[obs] report video cadence over LGMP

obs/frame_scheduler.c

@@ -0,0 +1,156 @@
+/**
+ * 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
+ */
+
+#include "frame_scheduler.h"
+
+#include <common/KVMFR.h>
+
+#include <string.h>
+
+#define FRAME_SCHEDULER_LEASE_MS        1000U
+#define FRAME_SCHEDULER_RENEW_NS        250000000ULL
+#define FRAME_SCHEDULER_FEEDBACK_NS     50000000ULL
+#define FRAME_SCHEDULER_TARGET_SLACK_NS 1000000ULL
+#define FRAME_SCHEDULER_MIN_PERIOD_NS   2000000ULL
+#define FRAME_SCHEDULER_MAX_PERIOD_NS   1000000000ULL
+
+void lgFrameSchedulerInit(LGFrameScheduler * scheduler, bool supported,
+    uint32_t clientID)
+{
+  memset(scheduler, 0, sizeof(*scheduler));
+  scheduler->supported = supported;
+  scheduler->clientID  = clientID;
+}
+
+void lgFrameSchedulerSetPeriod(LGFrameScheduler * scheduler,
+    uint64_t period)
+{
+  if (!scheduler->supported ||
+      period < FRAME_SCHEDULER_MIN_PERIOD_NS ||
+      period > FRAME_SCHEDULER_MAX_PERIOD_NS)
+    return;
+
+  bool reset = !scheduler->period;
+  if (!reset)
+  {
+    const uint64_t delta = scheduler->period > period ?
+      scheduler->period - period : period - scheduler->period;
+    reset = delta > scheduler->period / 20;
+  }
+
+  scheduler->period = period;
+  if (!reset)
+    return;
+
+  ++scheduler->generation;
+  scheduler->resetPending        = true;
+  scheduler->phaseError          = 0;
+  scheduler->feedbackFrameSerial = 0;
+  scheduler->feedbackSamples     = 0;
+  scheduler->feedbackDirty       = false;
+}
+
+void lgFrameSchedulerObserveFrame(LGFrameScheduler * scheduler,
+    uint32_t frameSerial, uint32_t generation, uint64_t readyTime)
+{
+  if (!generation ||
+      (scheduler->readyFrameSerial == frameSerial &&
+        scheduler->readyGeneration == generation))
+    return;
+
+  scheduler->readyFrameSerial = frameSerial;
+  scheduler->readyGeneration  = generation;
+  scheduler->readyTime        = readyTime;
+}
+
+void lgFrameSchedulerFeedback(LGFrameScheduler * scheduler,
+    uint32_t frameSerial, uint32_t generation, uint64_t neededTime)
+{
+  if (!scheduler->active || generation != scheduler->generation ||
+      frameSerial == scheduler->feedbackFrameSerial)
+    return;
+
+  uint64_t readyTime = neededTime;
+  if (scheduler->readyFrameSerial == frameSerial &&
+      scheduler->readyGeneration == generation)
+    readyTime = scheduler->readyTime;
+
+  const uint64_t measuredPhase = neededTime > readyTime ?
+    neededTime - readyTime : 0;
+  int64_t error = measuredPhase > FRAME_SCHEDULER_TARGET_SLACK_NS ?
+    (int64_t)(measuredPhase - FRAME_SCHEDULER_TARGET_SLACK_NS) :
+    -(int64_t)(FRAME_SCHEDULER_TARGET_SLACK_NS - measuredPhase);
+  const int64_t period = (int64_t)scheduler->period;
+  error %= period;
+  if (error > period / 2)
+    error -= period;
+  else if (error < -period / 2)
+    error += period;
+
+  if (!scheduler->feedbackSamples)
+    scheduler->phaseError = error;
+  else
+    scheduler->phaseError = (scheduler->phaseError * 7 + error) / 8;
+  if (scheduler->feedbackSamples < 32)
+    ++scheduler->feedbackSamples;
+
+  scheduler->feedbackFrameSerial = frameSerial;
+  scheduler->feedbackDirty       = true;
+}
+
+void lgFrameSchedulerUpdate(LGFrameScheduler * scheduler,
+    PLGMPClientQueue queue, uint64_t now)
+{
+  if (!scheduler->supported || !scheduler->period || !queue)
+    return;
+
+  const uint64_t interval = scheduler->feedbackDirty ?
+    FRAME_SCHEDULER_FEEDBACK_NS : FRAME_SCHEDULER_RENEW_NS;
+  if (scheduler->active && !scheduler->resetPending &&
+      now - scheduler->lastSend < interval)
+    return;
+
+  KVMFRFrameScheduleFlags flags = KVMFR_FRAME_SCHEDULE_ACTIVE;
+  if (scheduler->resetPending)
+    flags |= KVMFR_FRAME_SCHEDULE_RESET;
+
+  const uint32_t feedbackFrameSerial =
+    scheduler->feedbackFrameSerial;
+  const KVMFRFrameSchedule message = {
+    .msg.type            = KVMFR_MESSAGE_FRAME_SCHEDULE,
+    .clientID            = scheduler->clientID,
+    .generation          = scheduler->generation,
+    .flags               = flags,
+    .period              = scheduler->period,
+    .targetSlack         = FRAME_SCHEDULER_TARGET_SLACK_NS,
+    .phaseError          = scheduler->phaseError,
+    .feedbackFrameSerial = feedbackFrameSerial,
+    .lease               = FRAME_SCHEDULER_LEASE_MS,
+  };
+
+  if (lgmpClientSendData(queue, &message, sizeof(message), NULL) != LGMP_OK)
+    return;
+
+  scheduler->active       = true;
+  scheduler->resetPending = false;
+  scheduler->lastSend     = now;
+  if (scheduler->feedbackFrameSerial == feedbackFrameSerial)
+    scheduler->feedbackDirty = false;
+}