Note this may apply to other video players, not just mythtv.
Also sorry if you feel I should better be posting to any of the myth lists. But I already did, and the fact of the matter is that 90% of the myth people are on NV hardware anyway (for a good reason what I know now...) So I'm hoping to meet the real radeon OSS experts here.
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. With opengl 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.
So, finally, my question: is there anything one can do to improve the real-time performance of opengl video? What would you try or check on such a system?