CBaseAllocator.SetProperties method

Article
07/27/2023

[The feature associated with this page, DirectShow, is a legacy feature. It has been superseded by MediaPlayer, IMFMediaEngine, and Audio/Video Capture in Media Foundation. Those features have been optimized for Windows 10 and Windows 11. Microsoft strongly recommends that new code use MediaPlayer, IMFMediaEngine and Audio/Video Capture in Media Foundation instead of DirectShow, when possible. Microsoft suggests that existing code that uses the legacy APIs be rewritten to use the new APIs if possible.]

The SetProperties method specifies the number of buffers to allocate and the size of each buffer. This method implements the IMemAllocator::SetProperties method.

Syntax

HRESULT SetProperties(
   ALLOCATOR_PROPERTIES *pRequest,
   ALLOCATOR_PROPERTIES *pActual
);

Parameters

pRequest: Pointer to an ALLOCATOR_PROPERTIES structure that contains the buffer requirements.
pActual: Pointer to an ALLOCATOR_PROPERTIES structure that receives the actual buffer properties.

Return value

Returns one of the following HRESULT values.

Return code	Description
S_OK	Success.
E_POINTER	NULL pointer argument.
VFW_E_ALREADY_COMMITTED	Cannot change allocated memory while the filter is active.
VFW_E_BADALIGN	An invalid alignment was specified.
VFW_E_BUFFERS_OUTSTANDING	One or more buffers are still active.

Remarks

This method specifies the buffer requirements, but does not allocate any buffers. Call the CBaseAllocator::Commit method to allocate buffers.

The caller allocates two ALLOCATOR_PROPERTIES structures. The pRequest parameter contains the caller's buffer requirements, including the number of buffers and the size of each buffer. When the method returns, the pActual parameter contains the actual buffer properties, as set by the allocator. In the base class, assuming that the method succeeds, the actual properties always match the requested properties. Derived classes might override this behavior.

The allocator must not be committed, and must not have outstanding buffers. In the base class, the alignment must equal 1. The CMemAllocator class overrides this requirement.

Requirements

Requirement	Value
Header	Amfilter.h (include Streams.h)
Library	Strmbase.lib (retail builds); Strmbasd.lib (debug builds)