@minto-ai/xunfei-tts/src/worker/transcode-worker.ts

借助“讯飞在线语音合成API”实现浏览器端“文本转语音

import type { TranscodeWorkerReplyWorkerMessage, TranscodeWorkerSendWorkerData, TranscodeWorkerSendWorkerMessage } from './index'

function base64ToS16(base64AudioData: string): Int16Array {
  base64AudioData = atob(base64AudioData)
  const outputArray = new Uint8Array(base64AudioData.length)
  for (let i = 0; i < base64AudioData.length; i += 1) {
    outputArray[i] = base64AudioData.charCodeAt(i)
  }
  return new Int16Array(new DataView(outputArray.buffer).buffer)
}

function transS16ToF32(input: Int16Array): Float32Array {
  const tmpData = []
  for (let i = 0; i < input.length; i += 1) {
    const d = input[i] < 0 ? input[i] / 0x8000 : input[i] / 0x7FFF
    tmpData.push(d)
  }
  return new Float32Array(tmpData)
}

function transSamplingRate(data: Float32Array, fromRate: number = 44100, toRate: number = 16000): Float32Array {
  const fitCount = Math.round(data.length * (toRate / fromRate))
  const newData = new Float32Array(fitCount)
  const springFactor = (data.length - 1) / (fitCount - 1)
  newData[0] = data[0]
  for (let i = 1; i < fitCount - 1; i += 1) {
    const tmp = i * springFactor
    const before = Math.floor(tmp).toFixed() as unknown as number
    const after = Math.ceil(tmp).toFixed() as unknown as number
    const atPoint = tmp - Number(before)
    newData[i] = data[before] + (data[after] - data[before]) * atPoint
  }

  newData[fitCount - 1] = data[data.length - 1]
  return newData
}

function transToAudioData(data: TranscodeWorkerSendWorkerData, fromRate: number = 16000, toRate: number = 22505): void {
  const audioDataStr = data.original as string
  const outputS16 = base64ToS16(audioDataStr)
  let output: any = transS16ToF32(outputS16)
  output = transSamplingRate(output, fromRate, toRate)
  output = Array.from(output)

  globalThis.postMessage({
    type: 'success',
    data: {
      audioData: output,
      rawAudioData: Array.from(outputS16),
      uuid: data.uuid,
    },
  } as TranscodeWorkerReplyWorkerMessage)
}

function handleRun(data: TranscodeWorkerSendWorkerData): void {
  transToAudioData(data)
}

globalThis.addEventListener('message', (event: MessageEvent<TranscodeWorkerSendWorkerMessage>) => {
  const { type, data } = event.data
  if (type === 'send') {
    handleRun(data!)
  }
})