Re: Problem with frame managemnent in Performer
John Rohlf (jrohlf++at++tubes)
Wed, 22 Nov 95 14:44:54 PST
>
> Our company is currently developing an application using a 3 pipe
> ONYX, using IRIX 5.3 and Performer 1.2. The 3 pipes have been
> genlocked together, both via software (using setmon) and hardware
> (cabling the sync, genlock and swapbuffer ports as described in the
> SGI manuals).
>
> 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 ?
You are encountering a bug in 1.2. The video clocks used
by performer are not synchronized on all 3 pipes so the APP
gets out of phase with 1 or more pipes. The solution is to wait
for soon-to-be-released 2.0 or rendezvous all your pipes
together and call pfInitVClock(0) in each pipe at the same time
to sync the clocks.
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on Mon Aug 10 1998 - 17:52:03 PDT