尝试在C#中使用Google Speech2Text

下面的简单代码试图将波形文件发布到Google Speech2Text服务，但总是失败，出现"网关超时（504）"或一般异常"操作超时"。有人能帮忙吗？

  public void ProcessWaveFile(string path)
    {
        HttpWebRequest request = 
             (HttpWebRequest)HttpWebRequest.Create(
                 "https://www.google.com/"+ 
                 "speech-api/v1/recognize?"+ 
                 "xjerr=1&client=speech2text&lang=en-US&maxresults=10");
        ServicePointManager.ServerCertificateValidationCallback += 
                     delegate { return true; };
        request.Timeout = 60000;
        request.Method = "POST";
        request.KeepAlive = true;           
        request.ContentType = "audio/wav";
        request.UserAgent = "speech2text";
        FileInfo fInfo = new FileInfo(path);
        long numBytes = fInfo.Length;
        byte[] data;
        using (FileStream fStream = new FileStream(
                                          path, 
                                          FileMode.Open, 
                                          FileAccess.Read))
        {
            data = new byte[fStream.Length];
            fStream.Read(data, 0, (int)fStream.Length);
            fStream.Close();
        }
        using (Stream wrStream = request.GetRequestStream())
            wrStream.Write(data, 0, data.Length);
        try
        {
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            var resp = response.GetResponseStream();
            if (resp != null)
            {
                StreamReader sr = new StreamReader(resp);
                MessageBox.Show(sr.ReadToEnd());
                resp.Close();
                resp.Dispose();
            }
        }
        catch (System.Exception ee)
        {
            MessageBox.Show(ee.Message);
        }           
    }

非常感谢。

Shujaat

Request.ContentType = "audio/x-flac; rate=8000";