IEnumFilters Interface

The IFilterGraph::EnumFilters method returns the enumerator interface. It is based on the COM IEnum style of enumerators.

When to Implement

This interface is implemented on the filter graph manager and is not intended for implementation by developers.

When to Use

This interface is used by applications or other filters to determine what filters exist in the filter graph.

Methods in Vtable Order

IUnknown methods	Description
QueryInterface	Returns pointers to supported interfaces.
AddRef	Increments the reference count.
Release	Decrements the reference count.

IEnumFilters methods	Description
Next	Retrieves the specified number of filters in the enumeration sequence.
Skip	Skips a specified number of filters in the enumeration sequence.
Reset	Resets the enumeration sequence to the beginning.
Clone	Retrieves a duplicate enumerator containing the same enumeration state as the current one.

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IEnumFilters::Clone

IEnumFilters Interface

Retrieves a duplicate enumerator containing the same enumeration state as the current one.

HRESULT Clone(
  IEnumFilters ** ppEnum
  );

Parameters

ppEnum

[out] Duplicate of the enumerator.

Return Values

No return value.

Remarks

This method produces two enumerators (the original and the duplicate); both are set at the same filter. After they are created, however, they are independent; therefore, calling the IEnumFilters::Next method for one does not affect the other.

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IEnumFilters::Next

IEnumFilters Interface

Retrieves the specified number of filters in the enumeration sequence.

HRESULT Next(
  ULONG cFilters,
  IBaseFilter ** ppFilter,
  ULONG * pcFetched
  );

Parameters

cFilters

[in] Number of filters to place.

ppFilter

[out] Array in which to place IBaseFilter pointers.

pcFetched

[out] Actual number of filters placed in the array.

Return Values

Returns an HRESULT value that depends on the implementation. HRESULT can be one of the following standard constants, or other values not listed:

Value	Meaning
E_FAIL	Failure.
E_POINTER	Null pointer argument.
E_INVALIDARG	Invalid argument.
E_NOTIMPL	Method isn't supported.
S_OK or NOERROR	Success.

Remarks

The interface returned by this method has had its reference count incremented. Be sure to use IUnknown::Release on the interface to decrement the reference count when you have finished using the interface.

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IEnumFilters::Reset

IEnumFilters Interface

Resets the enumeration sequence to the beginning.

HRESULT Reset(void);

Return Values

Returns an HRESULT value that depends on the implementation. HRESULT can be one of the following standard constants, or other values not listed:

Value	Meaning
E_FAIL	Failure.
E_POINTER	Null pointer argument.
E_INVALIDARG	Invalid argument.
E_NOTIMPL	Method isn't supported.
S_OK or NOERROR	Success.

Remarks

This method affects the return value of the next call to the IEnumFilters::Next method.

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IEnumFilters::Skip

IEnumFilters Interface

Skips a specified number of filters in the enumeration sequence.

HRESULT Skip(
  ULONG cFilter
  );

Parameters

cFilter

[in] Number of filters to skip.

Return Values

No return value.

Remarks

This method affects the return value of the next call to the IEnumFilters::Next method.

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