C# 在C语言中，说话人二值化总是返回0和长音频#

我目前正在使用c#的谷歌云语音到文本SDK。我使用的nuget包是Google.Cloud.Speech.V1P1Beta1。我试图从较长视频的语音日记中获益，但无论音频中有多少扬声器，所有单词的扬声器标记中始终返回0。下面是我的代码

var longOperation = speech.LongRunningRecognize(new RecognitionConfig()
               {
                   Encoding = RecognitionConfig.Types.AudioEncoding.Linear16,
                   DiarizationSpeakerCount = 2,
                   EnableSpeakerDiarization = true,
                   SampleRateHertz = 16000,
                   LanguageCode = "en",
               }, RecognitionAudio.FromFile("testRecording.wav"));

               longOperation = longOperation.PollUntilCompleted();
               var response = longOperation.Result;
               Console.WriteLine("Response received successfully.");

               foreach (var result in response.Results)
               {
                   foreach (var alternative in result.Alternatives)
                   {
                       foreach (var word in alternative.Words)
                       {
                           Console.WriteLine($"{word.Word}: {word.SpeakerTag}");
                       }
                   }
               }