use utils

src/Audiovis.tsx

@@ -1,7 +1,7 @@
 import { FC, useEffect, useMemo, useRef, useState } from "react";
 import styles from "./Audiovis.module.css";
 import { useAudioCtx } from "./AudioCtxCtx";
-import FFT from "fft.js";
+import { spectrum, spectrumToImage } from "./util";
 
 export const Audiovis: FC<{ srcObject: Blob }> = ({ srcObject }) => {
   const url = useMemo(() => URL.createObjectURL(srcObject), [srcObject]);
@@ -91,68 +91,3 @@ const Sonogram: FC<{ audio: AudioBuffer }> = ({ audio }) => {
 
   return <canvas ref={canvas} className={styles.waveform} />;
 };
-
-// load the spectrum for an entire audio buffer
-function spectrum(
-  audio: AudioBuffer,
-  fftSize: 2 | 4 | 8 | 16 | 32 | 64 | 128 | 256 | 512 | 1024 | 2048 | 4096
-): Float32Array {
-  const fft = new FFT(fftSize);
-  const data = audio.getChannelData(0);
-
-  const chunks = Math.floor(audio.length / fftSize);
-  const target = new Float32Array(fftSize * chunks);
-
-  const sample = new Array(fftSize);
-  const out = fft.createComplexArray();
-
-  for (let i = 0; i < chunks; i++) {
-    const offset = i * fftSize;
-    for (let i = 0; i < sample.length; i++) sample[i] = data[i + offset];
-    fft.realTransform(out, sample);
-
-    for (let j = 0; j < fftSize; j++) {
-      target[i * fftSize + j] = Math.abs(out[j]);
-    }
-  }
-
-  return target;
-}
-
-// Render a spectrum as a visible image to be written to canvas
-function spectrumToImage(
-  spectrum: Float32Array,
-  fftSize: 2 | 4 | 8 | 16 | 32 | 64 | 128 | 256 | 512 | 1024 | 2048 | 4096
-) {
-  const chunks = spectrum.length / fftSize;
-
-  const image = new ImageData(chunks, fftSize);
-
-  const max = spectrum.reduce((a, b) => Math.max(a, b), -Infinity);
-
-  for (let i = 0; i < chunks; i++) {
-    for (let j = 0; j < fftSize; j++) {
-      const idx = j * chunks + i;
-      const value = spectrum[i * fftSize + j];
-
-      const scaledValue = Math.pow(value / max, 0.3); // Apply a power scale
-
-      const [r, g, b, a] = valueToColor(scaledValue);
-
-      image.data[idx * 4] = r;
-      image.data[idx * 4 + 1] = g;
-      image.data[idx * 4 + 2] = b;
-      image.data[idx * 4 + 3] = a;
-    }
-  }
-
-  return image;
-}
-
-function valueToColor(value: number) {
-  const r = value < 0.5 ? 0 : 255 * (value - 0.5) * 2;
-  const g = value < 0.5 ? 255 * value * 2 : 255 * (1 - value) * 2;
-  const b = value < 0.5 ? 255 * (1 - value * 2) : 0;
-  const a = value > 0.2 ? 255 : value * 5 * 255;
-  return [r, g, b, a];
-}