Vsync

[vrtainment]

Hi,

I have some trouble with syncing in an opengl based application ... when using export __GL_SYNC_TO_VBLANK the application produces jerky movements (though frame time require is much less than 16 ms) ... When using glxGetVideoSyncSGI instead, most of it is pretty good, but I get some tears (PageFlipping is activated) ...
Any idea?

hartwig

[dlyne]

I think I'm having the same problem. Have you managed to fix this yet?

[vrtainment]

fixed part of it, but not all.
I am not using the GL_SYNC variable, still using Page Flipping und the glXSGI function for syncing... I put glFlush at various parts in the code and I use glFinish() .... As long as I do not use GL_FSAA
all is fine now, but as soon as I use any AA-mode I get a clear tear in the image. Interstingly enough this tear does not move at all. it always stay at the same line .. also intersting, the vertical position of this line depends on the AA-mode choosen ...

that's all I can tell for the moment .... I would be gratefull for any further hints ..

hartwig

[dlyne]

We may have the same problem.

I get stutter with the GL_SYNC environment variable set. However, it is not dropped frames. It is actually extra frames! I'm not sure that this is the same as you. It could be.

I have posted a message about this at:

http://www.nvnews.net/vbulletin/showthread.php?s=&threadid=15415

[vrtainment]

There is a history to our project. Before we actually got into native OpenGL, we started the project using OpenGL Performer. Since we got jerky movement every now and then we started investigating this in more details. Performer provides as statistics graph. Part of this is the "load line". Watching the load line we saw that the load (using GL_SYNC) did continuously increase and then all of a sudden it dropped. When it dropped, we had the jerk in the movement ... So, similar to you we went to the most simple app. Just clear background and swapbuffers. But even there we found this load behaviour... I am still not sure what this behaviour tells us about the syncing mechanism (apart from knowing it is a poll) .... Do you have any idea?


hartwig