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Name
ANGLE_sync_control_rate
Name Strings
EGL_ANGLE_sync_control_rate
Contact
Jonah Ryan-Davis, Google (jonahr 'at' google.com)
Status
Draft.
Version
Version 1, 2020-03-24
Based on GLX_OML_sync_control Revision 6.0
Related to EGL_CHROMIUM_sync_control Revision 2.0
Number
142
Dependencies
The extension is written against the EGL 1.2 Specification, although it
should work on other versions of these specifications.
Overview
This extension provides counters which let applications know about the
timing of the last vertical retrace. By looking at the system clock, as
well as the refresh rate of the monitor, this should enable applications
to predict the position of future retraces so as to schedule an optimal
workload.
This extension incorporates the use of a counter that provides the
necessary synchronization. The graphics Media Stream Counter (or
graphics MSC) is a counter that is unique to the graphics subsystem
and increments for each vertical retrace that occurs.
By querying the MSC rate for a given surface, the application can
accurately predict the timing for the next vertical retraces and schedule
rendering accordingly.
Issues
None.
IP Status
No known issues.
New Procedures and Functions
Bool eglGetMscRateANGLE(EGLDisplay* dpy,
EGLSurface surface,
int32_t* numerator,
int32_t* denominator)
New Tokens
None
Additions to the EGL 1.3 Specification
The graphics MSC value is incremented once for each screen refresh.
For a non-interlaced display, this means that the graphics MSC value
is incremented for each frame. For an interlaced display, it means
that it will be incremented for each field. For a multi-monitor
system, the monitor used to determine MSC is the one where the surface
is located. If the surface spans multiple monitors, the monitor used
to determine MSC is the one with the biggest coverage in pixels.
eglGetMscRateANGLE returns the rate at which the MSC will be incremented
for the display associated with <dpy> and <surface>. The rate is expressed
in Hertz as <numerator> / <denominator>. If the MSC rate in Hertz is an
integer, then <denominator> will be 1 and <numerator> will be
the MSC rate.
Errors
The function eglGetMscRateANGLE returns FALSE on failure.
If <dpy> is not a valid EGLDisplay, EGL_BAD_DISPLAY is generated.
If <surface> is not a valid EGLSurface, EGL_BAD_SURFACE is generated.
If there is no current EGLContext, EGL_BAD_CONTEXT is generated.
New Implementation Dependent State
None
Revision History
Version 1, 2020-03-24 (Jonah Ryan-Davis)
- Initial draft, based on GLX_OML_sync_control revision 6.0.
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