IEnumRegFilters Interface
The purpose of the mapper is to help the filter graph manager avoid loading filters when attempting to build a filter graph to render a given media type. By looking at filter properties recorded in the registry, the number of filters that must be loaded and tried can be reduced.
The IFilterMapper::EnumMatchingFilters method returns the enumerator that enumerates the filters that match specific requirements. The enumerator returns descriptors of filters, including the globally unique identifiers (GUIDs) that the Win32 CoCreateInstance function can instantiate. The filters are not loaded. The IEnumRegFilters interface is a Component Object Model (COM) enumerator.
When to Implement
This interface is implemented by the filter mapper and need not be implemented elsewhere.
When to Use
Although the filter graph manager is the primary user of this interface, applications can also use it to determine available filters in the system — for example, to construct a unique filter graph by adding and connecting filters itself, or to allow users to choose from a list of available filters.
Methods in Vtable Order
The following table shows the methods that appear in the Vtable beneath the standard COM methods inherited from IUnknown.
| Method | Description |
|---|---|
| Next | Fills an array with the next filters that meet the requirements. |
| Skip | Skips a specified number of elements in the enumeration sequence. |
| Reset | Makes the Next method start again, beginning at the first filter. |
| Clone | Returns another enumerator containing the same enumeration state as the current one. |
Requirements
DirectShow applications and DirectShow filters have different include file and link library requirements. See Setting Up the Build Environment for more information.
OS Versions: Windows CE 2.12 and later. Version 2.12 requires DXPAK 1.0 or later.
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Last updated on Wednesday, April 13, 2005
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