This uses glXGetVideoSyncSGI() to check how many vsyncs happened since
the last flip_page() call. It allows checking a pattern of vsync
increments of at most 2 elements. For example, to check ~24 fps playback
on a ~60 Hz monitor, this can be used:
--vo=opengl:check-pattern=[3-2]:waitvsync
Whether the reported results are accurate or just plain wrong may depend
on the driver and if the waitvsync sub-option is used. There are no
guarantees.
This option is undocumented, and may be removed again in the near or
distant future.
wm4
cd2e4db8a5