mvGrabRelease(3dm)mvGrabRelease(3dm)NAME
mvGrabOpenGL, mvReleaseOpenGL - provide safe usage of graphics libraries
from Movie Playback Library clients
SYNOPSIS
#include <dmedia/movieplay.h>
void mvGrabOpenGL(void);
void mvReleaseOpenGL(void);
DESCRIPTIONmvGrabOpenGL(3dm) tells the Movie Playback Library that your application
wishes to use OpenGL. These functions temporarily suspend display of all
movie instances until you call mvReleaseOpenGL(3dm). mvGrabOpenGL(3dm)
does not stop playback; instead, it merely suspends the display of images
on the workstation screen.
Internally, the Movie Playback Library uses the sproc(2) system call to
provide asynchronous playback in a separate execution thread. Multiple
threads in the same process may have access to the graphics library, but
no two threads may issue a graphics library call simultaneously. Thus,
you must tell Movie Playback Library when you intend to use the graphics
library so that it can avoid making a graphics library call at the same
time you do. Currently under X11, in order to have multiple threads work
safely, each thread must have it's own display connection. The Movie
Playback Library opens up a separate display connection for each thread
that needs one and it uses the display connection provided via
mvOpenPort(3dm) or mvBindOpenGLWindow(3dm) in the thread in which those
calls were invoked.
If you perform graphics library rendering in the same process as you use
the Movie Playback Library for playback, you should call the relevant
grab function before and release function after those places in your code
where graphics library calls are invoked. The Movie Playback Library
will not update the on-screen images of the movies while you have grabbed
the graphics library, so if your rendering takes a long time, movie
playback will appear interrupted.
Once you grab the graphics library, you must always call
mvReleaseOpenGL(3dm) to resume normal movie playback. You must not call
mvReleaseOpenGL(3dm) without first calling mvGrabOpenGL(3dm). Finally,
you should not invoke two grab functions or two release functions in
succession without calling the counterpart function in between.
As an alternative to these calls, you may instead tell Movie Playback
Library not to display images on the screen altogether. To do this, use
mvSetEnableVideo(3dm). Then, you request frame events via the Movie
Playback Library event queue. When you receive a frame event, you can
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mvGrabRelease(3dm)mvGrabRelease(3dm)
tell Movie Playback Library to display the frame by calling
mvShowCurrentFrame(3dm). This alternate method will eliminate any chance
of contention for the graphics library, without requiring you to use
mvGrabOpenGL(3dm).
SEE ALSOmvBindOpenGLWindow(3dm), mvIntro(3dm), mvNextEvent(3dm), mvOpenPort(3dm),
mvRenderMovieToImageBuffer(3dm), mvRenderMovieToOpenGL(3dm),
mvSetEnableVideo(3dm), sproc(2)
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