Bill Storma (BILL++at++p3.enzian.com)
Wed, 22 Nov 1995 10:47:09 EDT
During the process of testing the different frame rate controls
(FREERUN, LIMIT, LOCK, FLOAT) using perfly, I have noticed that the
draw process does not always start at the proper time when running
LOCK mode. The draw process will start on a video refresh cycle, but
not necessarily on a frame cycle. As the frame rate is reduced, the
problem occurs more often. At 30 Hz, the problem shows up
occasionally; at 10 Hz, the problem always occurs. Perfly is set up
to use 3 pipes. The problem of the draw process starting at the
wrong time may occur in any of the three pipes; there does not appear
to be a consistent pattern. One pipe will always start properly;
the other two will start at different refresh cycles. I have also
informed Paradigm Simulation of this problem (we are using their Vega
products), and they could re- create it on their equipment.
Since the draw process does not start at the proper time, the frame
synchronization does not always take place properly. Example: if
the frame rate is set for 15 Hz, even though the draw process can run
well within the frame, the frames will drop to 7.5 to 10 Hz. This
apparently is because the draw process overruns the frame, because it
started late.
Because of this problem, I find it difficult to write a real-time
application that will run at the proper frame rate. Has SGI seen
this problem and if so, is there a fix to the problem ?
Any help would be appreciated.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Bill Storma Phone: 407-282-1884
Enzian Technology FAX: 407-282-3013
Orlando, Fl. 32822 e-mail: bill++at++p3.enzian.com
This archive was generated by hypermail 2.0b2 on Mon Aug 10 1998 - 17:52:03 PDT