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 Wave Channel Wavetable
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*
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* The GB wave channel uses a 32-sample wavetable with 4-bit resolution.
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* Each sample can be 0-15, giving the characteristic "digital staircase"
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* sound quality.
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*
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* The low resolution creates audible quantization that's part of the
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* GB's unique character - smoother than pulse but still distinctly digital.
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*
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* Reference: https://gbdev.io/pandocs/Audio_details.html#wave-channel
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*/
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/**
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* Number of samples in the wavetable
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*/
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export const WAVE_TABLE_SIZE = 32;
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/**
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* Maximum sample value (4-bit = 0-15)
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*/
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export const MAX_SAMPLE_VALUE = 15;
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/**
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* GB wave channel volume levels (bit-shift based)
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* 0 = mute, 1 = 100%, 2 = 50%, 3 = 25%
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*/
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export type WaveVolume = 0 | 1 | 2 | 3;
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/**
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* Volume multipliers matching GB behavior
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* GB uses right-shift for volume: 0=mute, 1=>>0, 2=>>1, 3=>>2
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*/
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export const VOLUME_MULTIPLIERS: Record<WaveVolume, number> = {
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0: 0,
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1: 1.0,
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2: 0.5,
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3: 0.25,
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};
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/**
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* Wavetable class for the GB wave channel.
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*/
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export class WaveTable {
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private samples: Uint8Array;
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constructor() {
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this.samples = new Uint8Array(WAVE_TABLE_SIZE);
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// Initialize with silence
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this.samples.fill(8); // 8 = center value (no DC offset)
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}
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/**
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* Quantize a float value (0-1) to 4-bit (0-15).
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*/
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private quantize(value: number): number {
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const clamped = Math.max(0, Math.min(1, value));
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return Math.floor(clamped * MAX_SAMPLE_VALUE);
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}
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/**
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* Load a waveform from a float array (0-1 range).
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* Values are quantized to 4-bit resolution.
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*/
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loadFromFloats(waveform: number[]): void {
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for (let i = 0; i < WAVE_TABLE_SIZE; i++) {
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const value = i < waveform.length ? waveform[i] : 0.5;
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this.samples[i] = this.quantize(value);
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}
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}
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/**
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* Load raw 4-bit samples directly.
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*/
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loadFromBytes(samples: number[]): void {
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for (let i = 0; i < WAVE_TABLE_SIZE; i++) {
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const value = i < samples.length ? samples[i] : 8;
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this.samples[i] = Math.max(0, Math.min(MAX_SAMPLE_VALUE, Math.floor(value)));
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}
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}
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/**
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* Get the raw sample array.
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*/
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getSamples(): Uint8Array {
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return this.samples;
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}
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/**
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* Create a Web Audio buffer from this wavetable.
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* The buffer is one cycle of the waveform.
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*/
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createBuffer(audioContext: BaseAudioContext): AudioBuffer {
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const buffer = audioContext.createBuffer(1, WAVE_TABLE_SIZE, audioContext.sampleRate);
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const data = buffer.getChannelData(0);
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for (let i = 0; i < WAVE_TABLE_SIZE; i++) {
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// Convert 0-15 to -1 to +1
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data[i] = (this.samples[i] / MAX_SAMPLE_VALUE) * 2 - 1;
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}
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return buffer;
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}
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/**
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* Create an extended buffer for better audio quality.
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* Repeats the waveform multiple times to avoid pitch artifacts.
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*/
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createExtendedBuffer(
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audioContext: BaseAudioContext,
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repetitions: number = 256
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): AudioBuffer {
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const totalSamples = WAVE_TABLE_SIZE * repetitions;
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const buffer = audioContext.createBuffer(1, totalSamples, audioContext.sampleRate);
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const data = buffer.getChannelData(0);
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for (let i = 0; i < totalSamples; i++) {
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const sampleIndex = i % WAVE_TABLE_SIZE;
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data[i] = (this.samples[sampleIndex] / MAX_SAMPLE_VALUE) * 2 - 1;
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}
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return buffer;
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}
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}
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/**
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* Generate a triangle wave with 4-bit quantization.
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* Classic GB bass sound.
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*/
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export function generateTriangleWave(): Uint8Array {
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const wave = new Uint8Array(WAVE_TABLE_SIZE);
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for (let i = 0; i < WAVE_TABLE_SIZE; i++) {
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// Triangle: ramp up for first half, down for second half
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const position = i / WAVE_TABLE_SIZE;
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let value: number;
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if (position < 0.5) {
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value = position * 2; // 0 to 1
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} else {
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value = 2 - position * 2; // 1 to 0
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}
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wave[i] = Math.floor(value * MAX_SAMPLE_VALUE);
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}
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return wave;
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}
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/**
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* Generate a sawtooth wave with 4-bit quantization.
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* Brighter, more aggressive sound.
