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ICreateDevEnum::CreateClassEnumerator method (strmif.h)

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[The feature associated with this page, DirectShow, is a legacy feature. It has been superseded by MediaPlayer, IMFMediaEngine, and Audio/Video Capture in Media Foundation. Those features have been optimized for Windows 10 and Windows 11. Microsoft strongly recommends that new code use MediaPlayer, IMFMediaEngine and Audio/Video Capture in Media Foundation instead of DirectShow, when possible. Microsoft suggests that existing code that uses the legacy APIs be rewritten to use the new APIs if possible.]

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

Syntax

HRESULT CreateClassEnumerator(
  [in]  REFCLSID     clsidDeviceClass,
  [out] IEnumMoniker **ppEnumMoniker,
  [in]  DWORD        dwFlags
);

Parameters

[in] clsidDeviceClass

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

[out] ppEnumMoniker

Receives a pointer to the IEnumMoniker interface. The caller must release the interface.

[in] dwFlags

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 value

Returns one of the following HRESULT values.

Return code Description
S_OK
 Success.
E_OUTOFMEMORY
 Out of memory.
S_FALSE
 The category specified by clsidDeviceClass does not exist or is empty.
E_POINTER
 NULL pointer argument.

Remarks

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:

C++ 
IEnumMoniker *pEnum = NULL;
hr = pSysDevEnum->CreateClassEnumerator(
    CLSID_VideoCompressorCategory, &pEnum, 0);
if (hr == S_OK) 
{
    // Safe to dereference pEnum.
    pEnum->Release();
}
Use the IEnumMoniker interface to enumerate monikers that represent the filters in the device category. Monikers support the IMoniker interface. The monikers created by CreateClassEnumerator also support the IGetCapabilitiesKey interface.

Requirements

Requirement Value
Minimum supported client Windows 2000 Professional [desktop apps only]
Minimum supported server Windows 2000 Server [desktop apps only]
Target Platform Windows
Header strmif.h (include Dshow.h)
Library Strmiids.lib

See also

Error and Success Codes

ICreateDevEnum Interface