1 Calls the GetCurrentPosition method. This call returns the current position as calculated by the filter graph manager.
2 Stops the filter graph (if the graph is paused or running).
3 Calls the SetPositions method on the filters, with the current position as the start time. This has the effect of resetting the stream time to zero.
4 Calls the SetRate method on the filters, with the new rate.
Resumes the filter graph, if it was paused or running.