如何检查是否正在使用我的DirectShow Renderer过滤器？

在我的DirectShow项目中，我创建了一个过滤器（从 CBaseVideoRenderer 派生）来渲染内存块。这在大多数情况下都很好，添加了过滤器

In my DirectShow project I create a filter (derived from CBaseVideoRenderer) to render to a block of memory. This works in most cases perfectly well, with me adding the filter

    mGraphBuilder->AddFilter(pInterfaceInfo, MemoryRendererName);

并依靠GraphBuilder做剩下的工作。但是在某些情况下，图形生成器和我的过滤器不能就一个通用格式达成一致，它会创建一个新的ActiveMovie窗口，绕过我的过滤器。

and relying on GraphBuilder to do the rest. However in some cases the graph builder and my filter cannot agree on a common format and it creates a new ActiveMovie window, bypassing my filter.

发生，所以我知道我的过滤器没有被使用，但不能解决如何。

I would like to detect when this occurs so that I know my filter is not being used, but cannot work out how.

我枚举图中的所有过滤器，寻找我的过滤器，使用以下方法：

I enumerate all filters in my graph, looking for my filter, using the following method:

（编辑：当我调用这个参数时，我传递了我的GraphBuilder对象作为pGraph参数）

( I pass my my GraphBuilder object as the pGraph parameter when I call this)

HRESULT MediaPlayer::CheckFilterGraphFor(IFilterGraph *pGraph, IBaseFilter* pFilterToLookFor)
{
    IEnumFilters *pEnum = NULL;
    IBaseFilter *pFilter;
    ULONG cFetched;

    HRESULT enumeratedFilterCount = 0;

    FILTER_INFO pRefFilterInfo;
    pFilterToLookFor->QueryFilterInfo(&pRefFilterInfo);

    HRESULT hr = pGraph->EnumFilters(&pEnum);
    if (SUCCEEDED(hr))
    {
        while(pEnum->Next(1, &pFilter, &cFetched) == S_OK)
        {
            enumeratedFilterCount--;

            FILTER_INFO FilterInfo;
            hr = pFilter->QueryFilterInfo(&FilterInfo);
            if (SUCCEEDED(hr))
            {   
                if(wcscmp(FilterInfo.achName, pRefFilterInfo.achName) == 0)
                {
                    pRefFilterInfo.pGraph->Release();
                    return S_OK;    
                }

                // 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();
    }

    pRefFilterInfo.pGraph->Release();
    return enumeratedFilterCount;
}

但它不能按预期工作，

But it does not work as expected, as my filter is always found regardless of whether it is in use or not.

我如何知道当我的过滤器用作DirectShow图形的视频渲染器时，以及当它不是

How can I tell when my filter is in use as the video renderer for my DirectShow graph, and when it is not?