sounds_demo/js/addWavHeader.js

/**
 * 将pcm音频添加头部信息转换为wav音频
 * @ date: 2019年10月17日
 * @ param ArrayBuffer samples Uint8Array || Uint16Array || Uint32Array
 * @ param int sampleRateTmp 采样率(8000 - ???)
 * @ param int sampleBits 采样精度(8 || 16 || 32)和samples对应
 * @ param int channelCount 声道(单声道1，双声道2)
 * @ return: ArrayBuffer
 */
function addWavHeader(samples, sampleRateTmp, sampleBits, channelCount){
  var dataLength = samples.byteLength;
  var buffer = new ArrayBuffer(44 + dataLength);
  var view = new DataView(buffer);
  function writeString(view, offset, string) {
    for (var i = 0; i < string.length; i++) {
      view.setUint8(offset + i, string.charCodeAt(i));
    }
  }
  var offset = 0;
  /* 资源交换文件标识符 */
  writeString(view, offset, 'RIFF'); offset += 4;
  /* 下个地址开始到文件尾总字节数,即文件大小-8 */
  view.setUint32(offset, /*32*/ 36 + dataLength, true); offset += 4;
  /* WAV文件标志 */
  writeString(view, offset, 'WAVE'); offset += 4;
  /* 波形格式标志 */
  writeString(view, offset, 'fmt '); offset += 4;
  /* 过滤字节,一般为 0x10 = 16 */
  view.setUint32(offset, 16, true); offset += 4;
  /* 格式类别 (PCM形式采样数据) */
  view.setUint16(offset, 1, true); offset += 2;
  /* 通道数 */
  view.setUint16(offset, channelCount, true); offset += 2;
  /* 采样率,每秒样本数,表示每个通道的播放速度 */
  view.setUint32(offset, sampleRateTmp, true); offset += 4;
  /* 波形数据传输率 (每秒平均字节数) 通道数×每秒数据位数×每样本数据位/8 */
  view.setUint32(offset, sampleRateTmp * channelCount * (sampleBits / 8), true); offset += 4;
  /* 快数据调整数 采样一次占用字节数 通道数×每样本的数据位数/8 */
  view.setUint16(offset, channelCount * (sampleBits / 8), true); offset += 2;
  /* 每样本数据位数 */
  view.setUint16(offset, sampleBits, true); offset += 2;
  /* 数据标识符 */
  writeString(view, offset, 'data'); offset += 4;
  /* 采样数据总数,即数据总大小-44 */
  
  view.setUint32(offset, dataLength, true); offset += 4;
  function floatTo32BitPCM(output, offset, input) {
    input = new Int32Array(input);
    for (var i = 0; i < input.length; i++, offset += 4) {
      // output.setFloat32(offset, (input[i]), true);
      output.setInt32(offset, input[i], true);
    }
  }
  function floatTo16BitPCM(output, offset, input) {
    input = new Int16Array(input);
    for (var i = 0; i < input.length; i++, offset += 2) {
      output.setInt16(offset, (input[i]), true);
    }
  }
  function floatTo8BitPCM(output, offset, input) {
    input = new Int8Array(input);
    for (var i = 0; i < input.length; i++, offset++) {
      output.setInt8(offset, input[i], true);
    }
  }
  if (sampleBits == 16) {
    floatTo16BitPCM(view, 44, samples);
  } else if (sampleBits == 8) {
    floatTo8BitPCM(view, 44, samples);
  } else {
    floatTo32BitPCM(view, 44, samples);
  }
  return view.buffer;
}