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*/
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export function generateSawtoothWave(): Uint8Array {
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const wave = new Uint8Array(WAVE_TABLE_SIZE);
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for (let i = 0; i < WAVE_TABLE_SIZE; i++) {
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wave[i] = Math.floor((i / (WAVE_TABLE_SIZE - 1)) * MAX_SAMPLE_VALUE);
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}
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return wave;
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}
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/**
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* Generate a sine-ish wave with 4-bit quantization.
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* Rounder, softer sound for pads.
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*/
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export function generateSineWave(): Uint8Array {
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const wave = new Uint8Array(WAVE_TABLE_SIZE);
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for (let i = 0; i < WAVE_TABLE_SIZE; i++) {
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const angle = (i / WAVE_TABLE_SIZE) * Math.PI * 2;
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const sine = (Math.sin(angle) + 1) / 2; // Normalize to 0-1
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wave[i] = Math.floor(sine * MAX_SAMPLE_VALUE);
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}
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return wave;
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}
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/**
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* Generate a square wave with 4-bit resolution.
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* Sharp, bright sound.
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*/
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export function generateSquareWave(): Uint8Array {
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const wave = new Uint8Array(WAVE_TABLE_SIZE);
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for (let i = 0; i < WAVE_TABLE_SIZE; i++) {
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wave[i] = i < WAVE_TABLE_SIZE / 2 ? MAX_SAMPLE_VALUE : 0;
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}
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return wave;
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}
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/**
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* Generate a bass-optimized waveform.
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* Combination of triangle with slight harmonics.
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*/
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export function generateBassWave(): Uint8Array {
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const wave = new Uint8Array(WAVE_TABLE_SIZE);
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for (let i = 0; i < WAVE_TABLE_SIZE; i++) {
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const position = i / WAVE_TABLE_SIZE;
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const angle = position * Math.PI * 2;
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// Fundamental + slight 2nd harmonic for warmth
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const value = (Math.sin(angle) * 0.8 + Math.sin(angle * 2) * 0.2 + 1) / 2;
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wave[i] = Math.floor(value * MAX_SAMPLE_VALUE);
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}
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return wave;
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}
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/**
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* Generate a pad-optimized waveform.
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* Softer, rounder character.
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*/
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export function generatePadWave(): Uint8Array {
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// Use sine wave for pads - smoothest option
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return generateSineWave();
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}
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/**
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* Generate a lead-optimized waveform.
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* Brighter with more harmonics.
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*/
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export function generateLeadWave(): Uint8Array {
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const wave = new Uint8Array(WAVE_TABLE_SIZE);
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for (let i = 0; i < WAVE_TABLE_SIZE; i++) {
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const position = i / WAVE_TABLE_SIZE;
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const angle = position * Math.PI * 2;
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// Mix of saw and triangle characteristics
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const saw = position;
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const tri = position < 0.5 ? position * 2 : 2 - position * 2;
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const value = saw * 0.6 + tri * 0.4;
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wave[i] = Math.floor(value * MAX_SAMPLE_VALUE);
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}
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return wave;
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}
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/**
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* Preset wavetables for easy access.
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*/
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export const WAVE_PRESETS = {
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triangle: generateTriangleWave,
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sawtooth: generateSawtoothWave,
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sine: generateSineWave,
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square: generateSquareWave,
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bass: generateBassWave,
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pad: generatePadWave,
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lead: generateLeadWave,
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} as const;
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export type WavePreset = keyof typeof WAVE_PRESETS;
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/**
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* Create a PeriodicWave from a wavetable for use with OscillatorNode.
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* This is more accurate than using AudioBufferSourceNode with playback rate.
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*/
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export function createPeriodicWaveFromTable(
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samples: Uint8Array | number[],
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audioContext: BaseAudioContext
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): PeriodicWave {
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const n = samples.length;
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// Convert samples to normalized audio values (-1 to +1)
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const normalized: number[] = [];
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for (let i = 0; i < n; i++) {
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const sample = typeof samples[i] === 'number' ? samples[i] : 0;
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normalized.push((sample / MAX_SAMPLE_VALUE) * 2 - 1);
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}
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// Number of harmonics - more harmonics = more accurate representation
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const numHarmonics = 64;
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// Calculate Fourier coefficients
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const real = new Float32Array(numHarmonics);
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const imag = new Float32Array(numHarmonics);
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// DC offset (real[0]) should be 0 for centered waveform
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real[0] = 0;
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imag[0] = 0;
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// Calculate each harmonic using DFT
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for (let k = 1; k < numHarmonics; k++) {
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let realSum = 0;
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let imagSum = 0;
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for (let i = 0; i < n; i++) {
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const angle = (2 * Math.PI * k * i) / n;
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realSum += normalized[i] * Math.cos(angle);
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imagSum -= normalized[i] * Math.sin(angle);
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}
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// Scale by 2/n for proper amplitude
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real[k] = (2 * realSum) / n;
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imag[k] = (2 * imagSum) / n;
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}
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return audioContext.createPeriodicWave(real, imag, {
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disableNormalization: false
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});
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}
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