Value
indicating the desired sync pulse generation interval. A sync pulse is
generated by the master stream at each mmtimeSync interval relative
to MMTIME 0. MMTIME is always specified in units of 1/3000th of a second.
If this parameter is NULL, the sync pulse interval in the negotiated stream
protocol control block (SPCB) for the master
stream is used. The SPCB for a data type and stream handler can be queried
using the SpiGetProtocol function.