Previewing Webcam using DirectShow - c++

Question

I keep getting "E_INVALIDARG" when calling RenderStream().
My program output is:
SUCCESS - Initialized COM library.
SUCCESS - Created the Filter Graph Manager.
SUCCESS - Created the Media Control and Media Event Interfaces.
SUCCESS - Enumerated devices.
--------------DEVICE INFORMATION--------------
Integrated Webcam
------------END DEVICE INFORMATION------------
SUCCESS - Bound to moniker.
Here is the code:
#include "stdafx.h"
#include <dshow.h> //direct show
#include <windows.h> //windows
#pragma comment(lib,"Strmiids.lib") //used for direct show
HRESULT InitCaptureGraphBuilder(
IGraphBuilder **ppGraph, // Receives the pointer.
ICaptureGraphBuilder2 **ppBuild // Receives the pointer.
)
{
if (!ppGraph || !ppBuild)
{
return E_POINTER;
}
IGraphBuilder *pGraph = NULL;
ICaptureGraphBuilder2 *pBuild = NULL;
// Create the Capture Graph Builder.
HRESULT hr = CoCreateInstance(CLSID_CaptureGraphBuilder2, NULL,
CLSCTX_INPROC_SERVER, IID_ICaptureGraphBuilder2, (void**)&pBuild );
if (SUCCEEDED(hr))
{
// Create the Filter Graph Manager.
hr = CoCreateInstance(CLSID_FilterGraph, 0, CLSCTX_INPROC_SERVER,
IID_IGraphBuilder, (void**)&pGraph);
if (SUCCEEDED(hr))
{
// Initialize the Capture Graph Builder.
pBuild->SetFiltergraph(pGraph);
// Return both interface pointers to the caller.
*ppBuild = pBuild;
*ppGraph = pGraph; // The caller must release both interfaces.
return S_OK;
}
else
{
pBuild->Release();
}
}
return hr; // Failed
}
HRESULT EnumerateDevices(REFGUID category, IEnumMoniker **ppEnum)
{
// Create the System Device Enumerator.
ICreateDevEnum *pDevEnum;
HRESULT hr = CoCreateInstance(CLSID_SystemDeviceEnum, NULL,
CLSCTX_INPROC_SERVER, IID_PPV_ARGS(&pDevEnum));
if (SUCCEEDED(hr))
{
// Create an enumerator for the category.
hr = pDevEnum->CreateClassEnumerator(category, ppEnum, 0);
if (hr == S_FALSE)
{
hr = VFW_E_NOT_FOUND; // The category is empty. Treat as an error.
}
pDevEnum->Release();
}
return hr;
}
void DisplayDeviceInformation(IEnumMoniker *pEnum, IMoniker** pMoniker)
{
while (pEnum->Next(1, pMoniker, NULL) == S_OK)
{
IPropertyBag *pPropBag;
HRESULT hr = (*pMoniker)->BindToStorage(0, 0, IID_PPV_ARGS(&pPropBag));
if (FAILED(hr))
{
(*pMoniker)->Release();
continue;
}
VARIANT var;
VariantInit(&var);
// Get description or friendly name.
hr = pPropBag->Read(L"Description", &var, 0);
if (FAILED(hr))
{
hr = pPropBag->Read(L"FriendlyName", &var, 0);
}
if (SUCCEEDED(hr))
{
printf("%S\n", var.bstrVal);
if(0 == wcscmp(var.bstrVal, L"Integrated Webcam"))
{
VariantClear(&var);
pPropBag->Release();
return;
}
VariantClear(&var);
}
hr = pPropBag->Write(L"FriendlyName", &var);
pPropBag->Release();
}
}
void main()
{
HRESULT hr = CoInitializeEx(NULL, COINIT_MULTITHREADED);
IGraphBuilder *pGraph = NULL;
ICaptureGraphBuilder2 *pBuild = NULL;
IMediaControl *pControl = NULL;
IMediaEvent *pEvent = NULL;
if (FAILED(hr))
{
printf("ERROR - Could not initialize COM library\n");
return;
}
printf("SUCCESS - Initialized COM library.\n");
hr = InitCaptureGraphBuilder(&pGraph, &pBuild);
if (FAILED(hr))
{
printf("ERROR - Could not create the Filter Graph Manager.\n");
return;
}
printf("SUCCESS - Created the Filter Graph Manager.\n");
hr = pGraph->QueryInterface(IID_IMediaControl, (void **)&pControl);
hr = pGraph->QueryInterface(IID_IMediaEvent, (void **)&pEvent);
if (FAILED(hr))
{
printf("ERROR - Could not create the Media Control or Media Event Interfaces.\n");
return;
}
printf("SUCCESS - Created the Media Control and Media Event Interfaces.\n");
IEnumMoniker *pEnum;
hr = EnumerateDevices(CLSID_VideoInputDeviceCategory, &pEnum);
if(FAILED(hr))
{
printf("ERROR - Failed to enumerate devices.\n");
return;
}
printf("SUCCESS - Enumerated devices.\n");
IMoniker* pMoniker = NULL;
printf("--------------DEVICE INFORMATION--------------\n");
DisplayDeviceInformation(pEnum, &pMoniker);
printf("------------END DEVICE INFORMATION------------\n");
IBaseFilter *pCap = NULL;
hr = pMoniker->BindToObject(0, 0, IID_IBaseFilter, (void**)&pCap);
if(FAILED(hr))
{
printf("ERROR - Failed to bind to moniker.\n");
return;
}
printf("SUCCESS - Bound to moniker.\n");
hr = pBuild->RenderStream(&PIN_CATEGORY_PREVIEW, &MEDIATYPE_Video, pCap, NULL, NULL);
if(FAILED(hr))
{
printf("ERROR - RenderStream() failed.\n");
return;
}
printf("SUCCESS - RenderStream() succeeded.\n");
hr = pControl->Run();
if(FAILED(hr))
{
printf("ERROR - Run() failed.\n");
return;
}
printf("SUCCESS - Running.\n");
long evCode;
hr = pEvent->WaitForCompletion(INFINITE, &evCode);
if(FAILED(hr))
{
printf("ERROR - WaitForCompletion() failed.\n");
return;
}
hr = pControl->Stop();
if(FAILED(hr))
{
printf("ERROR - Stop() failed.\n");
return;
}
printf("SUCCESS - Stopping.\n");
pControl->Release();
pEvent->Release();
pGraph->Release();
pMoniker->Release();
pEnum->Release();
CoUninitialize();
}

Answer 1

Before using RenderStream you need to IGraphBuilder::AddFilter your camera filter to the graph.