frame pacing fix

cmd/mxl-player/frame_pacing.go

@@ -0,0 +1,24 @@
+package main
+
+import "time"
+
+const guiFrameInterval = time.Second / 60
+
+// videoPollInterval bounds GUI latency when no video producer is waiting.
+// It is not a video-rate cap: Next returns immediately whenever a frame
+// arrives, including for sources faster than this interval.
+const videoPollInterval = 8 * time.Millisecond
+
+func remainingFrameTime(start, now time.Time, interval time.Duration) time.Duration {
+	remaining := interval - now.Sub(start)
+	if remaining < 0 {
+		return 0
+	}
+	return remaining
+}
+
+func paceFrame(start time.Time) {
+	if remaining := remainingFrameTime(start, time.Now(), guiFrameInterval); remaining > 0 {
+		time.Sleep(remaining)
+	}
+}