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ace-step-ui/server/public/demucs-web/src/processor.js
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JavaScript

/**
* Demucs audio processor - Core separation logic
*/
import { CONSTANTS } from './constants.js';
import { stft, istft, reflectPad } from './fft.js';
const { SAMPLE_RATE, FFT_SIZE, HOP_SIZE, TRAINING_SAMPLES, MODEL_SPEC_BINS, MODEL_SPEC_FRAMES, SEGMENT_OVERLAP, TRACKS } = CONSTANTS;
/**
* Convert model frequency output to complex spectrogram per track
*/
export function standaloneMask(freqOutput) {
const numTracks = 4;
const numChannels = 4;
const numBins = MODEL_SPEC_BINS;
const numFrames = MODEL_SPEC_FRAMES;
const result = [];
for (let t = 0; t < numTracks; t++) {
const trackSpec = {
leftReal: new Float32Array(numBins * numFrames),
leftImag: new Float32Array(numBins * numFrames),
rightReal: new Float32Array(numBins * numFrames),
rightImag: new Float32Array(numBins * numFrames)
};
for (let f = 0; f < numFrames; f++) {
for (let b = 0; b < numBins; b++) {
const baseIdx = t * numChannels * numBins * numFrames;
const outIdx = b * numFrames + f;
trackSpec.leftReal[outIdx] = freqOutput[baseIdx + 0 * numBins * numFrames + b * numFrames + f];
trackSpec.leftImag[outIdx] = freqOutput[baseIdx + 1 * numBins * numFrames + b * numFrames + f];
trackSpec.rightReal[outIdx] = freqOutput[baseIdx + 2 * numBins * numFrames + b * numFrames + f];
trackSpec.rightImag[outIdx] = freqOutput[baseIdx + 3 * numBins * numFrames + b * numFrames + f];
}
}
result.push(trackSpec);
}
return result;
}
/**
* Convert complex spectrogram back to time domain (iSTFT with proper offsets)
*/
export function standaloneIspec(trackSpec, targetLength) {
const numBins = MODEL_SPEC_BINS;
const numFrames = MODEL_SPEC_FRAMES;
const hopLength = HOP_SIZE;
const paddedBins = numBins + 1;
const paddedFrames = numFrames + 4;
const padChannel = (real, imag) => {
const paddedReal = new Float32Array(paddedFrames * paddedBins);
const paddedImag = new Float32Array(paddedFrames * paddedBins);
for (let f = 0; f < numFrames; f++) {
for (let b = 0; b < numBins; b++) {
const srcIdx = b * numFrames + f;
const dstFrame = f + 2;
const dstIdx = dstFrame * paddedBins + b;
paddedReal[dstIdx] = real[srcIdx];
paddedImag[dstIdx] = imag[srcIdx];
}
}
return { real: paddedReal, imag: paddedImag };
};
const leftPadded = padChannel(trackSpec.leftReal, trackSpec.leftImag);
const rightPadded = padChannel(trackSpec.rightReal, trackSpec.rightImag);
const centerPad = FFT_SIZE / 2;
const pad = Math.floor(hopLength / 2) * 3;
const istftLength = (paddedFrames - 1) * hopLength + FFT_SIZE;
const leftOut = istft(leftPadded.real, leftPadded.imag, paddedFrames, paddedBins, FFT_SIZE, hopLength, istftLength);
const rightOut = istft(rightPadded.real, rightPadded.imag, paddedFrames, paddedBins, FFT_SIZE, hopLength, istftLength);
const totalOffset = centerPad + pad;
const left = leftOut.subarray(totalOffset, totalOffset + targetLength);
const right = rightOut.subarray(totalOffset, totalOffset + targetLength);
return { left: new Float32Array(left), right: new Float32Array(right) };
}
/**
* Prepare model input from stereo audio
*/
export function prepareModelInput(leftChannel, rightChannel) {
const inputLength = TRAINING_SAMPLES;
const paddedLeft = new Float32Array(inputLength);
const paddedRight = new Float32Array(inputLength);
const copyLen = Math.min(leftChannel.length, inputLength);
paddedLeft.set(leftChannel.subarray(0, copyLen));
paddedRight.set(rightChannel.subarray(0, copyLen));
const le = Math.ceil(inputLength / HOP_SIZE);
