Enumerating Filters

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 IUnknown::Release on an interface to decrement the reference count.

void EnumFilters (IFilterGraph *pGraph) 
{
    IEnumFilters *pEnum = NULL;
    IBaseFilter *pFilter;
    ULONG cFetched;

    pGraph->EnumFilters(&pEnum);
    while(pEnum->Next(1, &pFilter, &cFetched) == S_OK)
    {
        FILTER_INFO FilterInfo;
        char szName[256];
        
        pFilter->QueryFilterInfo(&FilterInfo);
        WideCharToMultiByte(CP_ACP, 0, FilterInfo.achName, -1, szName, 256, 0, 0);
        MessageBox(NULL, szName, "Filter name", MB_OK);

        FilterInfo.pGraph->Release();
        pFilter->Release();
    }
    pEnum->Release();
}