@minto-ai/huoshan-tts/src/process/ios/decode-data.ts

借助“火山引擎在线语音合成API”实现浏览器端“文本转语音

import type { ParallelTaskExecuteContext } from '../../handler'

import { ParallelHandler } from '../../handler'

class DecodeData extends ParallelHandler<string, AudioBuffer> {
  private audioContext: AudioContext = new AudioContext({
    sampleRate: 44100,
  })

  public execute(
    context: ParallelTaskExecuteContext<string, AudioBuffer>,
  ): void {
    if (context.isLastExecute) {
      this.taskCompletedCallback(context.taskItem.uuid)
      return
    }
    if (!context.taskItem.original) {
      this.taskCompletedCallback(context.taskItem.uuid)
      return
    }
    // 至少需要100个字节才能构成有效的音频数据
    if (atob(context.taskItem.original).length < 100) {
      this.taskCompletedCallback(context.taskItem.uuid)
      return
    }

    const base64Data = this.convertPCMToWAV(context.taskItem.original!, 24000, 1, 16)
    const arrayBuffer = this.base64ToArrayBuffer(base64Data)

    this.audioContext.decodeAudioData(arrayBuffer, (audioData) => {
      this.forwardToHandler(audioData)
      this.taskCompletedCallback(context.taskItem.uuid)
    })
  }

  /**
   * 创建WAV文件头
   * @param  sampleRate - 采样率
   * @param  numChannels - 声道数
   * @param  bitsPerSample - 位深度
   * @param  dataLength - PCM数据长度
   * @returns {ArrayBuffer} WAV文件头
   */
  createWAVHeader(sampleRate: number, numChannels: number, bitsPerSample: number, dataLength: number): ArrayBuffer {
    const buffer = new ArrayBuffer(44)
    const view = new DataView(buffer)

    // RIFF标识符
    view.setUint32(0, 0x52494646, false) // "RIFF"
    // 文件大小
    view.setUint32(4, 36 + dataLength, true)
    // WAVE标识符
    view.setUint32(8, 0x57415645, false) // "WAVE"

    // fmt子块
    view.setUint32(12, 0x666D7420, false) // "fmt "
    // fmt子块大小
    view.setUint32(16, 16, true)
    // 音频格式（PCM = 1）
    view.setUint16(20, 1, true)
    // 声道数
    view.setUint16(22, numChannels, true)
    // 采样率
    view.setUint32(24, sampleRate, true)
    // 字节率
    view.setUint32(28, sampleRate * numChannels * bitsPerSample / 8, true)
    // 块对齐
    view.setUint16(32, numChannels * bitsPerSample / 8, true)
    // 位深度
    view.setUint16(34, bitsPerSample, true)

    // data子块
    view.setUint32(36, 0x64617461, false) // "data"
    // 数据大小
    view.setUint32(40, dataLength, true)

    return buffer
  }

  /**
   * 将原始PCM数据转换为完整的WAV格式
   * @param  base64PCMData - Base64编码的PCM数据
   * @param  sampleRate - 采样率（默认16000）
   * @param  numChannels - 声道数（默认1）
   * @param  bitsPerSample - 位深度（默认16）
   * @returns  Base64编码的WAV数据
   */
  convertPCMToWAV(base64PCMData: string, sampleRate: number = 24000, numChannels: number = 1, bitsPerSample: number = 16): string {
    try {
      // 解码Base64 PCM数据
      const binaryString = atob(base64PCMData)
      const pcmData = new Uint8Array(binaryString.length)
      for (let i = 0; i < binaryString.length; i++) {
        pcmData[i] = binaryString.charCodeAt(i)
      }

      // 创建WAV文件头
      const wavHeader = this.createWAVHeader(sampleRate, numChannels, bitsPerSample, pcmData.length)

      // 合并文件头和PCM数据
      const wavData = new Uint8Array(wavHeader.byteLength + pcmData.length)
      wavData.set(new Uint8Array(wavHeader), 0)
      wavData.set(pcmData, wavHeader.byteLength)

      // 转换为Base64
      let binaryStr = ''
      for (let i = 0; i < wavData.length; i++) {
        binaryStr += String.fromCharCode(wavData[i])
      }

      return btoa(binaryStr)
    }
    catch (error) {
      console.error('PCM转WAV失败:', error)
      throw error
    }
  }

  /**
   * 将Base64编码的WAV数据转换为ArrayBuffer
   * @param  base64Data - Base64编码的WAV数据
   * @returns  转换后的ArrayBuffer
   */
  base64ToArrayBuffer(base64Data: string): ArrayBuffer {
    const binaryString = atob(base64Data)
    const bytes = new Uint8Array(binaryString.length)
    for (let i = 0; i < binaryString.length; i++) {
      bytes[i] = binaryString.charCodeAt(i)
    }
    return bytes.buffer
  }

  protected onFinish(): void {
    if (this.audioContext) {
      this.audioContext.suspend()
      this.audioContext = new AudioContext()
    }
    this.executeController?.$bus.emit('_decodeDataFinish')
  }
}

export default DecodeData