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Fix 44.1k export resampling and add 16-bit TPDF dithering #4

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Merged
entrepeneur4lyf merged 4 commits into from
Feb 12, 2026
Merged

Fix 44.1k export resampling and add 16-bit TPDF dithering #4

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88c8cde
Fix 44.1k export resampling and add 16-bit TPDF dithering
entrepeneur4lyf Feb 12, 2026
6b6558b
Update web/app.js
entrepeneur4lyf Feb 12, 2026
be13eb8
Update web/ui/encoder.js
entrepeneur4lyf Feb 12, 2026
30a1bd1
Update web/app.js
entrepeneur4lyf Feb 12, 2026
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19 changes: 16 additions & 3 deletions web/app.js
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Original file line number Diff line number Diff line change
Expand Up @@ -40,6 +40,7 @@ import {
// Renderer
renderOffline,
renderToAudioBuffer,
resampleAudioBuffer,
// Waveform
initWaveSurfer,
destroyWaveSurfer,
Expand Down Expand Up @@ -1418,12 +1419,24 @@ async function processAudio() {
throw new Error('Cancelled');
}

updateProgress(85, 'Encoding WAV...');
let exportBuffer = result.audioBuffer;
if (exportBuffer.sampleRate !== parsedSampleRate) {
updateProgress(83, `Resampling to ${parsedSampleRate / 1000}kHz...`);
let exportBuffer = result.audioBuffer;
if (exportBuffer.sampleRate !== parsedSampleRate) {
updateProgress(86, `Resampling to ${parsedSampleRate / 1000}kHz...`);
exportBuffer = await resampleAudioBuffer(exportBuffer, parsedSampleRate);
}
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if (processingCancelled) {
throw new Error('Cancelled');
}

updateProgress(88, 'Encoding WAV...');
// Yield so the UI can repaint before encoding begins.
await new Promise(resolve => setTimeout(resolve, 0));

outputData = await encodeWAVAsync(result.audioBuffer, parsedSampleRate, parsedBitDepth, {
onProgress: (p) => updateProgress(Math.round(85 + p * 10), 'Encoding WAV...'),
outputData = await encodeWAVAsync(exportBuffer, parsedSampleRate, parsedBitDepth, {
onProgress: (p) => updateProgress(Math.round(88 + p * 10), 'Encoding WAV...'),
shouldCancel: () => processingCancelled
});
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} catch (workerErr) {
Expand Down
45 changes: 35 additions & 10 deletions web/ui/encoder.js
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Expand Up @@ -9,6 +9,20 @@ import { applyFinalFilters } from '../lib/dsp/final-filters.js';
// WAV Encoding
// ============================================================================

const DITHER_BUFFER_SIZE = 256;
const ditherBuffer = new Float32Array(DITHER_BUFFER_SIZE);
for (let i = 0; i < DITHER_BUFFER_SIZE; i++) {
ditherBuffer[i] = (Math.random() + Math.random()) - 1;
}
let ditherIndex = 0;

function triangularDither() {
// TPDF in integer (LSB) domain: [-1, 1]
const dither = ditherBuffer[ditherIndex];
ditherIndex = (ditherIndex + 1) % DITHER_BUFFER_SIZE;
return dither;
}
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/**
* Encode an AudioBuffer to WAV format (supports 16-bit and 24-bit)
* @param {AudioBuffer} audioBuffer - Source audio buffer
Expand All @@ -18,8 +32,9 @@ import { applyFinalFilters } from '../lib/dsp/final-filters.js';
*/
export function encodeWAV(audioBuffer, targetSampleRate, bitDepth) {
const numChannels = audioBuffer.numberOfChannels;
const safeBitDepth = bitDepth === 24 ? 24 : 16;
const sampleRate = targetSampleRate || audioBuffer.sampleRate;
const bytesPerSample = bitDepth / 8;
const bytesPerSample = safeBitDepth / 8;

