Using OleCreatePropertyFrame to set/inspect webcam capture pin properties - winapi

Question

I am trying to use OleCreatePropertyFrame() to set the WebCam properties on the filter Capture pin (controls frame rate, etc). The amcap program released by Microsoft does this.
The amcap program builds a filter graph, and then uses:
hr = gcap.pBuilder->FindInterface(&PIN_CATEGORY_CAPTURE,
&MEDIATYPE_Interleaved, gcap.pVCap,
IID_IAMVideoCompression, (void **)&gcap.pVC);
To find the interface for which to extract the property pages.
I want to get it work by directly finding the capture pin on the filter.
https://learn.microsoft.com/en-us/windows/win32/api/strmif/nn-strmif-iamstreamconfig
seems to imply this should work.
In the following code, the call to OleCreatePropertyFrame() segment faults.
I can't tell why ..
Is this approach just not going to work?
//==========================================================================
// first find the cam filter
// this parts works
// I can use pSrc to look at the filter property pages using OleCreatePropertyFrame()
//==========================================================================
IBaseFilter *pSrc = NULL;
HRESULT hr = S_OK;
IMoniker* pMoniker =NULL;
ICreateDevEnum *pDevEnum =NULL;
IEnumMoniker *pClassEnum = NULL;
hr = CoCreateInstance (CLSID_SystemDeviceEnum, NULL, CLSCTX_INPROC,
IID_ICreateDevEnum, (void **) &pDevEnum);
my_assert(!FAILED(hr),"");
hr = pDevEnum->CreateClassEnumerator (CLSID_VideoInputDeviceCategory, &pClassEnum, 0);
my_assert(!FAILED(hr) && pClassEnum!=NULL,"");
hr = pClassEnum->Next (1, &pMoniker, NULL); // pick first device
my_assert(!FAILED(hr),"");
hr = pMoniker->BindToObject(0,0,IID_IBaseFilter, (void**)&pSrc);
my_assert(!FAILED(hr),"");
SAFE_RELEASE(pMoniker);
SAFE_RELEASE(pDevEnum);
SAFE_RELEASE(pClassEnum);
//=======================================================
// now find the interface on the capture pin
// no assertions trigger, I believe I find the capture pin correctly
// It seems like I find the capture pin property pages correctly as well
// However, it segfaults when I call OleCreatePropertyFrame()
//==================================================================
ISpecifyPropertyPages *pProp = NULL;
IUnknown *pFilterUnk =NULL;
IAMStreamConfig *pConfig = NULL;
IEnumPins *pEnum = NULL;
IPin *pPin = NULL;
hr = pSrc->EnumPins(&pEnum);
my_assert(!FAILED(hr),"");
while(pEnum->Next(1, &pPin, 0) == S_OK){
IKsPropertySet *pKs = NULL;
hr = pPin->QueryInterface(IID_PPV_ARGS(&pKs));
my_assert(!FAILED(hr),"");
DWORD cbReturned = 0;
GUID myPinCategory;
hr = pKs->Get(AMPROPSETID_Pin, AMPROPERTY_PIN_CATEGORY, NULL, 0,
&myPinCategory, sizeof(GUID), &cbReturned);
my_assert(!FAILED(hr),"");
SAFE_RELEASE(pKs);
if (myPinCategory!=PIN_CATEGORY_CAPTURE){
pPin->Release();
continue;
}
//IAMStreamConfig *pConfig = NULL;
hr = pPin->QueryInterface(IID_PPV_ARGS(&pConfig));
my_assert(!FAILED(hr),"could not find stream config interface");
hr = pConfig->QueryInterface(IID_ISpecifyPropertyPages, (void **)&pProp);
my_assert(SUCCEEDED(hr),"");
pFilterUnk = (IUnknown *)pConfig;
pPin->Release();
break;
}
pEnum->Release();
if (pProp==NULL || pFilterUnk==NULL){
SAFE_RELEASE(pFilterUnk);
return("ERROR: can not find capture pin");
}
CAUUID caGUID;
hr = pProp->GetPages(&caGUID);
my_assert(SUCCEEDED(hr),"");
HWND ghApp = (HWND)pc->winId();
OleCreatePropertyFrame(
ghApp, // Parent window
0, 0, // location on the screen
filterName,
1, // Number of objects (just the filter)
&pFilterUnk, // Array of object pointers.
caGUID.cElems, // Number of property pages
caGUID.pElems, // Array of property page CLSIDs
0, // Locale identifier
0, NULL // Reserved
);
If order to use OleCreatePropertyFrame on webcam capture pins, it seems like the webcam filter must be in graph. This ends up being pretty easy to do:
hr = CoCreateInstance(CLSID_CaptureGraphBuilder2, NULL,
CLSCTX_INPROC_SERVER,IID_ICaptureGraphBuilder2, (void**)&pBuilder);
my_assert(pBuilder!=NULL && !FAILED(hr),"");
hr = CoCreateInstance(CLSID_FilterGraph, NULL, CLSCTX_INPROC,
IID_IGraphBuilder, (void **)&pFg);
my_assert(pFg!=NULL && !FAILED(hr),"");
hr = pBuilder->SetFiltergraph(pFg);
my_assert(!FAILED(hr),"");
hr = pFg->AddFilter(pSrc, L"my-cam");
my_assert(!FAILED(hr),"");
hr = pBuilder->FindInterface(&PIN_CATEGORY_CAPTURE,
&MEDIATYPE_Video, pSrc,IID_IAMStreamConfig,
(void **)&pConfig);
my_assert(pConfig!=NULL && !FAILED(hr),"");