UWP: create custom effect in Win32

Does anyone know how to create a custom effect for a UWP media composition in a Win32 program?

struct MyEffect : implements<IBasicVideoEffect, IVideoEffectDefinition>
{
public:
   // all properties and methods from the interface are defined without
   // the virtual keyword. 

   winrt::hstring ActivatableClassId () { return winrt::hstring(L"MyEffect")}

   IPropertySet Properties (){
     PropertySet set;
     return set;
    }
};

void setupEffect()
{
  MyEffect effect; 

  mediaClip.VideoEffectDefinitions().Append(effect);
  mediaCompositon.addClip(mediaClip);
  mediaCompositon.renderToFile(file);
}

Microsoft provides a code example showing the way it should work in C#:

Custom video effects

When I try this setup, I got an exception:

WinRT originate error - 0x80040154 : 'Failed to activate video effect'.

I could imagine that I have some troubles with this approach in C++ because ActivatableClassId for the example does not exist, as well as the video effect registration process.

I also tried to add the IVideoEffectDefinition interface to my MyEffect class, and the effect to the VideoEffectDEfinition array. During the renderToFile call, I get another exception:

Access violation reading location 0x0000000000000000