Replacing old reverb by better convolution

packages/superdough/reverb.mjs

@@ -1,23 +1,27 @@
-if (typeof AudioContext !== 'undefined') {
-  AudioContext.prototype.impulseResponse = function (duration, channels = 1) {
-    const length = this.sampleRate * duration;
-    const impulse = this.createBuffer(channels, length, this.sampleRate);
-    const IR = impulse.getChannelData(0);
-    for (let i = 0; i < length; i++) IR[i] = (2 * Math.random() - 1) * Math.pow(1 - i / length, duration);
-    return impulse;
-  };
+import reverbGen from './reverbGen.mjs';
 
-  AudioContext.prototype.createReverb = function (duration) {
+if (typeof AudioContext !== 'undefined') {
+  AudioContext.prototype.generateReverb = reverbGen.generateReverb;
+  AudioContext.prototype.createReverb = function(duration, audioContext) {
     const convolver = this.createConvolver();
     convolver.setDuration = (d) => {
-      convolver.buffer = this.impulseResponse(d);
-      convolver.duration = duration;
-      return convolver;
+      this.generateReverb(
+        {
+          audioContext,
+          sampleRate: 44100,
+          numChannels: 2,
+          decayTime: d,
+          fadeInTime: d,
+          lpFreqStart: 2000,
+          lpFreqEnd: 15000,
+        },
+        (buffer) => {
+          convolver.buffer = buffer;
+        }
+      );
+      convolver.duration = d;
     };
     convolver.setDuration(duration);
     return convolver;
   };
 }
-
-// TODO: make the reverb more exciting
-// check out https://blog.gskinner.com/archives/2019/02/reverb-web-audio-api.html

