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src/spectral-synthesis/audio/export.ts

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+/**
+ * Create WAV buffer from audio data
+ */
+export function createWAVBuffer(audioData: Float32Array, sampleRate: number): ArrayBuffer {
+  const length = audioData.length
+  const buffer = new ArrayBuffer(44 + length * 2)
+  const view = new DataView(buffer)
+
+  // WAV header
+  writeString(view, 0, 'RIFF')
+  view.setUint32(4, 36 + length * 2, true) // file length - 8
+  writeString(view, 8, 'WAVE')
+  writeString(view, 12, 'fmt ')
+  view.setUint32(16, 16, true) // format chunk length
+  view.setUint16(20, 1, true) // PCM format
+  view.setUint16(22, 1, true) // mono
+  view.setUint32(24, sampleRate, true)
+  view.setUint32(28, sampleRate * 2, true) // byte rate
+  view.setUint16(32, 2, true) // block align
+  view.setUint16(34, 16, true) // bits per sample
+  writeString(view, 36, 'data')
+  view.setUint32(40, length * 2, true) // data chunk length
+
+  // Convert float samples to 16-bit PCM
+  let offset = 44
+  for (let i = 0; i < length; i++) {
+    const sample = Math.max(-1, Math.min(1, audioData[i]))
+    view.setInt16(offset, sample * 0x7FFF, true)
+    offset += 2
+  }
+
+  return buffer
+}
+
+function writeString(view: DataView, offset: number, string: string) {
+  for (let i = 0; i < string.length; i++) {
+    view.setUint8(offset + i, string.charCodeAt(i))
+  }
+}
+
+/**
+ * Download audio as WAV file
+ */
+export function downloadWAV(audioData: Float32Array, sampleRate: number, filename: string) {
+  const buffer = createWAVBuffer(audioData, sampleRate)
+  const blob = new Blob([buffer], { type: 'audio/wav' })
+  const url = URL.createObjectURL(blob)
+
+  const a = document.createElement('a')
+  a.href = url
+  a.download = filename
+  a.click()
+
+  URL.revokeObjectURL(url)
+}
+
+/**
+ * Play audio in browser
+ */
+export async function playAudio(audioData: Float32Array, sampleRate: number): Promise<void> {
+  const audioContext = new (window.AudioContext || (window as any).webkitAudioContext)()
+
+  if (audioContext.sampleRate !== sampleRate) {
+    console.warn(`Audio context sample rate (${audioContext.sampleRate}) differs from data sample rate (${sampleRate})`)
+  }
+
+  const buffer = audioContext.createBuffer(1, audioData.length, sampleRate)
+  buffer.copyToChannel(audioData, 0)
+
+  const source = audioContext.createBufferSource()
+  source.buffer = buffer
+  source.connect(audioContext.destination)
+  source.start()
+
+  return new Promise(resolve => {
+    source.onended = () => resolve()
+  })
+}