[mythtv] Interesting video jitter effect

[Kyle Rose]

> I think you're probably seeing an effect that's taken care of in the 
> video sync methods that can actually track the retrace time (phase) of 
> the video refresh, rather than just its period.  Those methods are 
> nVidia, DRI (I think), and OpenGL.  nVidia works for driver versions 
> 43xx and older, and OpenGL works (properly) for 6111 and newer.

Is there anything special I need to do to get OpenGL sync to work?
I've got the OpenGL-related lines in settings.pro uncommented, and I
have the nvidia-glx/nvidia-kernel-common/nvidia-kernel-`uname -r`
packages installed, yet mythfrontend still reports that it's using the
RTC method for video sync.  (FWIW, the nvidia method doesn't get used
either, but according to the above this only works for older drivers).

I am using an FX5200 with driver rev. 6629.

I'm thinking there is some bug in the glXQueryExtensionsString
function, because it returns only "GLX_EXT_visual_info
GLX_EXT_visual_rating" when glxinfo reports the following:

server glx extensions:
    GLX_EXT_visual_info, GLX_EXT_visual_rating, GLX_SGIX_fbconfig, 
    GLX_SGIX_pbuffer, GLX_SGI_video_sync, GLX_SGI_swap_control, 
    GLX_ARB_multisample, GLX_NV_float_buffer
client glx extensions:
    GLX_ARB_get_proc_address, GLX_ARB_multisample, GLX_EXT_visual_info, 
    GLX_EXT_visual_rating, GLX_EXT_import_context, GLX_SGI_video_sync, 
    GLX_NV_swap_group, GLX_NV_video_out, GLX_SGIX_fbconfig, GLX_SGIX_pbuffer, 
    GLX_SGI_swap_control, GLX_NV_float_buffer
GLX extensions:
    GLX_EXT_visual_info, GLX_EXT_visual_rating, GLX_SGIX_fbconfig, 
    GLX_SGIX_pbuffer, GLX_SGI_video_sync, GLX_SGI_swap_control, 
    GLX_ARB_multisample, GLX_NV_float_buffer, GLX_ARB_get_proc_address

all of which include GLX_SGI_video_sync.  I don't believe this is a
permissions problem because even a setuid root binary has the same
problem.  Maybe someone stuck a null at the end of
GLX_EXT_visual_rating? :) Other suggestions?

Cheers,
Kyle