packages/superdough/reverbGen.mjs

@@ -0,0 +1,209 @@
+// Copyright 2014 Alan deLespinasse
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+"use strict";
+
+
+var reverbGen = {};
+
+/** Generates a reverb impulse response.
+
+    @param {!Object} params TODO: Document the properties.
+    @param {!function(!AudioBuffer)} callback Function to call when
+      the impulse response has been generated. The impulse response
+      is passed to this function as its parameter. May be called
+      immediately within the current execution context, or later. */
+reverbGen.generateReverb = function(params, callback) {
+  var audioContext = params.audioContext || new AudioContext();
+  var sampleRate = params.sampleRate || 44100;
+  var numChannels = params.numChannels || 2;
+  // params.decayTime is the -60dB fade time. We let it go 50% longer to get to -90dB.
+  var totalTime = params.decayTime * 1.5;
+  var decaySampleFrames = Math.round(params.decayTime * sampleRate);
+  var numSampleFrames = Math.round(totalTime * sampleRate);
+  var fadeInSampleFrames = Math.round((params.fadeInTime || 0) * sampleRate);
+  // 60dB is a factor of 1 million in power, or 1000 in amplitude.
+  var decayBase = Math.pow(1 / 1000, 1 / decaySampleFrames);
+  var reverbIR = audioContext.createBuffer(numChannels, numSampleFrames, sampleRate);
+  for (var i = 0; i < numChannels; i++) {
+    var chan = reverbIR.getChannelData(i);
+    for (var j = 0; j < numSampleFrames; j++) {
+      chan[j] = randomSample() * Math.pow(decayBase, j);
+    }
+    for (var j = 0; j < fadeInSampleFrames; j++) {
+      chan[j] *= (j / fadeInSampleFrames);
+    }
+  }
+
+  applyGradualLowpass(reverbIR, params.lpFreqStart || 0, params.lpFreqEnd || 0, params.decayTime, callback);
+};
+
+/** Creates a canvas element showing a graph of the given data.
+
+    @param {!Float32Array} data An array of numbers, or a Float32Array.
+    @param {number} width Width in pixels of the canvas.
+    @param {number} height Height in pixels of the canvas.
+    @param {number} min Minimum value of data for the graph (lower edge).
+    @param {number} max Maximum value of data in the graph (upper edge).
+    @return {!CanvasElement} The generated canvas element. */
+reverbGen.generateGraph = function(data, width, height, min, max) {
+  var canvas = document.createElement('canvas');
+  canvas.width = width;
+  canvas.height = height;
+  var gc = canvas.getContext('2d');
+  gc.fillStyle = '#000';
+  gc.fillRect(0, 0, canvas.width, canvas.height);
+  gc.fillStyle = '#fff';
+  var xscale = width / data.length;
+  var yscale = height / (max - min);
+  for (var i = 0; i < data.length; i++) {
+    gc.fillRect(i * xscale, height - (data[i] - min) * yscale, 1, 1);
+  }
+  return canvas;
+}
+
+/** Saves an AudioBuffer as a 16-bit WAV file on the client's host
+    file system. Normalizes it to peak at +-32767, and optionally
+    truncates it if there's a lot of "silence" at the end.
+
+    @param {!AudioBuffer} buffer The buffer to save.
+    @param {string} name Name of file to create.
+    @param {number?} opt_minTail Defines what counts as "silence" for
+    auto-truncating the buffer. If there is a point past which every
+    value of every channel is less than opt_minTail, then the buffer
+    is truncated at that point. This is expressed as an integer,
+    applying to the post-normalized and integer-converted
+    buffer. The default is 0, meaning don't truncate. */
+reverbGen.saveWavFile = function(buffer, name, opt_minTail) {
+  var bitsPerSample = 16;
+  var bytesPerSample = 2;
+  var sampleRate = buffer.sampleRate;
+  var numChannels = buffer.numberOfChannels;
+  var channels = getAllChannelData(buffer);
+  var numSampleFrames = channels[0].length;
+  var scale = 32767;
+  // Find normalization constant.
+  var max = 0;
+  for (var i = 0; i < numChannels; i++) {
+    for (var j = 0; j < numSampleFrames; j++) {
+      max = Math.max(max, Math.abs(channels[i][j]));
+    }
+  }
+  if (max) {
+    scale = 32767 / max;
+  }
+  // Find truncation point.
+  if (opt_minTail) {
+    var truncateAt = 0;
+    for (var i = 0; i < numChannels; i++) {
+      for (var j = 0; j < numSampleFrames; j++) {
+        var absSample = Math.abs(Math.round(scale * channels[i][j]));
+        if (absSample > opt_minTail) {
+          truncateAt = j;
+        }
+      }
+    }
+    numSampleFrames = truncateAt + 1;
+  }
+  var sampleDataBytes = bytesPerSample * numChannels * numSampleFrames;
+  var fileBytes = sampleDataBytes + 44;
+  var arrayBuffer = new ArrayBuffer(fileBytes);
+  var dataView = new DataView(arrayBuffer);
+  dataView.setUint32(0, 1179011410, true); // "RIFF"
+  dataView.setUint32(4, fileBytes - 8, true); // file length
+  dataView.setUint32(8, 1163280727, true); // "WAVE"
+  dataView.setUint32(12, 544501094, true); // "fmt "
+  dataView.setUint32(16, 16, true)         // fmt chunk length
+  dataView.setUint16(20, 1, true);         // PCM format
+  dataView.setUint16(22, numChannels, true); // NumChannels
+  dataView.setUint32(24, sampleRate, true);  // SampleRate
+  var bytesPerSampleFrame = numChannels * bytesPerSample;
+  dataView.setUint32(28, sampleRate * bytesPerSampleFrame, true); // ByteRate
+  dataView.setUint16(32, bytesPerSampleFrame, true);              // BlockAlign
+  dataView.setUint16(34, bitsPerSample, true);                           // BitsPerSample
+  dataView.setUint32(36, 1635017060, true);                   // "data"
+  dataView.setUint32(40, sampleDataBytes, true);
+  for (var j = 0; j < numSampleFrames; j++) {
+    for (var i = 0; i < numChannels; i++) {
+      dataView.setInt16(44 + j * bytesPerSampleFrame + i * bytesPerSample,
+        Math.round(scale * channels[i][j]), true);
+    }
+  }
+  var blob = new Blob([arrayBuffer], { 'type': 'audio/wav' });
+  var url = window.URL.createObjectURL(blob);
+  var linkEl = document.createElement('a');
+  linkEl.href = url;
+  linkEl.download = name;
+  linkEl.style.display = 'none';
+  document.body.appendChild(linkEl);
+  linkEl.click();
+};
+
+/** Applies a constantly changing lowpass filter to the given sound.
+
+    @private
+    @param {!AudioBuffer} input
+    @param {number} lpFreqStart
+    @param {number} lpFreqEnd
+    @param {number} lpFreqEndAt
+    @param {!function(!AudioBuffer)} callback May be called
+    immediately within the current execution context, or later.*/
+var applyGradualLowpass = function(input, lpFreqStart, lpFreqEnd, lpFreqEndAt, callback) {
+  if (lpFreqStart == 0) {
+    callback(input);
+    return;
+  }
+  var channelData = getAllChannelData(input);
+  var context = new OfflineAudioContext(input.numberOfChannels, channelData[0].length, input.sampleRate);
+  var player = context.createBufferSource();
+  player.buffer = input;
+  var filter = context.createBiquadFilter();
+
+  lpFreqStart = Math.min(lpFreqStart, input.sampleRate / 2);
+  lpFreqEnd = Math.min(lpFreqEnd, input.sampleRate / 2);
+
+  filter.type = "lowpass";
+  filter.Q.value = 0.0001;
+  filter.frequency.setValueAtTime(lpFreqStart, 0);
+  filter.frequency.linearRampToValueAtTime(lpFreqEnd, lpFreqEndAt);
+
+  player.connect(filter);
+  filter.connect(context.destination);
+  player.start();
+  context.oncomplete = function(event) {
+    callback(event.renderedBuffer);
+  };
+  context.startRendering();
+
+  window.filterNode = filter;
+};
+
+/** @private
+    @param {!AudioBuffer} buffer
+    @return {!Array.<!Float32Array>} An array containing the Float32Array of each channel's samples. */
+var getAllChannelData = function(buffer) {
+  var channels = [];
+  for (var i = 0; i < buffer.numberOfChannels; i++) {
+    channels[i] = buffer.getChannelData(i);
+  }
+  return channels;
+};
+
+/** @private
+    @return {number} A random number from -1 to 1. */
+var randomSample = function() {
+  return Math.random() * 2 - 1;
+};
+
+export default reverbGen;

packages/superdough/superdough.mjs

@@ -107,17 +107,24 @@ function getDelay(orbit, delaytime, delayfeedback, t) {
 }
 
 let reverbs = {};
+
 function getReverb(orbit, duration = 2) {
+
+  // If no reverb has been created for a given orbit, create one
   if (!reverbs[orbit]) {
     const ac = getAudioContext();
-    const reverb = ac.createReverb(duration);
+    const reverb = ac.createReverb(duration, getAudioContext());
     reverb.connect(getDestination());
+    console.log(reverb)
     reverbs[orbit] = reverb;
   }
+
+  // Update the reverb duration if needed after instanciation
   if (reverbs[orbit].duration !== duration) {
     reverbs[orbit] = reverbs[orbit].setDuration(duration);
     reverbs[orbit].duration = duration;
   }
+
   return reverbs[orbit];
 }