refactor: extract typed spectrum math

2026-08-01 18:19:02 +02:00
parent e300cc343d
commit 5136704826
4 changed files with 213 additions and 138 deletions
@@ -0,0 +1,51 @@
+// SPDX-FileCopyrightText: 2026 Stan Grams <sjg@haxx.space>
+//
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+import assert from "node:assert/strict";
+import test from "node:test";
+import vm from "node:vm";
+import { build } from "esbuild";
+
+async function loadSpectrumMath() {
+  const result = await build({
+    entryPoints: [new URL("../src/features/spectrum/math.ts", import.meta.url).pathname],
+    bundle: true,
+    format: "cjs",
+    platform: "browser",
+    target: "es2022",
+    write: false,
+  });
+  const module = { exports: {} };
+  vm.runInNewContext(result.outputFiles[0].text, {
+    module,
+    exports: module.exports,
+    Array,
+    ArrayBuffer,
+    DataView,
+    Float32Array,
+    Float64Array,
+    Int8Array,
+    Uint8Array,
+    Number,
+    Math,
+    TypeError,
+  });
+  return module.exports;
+}
+
+test("compact spectrum frames decode signed i8 bins", async () => {
+  const { decodeBase64Int8 } = await loadSpectrumMath();
+  const bins = decodeBase64Int8("/4AAfw==");
+  assert.deepEqual(Array.from(bins), [-1, -128, 0, 127]);
+  assert.throws(() => decodeBase64Int8("%%%"), /Invalid base64/);
+});
+
+test("noise floor uses the lower spectrum percentile without sorting input", async () => {
+  const { estimateNoiseFloorDb } = await loadSpectrumMath();
+  const bins = new Float32Array([-70, -100, -95, -90, -80, -85, -75]);
+  const original = Array.from(bins);
+  assert.equal(estimateNoiseFloorDb(bins), -95);
+  assert.deepEqual(Array.from(bins), original);
+  assert.equal(estimateNoiseFloorDb(new Float32Array()), null);
+});