Add v2 Game Boy sound engine (isolated from v1)
- Authentic DMG-CPU sound chip implementation: - 4 Pulse channels with duty cycle control (12.5%, 25%, 50%, 75%) - 2 Wave channels with 4-bit wavetables - 2 Noise channels with LFSR (7-bit and 15-bit modes) - GameBoy Colorizer effect chain: - Low-pass filter (natural GB rolloff) - Bit-crushing (4-bit DAC simulation) - Sample rate reduction - Saturation and high-pass filter - Presets: DMG, GBC, GBA, Clean - Intelligent MIDI processing: - Track analysis and role detection (bass, lead, drums, etc.) - Automatic channel mapping to GB channels - Chord arpeggiator for polyphony handling - GameBoy Arranger for fuller sound - BitMidi search integration - Completely isolated from v1 (no changes to src/)
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b1rdmania
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/**
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* Game Boy Colorizer
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*
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* Applies authentic Game Boy audio characteristics to the output:
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* - Low-pass filter (GB has ~8kHz natural rolloff)
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* - Bit-crushing (4-bit DAC simulation)
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* - Sample rate reduction (mimics ~32kHz internal rate)
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* - Subtle saturation (hardware non-linearity)
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* - Characteristic noise floor
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*/
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export interface ColorizerConfig {
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/** Enable/disable the colorizer */
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enabled: boolean;
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/** Low-pass filter cutoff (Hz). Real GB is ~8-10kHz */
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lowpassFreq: number;
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/** Bit depth for crushing (4 = authentic, higher = cleaner) */
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bitDepth: number;
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/** Sample rate reduction factor (1 = none, 2 = half, etc.) */
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sampleRateReduction: number;
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/** Saturation amount (0-1) */
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saturation: number;
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/** High-pass filter to remove DC offset and sub-bass (Hz) */
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highpassFreq: number;
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}
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const DEFAULT_CONFIG: ColorizerConfig = {
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enabled: true,
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lowpassFreq: 10000, // GB natural rolloff (slightly higher)
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bitDepth: 8, // Less aggressive bit crushing (4 was too harsh)
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sampleRateReduction: 1, // No sample rate reduction (was causing artifacts)
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saturation: 0.2, // Subtle warmth
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highpassFreq: 20, // LOW - allow bass through!
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};
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export class GameBoyColorizer {
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private audioContext: AudioContext;
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private config: ColorizerConfig;
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// Audio nodes
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private inputGain: GainNode;
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private outputGain: GainNode;
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private highpassFilter: BiquadFilterNode;
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private lowpassFilter: BiquadFilterNode;
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private bitCrusher: AudioWorkletNode | ScriptProcessorNode | null = null;
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private waveshaper: WaveShaperNode;
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private limiter: DynamicsCompressorNode;
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private isInitialized = false;
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constructor(audioContext: AudioContext, config: Partial<ColorizerConfig> = {}) {
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this.audioContext = audioContext;
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this.config = { ...DEFAULT_CONFIG, ...config };
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// Create basic nodes
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this.inputGain = audioContext.createGain();
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this.outputGain = audioContext.createGain();
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// High-pass filter (remove DC and sub-bass)
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this.highpassFilter = audioContext.createBiquadFilter();
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this.highpassFilter.type = 'highpass';
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this.highpassFilter.frequency.value = this.config.highpassFreq;
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this.highpassFilter.Q.value = 0.7;
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// Low-pass filter (GB characteristic rolloff)
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this.lowpassFilter = audioContext.createBiquadFilter();
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this.lowpassFilter.type = 'lowpass';
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this.lowpassFilter.frequency.value = this.config.lowpassFreq;
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this.lowpassFilter.Q.value = 0.7;
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// Waveshaper for saturation
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this.waveshaper = audioContext.createWaveShaper();
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this.waveshaper.curve = this.createSaturationCurve(this.config.saturation);
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this.waveshaper.oversample = '2x';
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// Limiter to prevent clipping
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this.limiter = audioContext.createDynamicsCompressor();
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this.limiter.threshold.value = -6;
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this.limiter.knee.value = 6;
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this.limiter.ratio.value = 12;
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this.limiter.attack.value = 0.001;
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this.limiter.release.value = 0.1;
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// Initialize chain (without bit crusher for now)
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this.initializeBasicChain();
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}
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/**
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* Initialize the basic audio chain without bit crusher.
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*/
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private initializeBasicChain(): void {
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// Chain: input -> highpass -> lowpass -> waveshaper -> limiter -> output
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this.inputGain.connect(this.highpassFilter);
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this.highpassFilter.connect(this.lowpassFilter);
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this.lowpassFilter.connect(this.waveshaper);
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this.waveshaper.connect(this.limiter);
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this.limiter.connect(this.outputGain);
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this.isInitialized = true;
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}
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/**
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* Initialize with bit crusher using ScriptProcessor (fallback).
