Microsoft DirectX 9.0


The CreateClassEnumerator method creates an enumerator for a specified device category.


HRESULT CreateClassEnumerator(
  REFCLSID clsidDeviceClass,
  IEnumMoniker **ppEnumMoniker,
  DWORD dwFlags



[in] Specifies the class identifier (CLSID) of the device category. See Filter Categories.


[out] Address of a variable that receives an IEnumMoniker interface pointer.


[in] Bitwise combination of zero or more flags. If zero, the method enumerates every filter in the category. If any flags are set, the enumeration includes only filters that match the specified flags. The following flags are defined:

Flag Description
CDEF_DEVMON_CMGR_DEVICE Enumerate audio or video codecs, using the audio compression manager (ACM) or video compression manager (VCM).
CDEF_DEVMON_DMO Enumerate DirectX Media Objects (DMOs).
CDEF_DEVMON_FILTER Enumerate native DirectShow filters.
CDEF_DEVMON_PNP_DEVICE Enumerate Plug and Play hardware devices.

Return Values

Returns one of the following HRESULT values.

Return code Description
S_OK Success.
E_OUTOFMEMORY There is not enough memory available to create a class enumerator.
S_FALSE The category specified by clsidDeviceClass does not exist or is empty.
E_POINTER NULL pointer argument.


If the category does not exist or is empty, the return value is S_FALSE, and the ppEnumMoniker parameter receives the value NULL. Therefore, test for the return value S_OK instead of using the SUCCEEDED macro:

IEnumMoniker *pEnum = NULL;
hr = pSysDevEnum->CreateClassEnumerator(
    CLSID_VideoCompressorCategory, &pEnum, 0);
if (hr == S_OK) 
    // Safe to dereference pEnum.

The returned IEnumMoniker interface has an outstanding reference count. The caller must release the interface.

See Also