The PCFILTER_NODE constant is the null node ID for the FromNode or ToNode field in a PCCONNECTION_DESCRIPTOR structure. If the structure's FromNode or ToNode member is set to PCFILTER_NODE, the pin on this end of the connection is an input or output pin on the filter. Otherwise, it is a logical pin on a node inside the filter.
PCFILTER_NODE is defined to be the value ((ULONG)-1).