The current implementation of MIDISetup provides the functionality to obtain the maximum length of a real-time SysEx message and a pointer to the RTMIDI timer.
Do not confuse the RTMIDI timer with the timer returned from TimerGetPointer. The pointer returned by MIDISetup is a pointer to the RTMIDI timer, as opposed to the pointer returned from TimerGetPointer, which is a pointer to the high-resolution timer (HRT).
The RTMIDI timer should be used to provide values for the timestamp field (ulTime of the MESSAGE structure) for the MIDISendMessages function.
This timer can be synchronized to external events, such as SMPTE time clock or OS/2 multimedia, which is why it must be used instead of the high-resolution timer.