Be sure to release the interface when you are finished using it. Interface Retrieves the vendor string. Pointer to a variable that receives a BSTR containing the vendor string. The method allocates memory for the string. The application must call SysFreeString to free the memory.
Interface Creates the previewing portion of the filter graph.
Before calling this method, call ConnectFrontEnd to build the front end of the graph. To perform an operation other than preview, do not call this method. Instead, call GetGroupOutputPin to obtain pointers to the output pins. There will not be audio preview in this case, but video preview is unaffected. If the pin is from a video group, this method creates a video window.