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IMemAllocator Interface (Compact 2013)

3/26/2014

This interface allocates IMediaSample blocks 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 IMediaSample object by calling the IUnknown::Release method.

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 CBaseAllocator class to implement the IMemAllocator interface.

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

SetProperties

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

GetProperties

Determines the size, number, and alignment of blocks.

Commit

Commits the memory for the specified buffers.

Decommit

Releases the memory for the specified buffers.

GetBuffer

Retrieves a container for a sample.

ReleaseBuffer

Releases a container for a sample.

Requirements

Header

dshow.h

Library

Strmiids.lib

See Also

Reference

DirectShow Interfaces