DirectShow 设置回调函数返回失败

如下设置回调函数 hr = m_pF->QueryInterface(IID_IVRControl, (void **)(&m_pVRControl)); 返回m_pVRControl为空；是否IID_IVRControl错误? 有人遇到过吗？// 接口的 GUID
static const GUID IID_IVRControl = {0x244df760, 0x7e93, 0x4cf0, {0x92, 0xf4, 0xdc, 0xb7, 0x9f, 0x64, 0x6b, 0x7e}};IID_IVRControlBOOL CDXGraph::CreateGrabber()
{
if(mGraph == NULL)
return FALSE; HRESULT hr; hr = CoCreateInstance(CLSID_lwVideoRenderer, NULL, CLSCTX_INPROC_SERVER,
IID_IBaseFilter, (void **)(&m_pF)); if(NULL == m_pF)
{ return false;
} hr = mGraph->AddFilter(m_pF, L"VideoRenderer"); hr = m_pF->QueryInterface(IID_IVRControl, (void **)(&m_pVRControl)); return TRUE;
}