Recover analyzer DSP and realtime pipeline corrections

scripts/test_spectrogram.mjs

@@ -0,0 +1,113 @@
+import assert from 'node:assert/strict';
+import fs from 'node:fs';
+import vm from 'node:vm';
+
+const viewSource = fs.readFileSync(new URL('../www/views/spectrogram.js', import.meta.url), 'utf8');
+const timingSource = viewSource.match(/export function stepScrollAccumulator[\s\S]*?\n\}/)?.[0];
+assert.ok(timingSource, 'stepScrollAccumulator must remain testable');
+const timingContext = vm.createContext({ Number, Math });
+vm.runInContext(timingSource.replace('export function', 'function'), timingContext);
+const { stepScrollAccumulator } = timingContext;
+const pixelsSource = viewSource.match(/export function spectrogramPixelsPerSourceFrame[\s\S]*?\n\}/)?.[0];
+assert.ok(pixelsSource, 'spectrogramPixelsPerSourceFrame must remain testable');
+timingContext.BASE_SCROLL_CSS_PX_PER_SECOND = 60;
+vm.runInContext(pixelsSource.replace('export function', 'function'), timingContext);
+const { spectrogramPixelsPerSourceFrame } = timingContext;
+
+function emittedColumns(rate, frames, pixelScale = 1) {
+  let accumulator = 0;
+  let columns = 0;
+  for (let frame = 0; frame < frames; frame++) {
+    const step = stepScrollAccumulator(accumulator, rate * pixelScale, 1);
+    accumulator = step.accumulator;
+    columns += step.columns;
+  }
+  return columns;
+}
+
+assert.equal(emittedColumns(0.5, 20), 10, '0.5x must emit every second source frame');
+assert.equal(emittedColumns(1, 20), 20);
+assert.equal(emittedColumns(2, 20), 40);
+assert.equal(emittedColumns(4, 20), 80);
+assert.equal(emittedColumns(6, 20), 120);
+assert.equal(emittedColumns(1, 10, 1.7), 17, 'DPR scaling must preserve CSS scroll speed');
+
+function emittedInOneSecond(rate, fftSize) {
+  const sampleRate = 48000;
+  const hop = Math.max(128, Math.floor(fftSize / 8));
+  const sourceFrames = sampleRate / hop;
+  const pixelsPerFrame = spectrogramPixelsPerSourceFrame(rate, sampleRate, fftSize);
+  return emittedColumns(pixelsPerFrame, sourceFrames);
+}
+
+assert.equal(emittedInOneSecond(0.5, 4096), 30);
+assert.equal(emittedInOneSecond(1, 4096), 60);
+assert.equal(emittedInOneSecond(1, 8192), 60, 'FFT size must not alter real-time scroll speed');
+assert.equal(emittedInOneSecond(2, 8192), 120);
+assert.equal(emittedInOneSecond(4, 8192), 240);
+assert.equal(emittedInOneSecond(6, 8192), 360);
+
+const messages = [];
+const calls = { drawImage: 0, putImageData: [] };
+const context2d = {
+  imageSmoothingEnabled: true,
+  globalCompositeOperation: 'source-over',
+  fillStyle: '#000',
+  save() {},
+  restore() {},
+  fillRect() {},
+  drawImage() { calls.drawImage += 1; },
+  createImageData(width, height) {
+    return { width, height, data: new Uint8ClampedArray(width * height * 4) };
+  },
+  putImageData(image, x, y) { calls.putImageData.push({ image, x, y }); },
+};
+const canvas = {
+  width: 0,
+  height: 0,
+  getContext() { return context2d; },
+};
+const workerContext = vm.createContext({
+  self: {},
+  postMessage(message) { messages.push(message); },
+  performance: { now: (() => { let now = 0; return () => ++now; })() },
+  Float32Array,
+  Uint8ClampedArray,
+  Number,
+  Math,
+});
+const workerSource = fs.readFileSync(new URL('../www/workers/spectrogram.worker.js', import.meta.url), 'utf8');
+vm.runInContext(workerSource, workerContext, { filename: 'spectrogram.worker.js' });
+
+workerContext.self.onmessage({
+  data: { type: 'init', canvas, width: 8, height: 4, topDb: 0, bottomDb: -80, gamma: 1 },
+});
+assert.equal(messages.at(-1)?.type, 'ready');
+
+workerContext.self.onmessage({
+  data: { type: 'column', id: 7, repeat: 2, data: new Float32Array([-80, -40, -20, 0]) },
+});
+const ack = messages.at(-1);
+assert.equal(ack.type, 'drawn');
+assert.equal(ack.id, 7);
+assert.equal(ack.repeat, 2);
+assert.equal(calls.drawImage, 1, 'existing canvas should be shifted once');
+assert.equal(calls.putImageData.length, 1, 'only the new stripe should be uploaded');
+assert.equal(calls.putImageData[0].image.width, 2);
+assert.equal(calls.putImageData[0].x, 6);
+
+// Roughly ten minutes at 100 source columns/s. The worker has no history or
+// pending-message collection that can grow with runtime.
+messages.length = 0;
+context2d.putImageData = () => {};
+const longRunColumn = new Float32Array([-80, -40, -20, 0]);
+for (let index = 0; index < 60_000; index++) {
+  workerContext.self.onmessage({
+    data: { type: 'column', id: 100 + index, repeat: 1, data: longRunColumn },
+  });
+}
+assert.equal(messages.length, 60_000);
+assert.equal(messages.at(-1)?.type, 'drawn');
+assert.equal(messages.at(-1)?.id, 60_099);
+
+console.log('spectrogram timing and worker tests passed');