Override the CheckTransform Member Function (Windows Embedded CE 6.0)
1/6/2010
Copy transform filters can transform the media type from the input pin to output pin.
Therefore, if the output pin is connected (so its media type is known), when the CTransformInputPin::CheckMediaType member function is called during connection, the CheckTransform member function of the derived class is called to verify that the transform from the input type to the output type is valid.
It is also called when CTransformOutputPin::CheckMediaType is called.
In the CTransInPlaceFilter class, this member function is implemented in the base class header file to simply return S_OK, because the functions from CTransformFilter that call this member function are overridden in CTransInPlaceFilter to call CheckInputType instead.
This assumes that the media type does not change in a transform-inplace filter, as it might in a copy transform filter.