Question

我正在构建一个应用程序，用户可以在其中查看成绩单以及播放音频。而且他随时可以选择转录的一部分并生成音频文件（可能是wav或mp3），然后让他下载或保存到服务器。

我正在像这样计算字节缓冲区并将其发送到服务器并保存为.wav文件，但它没有播放任何内容：

var getMsFromSecs = function (sel) {
  var from = sel.baseNode.parentElement.getAttribute('starttime').split('.');
  var to = sel.focusNode.parentElement.getAttribute('endtime').split('.');
  return {
    from : Number(from[0]) * 1000 + Number(from[1]),
    to : Number(to[0]) * 1000 + Number(to[1])
  }
};

var trimAudio = function () {
  var sel=window.getSelection();
  if (!sel.baseNode.parentElement.getAttribute('starttime')) {
    alert('Please select a text range and try again');
    return;
  }
  $('#shareArea').val('Please Wait...');
  var timesObj = getMsFromSecs(sel);
  var fromTimeInMs = timesObj.from;
  var toTimeInMs = timesObj.to;
  var totalTimeInMs = audio.duration * 1000;
  var totalBufferSize = audioBuffer.byteLength;
  var bytesPerMs = totalBufferSize/totalTimeInMs;
  var u8a = new Uint8Array(audioBuffer);
  var selDurationBytes = u8a.subarray(bytesPerMs * fromTimeInMs, bytesPerMs * toTimeInMs);
  var xhr = new XMLHttpRequest();
  xhr.open('POST', './trimAudioFile');
  xhr.setRequestHeader('Content-Type', 'application/octet-stream');
  xhr.send(selDurationBytes);
  xhr.onload = function (res) {
    $('#shareArea').val(res);
  }
};

和服务器端：

app.use(bodyParser.raw({type: '/trimAudioFile'}));
var body, i = 0;
router.post('/trimAudioFile', async (req, res, next) => {
  if (!body) {
    i = 0;
    body = new Buffer(parseInt(req.headers['content-length']));
    console.log('bodylength ', body.length);
  }
  req.on('data', function(data) {
      var tempBuffer = new Buffer(data);
      for (var j = 0; j < data.length; j++) {
        body[i++] = tempBuffer[j];
      }
  });
  req.on('end', function () {
        fs.appendFile('test.wav', body, function() {
          body = null;
            res.end();
        });
    });
});

添加适当的元数据后更新代码：

var audioArray = new Uint8Array(audioBuffer);
var partFileLength = Math.floor((bytesPerMs * toTimeInMs) - (bytesPerMs * fromTimeInMs));
var u8a = new Uint8Array(44 + partFileLength);
for (var idx = 0, idxx = Math.floor(bytesPerMs * fromTimeInMs); idx < partFileLength + 44; idx++) {
  if (idx < 44) {
    if (idx > 3 && idx < 8) {
      var fileSize = u8a.byteLength - 8;
      u8a[idx] = (fileSize>>0)&0xFF;
      u8a[idx + 1] = (fileSize>>8)&0xFF;
      u8a[idx + 2] = (fileSize>>16)&0xFF;
      u8a[idx + 3] = (fileSize>>24)&0xFF;
      idx = idx + 4;
    } else if (idx > 39 && idx < 44) {
      var fileData = u8a.byteLength - 44;
      u8a[idx] = (fileData>>0)&0xFF;
      u8a[idx + 1] = (fileData>>8)&0xFF;
      u8a[idx + 2] = (fileData>>16)&0xFF;
      u8a[idx + 3] = (fileData>>24)&0xFF;
      idx = idx + 4;
    } else {
      u8a[idx] = audioArray[idx];
    }          
  } else {
    u8a[idx] = audioArray[idxx++];
  }
}

如何从字节数组创建音频WAV文件

0 个答案: