Microsoft DirectX 9.0 |
The Filter Graph Manager supports the IFilterGraph::EnumFilters method, which enumerates all the filters in the filter graph. It returns a pointer to the IEnumFilters interface. The IEnumFilters::Next method retrieves IBaseFilter interface pointers.
The following example shows a function that enumerates the filters in a graph and displays a message box with each filter's name. It uses the IBaseFilter::QueryFilterInfo method to retrieve the name of the filter. Note the places where the function calls Release on an interface to decrement the reference count.
HRESULT EnumFilters (IFilterGraph *pGraph)
{
IEnumFilters *pEnum = NULL;
IBaseFilter *pFilter;
ULONG cFetched;
HRESULR hr = pGraph->EnumFilters(&pEnum);
if (FAILED(hr)) return hr;
while(pEnum->Next(1, &pFilter, &cFetched) == S_OK)
{
FILTER_INFO FilterInfo;
hr = pFilter->QueryFilterInfo(&FilterInfo);
if (FAILED(hr))
{
MessageBox(NULL, TEXT("Could not get the filter info"),
TEXT("Error"), MB_OK | MB_ICONERROR);
continue; // Maybe the next one will work.
}
#ifdef UNICODE
MessageBox(NULL, FilterInfo.achName, TEXT("Filter Name"), MB_OK);
#else
char szName[MAX_FILTER_NAME];
int cch = WideCharToMultiByte(CP_ACP, 0, FilterInfo.achName,
MAX_FILTER_NAME, szName, MAX_FILTER_NAME, 0, 0);
if (chh > 0)
MessageBox(NULL, szName, TEXT("Filter Name"), MB_OK);
#endif
// The FILTER_INFO structure holds a pointer to the Filter Graph
// Manager, with a reference count that must be released.
if (FilterInfo.pGraph != NULL)
{
FilterInfo.pGraph->Release();
}
pFilter->Release();
}
pEnum->Release();
return S_OK;
}