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This interface allocates IMediaSampleblocks to be used for data transfer between pins.

The blocks can be provided by the input pin, output pin, or a third party.

Release the IMediaSampleobject by calling the IUnknown::Releasemethod.

When to Implement

Implement this interface if you are providing a buffer for media samples.

This is typically done by filters that originate, copy, or provide a destination for the media stream. For example, a source filter provides an allocator corresponding to the incoming media, and a renderer filter provides an allocator corresponding to the hardware memory (DirectX®, for example).

Intermediate transform filters can create their own allocator if copying samples and not writing directly to the renderer's allocator.

Use the CBaseAllocatorclass to implement the IMemAllocatorinterface.

When to Use

Filters use this interface when retrieving or sending media samples.

The allocator used might belong to a filter further upstream or downstream than the next filter, because many filters can pass the allocators through and modify the data in place.

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


Specifies a desired number of blocks, size of the blocks, and block alignment figure. This method returns the actual values for the same.


Determines the size, number, and alignment of blocks.


Commits the memory for the specified buffers.


Releases the memory for the specified buffers.


Retrieves a container for a sample.


Releases a container for a sample.


Windows Embedded CE Windows CE 2.12 and later
Windows Mobile Pocket PC for Windows Mobile Version 5.0 and later, Smartphone for Windows Mobile Version 5.0 and later
Note Microsoft DirectShow applications and DirectShow filters have different include file and Library requirements
For more information, see Setting Up the Build Environment

See Also