Getting a SharpDX XAudio2 custom XAPO working in Windows 8 app

Question

I'm using SharpDX and XAudio2 in a Windows Store app. I'm trying to create a custom XAPO and I can't even get started.

OnNavigatedTo method for the app:

protected override void OnNavigatedTo(NavigationEventArgs e)
{
  XAudio2 engine = new XAudio2();
  MasteringVoice master = new MasteringVoice(engine);
  NativeFileStream fileStream = new NativeFileStream(@"Assets\sample.wav", NativeFileMode.Open, NativeFileAccess.Read);
  SoundStream soundStream = new SoundStream(fileStream);
  SourceVoice source = new SourceVoice(engine, soundStream.Format);
  AudioBuffer audioBuffer =  new AudioBuffer()
  {
    Stream = soundStream.ToDataStream(),
    AudioBytes = (int)soundStream.Length,
    Flags = SharpDX.XAudio2.BufferFlags.EndOfStream
  };

  EmptyEffect customEffect = new EmptyEffect();
  EffectDescriptor effectDescriptor = new EffectDescriptor(customEffect);
  source.SetEffectChain(effectDescriptor);
  source.EnableEffect(0);

  source.SubmitSourceBuffer(audioBuffer, soundStream.DecodedPacketsInfo);
  source.Start();
}

Empty Custom XAPO:

[StructLayout(LayoutKind.Sequential)]
public struct ModulatorParam
{
}

public class EmptyEffect : AudioProcessorBase<ModulatorParam>
{
  public EmptyEffect()
  {
    RegistrationProperties = new RegistrationProperties()
    {
      Clsid = Utilities.GetGuidFromType(typeof(EmptyEffect)),
      CopyrightInfo = "Copyright",
      FriendlyName = "Modulator",
      MaxInputBufferCount = 1,
      MaxOutputBufferCount = 1,
      MinInputBufferCount = 1,
      MinOutputBufferCount = 1,
      Flags = PropertyFlags.Default
    };
  }

public override void Process(BufferParameters[] inputProcessParameters, BufferParameters[] outputProcessParameters, bool isEnabled)
  {
  }
}

If I remove the line to enable the effect then the empty process method never runs. If I keep it in, the following useless error occurs:

Answer 1

This turned out to be an issue with the SharpDX implementation. See Issue 272 on the SharpDX Google Code page:

Issue: The errors are preventing both Effects and SubMixVoices not to work.

File: Voice.cs

Cause: The EffectChain // SendList always gets resetet after being set by the function call. Both cases caused by missing else surrounding the following lines:

SetOutputVoices((VoiceSendDescriptors?)null); in function SetOutputVoices

and

SetEffectChain((EffectChain?)null); in function SetEffectChain

Solved by downloading the latest source that includes this fix and building the binaries from scratch.