NAudio waveout stops after half 1 second

Question

Hey im using NAudio to playback SpeechSynthesizer with some strange result.

There are to different outputs the first works perfect the second is exactly the same just with an other input text but the playback stops after half 1 second and the PlaybackState never leave PlaybackState.Playing. This  happens also if both inputs are the same.

 

but lets have a look at my code:

 

 

waveOut = new WaveOut();
if (SayText == "")
{
   MemoryStream stream = new MemoryStream();
   try
   {
      IWaveProvider provider = null;
      using (var synth = new SpeechSynthesizer())
      {
         synth.SetOutputToAudioStream(stream,
         new SpeechAudioFormatInfo(44100, AudioBitsPerSample.Sixteen, AudioChannel.Stereo));
         lock (textoutput)
         {
            synth.Speak(textoutput);  // Example: textoutput = Hallo
         }
         stream.Seek(0, SeekOrigin.Begin);
         provider = new RawSourceWaveStream(stream, new WaveFormat(44100, 16, 2));
      }
      waveOut.DeviceNumber = getDevices("tts");  // getDevices returns 1
      waveOut.Init(provider);
      waveOut.Play();
      do  {}
      while (waveOut.PlaybackState == PlaybackState.Playing);
      waveOut.Dispose();
   }
   catch (System.Exception e)
   {
      MessageBox.Show("Error playing sound: " + e.Message);
   }
}
else
{
   MemoryStream stream = new MemoryStream();
   try
   {
      IWaveProvider provider = null;
      using (var synth = new SpeechSynthesizer())
      {
         synth.SetOutputToAudioStream(stream,
         new SpeechAudioFormatInfo(44100, AudioBitsPerSample.Sixteen, AudioChannel.Mono));
         lock (SayText)
         {
         synth.Speak(SayText);  // Example: SayText = Hallo
         }
         stream.Seek(0, SeekOrigin.Begin);
         provider = new RawSourceWaveStream(stream, new WaveFormat(44100, 16, 1));
      }
      waveOut.DeviceNumber = getDevices("say");  // getDevices returns 1
      waveOut.Init(provider);
      waveOut.Play();  // after that step the waveout stops directly and the following loop never ends because waveOut.PlaybackState is always Playing
      do  {}
      while (waveOut.PlaybackState == PlaybackState.Playing);
      waveOut.Dispose();
      }
      catch (System.Exception e)
      {
         MessageBox.Show("Error playing sound: " + e.Message);
      }
      SayText = "";
}