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* Call this after user interaction for iOS compatibility.
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*/
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initializeBitCrusher(): void {
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if (this.bitCrusher) return;
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// Disconnect current chain
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this.lowpassFilter.disconnect();
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// Create bit crusher using ScriptProcessor (deprecated but widely supported)
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const bufferSize = 4096;
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const crusher = this.audioContext.createScriptProcessor(bufferSize, 1, 1);
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const bitDepth = this.config.bitDepth;
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const sampleRateReduction = this.config.sampleRateReduction;
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const levels = Math.pow(2, bitDepth);
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let lastSample = 0;
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let sampleCounter = 0;
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crusher.onaudioprocess = (event) => {
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const input = event.inputBuffer.getChannelData(0);
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const output = event.outputBuffer.getChannelData(0);
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for (let i = 0; i < input.length; i++) {
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sampleCounter++;
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// Sample rate reduction
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if (sampleCounter >= sampleRateReduction) {
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sampleCounter = 0;
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// Bit crushing: quantize to bitDepth levels
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const sample = input[i];
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lastSample = Math.round(sample * levels) / levels;
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}
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output[i] = lastSample;
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}
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};
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this.bitCrusher = crusher;
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// Reconnect chain with crusher
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this.lowpassFilter.connect(crusher as unknown as AudioNode);
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(crusher as unknown as AudioNode).connect(this.waveshaper);
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}
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/**
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* Create a saturation curve for the waveshaper.
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*/
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private createSaturationCurve(amount: number): Float32Array {
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const samples = 44100;
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const curve = new Float32Array(samples);
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const deg = Math.PI / 180;
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for (let i = 0; i < samples; i++) {
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const x = (i * 2) / samples - 1;
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if (amount === 0) {
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// No saturation - linear
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curve[i] = x;
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} else {
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// Soft clipping curve
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const k = 2 * amount / (1 - amount);
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curve[i] = ((1 + k) * x) / (1 + k * Math.abs(x));
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}
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}
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return curve;
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}
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/**
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* Get the input node (connect your audio source to this).
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*/
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getInput(): GainNode {
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return this.inputGain;
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}
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/**
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* Get the output node (connect this to destination or other effects).
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*/
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getOutput(): GainNode {
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return this.outputGain;
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}
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/**
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* Enable/disable the colorizer.
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*/
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setEnabled(enabled: boolean): void {
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this.config.enabled = enabled;
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// When disabled, bypass could be implemented
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// For now, just set gain to 0 or 1
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this.inputGain.gain.value = enabled ? 1 : 0;
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}
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/**
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* Update configuration.
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*/
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setConfig(config: Partial<ColorizerConfig>): void {
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this.config = { ...this.config, ...config };
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// Update filter frequencies
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this.highpassFilter.frequency.value = this.config.highpassFreq;
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this.lowpassFilter.frequency.value = this.config.lowpassFreq;
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// Update saturation curve
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this.waveshaper.curve = this.createSaturationCurve(this.config.saturation);
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}
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/**
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* Get current configuration.
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*/
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getConfig(): ColorizerConfig {
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return { ...this.config };
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}
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/**
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* Create a preset configuration.
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*/
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static createPreset(preset: 'dmg' | 'gbc' | 'gba' | 'clean'): Partial<ColorizerConfig> {
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switch (preset) {
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case 'dmg':
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// Original Game Boy - lo-fi but with bass
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return {
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enabled: true,
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lowpassFreq: 8000,
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bitDepth: 8, // Less harsh than 4-bit
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sampleRateReduction: 1, // No SR reduction (causes artifacts)
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saturation: 0.3,
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highpassFreq: 30, // Let bass through!
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};
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case 'gbc':
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// Game Boy Color - slightly cleaner
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return {
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enabled: true,
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lowpassFreq: 10000,
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bitDepth: 8,
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sampleRateReduction: 1,
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saturation: 0.2,
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highpassFreq: 25,
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};
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case 'gba':
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// Game Boy Advance - cleaner still
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return {
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enabled: true,
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lowpassFreq: 14000,
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bitDepth: 12,
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sampleRateReduction: 1,
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saturation: 0.1,
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highpassFreq: 20,
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};
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case 'clean':
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// No processing
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return {
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enabled: false,
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lowpassFreq: 20000,
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bitDepth: 16,
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sampleRateReduction: 1,
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saturation: 0,
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highpassFreq: 20,
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};
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}
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}
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}
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