fix underflow

1 files changed, 6 insertions, 3 deletions

diff --git a/main/main-impl.cpp b/main/main-impl.cpp
index f4593344..d2ea74cc 100644
--- a/main/main-impl.cpp
+++ b/main/main-impl.cpp
@@ -244,17 +244,20 @@ void main_impl::drawEvent()
 #ifdef _WIN32
         constexpr float eps = 1e-3f;
 #else
-        constexpr float eps = 2e-4f;
+        constexpr float eps = 1e-4f;
 #endif
 
-        const float dt0 = timeline.currentFrameDuration(), sleep_secs = dt_expected.value - dt0 - dt_expected.jitter;
+        const float Δt൦ = timeline.currentFrameDuration(), sleep_secs = dt_expected.value - Δt൦ - dt_expected.jitter;
         if (sleep_secs > eps)
         {
             //fm_debug("sleeping for %.1f <- %.1f\n", sleep_secs*1000, dt0*1000);
             std::this_thread::sleep_for(std::chrono::nanoseconds((long long)(sleep_secs * 1e9f)));
         }
         //fm_debug("jitter:%.1f sleep:%.0f", dt_expected.jitter*1000, sleep_secs*1000);
-        dt_expected.jitter += 0.1f * (timeline.currentFrameDuration() - dt_expected.value);
+        const float Δt = (timeline.currentFrameDuration() - dt_expected.value);
+        constexpr float α = .1f;
+        dt_expected.jitter = std::fmax(dt_expected.jitter + Δt * α,
+                                       dt_expected.jitter * (1-α) + Δt * α);
         dt_expected.jitter = std::copysignf(std::fminf(dt_expected.value, std::fabsf(dt_expected.jitter)), dt_expected.jitter);
     }
     else