glXGetVideoSyncSGI(3G) OpenGL Reference - GLX glXGetVideoSyncSGI(3G)NAME
glXGetVideoSyncSGI - obtain value of vertical retrace counter
C SPECIFICATION
int glXGetVideoSyncSGI( unsigned int *count )
PARAMETERS
count Pointer to variable which receives the value of the vertical
retrace counter of the graphics pipeline associated with the
current context.
DESCRIPTION
glXGetVideoSyncSGI is part of the SGI_video_sync extension. This
extension provides a way to synchronize with the video frame rate of a
monitor (in the case of an interlaced display, the synchronization is
actually with the field rate).
A vertical retrace precedes the display of each video frame. The kernel
maintains a 32-bit unsigned integer counter for each graphics pipe in the
system. This counter is initialized via the /usr/gfx/gfxinit command,
and incremented upon each vertical retrace. Since all the video output
channels of a graphics pipe must be genlocked, one counter suffices for
all the monitors driven by a pipe.
A process can query or sleep on the counter of the graphics pipe
associated with its current OpenGL rendering context, provided that the
rendering context is direct. (See glXCreateContext.)
If the current context is direct, glXGetVideoSyncSGI places the value of
the vertical retrace counter in the location referenced by count, then
returns zero. Otherwise, glXGetVideoSyncSGI returns GLX_BAD_CONTEXT_SGI.
SEE ALSO
glXWaitVideoSyncSGI, glXCreateContext, glXQueryVersion, glGetString
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