IAsyncReader::RequestAllocator

  • Article

This method retrieves the actual allocator to be used.

HRESULT RequestAllocator(
  IMemAllocator* pPreferred,
  ALLOCATOR_PROPERTIES* pProps,
  IMemAllocator** ppActual
);

Parameters

  • pPreferred
    [in] Preferred allocator.
  • pProps
    [in] Preferred allocator properties (size, count, and alignment).
  • ppActual
    [out] Actual allocator used.

Return Values

Returns an HRESULT value that depends on the implementation of the interface. Current DirectShow implementation return values include the following.

Value Description
E_FAIL Failure to initialize an allocator.
VFW_E_BADALIGN An invalid alignment was specified.
S_OK Allocator was returned.

Remarks

The preferred allocator and preferred allocator properties must be passed in. This method returns the actual allocator to be used.

IMemAllocator::GetProperties should be called on the returned allocator to learn the alignment and prefix chosen. This allocator will not be committed and decommitted by the asynchronous reader, only by the consumer. This method must be called before calling IAsyncReader::Request.

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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