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comp: wait for next frame in xrWaitFrame

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fixes 6e396ed

It was unnecessary to move the wait to xrEndFrame.
It does not matter if the compositor renders the frame immediately because the
frame physically can not be displayed before the next HMD refresh.

On the other hand, leaving too short of a time for the compositor to render
may delay the frame past its predicted time.
This commit is contained in:
Christoph Haag 2019-08-19 19:18:50 +02:00 committed by Jakob Bornecrantz
parent 24184969ab
commit d9736ba3b7
1 changed files with 21 additions and 17 deletions
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38
src/xrt/compositor/main/comp_compositor.c
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@ -82,14 +82,32 @@ compositor_wait_frame(struct xrt_compositor *xc,
{
struct comp_compositor *c = comp_compositor(xc);
COMP_SPEW(c, "WAIT_FRAME");
// HACK: Wait until the frame is predicted to be displayed.
// This needs improvement, but blocks for plausible timings.
int64_t already_used =
time_state_get_now(c->timekeeping) - c->last_frame_time_ns;
int64_t remaining_usec =
((int64_t)c->settings.nominal_frame_interval_ns - already_used) /
1000;
// leave 1.25 ms for overhead
if (remaining_usec > 1250)
usleep(remaining_usec - 1250);
*predicted_display_period = c->settings.nominal_frame_interval_ns;
*predicted_display_time =
c->last_frame_time_ns + c->settings.nominal_frame_interval_ns;
//! @todo set *predicted_display_time
// if frame intervals were missed, keep adding intervals until we
// predict the next one in the future. Also make sure we leave the
// application at least half a frame interval for rendering.
// *predicted_display_time = 0;
// *predicted_display_period = 0;
int64_t now = time_state_get_now(c->timekeeping);
while (*predicted_display_time <
now - (int64_t)c->settings.nominal_frame_interval_ns / 2)
*predicted_display_time +=
c->settings.nominal_frame_interval_ns;
}
static void
@ -120,20 +138,6 @@ compositor_end_frame(struct xrt_compositor *xc,
struct comp_swapchain_image *right;
struct comp_swapchain_image *left;
//! HACK: Wait until the frame is predicted to be displayed.
// This needs improvement, but blocks for plausible timings.
uint64_t now = time_state_get_now(c->timekeeping);
uint64_t already_used = now - c->last_frame_time_ns;
if (already_used < c->settings.nominal_frame_interval_ns) {
uint64_t remaining_usec =
(c->settings.nominal_frame_interval_ns - already_used) /
1000;
remaining_usec -= 500; // HACK: leave a bit of time for overhead
// printf("Remaining usec before this frame is displayed :
// %lu\n", remaining_usec);
usleep(remaining_usec);
}
// Stereo!
if (num_swapchains == 2) {
left = &comp_swapchain(xscs[0])->images[image_index[0]];