const pad = Math.floor(HOP_SIZE / 2) * 3;
const padRight = pad + le * HOP_SIZE - inputLength;
const stftInputLeft = reflectPad(paddedLeft, pad, padRight);
const stftInputRight = reflectPad(paddedRight, pad, padRight);
const centerPad = FFT_SIZE / 2;
const centeredLeft = reflectPad(stftInputLeft, centerPad, centerPad);
const centeredRight = reflectPad(stftInputRight, centerPad, centerPad);
const stftLeft = stft(centeredLeft, FFT_SIZE, HOP_SIZE);
const stftRight = stft(centeredRight, FFT_SIZE, HOP_SIZE);
const numBins = MODEL_SPEC_BINS;
const numFrames = MODEL_SPEC_FRAMES;
const frameOffset = 2;
const magSpec = new Float32Array(4 * numBins * numFrames);
for (let f = 0; f < numFrames; f++) {
const srcFrame = f + frameOffset;
for (let b = 0; b < numBins; b++) {
const srcIdx = srcFrame * stftLeft.numBins + b;
magSpec[0 * numBins * numFrames + b * numFrames + f] = stftLeft.real[srcIdx];
magSpec[1 * numBins * numFrames + b * numFrames + f] = stftLeft.imag[srcIdx];
magSpec[2 * numBins * numFrames + b * numFrames + f] = stftRight.real[srcIdx];
magSpec[3 * numBins * numFrames + b * numFrames + f] = stftRight.imag[srcIdx];
}
}
const waveform = new Float32Array(2 * inputLength);
waveform.set(paddedLeft, 0);
waveform.set(paddedRight, inputLength);
return { waveform, magSpec, numBins, numFrames, originalLength: leftChannel.length };
}
/**
* Main Demucs processor class
*/
export class DemucsProcessor {
constructor(options = {}) {
this.ort = options.ort || null;
this.session = null;
this.modelPath = options.modelPath || './htdemucs_embedded.onnx';
this.sessionOptions = options.sessionOptions || {};
this.onProgress = options.onProgress || (() => {});
this.onLog = options.onLog || (() => {});
this.onDownloadProgress = options.onDownloadProgress || (() => {});
}
async loadModel(modelPathOrBuffer) {
if (!this.ort) {
throw new Error('ONNX Runtime not provided. Pass ort in constructor options.');
}
this.onLog('model', 'Loading model...');
let modelBuffer;
if (modelPathOrBuffer instanceof ArrayBuffer) {
modelBuffer = modelPathOrBuffer;
} else {
const response = await fetch(modelPathOrBuffer || this.modelPath);
// Check if we can track progress
const contentLength = response.headers.get('Content-Length');
if (contentLength && response.body) {
const totalSize = parseInt(contentLength, 10);
const reader = response.body.getReader();
const chunks = [];
let loadedSize = 0;
while (true) {
const { done, value } = await reader.read();
if (done) break;
chunks.push(value);
loadedSize += value.length;
this.onDownloadProgress(loadedSize, totalSize);
}
// Combine chunks into single ArrayBuffer
const combined = new Uint8Array(loadedSize);
let offset = 0;
for (const chunk of chunks) {
combined.set(chunk, offset);
offset += chunk.length;
}
modelBuffer = combined.buffer;
} else {
// Fallback: no progress tracking
modelBuffer = await response.arrayBuffer();
}
}
const defaultSessionOptions = {
executionProviders: ['webgpu', 'wasm'],
graphOptimizationLevel: 'basic'
};
this.session = await this.ort.InferenceSession.create(modelBuffer, {
...defaultSessionOptions,
...this.sessionOptions
});
this.onLog('model', 'Model loaded successfully');
return this.session;
}
async separate(leftChannel, rightChannel) {
if (!this.session) {
throw new Error('Model not loaded. Call loadModel() first.');
}
const totalSamples = leftChannel.length;
const stride = Math.floor(TRAINING_SAMPLES * (1 - SEGMENT_OVERLAP));
const numSegments = Math.ceil((totalSamples - TRAINING_SAMPLES) / stride) + 1;
const outputs = TRACKS.map(() => ({
left: new Float32Array(totalSamples),
right: new Float32Array(totalSamples)
}));
