feuerwerk/src/viewport/fxWorklet.ts

/**
 * The audio thread's side of the effects that Web Audio has no node for. A pitched voice (#317)
 * plays one sound through a `PitchPlayer`, its pitch the AudioParam `pitch` in semitones, so it
 * glides, ramps and eases like any other knob. A Bitcrusher (#322) runs a `Crusher`, a Chip
 * (#329) a `ChipPlayer`. Loaded into the context once by the sound library; nothing on the page
 * imports it.
 */
import { type ChipShape, ChipPlayer } from '../core/soundfx/chip';
import { Crusher } from '../core/soundfx/crusher';
import { PitchPlayer } from '../core/soundfx/pitchPlayer';

/** What the audio thread has and the page's types do not. */
declare const sampleRate: number;
declare const currentTime: number;
declare class AudioWorkletProcessor {
  readonly port: MessagePort;
}
declare function registerProcessor<T>(
  name: string,
  processor: new (options: { processorOptions: T }) => object,
): void;

export interface PitchOptions {
  /** The file the samples are of: they are sent with the first voice of it only and kept here. */
  file: string;
  channels?: Float32Array[];
  /** The sound's rate over the context's. */
  step: number;
  loop: boolean;
  /** Where a loop runs, in samples of the sound (#331); without them it is the whole sound. */
  loopStart?: number;
  loopEnd?: number;
  /** The second of the audio clock its first sample is heard at (#332); before it, silence. */
  startAt?: number;
  /** Samples of the sound before where it starts, for a clip of a song taken up mid-way (#334). */
  skip?: number;
}

/** Every sound a voice has been played from, for the next voice of it – processors share this scope. */
const sounds = new Map<string, Float32Array[]>();

class PitchProcessor extends AudioWorkletProcessor {
  private readonly player: PitchPlayer;
  private stopped = false;
  private startAt: number;

  constructor({ processorOptions }: { processorOptions: PitchOptions }) {
    super();
    const { file, channels, step, loop, loopStart, loopEnd, startAt, skip } = processorOptions;
    this.startAt = startAt ?? 0;
    if (channels) sounds.set(file, channels);
    const region = loop && loopEnd !== undefined ? { start: loopStart ?? 0, end: loopEnd } : loop;
    this.player = new PitchPlayer(sounds.get(file) ?? [], step, sampleRate, region, skip);
    this.port.onmessage = (event: MessageEvent) => {
      if (event.data === 'leave') this.player.leaveLoop();
      else this.stopped = true;
    };
  }

  process(
    _inputs: Float32Array[][],
    outputs: Float32Array[][],
    parameters: Record<string, Float32Array>,
  ): boolean {
    if (this.stopped) return false;
    let out = outputs[0]!;
    let pitch = parameters.pitch!;
    // A block is silence until then, the one it falls in starts on that sample.
    if (this.startAt > currentTime) {
      const wait = Math.round((this.startAt - currentTime) * sampleRate);
      if (wait >= (out[0]?.length ?? 0)) return true;
      out = out.map((channel) => channel.subarray(wait));
      if (pitch.length > 1) pitch = pitch.subarray(wait);
      this.startAt = 0;
    }
    if (this.player.render(out, pitch)) return true;
    this.port.postMessage('ended');
    return false;
  }

  static get parameterDescriptors() {
    return [{ name: 'pitch', defaultValue: 0 }];
  }
}

registerProcessor('pitch-player', PitchProcessor);

/** A Bitcrusher (#322) between two stages of a voice; it runs until the voice tells it to stop. */
class CrushProcessor extends AudioWorkletProcessor {
  private readonly crusher = new Crusher(sampleRate);
  private stopped = false;

  constructor() {
    super();
    this.port.onmessage = () => {
      this.stopped = true;
    };
  }

  process(
    inputs: Float32Array[][],
    outputs: Float32Array[][],
    parameters: Record<string, Float32Array>,
  ): boolean {
    if (this.stopped) return false;
    this.crusher.render(inputs[0] ?? [], outputs[0]!, parameters.bits!, parameters.rate!, parameters.mix!);
    return true;
  }

  static get parameterDescriptors() {
    return [
      { name: 'bits', defaultValue: 16 },
      { name: 'rate', defaultValue: 48000 },
      { name: 'mix', defaultValue: 0 },
    ];
  }
}

registerProcessor('bit-crusher', CrushProcessor);

export interface ChipOptions extends ChipShape {
  /** The second of the audio clock its first sample is heard at; before it, silence. */
  startAt: number;
}

/** The Chip of a note (#329): a source of its own, its frequency, duty and pitch AudioParams. */
class ChipProcessor extends AudioWorkletProcessor {
  private readonly player: ChipPlayer;
  private stopped = false;
  private startAt: number;

  constructor({ processorOptions }: { processorOptions: ChipOptions }) {
    super();
    this.player = new ChipPlayer(processorOptions, sampleRate);
    this.startAt = processorOptions.startAt;
    this.port.onmessage = () => {
      this.stopped = true;
    };
  }

  process(
    _inputs: Float32Array[][],
    outputs: Float32Array[][],
    parameters: Record<string, Float32Array>,
  ): boolean {
    if (this.stopped) return false;
    let out = outputs[0]!;
    let { frequency, duty, pitch } = parameters as Record<'frequency' | 'duty' | 'pitch', Float32Array>;
    if (this.startAt > currentTime) {
      const wait = Math.round((this.startAt - currentTime) * sampleRate);
      if (wait >= (out[0]?.length ?? 0)) return true;
      const from = (values: Float32Array) => (values.length > 1 ? values.subarray(wait) : values);
      out = out.map((channel) => channel.subarray(wait));
      [frequency, duty, pitch] = [from(frequency), from(duty), from(pitch)];
      this.startAt = 0;
    }
    if (this.player.render(out, frequency, duty, pitch)) return true;
    this.port.postMessage('ended');
    return false;
  }

  static get parameterDescriptors() {
    return [
      { name: 'frequency', defaultValue: 440 },
      { name: 'duty', defaultValue: 0.5 },
      { name: 'pitch', defaultValue: 0 },
    ];
  }
}

registerProcessor('chip-player', ChipProcessor);