const channelData = [];
for (let ch = 0; ch < numChannels; ch++) {
Expand Down Expand Up @@ -47,22 +62,27 @@ export function encodeWAV(audioBuffer, targetSampleRate, bitDepth) {
view.setUint32(24, sampleRate, true);
view.setUint32(28, sampleRate * numChannels * bytesPerSample, true);
view.setUint16(32, numChannels * bytesPerSample, true);
view.setUint16(34, bitDepth, true);
view.setUint16(34, safeBitDepth, true);
writeString(36, 'data');
view.setUint32(40, dataSize, true);

let offset = 44;
const maxVal = bitDepth === 16 ? 32767 : 8388607;
const maxVal = safeBitDepth === 16 ? 32767 : 8388607;

for (let i = 0; i < numSamples; i++) {
for (let ch = 0; ch < numChannels; ch++) {
const sample = Math.max(-1, Math.min(1, channelData[ch][i]));
const intSample = Math.round(sample * maxVal);

if (bitDepth === 16) {
view.setInt16(offset, intSample, true);
const scaled = sample * maxVal;
// Dither is only needed for 16-bit export where quantization noise is audible.
const intSample = safeBitDepth === 16
? Math.round(scaled + triangularDither())
: Math.round(scaled);

if (safeBitDepth === 16) {
const clampedSample = Math.max(-32768, Math.min(32767, intSample));
view.setInt16(offset, clampedSample, true);
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offset += 2;
} else if (bitDepth === 24) {
} else if (safeBitDepth === 24) {
// Clamp to prevent overflow in bitwise operations
const clampedSample = Math.max(-8388607, Math.min(8388607, intSample));
view.setUint8(offset, clampedSample & 0xFF);
Expand Down Expand Up @@ -145,10 +165,15 @@ export async function encodeWAVAsync(audioBuffer, targetSampleRate, bitDepth, op
for (let s = i; s < end; s++) {
for (let ch = 0; ch < numChannels; ch++) {
const sample = Math.max(-1, Math.min(1, channelData[ch][s]));
const intSample = Math.round(sample * maxVal);
const scaled = sample * maxVal;
// Dither is only needed for 16-bit export where quantization noise is audible.
const intSample = safeBitDepth === 16
? Math.round(scaled + triangularDither())
: Math.round(scaled);

if (safeBitDepth === 16) {
view.setInt16(offset, intSample, true);
const clampedSample = Math.max(-32768, Math.min(32767, intSample));
view.setInt16(offset, clampedSample, true);
offset += 2;
} else {
const clampedSample = Math.max(-8388607, Math.min(8388607, intSample));
Expand Down
24 changes: 24 additions & 0 deletions web/ui/renderer.js
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Original file line number Diff line number Diff line change
Expand Up @@ -162,6 +162,30 @@ function applyDSPChain(buffer, settings, onProgress = null, logPrefix = '[DSP]')
return { buffer: renderedBuffer, measuredLufs };
}

/**
* Resample an AudioBuffer to a target sample rate.
* Uses OfflineAudioContext so output sample data and WAV header stay aligned.
* @param {AudioBuffer} sourceBuffer - Source audio buffer
* @param {number} targetSampleRate - Target sample rate in Hz
* @returns {Promise<AudioBuffer>} Resampled buffer (or original if unchanged)
*/
export async function resampleAudioBuffer(sourceBuffer, targetSampleRate) {
if (!sourceBuffer || !targetSampleRate || sourceBuffer.sampleRate === targetSampleRate) {
return sourceBuffer;
}

const numChannels = sourceBuffer.numberOfChannels;
const numSamples = Math.ceil(sourceBuffer.duration * targetSampleRate);
const offlineCtx = new OfflineAudioContext(numChannels, numSamples, targetSampleRate);
const source = offlineCtx.createBufferSource();

source.buffer = sourceBuffer;
source.connect(offlineCtx.destination);
source.start(0);

return offlineCtx.startRendering();
}

// ============================================================================
// Offline Rendering (Export)
// ============================================================================
Expand Down
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