OpenGL video performance

Greg G. dargllun at
Wed Apr 25 09:34:22 PDT 2012


I've posted the following inquiry to the Phoronix forum already and was 
advised to post this to a more appropriate mailing list, such as this one.

Upfront, I'm sorry if you feel I should better be posting to any of the 
mythtv lists. But I already did, and the fact of the matter is that 90% 
of the myth people are on NV hardware anyway (can't blame them, to be 
honest). So maybe this place is more appropriate.

With that being said, here's my question: is there anything one can do 
to improve the real-time performance of opengl video? What would you try 
or check on my system?

Background: for some time now I've repeatedly trying to get my HD3200 
equipped mythtv box to use the OpenGL renderer. While things have gotten 
*much* better in the course of the last 1.5 years, I still find that Xv 
rendering is much more "real-time", meaning that when I use a proper 
deinterlacer (hard requirement) with Xv I get smooth rendering with no 
judder at all. WithOpenGL it's pretty jerky. My test case is to play 
some piece of recording from a news channel with a horizontal scoll text 
(like stock prices), this way you see even slight hickups. Note I'm not 
even talking about h.264 output (which is, btw, also great on Xv), but 
merely SD material.

I'm using Ubuntu and the fabulous oibaf drivers, and KMS. Myth is 
configured to use real-time priorities. "Top" shows that there is ample 
CPU time. Blanking method is DRM.

The reason for wanting opengl output is simply that in the long run the 
mythtv devs plan on removing support for Xv. Also, the quality of the 
onscreen menu is much better with opengl.

Any hints/tips/pointers appreciated!


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