bmh@tigger.cs.unc.edu (Brad Hemminger) (07/06/90)
For some vision experiments we would like to do I need to be able to display a blank screen, then exactly n frames of a image, then blank screen, etc, etc. Question: is there any way to have this fine a level of control under X11? E.g. some machines might allow me to see a vertical retrace interrupt, but so far under X I don't see anything at that level (e.g. no X events that indicate vertical retrace, etc). If anyone has any answers, or hints on how to do this I would greatly appreciate it. The best I have come up with so far is to use gettimeofday to delay for the amount of time equal to n*(time each frame is displayed); however, this may in certain cases cause the display of n-1 or n+1 frames instead of n. thanks, Brad Hemminger Dept of Radiology UNC bmh@rad.unc.edu
jch@Stardent.COM (Jan Hardenbergh @stardent) (07/12/90)
> From: uunet!mcnc.org!thorin!tigger!bmh (Brad Hemminger) > Subject: How to display exactly n frames of an image? > For some vision experiments we would like to do I need to be able to > display a blank screen, then exactly n frames of a image, then blank > screen, etc, etc. Question: is there any way to have this fine a level > of control under X11? E.g. some machines might allow me to see a > vertical retrace interrupt, but so far under X I don't see anything at > that level (e.g. no X events that indicate vertical retrace, etc). > If anyone has any answers, or hints on how to do this I would greatly > appreciate it. The best I have come up with so far is to use gettimeofday > to delay for the amount of time equal to n*(time each frame is displayed); > however, this may in certain cases cause the display of n-1 or n+1 frames > instead of n. You are looking for the multibuffering extension. See X11R4/mit/doc/extensions/buffer.text for a description. Here's one of the goals. > o Display a series of buffers in a window in rapid suc- > cession to achieve a smooth animation. It does have an implementation for the sample server - see X11R4/mit/extensions/server/multibuf.c. As far as I know it is not a blessed extension, yet. But it seems to have no serious oposition. -- -Jan "YON" Hardenbergh - jch@stardent.com uunet!stardent!jch Stardent Computer, Inc., 95 Wells Ave., Newton, MA 02159 (617)964-6228x261