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[client] x11: added code to calibrate a delay for presentation

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XPresent doesn't give us the time before presentation, but the time just
after. This code calculates and calibrates a delay to sleep for before
signaling the wait event for render when using jitRender
This commit is contained in:
Geoffrey McRae 2021-08-03 07:51:03 +10:00
parent 504bf02855
commit 03ed8b7304
1 changed files with 61 additions and 1 deletions
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62
client/displayservers/X11/x11.c
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@ -1030,12 +1030,72 @@ static void x11XInputEvent(XGenericEventCookie *cookie)
static void x11XPresentEvent(XGenericEventCookie *cookie)
{
#define CALIBRATION_COUNT 200
uint64_t deltats = 0;
uint64_t deltamsc = 0;
switch(cookie->evtype)
{
case PresentCompleteNotify:
{
lgSignalEvent(x11.frameEvent);
x11DoPresent();
XPresentCompleteNotifyEvent * e = cookie->data;
/* calibrate a delay to push our presentation time forward as far as
* possible without skipping frames */
static int calibrate = 0;
static uint64_t lastts = 0;
static uint64_t lastmsc = 0;
static uint64_t delay = 0;
if (lastts)
{
deltats = e->ust - lastts;
deltamsc = e->msc - lastmsc;
if (calibrate == 0)
{
if (!delay)
delay = deltats / 2;
else
{
/* increase the delay until we see a skip */
if (deltamsc < 2)
delay += 100;
else
{
delay -= 100;
++calibrate;
}
}
}
else
{
if (calibrate < CALIBRATION_COUNT)
{
/* every skip we back off the delay */
if (deltamsc > 1)
{
delay -= 100;
calibrate = 1;
}
/* if we have finished, print out the delay */
if (++calibrate == CALIBRATION_COUNT)
DEBUG_INFO("Calibration done, delay = %lu us", delay);
}
}
}
lastts = e->ust;
lastmsc = e->msc;
/* minor adjustments if we are still seeing odd skips */
if (deltamsc > 1)
delay -= 10;
usleep(delay);
lgSignalEvent(x11.frameEvent);
break;
}
}