我在unity中使用C#发送API请求识别语音转文字，使用了示例里的声音test.pcm结果输出为：

{"err_msg":"parameters error.","err_no":3300,"sn":""}

我多次对比了示例和文档都没有发现有哪个参数有错误，请知道的朋友指导一下，具体代码如下：

public IEnumerator SpeechRecognitionFunction(string wavStream)

{

WWWForm form = new WWWForm();

form.AddField("format", "pcm");

form.AddField("rate", 8000);

form.AddField("channel", "1");

form.AddField("token", access_token);

form.AddField("cuid", "Baidu_VrWorld12344");

form.AddField("lan", "zh");  // 选择语言 zh中文 ct粤语 en 英文

var filepath = Path.Combine(Application.streamingAssetsPath, "SpeechRecognition/test.pcm");  

System.IO.FileStream fs = System.IO.File.OpenRead(filepath);//传文件的路径即可

System.IO.BinaryReader br = new System.IO.BinaryReader(fs);

byte[] bt = br.ReadBytes(System.Convert.ToInt32(fs.Length));

string base64String = System.Convert.ToBase64String(bt);

form.headers["Content-Type"] = "application/json";

form.AddField("len", (int)fs.Length);

form.AddField("speech", base64String);

Dictionary dict = new Dictionary ();

WWW www = new WWW(serverURL, form);

yield return www;

fWaitProgress = www.progress;

br.Close();

fs.Close();

if (www.error != null)

{

//POST请求失败  

strResult = "error :" + www.error;

}

else

{

//POST请求成功  

speechTxt = www.text;

print ("~speechTxt:"+speechTxt);

}

}