor, getWorklet } from './helpers.mjs';
 import { map } from 'nanostores';
 import { logger } from './logger.mjs';
 import { loadBuffer } from './sampler.mjs';
@@ -50,14 +50,6 @@ function loadWorklets() {
   return workletsLoading;
 }
 
-export function getWorklet(ac, processor, params, config) {
-  const node = new AudioWorkletNode(ac, processor, config);
-  Object.entries(params).forEach(([key, value]) => {
-    node.parameters.get(key).value = value;
-  });
-  return node;
-}
-
 // this function should be called on first user interaction (to avoid console warning)
 export async function initAudio(options = {}) {
   const { disableWorklets = false } = options;
@@ -186,10 +178,14 @@ function getPhaser(orbit, t, speed = 1, depth = 0.5, centerFrequency = 1000, swe
   return filterChain[filterChain.length - 1];
 }
 
-let reverbs = {};
+function getFilterType(ftype) {
+  ftype = ftype ?? 0;
+  const filterTypes = ['12db', 'ladder', '24db'];
+  return typeof ftype === 'number' ? filterTypes[Math.floor(_mod(ftype, filterTypes.length))] : ftype;
+}
 
+let reverbs = {};
 let hasChanged = (now, before) => now !== undefined && now !== before;
-
 function getReverb(orbit, duration, fade, lp, dim, ir) {
   // If no reverb has been created for a given orbit, create one
   if (!reverbs[orbit]) {
@@ -288,8 +284,9 @@ export const superdough = async (value, t, hapDuration) => {
     postgain = 1,
     density = 0.03,
     // filters
-    ftype = '12db',
+
     fanchor = 0.5,
+    drive = 0.69,
     // low pass
     cutoff,
     lpenv,
@@ -394,6 +391,8 @@ export const superdough = async (value, t, hapDuration) => {
   // gain stage
   chain.push(gainNode(gain));
 
+  //filter
+  const ftype = getFilterType(value.ftype);
   if (cutoff !== undefined) {
     let lp = () =>
       createFilter(
@@ -409,6 +408,8 @@ export const superdough = async (value, t, hapDuration) => {
         t,
         t + hapDuration,
         fanchor,
+        ftype,
+        drive,
       );
     chain.push(lp());
     if (ftype === '24db') {

packages/superdough/synth.mjs

@@ -1,5 +1,5 @@
 import { clamp, midiToFreq, noteToMidi } from './util.mjs';
-import { registerSound, getAudioContext, getWorklet } from './superdough.mjs';
+import { registerSound, getAudioContext } from './superdough.mjs';
 import {
   applyFM,
   gainNode,
@@ -8,6 +8,7 @@ import {
   getPitchEnvelope,
   getVibratoOscillator,
   webAudioTimeout,
+  getWorklet,
 } from './helpers.mjs';
 import { getNoiseMix, getNoiseOscillator } from './noise.mjs';
 

packages/superdough/worklets.mjs

@@ -1,6 +1,6 @@
 // coarse, crush, and shape processors adapted from dktr0's webdirt: https://github.com/dktr0/WebDirt/blob/5ce3d698362c54d6e1b68acc47eb2955ac62c793/dist/AudioWorklets.js
 // LICENSE GNU General Public License v3.0 see https://github.com/dktr0/WebDirt/blob/main/LICENSE
-
+import { clamp } from './util.mjs';
 const blockSize = 128;
 class CoarseProcessor extends AudioWorkletProcessor {
   static get parameterDescriptors() {
@@ -106,6 +106,77 @@ class ShapeProcessor extends AudioWorkletProcessor {
 }
 registerProcessor('shape-processor', ShapeProcessor);
 
+function fast_tanh(x) {
+  const x2 = x * x;
+  return (x * (27.0 + x2)) / (27.0 + 9.0 * x2);
+}
+const _PI = 3.14159265359;
+//adapted from https://github.com/TheBouteillacBear/webaudioworklet-wasm?tab=MIT-1-ov-file
+class LadderProcessor extends AudioWorkletProcessor {
+  static get parameterDescriptors() {
+    return [
+      { name: 'frequency', defaultValue: 500 },
+      { name: 'q', defaultValue: 1 },
+      { name: 'drive', defaultValue: 0.69 },
+    ];
+  }
+
+  constructor() {
+    super();
+    this.started = false;
+    this.p0 = [0, 0];
+    this.p1 = [0, 0];
+    this.p2 = [0, 0];
+    this.p3 = [0, 0];
+    this.p32 = [0, 0];
+    this.p33 = [0, 0];
+    this.p34 = [0, 0];
+  }
+
+  process(inputs, outputs, parameters) {
+    const input = inputs[0];
+    const output = outputs[0];
+
+    const hasInput = !(input[0] === undefined);
+    if (this.started && !hasInput) {
+      return false;
+    }
+
+    this.started = hasInput;
+
+    const resonance = parameters.q[0];
+    const drive = clamp(Math.exp(parameters.drive[0]), 0.1, 2000);
+
+    let cutoff = parameters.frequency[0];
+    // eslint-disable-next-line no-undef
+    cutoff = (cutoff * 2 * _PI) / sampleRate;
+    cutoff = cutoff > 1 ? 1 : cutoff;
+
+    const k = Math.min(8, resonance * 0.4);
+    //               drive makeup  * resonance volume loss makeup
+    let makeupgain = (1 / drive) * Math.min(1.75, 1 + k);
+
+    for (let n = 0; n < blockSize; n++) {
+      for (let i = 0; i < input.length; i++) {
+        const out = this.p3[i] * 0.360891 + this.p32[i] * 0.41729 + this.p33[i] * 0.177896 + this.p34[i] * 0.0439725;
+
+        this.p34[i] = this.p33[i];
+        this.p33[i] = this.p32[i];
+        this.p32[i] = this.p3[i];
+
+        this.p0[i] += (fast_tanh(input[i][n] * drive - k * out) - fast_tanh(this.p0[i])) * cutoff;
+        this.p1[i] += (fast_tanh(this.p0[i]) - fast_tanh(this.p1[i])) * cutoff;
+        this.p2[i] += (fast_tanh(this.p1[i]) - fast_tanh(this.p2[i])) * cutoff;
+        this.p3[i] += (fast_tanh(this.p2[i]) - fast_tanh(this.p3[i])) * cutoff;
+
+        output[i][n] = out * makeupgain;
+      }
+    }
+    return true;
+  }
+}
+registerProcessor('ladder-processor', LadderProcessor);
+
 class DistortProcessor extends AudioWorkletProcessor {
   static get parameterDescriptors() {
     return [