Name
ANDROID_get_frame_timestamps
Name Strings
EGL_ANDROID_get_frame_timestamps
Contributors
Brian Anderson
Dan Stoza
Pablo Ceballos
Jesse Hall
Fabien Sanglard
Contact
Brian Anderson, Google Inc. (brianderson 'at' google.com)
Dan Stoza, Google Inc. (stoza 'at' google.com)
Pablo Ceballos, Google Inc. (pceballos 'at' google.com)
Jesse Hall, Google Inc. (jessehall 'at' google.com)
Fabien Sanglard, Google Inc. (sanglardf 'at' google.com)
Status
Draft
Version
Version 8, April 11, 2017
Number
EGL Extension #XXX
Dependencies
Requires EGL 1.2
This extension is written against the wording of the EGL 1.5 Specification
Overview
This extension allows querying various timestamps related to the composition
and display of window surfaces.
Some examples of how this might be used:
- The display present time can be used to calculate end-to-end latency
of the entire graphics pipeline.
- The queue time and rendering complete time can be used to determine
how long the application's rendering took to complete. Likewise, the
composition start time and finish time can be used to determine how
long the compositor's rendering work took. In combination these can be
used to help determine if the system is GPU or CPU bound.
New Types
/*
* EGLnsecsANDROID is a signed integer type for representing a time in
* nanoseconds.
*/
#include <khrplatform.h>
typedef khronos_stime_nanoseconds_t EGLnsecsANDROID;
New Procedures and Functions
EGLBoolean eglGetNextFrameIdANDROID(EGLDisplay dpy, EGLSurface surface,
EGLuint64KHR *frameId);
EGLBoolean eglGetCompositorTimingANDROID(EGLDisplay dpy,
EGLSurface surface, EGLint numTimestamps,
const EGLint *names, EGLnsecsANDROID *values);
EGLBoolean eglGetFrameTimestampsANDROID(EGLDisplay dpy, EGLSurface surface,
EGLuint64KHR frameId, EGLint numTimestamps,
const EGLint *timestamps, EGLnsecsANDROID *values);
EGLBoolean eglQueryTimestampSupportedANDROID(EGLDisplay dpy,
EGLSurface surface, EGLint timestamp);
New Tokens
EGL_TIMESTAMPS_ANDROID 0x3430
EGL_COMPOSITE_DEADLINE_ANDROID 0x3431
EGL_COMPOSITE_INTERVAL_ANDROID 0x3432
EGL_COMPOSITE_TO_PRESENT_LATENCY_ANDROID 0x3433
EGL_REQUESTED_PRESENT_TIME_ANDROID 0x3434
EGL_RENDERING_COMPLETE_TIME_ANDROID 0x3435
EGL_COMPOSITION_LATCH_TIME_ANDROID 0x3436
EGL_FIRST_COMPOSITION_START_TIME_ANDROID 0x3437
EGL_LAST_COMPOSITION_START_TIME_ANDROID 0x3438
EGL_FIRST_COMPOSITION_GPU_FINISHED_TIME_ANDROID 0x3439
EGL_DISPLAY_PRESENT_TIME_ANDROID 0x343A
EGL_DEQUEUE_READY_TIME_ANDROID 0x343B
EGL_READS_DONE_TIME_ANDROID 0x343C
EGL_TIMESTAMP_PENDING_ANDROID -2
EGL_TIMESTAMP_INVALID_ANDROID -1
Add to the list of supported tokens for eglSurfaceAttrib in section 3.5.6
"Surface Attributes", page 43:
If attribute is EGL_TIMESTAMPS_ANDROID, then values specifies whether to
enable/disable timestamp collection for this surface. A value of EGL_TRUE
enables timestamp collection, while a value of EGL_FALSE disables it. The
initial value is false. If surface is not a window surface this has no
effect.
Changes to Chapter 3 of the EGL 1.5 Specification (EGL Functions and Errors)
Add a new subsection under Section 3,
"3.13 Composition and Display Timestamps
The function
EGLBoolean eglGetNextFrameIdANDROID(EGLDisplay dpy, EGLSurface surface,
EGLuint64KHR *frameId);
Returns an identifier for the next frame to be swapped. The identifier can
be used to correlate a particular eglSwapBuffers with its timestamps in
eglGetFrameTimestampsANDROID. If any error is generated, the function will
return EGL_FALSE.
The function
EGLBoolean eglGetCompositorTimingANDROID(EGLDisplay dpy,
EGLSurface surface, EGLint numTimestamps,
const EGLint *names, EGLnsecsANDROID *values);
allows querying anticipated timestamps and durations related to the
composition and display of a window surface. The values are not associated
with a particular frame and can be retrieved before the first swap.
The eglGetCompositorTimingANDROID function takes an array of names to
query and returns their values in the corresponding indices of the values
array. The possible names that can be queried are:
- EGL_COMPOSITE_DEADLINE_ANDROID - The timestamp of the next time the
compositor will begin composition. This is effectively the deadline
for when the compositor must receive a newly queued frame.
- EGL_COMPOSITE_INTERVAL_ANDROID - The time delta between subsequent
composition events.
