Using a custom DirectShow filter (DLL, registered)

I've written a small transform filter (derived from TransInPlaceFilter baseclass), and managed to make it work properly in a Directshow graph, entirely coded in C++. I basically followed the 5 first steps described on MSDN, and the last part of the 6th step (in order to use the filter directly within an application).

For a lot of reasons (including being able to use the filter in GraphEdit), I need to export that filter in a DLL and register it.

I've been trying to follow these steps : setting up the "CreateInstance" method, the CFactoryTemplate class, filter/pins description (AMOVIESETUP_FILTER, AMOVIESETUP_PIN, AMOVIESETUP_MEDIA), Registering/Unregistering functions, and finally DLLmain/entrypoint.

The code successfully compiles and provides a DLL, which seems to register without any problem using Regsvr32.

But then I'm unable to use the filter :

• It appears in the list in GraphEdit, but fails when I try to insert it : 0x800401f9 ("Error in DLL").
• When I try to create it in C++ (using pCustomFilter.CoCreateInstance(CLSID_Custom), after defining the correct GUID), I get error 0x80040154 (REGDB_E_CLASSNOTREG)

I'm quite confused here. Have I missed something in the DLL/registration code ? I'm posting most of the code I'm using, if it's of any use.

Any help would be greatly appreciated.

static const WCHAR g_wszName[] = L"Custom Filter";

AMOVIESETUP_MEDIATYPE sudMediaTypes[] = {
    { &MEDIATYPE_Video, &MEDIASUBTYPE_NULL },
    { &MEDIATYPE_Audio, &MEDIASUBTYPE_NULL },
};

AMOVIESETUP_PIN sudPins[2] = {
    {
        L"Input",            // Name
        FALSE,          // Is this pin rendered?
        FALSE,          // Is it an output pin?
        FALSE,          // Can the filter create zero instances?
        FALSE,          // Does the filter create multiple instances?
        &GUID_NULL,     // Obsolete.
        NULL,           // Obsolete.
        2,              // Number of media types.
        sudMediaTypes   // Pointer to media types.
    },
    {
        L"Output",            // Name
        FALSE,          // Is this pin rendered?
        TRUE,           // Is it an output pin?
        FALSE,          // Can the filter create zero instances?
        FALSE,          // Does the filter create multiple instances?
        &GUID_NULL,     // Obsolete.
        NULL,           // Obsolete.
        2,              // Number of media types.
        sudMediaTypes   // Pointer to media types.
    }
};

AMOVIESETUP_FILTER sudFilterReg = {
    &CLSID_Custom,          // Filter CLSID.
    g_wszName,              // Filter name.
    MERIT_DO_NOT_USE,       // Merit.
    2,                      // Number of pin types.
    sudPins             // Pointer to pin information.
};


CFactoryTemplate g_Templates[] = 
{
  { 
    g_wszName,
    &CLSID_Custom,
    CCustomFilter::CreateInstance,
    NULL,
    &sudFilterReg
  }
};

int g_cTemplates = sizeof(g_Templates) / sizeof(g_Templates[0]);

STDAPI DllRegisterServer()
{
    return AMovieDllRegisterServer2( TRUE );
}
STDAPI DllUnregisterServer()
{
    return AMovieDllRegisterServer2( FALSE );
}


extern "C" BOOL WINAPI DllEntryPoint(HINSTANCE, ULONG, LPVOID);

BOOL WINAPI DllMain(HANDLE hDllHandle, DWORD dwReason, LPVOID lpReserved)
{
    return DllEntryPoint(reinterpret_cast<HINSTANCE>(hDllHandle), dwReason, lpReserved);
}

// ---
// Meanwhile, in my filter class...
// ---
CUnknown * WINAPI CCustomFilter::CreateInstance(LPUNKNOWN pUnk, HRESULT *pHr)
{
    CCustomFilter *pFilter = new CCustomFilter();
    if (pFilter== NULL) 
    {
        *pHr = E_OUTOFMEMORY;
    }
    return pFilter;
}

Problem solved. It was actually two things :

1. Directly debugging the DLL (somthing I hadn't thought of...), more specifically the CoCreateInstance function, helped me notice an issue with string macros. The constructor for TransInPlaceFilter was called with a bad argument, which caused the crash.

2. Someone made me notice I wasn't exporting every required function (as described here on MSDN). My .def file was lacking DllMain, DllGetClassObject and DllCanUnloadNow. Those 2 last functions just need to appear in the def, as they are already defined in the baseclasses library.

LIBRARY "custom_filter"
EXPORTS
    DllMain                 PRIVATE /* missing */
    DllGetClassObject       PRIVATE /* missing */
    DllCanUnloadNow         PRIVATE /* missing */
    DllRegisterServer       PRIVATE
    DllUnregisterServer     PRIVATE

Thanks a lot for your help !