async Task<object> Start(int seconds)
    {
    	if (NAudio.Wave.WaveIn.DeviceCount < 1) { MessageBox.Show("No microphone!"); return -1; }

    	var streamingCall = SpeechClient.Create().StreamingRecognize();
    	await streamingCall.WriteAsync(
    		new StreamingRecognizeRequest()
    		{
    			StreamingConfig = new StreamingRecognitionConfig()
    			{
    				Config = new RecognitionConfig()
    				{
    					Encoding = RecognitionConfig.Types.AudioEncoding.Linear16,
    					MaxAlternatives = 1,
    					SampleRateHertz = 16000,
    					LanguageCode = "en-US",
    			},
    				InterimResults = true,
    				SingleUtterance = false
    			}
    		}
    	);

    	// Print responses as they arrive
    	Task prinResp = Task.Run(async () =>
    	{
    		while (await streamingCall.ResponseStream.MoveNext(default(CancellationToken)))
    		{
    			foreach (var result in streamingCall.ResponseStream.Current.Results)
    			{
    				MessageBox.Show(result.Alternatives[0].Transcript.ToString());
    			}
    		}
    	});

    	// Read from the microphone and stream to API.
    	object writeLock = new object();
    	bool writeMore = true;
    	var waveIn = new NAudio.Wave.WaveInEvent();
    	waveIn.DeviceNumber = 0;
    	waveIn.WaveFormat = new NAudio.Wave.WaveFormat(16000, 1);
    	waveIn.DataAvailable +=
    	  (object sender, NAudio.Wave.WaveInEventArgs args) =>
    	  {
    		lock (writeLock)
    		{
    		  if (!writeMore) return;
    		  streamingCall.WriteAsync( new StreamingRecognizeRequest() { AudioContent = Google.Protobuf.ByteString.CopyFrom(args.Buffer, 0, args.BytesRecorded) }).Wait();
    		}
    	  };
    	waveIn.StartRecording();
    	MessageBox.Show("Speak now.");
    	await Task.Delay(TimeSpan.FromSeconds(seconds));
    	waveIn.StopRecording();
    	lock (writeLock) writeMore = false;
    	await streamingCall.WriteCompleteAsync();
    	await prinResp; //wait before printout finished
    	return 0;
    }