refactor(audio,stage-ui): simplify code

packages/audio/src/encoding/wav.test.ts

@@ -0,0 +1,33 @@
+import { describe, expect, it } from 'vitest'
+
+import { toWav, toWavFromPCM16 } from './wav'
+
+describe('toWav', () => {
+  it('converts Float32 samples to PCM16 bytes by default', () => {
+    const samples = new Float32Array([-1, 0, 1])
+    const wav = toWav(samples.buffer, 24000)
+    const view = new DataView(wav)
+
+    expect(view.getInt16(44, true)).toBe(-32768)
+    expect(view.getInt16(46, true)).toBe(0)
+    expect(view.getInt16(48, true)).toBe(32767)
+  })
+
+  it('preserves PCM16 bytes and writes the WAV metadata', () => {
+    const pcmBytes = new Uint8Array([0x00, 0x80, 0xFF, 0x7F])
+    const wav = toWavFromPCM16(pcmBytes, 24000)
+    const view = new DataView(wav)
+
+    expect(new TextDecoder().decode(new Uint8Array(wav, 0, 4))).toBe('RIFF')
+    expect(view.getUint32(4, true)).toBe(40)
+    expect(new TextDecoder().decode(new Uint8Array(wav, 8, 4))).toBe('WAVE')
+    expect(view.getUint16(20, true)).toBe(1)
+    expect(view.getUint16(22, true)).toBe(1)
+    expect(view.getUint32(24, true)).toBe(24000)
+    expect(view.getUint32(28, true)).toBe(48000)
+    expect(view.getUint16(32, true)).toBe(2)
+    expect(view.getUint16(34, true)).toBe(16)
+    expect(view.getUint32(40, true)).toBe(pcmBytes.byteLength)
+    expect([...new Uint8Array(wav, 44)]).toEqual([...pcmBytes])
+  })
+})