Pins
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4/8/2010
As described earlier, the multimedia data in a filter graph moves downstream from a source filter through zero or more intermediate filters and finally to a renderer filter. Pins handle the low-level details of the data transfer between filters. A pin is a COM object which supports the IPin COM interface, has a direction (input or output), and is associated with a particular filter in the graph. A pin represents the point of connection with another filter. An output pin on an upstream filter connects to an input pin on the next filter downstream. Pins know what media types they can support and they negotiate the media type when two filters initially connect. Once the media type is agreed upon, the pins negotiate the details of how they will transfer data once the filter graph starts running.