xine drops most of the frames from deinterlaced video when using opengl output

Recently, I had to switch from xv output to opengl, because Intel's 
sandybridge integrated graphics lacks vsync support for xv. 
Unfortunately, there is some problem with opengl output when tvtime 
deinterlacing is used. Most of the frames are dropped and the video is 
unwatchable.

Steps to reproduce are simple:
- download http://www.w6rz.net/vertrezmotion.zip
- run
   xine -V opengl \
      --post 
tvtime:method=Greedy2Frame,enable=1,cheap=0,chroma_filter=0,pulldown=none,framerate_mode=full,judder_correction=1,use_progressive_frame_flag=1 
\
      --post pp:quality=0 \
      vertrezmotion.ts

If I use xv instead of opengl then everything works fine (except the 
tearing caused by missing vsync).

CPU usage is minimal. I've added a logging of frames_to_skip to function 
vo_frame_draw() in video_out.c. In case of xv output it settles around 
-14 after a while. And in case of opengl it oscillates between ca. -10 
and 24. Does anybody have an idea what could be wrong?


Michal

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