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IAMBufferNegotiation::SuggestAllocatorProperties

  • Artículo
 
Microsoft DirectShow 9.0

IAMBufferNegotiation::SuggestAllocatorProperties

The SuggestAllocatorProperties method informs the pin of the application's preferred allocator properties. Call this method before the pin connects.

Syntax

  HRESULT SuggestAllocatorProperties(
  const ALLOCATOR_PROPERTIES *pprop
);

Parameters

pprop

[in]  Pointer to an ALLOCATOR_PROPERTIES structure that contains the requested properties. A negative value for any member indicates that the pin should use its default setting for that property.

Return Values

Returns an HRESULT value. Possible values include the following.

Return code Description
S_OK Success.
E_FAIL Failure.
E_POINTER NULL pointer argument.
VFW_E_ALREADY_CONNECTED Pin is already connected.

Remarks

If both pins in the connection expose the IAMBufferNegotiation interface, call this method on each pin, to ensure that one pin does not override the other.

To request a particular number of buffers, set the cBuffers member of the ALLOCATOR_PROPERTIES structure. To request a particular buffer size, set the cbBuffer member. An application typically should not specify the alignment or prefix. If the number of buffers or size of each buffer is too small, the filter graph might drop samples.

Example Code

ALLOCATOR_PROPERTIES AllocProp;
AllocProp.cbAlign = -1;  // -1 means no preference.
AllocProp.cbBuffer = dwBytesPerSec *  dwLatencyInMilliseconds / 1000;
AllocProp.cbPrefix = -1;
AllocProp.cBuffers = -1;
pIAMBufferNegotiation->SuggestAllocatorProperties(&AllocProp);

Requirements

Header: Declared in Strmif.h; include Dshow.h.

Library: Use Strmiids.lib.

See Also