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Slightly improve frame prediction cutoff point

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* frame_clock.c (PostEndFrame): Use 5000 us by default, only
reverting to the old algorithm if the presentation time is less
than that.
This commit is contained in:
hujianwei 2022-10-23 13:18:32 +00:00
parent 19f6f6454c
commit 491f1a6a1c
1 changed files with 16 additions and 5 deletions
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21
frame_clock.c
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@ -29,7 +29,11 @@ typedef struct _CursorClockCallback CursorClockCallback;
enum
{
/* 150ms. */
MaxPresentationAge = 150000,
MaxPresentationAge = 150000,
/* 5000 microseconds. This arbitrary value is the longest it
normally takes for a sync counter update to be processed by the
compositor. */
PresentationThreshold = 5000,
};
/* Whether or not the compositor supports frame synchronization. */
@ -333,10 +337,17 @@ PostEndFrame (FrameClock *clock)
return;
}
/* Use 3/4ths of the presentation time. Any more and we risk the
counter value change signalling the end of the frame arriving
after the presentation deadline. */
target = target - (clock->presentation_time / 4 * 3);
/* Use 5000 microseconds before the presentation time, or 3/4th of
it if it is less than 5000. Any more and we risk the counter
value change signalling the end of the frame arriving after the
presentation deadline. */
if (clock->presentation_time > PresentationThreshold)
target = target - (clock->presentation_time - PresentationThreshold);
else
/* However, if the presentation time is less than 5000
microseconds, use 3/4ths of it. This computation seems to be a
good enough fallback. */
target = target - (clock->presentation_time / 4 * 3);
/* Add the remainder of now if it was probably truncated by the
compositor. */