- EGL_COMPOSITE_TO_PRESENT_LATENCY_ANDROID - The time delta between
the start of composition and the expected present time of that
composition. This can be used to estimate the latency of the
actual present time.
The function
EGLBoolean eglGetFrameTimestampsANDROID(EGLDisplay dpy,
EGLSurface surface, EGLuint64KHR frameId, EGLint numTimestamps,
const EGLint *timestamps, EGLnsecsANDROID *values);
allows querying various timestamps related to the composition and display
of specific frames of a window surface.
The frameId indicates which frame to query. The implementation maintains a
limited history of timestamp data. If a query is made for a frame whose
timestamp history no longer exists then EGL_BAD_ACCESS is generated. If
timestamp collection has not been enabled for the surface then
EGL_BAD_SURFACE is generated. Timestamps for events that might still occur
will have the value EGL_TIMESTAMP_PENDING_ANDROID. Timestamps for events
that did not occur will have the value EGL_TIMESTAMP_INVALID_ANDROID.
Otherwise, the timestamp will be valid and indicate the event has occured.
Timestamp queries that are not supported will generate an EGL_BAD_PARAMETER
error. If any error is generated the function will return EGL_FALSE.
The application can poll for the timestamp of particular events by calling
eglGetFrameTimestamps over and over without needing to call any other EGL
function between calls. This is true even for the most recently swapped
frame. eglGetFrameTimestamps is thread safe and can be called from a
different thread than the swapping thread.
The eglGetFrameTimestampsANDROID function takes an array of timestamps to
query and returns timestamps in the corresponding indices of the values
array. The possible timestamps that can be queried are:
- EGL_REQUESTED_PRESENT_TIME_ANDROID - The time the application
requested this frame be presented. See EGL_ANDROID_presentation_time.
If the application does not request a presentation time explicitly,
this will correspond to buffer's queue time.
- EGL_RENDERING_COMPLETE_TIME_ANDROID - The time when all of the
application's rendering to the surface was completed.
- EGL_COMPOSITION_LATCH_TIME_ANDROID - The time when the compositor
selected this frame as the one to use for the next composition. The
latch is the earliest indication that the frame was submitted in time
to be composited.
- EGL_FIRST_COMPOSITION_START_TIME_ANDROID - The first time at which
the compositor began preparing composition for this frame.
- EGL_LAST_COMPOSITION_START_TIME_ANDROID - The last time at which the
compositor began preparing composition for this frame. If this frame
is composited only once, it will have the same value as
EGL_FIRST_COMPOSITION_START_TIME_ANDROID. If the value is not equal,
that indicates the subsequent frame was not submitted in time to be
latched by the compositor. Note: The value may not be updated for
every display refresh if the compositor becomes idle.
- EGL_FIRST_COMPOSITION_GPU_FINISHED_TIME_ANDROID - The time at which
the compositor's rendering work for this frame finished. This will be
zero if composition was handled by the display and the compositor
didn't do any rendering.
- EGL_DISPLAY_PRESENT_TIME_ANDROID - The time at which this frame
started to scan out to the physical display.
- EGL_DEQUEUE_READY_TIME_ANDROID - The time when the buffer became
available for reuse as a buffer the client can target without
blocking. This is generally the point when all read commands of the
buffer have been submitted, but not necessarily completed.
- EGL_READS_DONE_TIME_ANDROID - The time at which all reads for the
purpose of display/composition were completed for this frame.
Not all implementations may support all of the above timestamp queries. The
functions
EGLBoolean eglGetCompositorTimingSupportedANDROID(EGLDisplay dpy,
EGLSurface surface, EGLint name);
and
EGLBoolean eglGetFrameTimestampsSupportedANDROID(EGLDisplay dpy,
EGLSurface surface, EGLint timestamp);
allows querying which values are supported by the implementations of
eglGetCompositoTimingANDROID and eglGetFrameTimestampsSupportedANDROID
respectively."
Issues
None
Revision History
#8 (Brian Anderson, April 11, 2017)
- Use reserved enumerant values.
#7 (Brian Anderson, March 21, 2017)
- Differentiate between pending events and events that did not occur.
#6 (Brian Anderson, March 16, 2017)
- Remove DISPLAY_RETIRE_TIME_ANDROID.
#5 (Brian Anderson, January 13, 2017)
- Add eglGetCompositorTimingANDROID.
#4 (Brian Anderson, January 10, 2017)
- Use an absolute frameId rather than a relative framesAgo.
#3 (Brian Anderson, November 30, 2016)
- Add EGL_COMPOSITION_LATCH_TIME_ANDROID,
EGL_LAST_COMPOSITION_START_TIME_ANDROID, and
EGL_DEQUEUE_READY_TIME_ANDROID.
#2 (Brian Anderson, July 22, 2016)
- Replace EGL_QUEUE_TIME_ANDROID with EGL_REQUESTED_PRESENT_TIME_ANDROID.
- Add DISPLAY_PRESENT_TIME_ANDROID.
#1 (Pablo Ceballos, May 31, 2016)
- Initial draft.