如何获得filter或者pin的接口指针
一般来说，我们都是通过Filter图表管理器来进行一些操作，但是，有时候，我们也直接调用filter或者pin的一些方法，因此，我们需要获取filter或pin的接口指针。
对于filter的接口指针，可以通过IEnumFilters来枚举filter的指针，看下面的代码：
HRESULT FindFilterInterface(
IGraphBuilder *pGraph, // Pointer to the Filter Graph Manager.
REFGUID iid, // IID of the interface to retrieve.
void **ppUnk) // Receives the interface pointer.
{
if (!pGraph || !ppUnk) return E_POINTER;
HRESULT hr = E_FAIL;
IEnumFilters *pEnum = NULL;
IBaseFilter *pF = NULL;
if (FAILED(pGraph->EnumFilters(&pEnum)))
{
return E_FAIL;
}
// Query every filter for the interface.
while (S_OK == pEnum->Next(1, &pF, 0))
{
hr = pF->QueryInterface(iid, ppUnk);
pF->Release();
if (SUCCEEDED(hr))
{
break;
}
}
pEnum->Release();
return hr;
} |
用IEnumPins来获得pin的接口指针，其实就是枚举。
HRESULT FindPinInterface(
IBaseFilter *pFilter, // Pointer to the filter to search.
REFGUID iid, // IID of the interface.
void **ppUnk) // Receives the interface pointer.
{
if (!pFilter || !ppUnk) return E_POINTER;
HRESULT hr = E_FAIL;
IEnumPins *pEnum = 0;
if (FAILED(pFilter->EnumPins(&pEnum)))
{
return E_FAIL;
}
// Query every pin for the interface.
IPin *pPin = 0;
while (S_OK == pEnum->Next(1, &pPin, 0))
{
hr = pPin->QueryInterface(iid, ppUnk);
pPin->Release();
if (SUCCEEDED(hr))
{
break;
}
}
pEnum->Release();
return hr;
} |
下面的代码演示了如何搜索任意的filter和pin的接口：
HRESULT FindInterfaceAnywhere(
IGraphBuilder *pGraph,
REFGUID iid,
void **ppUnk)
{
if (!pGraph || !ppUnk) return E_POINTER;
HRESULT hr = E_FAIL;
IEnumFilters *pEnum = 0;
if (FAILED(pGraph->EnumFilters(&pEnum)))
{
return E_FAIL;
}
// Loop through every filter in the graph.
IBaseFilter *pF = 0;
while (S_OK == pEnum->Next(1, &pF, 0))
{
hr = pF->QueryInterface(iid, ppUnk);
if (FAILED(hr))
{
// The filter does not expose the interface, but maybe
// one of its pins does. //调用的是上面的搜索pin的函数
hr = FindPinInterface(pF, iid, ppUnk);
}
pF->Release();
if (SUCCEEDED(hr))
{
break;
}
}
pEnum->Release();
return hr;
} |
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