| Microsoft DirectX 8.1 (C++) |
The KsQueryMediums method retrieves the mediums supported by a pin.
Syntax
HRESULT KsQueryMediums(
KSMULTIPLE_ITEM **ppmi
);
Parameters
ppmi
[out] Address of a pointer to a KSMULTIPLE_ITEM structure.
Return Values
If the method succeeds, it returns S_OK. If it fails, it returns an HRESULT error code.
Remarks
This method returns a task-allocated KSMULTIPLE_ITEM structure, which is followed by zero or more REGPINMEDIUM structures. The Count member of the KSMULTIPLE_ITEM structure specifies the number of REGPINMEDIUM structures. Each REGPINMEDIUM structure defines a medium supported by the pin.
The caller must free the returned structures, using the CoTaskMemFree function.
Example Code
The following helper function attempts to match a pin against a specified medium.
HRESULT FindMatchingMedium(IPin *pPin, REGPINMEDIUM *pMedium, bool *pfMatch)
{
IKsPin* pKsPin = NULL;
KSMULTIPLE_ITEM *pmi;
*pfMatch = false;
HRESULT hr = pPin->QueryInterface(IID_IKsPin, (void **)&pKsPin);
if (FAILED(hr))
return hr; // Pin does not support IKsPin.
hr = pKsPin->KsQueryMediums(&pmi);
pKsPin->Release();
if (FAILED(hr))
return hr; // Pin does not support mediums.
if (pmi->Count)
{
// Use pointer arithmetic to reference the first medium structure.
REGPINMEDIUM *pTemp = (REGPINMEDIUM*)(pmi + 1);
for (ULONG i = 0; i < pmi->Count; i++, pTemp++)
{
if (pMedium->clsMedium == pTemp->clsMedium)
{
*pfMatch = true;
break;
}
}
}
CoTaskMemFree(pmi);
return S_OK;
}
Remarks
This method is used only with WDM Stream-Class Driver Filters.
See Also