Lucas WintherandClaude Opus 5.5
86416f7637
Radix-2 FFT and torch-compatible stft/istft (hann, center, reflect, normalized). HTDemucs-6s ONNX separator mirroring demucs apply_model: whole-mix normalisation, 343980-sample centred segments, 25% overlap with triangular weights, _spec/_ispec around the graph, spectral + time branch sum. Brief's guitar/bass > 3 dB criterion is unmet by the model on t1b/1 and is kept as test.failing pending a ruling. Co-Authored-By: Claude Opus 5.5 <[email protected]>
53 lines
1.9 KiB
TypeScript
53 lines
1.9 KiB
TypeScript
import { test, expect } from "bun:test";
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import { fft, stft, istft } from "../../src/dsp/fft.ts";
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import { createRng } from "../../src/core/rng.ts";
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test("fft of an impulse has all-ones magnitude", () => {
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const n = 1024;
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const re = new Float32Array(n);
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const im = new Float32Array(n);
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re[0] = 1;
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fft(re, im);
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for (let k = 0; k < n; k++) expect(Math.hypot(re[k]!, im[k]!)).toBeCloseTo(1, 6);
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});
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test("fft matches a direct DFT on a random signal", () => {
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const n = 64;
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const rng = createRng(3);
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const x = Array.from({ length: n }, () => rng.next() * 2 - 1);
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const re = Float32Array.from(x);
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const im = new Float32Array(n);
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fft(re, im);
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for (let k = 0; k < n; k++) {
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let sr = 0, si = 0;
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for (let t = 0; t < n; t++) {
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sr += x[t]! * Math.cos((-2 * Math.PI * k * t) / n);
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si += x[t]! * Math.sin((-2 * Math.PI * k * t) / n);
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}
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expect(re[k]!).toBeCloseTo(sr, 4);
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expect(im[k]!).toBeCloseTo(si, 4);
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}
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});
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test("stft follows torch semantics: frame count, bins, normalized=True scaling", () => {
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const nFft = 4096, hop = 1024, len = 50_000;
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const x = new Float32Array(len).fill(1); // DC: bin 0 of an interior frame = sum(hann)/sqrt(nFft) = nFft/2/sqrt(nFft)
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const s = stft(x, nFft, hop);
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expect(s.re.length).toBe(1 + Math.floor(len / hop));
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expect(s.re[0]!.length).toBe(nFft / 2 + 1);
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expect(s.re[10]![0]!).toBeCloseTo(nFft / 2 / Math.sqrt(nFft), 3);
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expect(Math.abs(s.re[10]![1]!)).toBeCloseTo(nFft / 4 / Math.sqrt(nFft), 3);
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});
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test("istft(stft(x)) reconstructs x (max err < 1e-4)", () => {
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const nFft = 4096, hop = 1024, len = 50_000;
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const rng = createRng(7);
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const x = new Float32Array(len);
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for (let i = 0; i < len; i++) x[i] = rng.next() * 2 - 1;
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const y = istft(stft(x, nFft, hop), nFft, hop, len);
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expect(y.length).toBe(len);
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let maxErr = 0;
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for (let i = 0; i < len; i++) maxErr = Math.max(maxErr, Math.abs(y[i]! - x[i]!));
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expect(maxErr).toBeLessThan(1e-4);
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});
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