[obs] report video cadence over LGMP

obs/frame_scheduler.h

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+/**
+ * Looking Glass
+ * Copyright © 2017-2026 The Looking Glass Authors
+ * https://looking-glass.io
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc., 59
+ * Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#ifndef LG_OBS_FRAME_SCHEDULER_H
+#define LG_OBS_FRAME_SCHEDULER_H
+
+#include <lgmp/client.h>
+
+#include <stdbool.h>
+#include <stdint.h>
+
+typedef struct LGFrameScheduler
+{
+  bool     supported;
+  bool     active;
+  bool     resetPending;
+  bool     feedbackDirty;
+  uint32_t clientID;
+  uint32_t generation;
+  uint64_t period;
+  uint64_t lastSend;
+
+  int64_t  phaseError;
+  uint32_t feedbackFrameSerial;
+  unsigned feedbackSamples;
+
+  uint32_t readyFrameSerial;
+  uint32_t readyGeneration;
+  uint64_t readyTime;
+}
+LGFrameScheduler;
+
+void lgFrameSchedulerInit(LGFrameScheduler * scheduler, bool supported,
+    uint32_t clientID);
+void lgFrameSchedulerSetPeriod(LGFrameScheduler * scheduler,
+    uint64_t period);
+void lgFrameSchedulerObserveFrame(LGFrameScheduler * scheduler,
+    uint32_t frameSerial, uint32_t generation, uint64_t readyTime);
+void lgFrameSchedulerFeedback(LGFrameScheduler * scheduler,
+    uint32_t frameSerial, uint32_t generation, uint64_t neededTime);
+void lgFrameSchedulerUpdate(LGFrameScheduler * scheduler,
+    PLGMPClientQueue queue, uint64_t now);
+
+#endif