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Negotiates the allocator to use (uses the allocator from the upstream output pin).
HRESULT DecideAllocator( IMemInputPin * pPin, IMemAllocator ** ppAlloc );
Parameters
- pPin
- Pointer to the IMemInputPininterface of the downstream input pin.
- ppAlloc
- Returned allocator pointer.
Return Values
Returns NOERROR if successful. Otherwise, returns VFW_E_NO_ALLOCATOR if there is no allocator, or an error from calling GetAllocator, InitAllocator, GetAllocatorRequirements, DecideBufferSize, or NotifyAllocator.
Remarks
This member function overrides the CBaseOutputPin::DecideAllocatormember function. This implementation uses the allocator that is negotiated by its input pin because a transform-inplace filter does not supply its own allocator. It then calls IMemInputPin::NotifyAllocatoron the downstream input pin with that allocator.
If you want to use your own allocator, it is better to derive from CTransformFilterthan from CTransInPlaceFilter, because the purpose of a transform-inplace filter is to use an existing allocator.