const weights = new Float32Array(totalSamples);
let segmentIdx = 0;
for (let start = 0; start < totalSamples; start += stride) {
const end = Math.min(start + TRAINING_SAMPLES, totalSamples);
const segmentLength = end - start;
const segLeft = new Float32Array(TRAINING_SAMPLES);
const segRight = new Float32Array(TRAINING_SAMPLES);
for (let i = 0; i < segmentLength; i++) {
segLeft[i] = leftChannel[start + i];
segRight[i] = rightChannel[start + i];
}
const input = prepareModelInput(segLeft, segRight);
const waveformTensor = new this.ort.Tensor('float32', input.waveform, [1, 2, TRAINING_SAMPLES]);
const magSpecTensor = new this.ort.Tensor('float32', input.magSpec, [1, 4, MODEL_SPEC_BINS, MODEL_SPEC_FRAMES]);
const feeds = {};
feeds[this.session.inputNames[0]] = waveformTensor;
if (this.session.inputNames.length > 1) {
feeds[this.session.inputNames[1]] = magSpecTensor;
}
const inferResults = await this.session.run(feeds);
let timeData = null, timeShape = null;
let freqData = null;
for (const name of this.session.outputNames) {
const tensor = inferResults[name];
if (tensor.dims.length === 4 && tensor.dims[2] === 2) {
timeData = tensor.data;
timeShape = tensor.dims;
} else if (tensor.dims.length === 5 && tensor.dims[2] === 4) {
freqData = tensor.data;
}
}
if (!timeData) {
throw new Error('Could not find time-domain output tensor');
}
let combinedOutputs = null;
if (freqData) {
const trackSpecs = standaloneMask(freqData);
combinedOutputs = [];
for (let t = 0; t < 4; t++) {
const freqOutput = standaloneIspec(trackSpecs[t], TRAINING_SAMPLES);
const numChannels = timeShape[2];
const samples = timeShape[3];
const timeLeft = new Float32Array(samples);
const timeRight = new Float32Array(samples);
for (let i = 0; i < samples; i++) {
timeLeft[i] = timeData[t * numChannels * samples + 0 * samples + i];
timeRight[i] = timeData[t * numChannels * samples + 1 * samples + i];
}
const combined = {
left: new Float32Array(samples),
right: new Float32Array(samples)
};
for (let i = 0; i < samples; i++) {
combined.left[i] = timeLeft[i] + (freqOutput.left[i] || 0);
combined.right[i] = timeRight[i] + (freqOutput.right[i] || 0);
}
combinedOutputs.push(combined);
}
}
const numTracks = timeShape[1];
const numChannels = timeShape[2];
const samples = timeShape[3];
const overlapWindow = new Float32Array(segmentLength);
for (let i = 0; i < segmentLength; i++) {
const fadeIn = Math.min(i / (stride * 0.5), 1);
const fadeOut = Math.min((segmentLength - i) / (stride * 0.5), 1);
overlapWindow[i] = Math.min(fadeIn, fadeOut);
}
for (let t = 0; t < numTracks; t++) {
for (let i = 0; i < segmentLength && start + i < totalSamples; i++) {
let leftVal, rightVal;
if (combinedOutputs) {
leftVal = combinedOutputs[t].left[i];
rightVal = combinedOutputs[t].right[i];
} else {
const leftIdx = t * numChannels * samples + 0 * samples + i;
const rightIdx = t * numChannels * samples + 1 * samples + i;
leftVal = timeData[leftIdx];
rightVal = timeData[rightIdx];
}
outputs[t].left[start + i] += leftVal * overlapWindow[i];
outputs[t].right[start + i] += rightVal * overlapWindow[i];
}
}
for (let i = 0; i < segmentLength && start + i < totalSamples; i++) {
weights[start + i] += overlapWindow[i];
}
segmentIdx++;
this.onProgress({
progress: segmentIdx / numSegments,
currentSegment: segmentIdx,
totalSegments: numSegments
});
}
for (let t = 0; t < TRACKS.length; t++) {
for (let i = 0; i < totalSamples; i++) {
if (weights[i] > 0) {
outputs[t].left[i] /= weights[i];
outputs[t].right[i] /= weights[i];
}
}
}
return {
drums: outputs[0],
bass: outputs[1],
other: outputs[2],
vocals: outputs[3]
};
}
}