BYW-VoiceHub/app/workers/audioEncoderWorker.js

import { createMp3Encoder } from 'wasm-media-encoders'

const clamp = (value, min, max) => Math.max(min, Math.min(max, value))

const normalizeStereo = (left, right, targetDb) => {
  const targetGain = Math.pow(10, targetDb / 20)
  let maxPeak = 0
  for (let i = 0; i < left.length; i++) {
    const l = Math.abs(left[i])
    const r = Math.abs(right[i])
    if (l > maxPeak) maxPeak = l
    if (r > maxPeak) maxPeak = r
  }
  if (maxPeak === 0) return
  const gain = targetGain / maxPeak
  for (let i = 0; i < left.length; i++) {
    left[i] *= gain
    right[i] *= gain
  }
}

const resampleLinear = (source, sourceRate, targetRate) => {
  if (sourceRate === targetRate) return source
  const ratio = targetRate / sourceRate
  const targetLength = Math.max(1, Math.floor(source.length * ratio))
  const output = new Float32Array(targetLength)
  for (let i = 0; i < targetLength; i++) {
    const origin = i / ratio
    const left = Math.floor(origin)
    const right = Math.min(source.length - 1, left + 1)
    const weight = origin - left
    output[i] = source[left] * (1 - weight) + source[right] * weight
  }
  return output
}

const interleave = (left, right) => {
  const result = new Float32Array(left.length + right.length)
  let index = 0
  for (let i = 0; i < left.length; i++) {
    result[index++] = left[i]
    result[index++] = right[i]
  }
  return result
}

const writeString = (view, offset, text) => {
  for (let i = 0; i < text.length; i++) {
    view.setUint8(offset + i, text.charCodeAt(i))
  }
}

const floatTo16BitPCM = (view, offset, input) => {
  for (let i = 0; i < input.length; i++, offset += 2) {
    const s = clamp(input[i], -1, 1)
    view.setInt16(offset, s < 0 ? s * 0x8000 : s * 0x7fff, true)
  }
}

const encodeWavBlob = (left, right, sampleRate) => {
  const interleaved = interleave(left, right)
  const numChannels = 2
  const bitDepth = 16
  const bytesPerSample = bitDepth / 8
  const blockAlign = numChannels * bytesPerSample
  const buffer = new ArrayBuffer(44 + interleaved.length * bytesPerSample)
  const view = new DataView(buffer)
  writeString(view, 0, 'RIFF')
  view.setUint32(4, 36 + interleaved.length * bytesPerSample, true)
  writeString(view, 8, 'WAVE')
  writeString(view, 12, 'fmt ')
  view.setUint32(16, 16, true)
  view.setUint16(20, 1, true)
  view.setUint16(22, numChannels, true)
  view.setUint32(24, sampleRate, true)
  view.setUint32(28, sampleRate * blockAlign, true)
  view.setUint16(32, blockAlign, true)
  view.setUint16(34, bitDepth, true)
  writeString(view, 36, 'data')
  view.setUint32(40, interleaved.length * bytesPerSample, true)
  floatTo16BitPCM(view, 44, interleaved)
  return new Blob([view], { type: 'audio/wav' })
}

const encodeMp3Blob = async (left, right, sampleRate) => {
  const encoder = await createMp3Encoder()
  encoder.configure({
    sampleRate,
    channels: 2,
    bitrate: 192,
    outputSampleRate: sampleRate
  })
  const chunkSize = sampleRate * 2
  let processed = 0
  const total = left.length
  const chunks = []
  while (processed < total) {
    const end = Math.min(processed + chunkSize, total)
    const leftChunk = left.subarray(processed, end)
    const rightChunk = right.subarray(processed, end)
    const chunk = encoder.encode([leftChunk, rightChunk])
    if (chunk.length > 0) {
      const copy = new Uint8Array(chunk.length)
      copy.set(chunk)
      chunks.push(copy)
    }
    processed = end
    postMessage({
      type: 'progress',
      stage: 'encode',
      value: Math.round((processed / total) * 100)
    })
  }
  const finalized = encoder.finalize()
  if (finalized.length > 0) {
    const copy = new Uint8Array(finalized.length)
    copy.set(finalized)
    chunks.push(copy)
  }
  return new Blob(chunks, { type: 'audio/mp3' })
}

self.onmessage = async (event) => {
  const payload = event.data
  if (payload?.cmd !== 'encode' || !payload.tracks?.length) return
  try {
    let baseSampleRate = Math.max(...payload.tracks.map((track) => track.sampleRate))
    if (payload.format === 'mp3' && baseSampleRate > 48000) {
      baseSampleRate = 48000
    }
    const normalizedTracks = payload.tracks.map((track, index) => {
      let left = new Float32Array(track.left)
      let right = new Float32Array(track.right)
      if (payload.normalize) {
        normalizeStereo(left, right, payload.targetDb)
      }
      if (track.sampleRate !== baseSampleRate) {
        left = resampleLinear(left, track.sampleRate, baseSampleRate)
        right = resampleLinear(right, track.sampleRate, baseSampleRate)
      }
      postMessage({
        type: 'progress',
        stage: 'prepare',
        value: Math.round(((index + 1) / payload.tracks.length) * 100)
      })
      return {
        left,
        right
      }
    })
    const totalLength = normalizedTracks.reduce((sum, item) => sum + item.left.length, 0)
    const mergedLeft = new Float32Array(totalLength)
    const mergedRight = new Float32Array(totalLength)
    let offset = 0
    for (let i = 0; i < normalizedTracks.length; i++) {
      const item = normalizedTracks[i]
      mergedLeft.set(item.left, offset)
      mergedRight.set(item.right, offset)
      offset += item.left.length
      postMessage({
        type: 'progress',
        stage: 'merge',
        value: Math.round(((i + 1) / normalizedTracks.length) * 100)
      })
    }
    let blob
    if (payload.format === 'wav') {
      postMessage({
        type: 'progress',
        stage: 'encode',
        value: 20
      })
      blob = encodeWavBlob(mergedLeft, mergedRight, baseSampleRate)
      postMessage({
        type: 'progress',
        stage: 'encode',
        value: 100
      })
    } else {
      blob = await encodeMp3Blob(mergedLeft, mergedRight, baseSampleRate)
    }
    postMessage({
      type: 'done',
      blob,
      sampleRate: baseSampleRate
    })
  } catch (error) {
    postMessage({
      type: 'error',
      message: error?.message || '编码失败'
    })
  }
}