strudel-docker/packages/superdough/worklets.mjs

const processSample = (inputs, outputs, processBlock) => {
  const input = inputs[0];
  const output = outputs[0];
  const blockSize = 128;
  if (input == null || output == null) {
    return false;
  }

  for (let n = 0; n < blockSize; n++) {
    input.forEach((inChannel, i) => {
      const outChannel = output[i % output.length];
      const block = inChannel[n];
      outChannel[n] = processBlock(block, n, inChannel, outChannel);
    });
  }
  return true;
};

// 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
class CoarseProcessor extends AudioWorkletProcessor {
  static get parameterDescriptors() {
    return [{ name: 'coarse', defaultValue: 1 }];
  }

  constructor() {
    super();
  }

  process(inputs, outputs, parameters) {
    let coarse = parameters.coarse[0] ?? 0;
    coarse = Math.max(1, coarse);
    return processSample(inputs, outputs, (block, n, inChannel, outChannel) => {
      const value = n % coarse === 0 ? block : outChannel[n - 1];
      return value;
    });
  }
}

registerProcessor('coarse-processor', CoarseProcessor);

class CrushProcessor extends AudioWorkletProcessor {
  static get parameterDescriptors() {
    return [{ name: 'crush', defaultValue: 0 }];
  }

  constructor() {
    super();
  }

  process(inputs, outputs, parameters) {
    let crush = parameters.crush[0] ?? 8;
    crush = Math.max(1, crush);

    return processSample(inputs, outputs, (block) => {
      const x = Math.pow(2, crush - 1);
      return Math.round(block * x) / x;
    });
  }
}
registerProcessor('crush-processor', CrushProcessor);

class ShapeProcessor extends AudioWorkletProcessor {
  static get parameterDescriptors() {
    return [
      { name: 'shape', defaultValue: 0 },
      { name: 'postgain', defaultValue: 1 },
    ];
  }

  constructor() {
    super();
  }

  process(inputs, outputs, parameters) {
    let shape = parameters.shape[0];
    const postgain = Math.max(0.001, Math.min(1, parameters.postgain[0]));
    shape = shape < 1 ? shape : 1.0 - 4e-10;
    shape = (2.0 * shape) / (1.0 - shape);
    return processSample(inputs, outputs, (block) => {
      const val = ((1 + shape) * block) / (1 + shape * Math.abs(block));
      return val * postgain;
    });
  }
}

registerProcessor('shape-processor', ShapeProcessor);

class DistortProcessor extends AudioWorkletProcessor {
  static get parameterDescriptors() {
    return [
      { name: 'distort', defaultValue: 0 },
      { name: 'postgain', defaultValue: 1 },
    ];
  }

  constructor() {
    super();
  }

  process(inputs, outputs, parameters) {
    let shape = parameters.distort[0];
    const postgain = Math.max(0.001, Math.min(1, parameters.postgain[0]));
    shape = Math.expm1(shape);
    return processSample(inputs, outputs, (block) => {
      const val = ((1 + shape) * block) / (1 + shape * Math.abs(block));
      return val * postgain;
    });
  }
}

registerProcessor('distort-processor', DistortProcessor);

// adjust waveshape to remove frequencies above nyquist to prevent aliasing
// referenced from https://www.kvraudio.com/forum/viewtopic.php?t=375517
const polyBlep = (phase, dt) => {
  // 0 <= phase < 1
  if (phase < dt) {
    phase /= dt;
    // 2 * (phase - phase^2/2 - 0.5)
    return phase + phase - phase * phase - 1;
  }

  // -1 < phase < 0
  else if (phase > 1 - dt) {
    phase = (phase - 1) / dt;
    // 2 * (phase^2/2 + phase + 0.5)
    return phase * phase + phase + phase + 1;
  }

  // 0 otherwise
  else {
    return 0;
  }
};

const saw = (phase, dt) => {
  // Correct phase, so it would be in line with sin(2.*M_PI * phase)
  phase += 0.5;
  if (phase >= 1) phase -= 1;
  const v = 2 * phase - 1;
  return v - polyBlep(phase, dt);
};

class SuperSawOscillatorProcessor extends AudioWorkletProcessor {
  constructor() {
    super();
    this.phase = [];
  }
  static get parameterDescriptors() {
    return [
      {
        name: 'begin',
        defaultValue: 0,
        max: Number.POSITIVE_INFINITY,
        min: 0,
      },

      {
        name: 'end',
        defaultValue: 0,
        max: Number.POSITIVE_INFINITY,
        min: 0,
      },

      {
        name: 'frequency',
        defaultValue: 440,
        min: Number.EPSILON,
      },

      {
        name: 'panspread',
        defaultValue: 0.4,
        min: 0,
        max: 1,
      },
      {
        name: 'freqspread',
        defaultValue: 0.2,
        min: 0,
      },
      {
        name: 'detune',
        defaultValue: 0,
        min: 0,
      },

      {
        name: 'voices',
        defaultValue: 6,
        min: 1,
      },
    ];
  }
  process(input, outputs, params) {
    if (currentTime <= params.begin[0]) {
      return true;
    }
    if (currentTime >= params.end[0]) {
      return false;
    }
    let frequency = params.frequency[0];
    //apply detune in cents
    frequency = frequency * Math.pow(2, params.detune[0] / 1200);

    const output = outputs[0];
    const voices = params.voices[0];
    const freqspread = params.freqspread[0];
    let panspread = params.panspread[0];
    panspread = panspread * 0.5 + 0.5;
    const gainAdjustment = 1;

    for (let n = 0; n < voices; n++) {
      let adj = 0;
      const isOdd = n % 2 === 1;
      if (n > 0) {
        adj = isOdd ? n * freqspread : -((n - 1) * freqspread);
      }
      const freq = Math.min(16744, Math.max(1, frequency + adj * 0.01 * frequency));
      const balance = isOdd ? 1 - panspread : panspread;
      const dt = freq / sampleRate;

      for (let i = 0; i < output[0].length; i++) {
        this.phase[n] = this.phase[n] ?? Math.random();
        const v = saw(this.phase[n], dt);

        output[0][i] = (output[0][i] + v * (1 - balance)) * gainAdjustment;
        output[1][i] = (output[1][i] + v * balance) * gainAdjustment;

        this.phase[n] += dt;

        if (this.phase[n] > 1.0) {
          this.phase[n] = this.phase[n] - 1;
        }
      }
    }
    return true;
  }
}

registerProcessor('supersaw-oscillator', SuperSawOscillatorProcessor);