[obs] scheduler: release ownership when source is idle

Renew frame scheduling only while the source is active and OBS is
delivering video ticks. Release ownership after deactivation or a stale
tick stream.

Reacquire with a new generation and an immediate frame when ticking
resumes.

obs/frame_scheduler.c

@@ -27,10 +27,26 @@
 #define FRAME_SCHEDULER_LEASE_MS        1000U
 #define FRAME_SCHEDULER_RENEW_NS        250000000ULL
 #define FRAME_SCHEDULER_FEEDBACK_NS     50000000ULL
+#define FRAME_SCHEDULER_TICK_GRACE_NS   500000000ULL
 #define FRAME_SCHEDULER_TARGET_SLACK_NS 1000000ULL
 #define FRAME_SCHEDULER_MIN_PERIOD_NS   2000000ULL
 #define FRAME_SCHEDULER_MAX_PERIOD_NS   1000000000ULL
 
+static void lgFrameSchedulerResetFeedback(LGFrameScheduler * scheduler)
+{
+  scheduler->phaseError             = 0;
+  scheduler->feedbackFrameSerial    = 0;
+  scheduler->feedbackScheduleEpoch  = 0;
+  scheduler->feedbackDeadlineSerial = 0;
+  scheduler->feedbackSamples        = 0;
+  scheduler->feedbackDirty          = false;
+  scheduler->readyFrameSerial       = 0;
+  scheduler->readyGeneration        = 0;
+  scheduler->readyScheduleEpoch     = 0;
+  scheduler->readyDeadlineSerial    = 0;
+  scheduler->readyTime              = 0;
+}
+
 void lgFrameSchedulerInit(LGFrameScheduler * scheduler, bool supported,
     uint32_t clientID)
 {
@@ -40,14 +56,30 @@ void lgFrameSchedulerInit(LGFrameScheduler * scheduler, bool supported,
   scheduler->clientID         = clientID;
 }
 
-void lgFrameSchedulerSetPeriod(LGFrameScheduler * scheduler,
+void lgFrameSchedulerSetActive(LGFrameScheduler * scheduler, bool active)
-    uint64_t period)
 {
-  if (!scheduler->supported ||
+  if (!scheduler->supported || scheduler->sourceActive == active)
-      period < FRAME_SCHEDULER_MIN_PERIOD_NS ||
-      period > FRAME_SCHEDULER_MAX_PERIOD_NS)
     return;
 
+  scheduler->sourceActive = active;
+  if (!active)
+    scheduler->lastTick = 0;
+}
+
+void lgFrameSchedulerSetPeriod(LGFrameScheduler * scheduler,
+    uint64_t period, uint64_t tickTime)
+{
+  if (!scheduler->supported)
+    return;
+
+  scheduler->lastTick = tickTime;
+  if (period < FRAME_SCHEDULER_MIN_PERIOD_NS ||
+      period > FRAME_SCHEDULER_MAX_PERIOD_NS)
+  {
+    scheduler->period = 0;
+    return;
+  }
+
   bool reset = !scheduler->period;
   if (!reset)
   {
@@ -63,12 +95,7 @@ void lgFrameSchedulerSetPeriod(LGFrameScheduler * scheduler,
   ++scheduler->generation;
   scheduler->resetPending           = true;
   scheduler->immediatePending       = true;
-  scheduler->phaseError             = 0;
+  lgFrameSchedulerResetFeedback(scheduler);
-  scheduler->feedbackFrameSerial    = 0;
-  scheduler->feedbackScheduleEpoch  = 0;
-  scheduler->feedbackDeadlineSerial = 0;
-  scheduler->feedbackSamples        = 0;
-  scheduler->feedbackDirty          = false;
 }
 
 void lgFrameSchedulerRequestImmediate(LGFrameScheduler * scheduler)
@@ -145,9 +172,35 @@ void lgFrameSchedulerFeedback(LGFrameScheduler * scheduler,
 void lgFrameSchedulerUpdate(LGFrameScheduler * scheduler,
     PLGMPClientQueue queue, uint64_t now)
 {
-  if (!scheduler->supported || !scheduler->period || !queue)
+  if (!scheduler->supported || !queue)
     return;
 
+  const bool tickStale = !scheduler->lastTick ||
+    now - scheduler->lastTick > FRAME_SCHEDULER_TICK_GRACE_NS;
+  if (!scheduler->sourceActive || tickStale || !scheduler->period)
+  {
+    if (!scheduler->active)
+      return;
+
+    const KVMFRFrameSchedule message = {
+      .msg.type   = KVMFR_MESSAGE_FRAME_SCHEDULE,
+      .clientID   = scheduler->clientID,
+      .generation = scheduler->generation,
+      .flags      = KVMFR_FRAME_SCHEDULE_RELEASE,
+    };
+
+    if (lgmpClientSendData(queue, &message, sizeof(message), NULL) != LGMP_OK)
+      return;
+
+    scheduler->active           = false;
+    scheduler->resetPending     = false;
+    scheduler->immediatePending = true;
+    scheduler->period           = 0;
+    scheduler->lastSend         = now;
+    lgFrameSchedulerResetFeedback(scheduler);
+    return;
+  }
+
   const uint64_t interval = scheduler->feedbackDirty ?
     FRAME_SCHEDULER_FEEDBACK_NS : FRAME_SCHEDULER_RENEW_NS;
   if (scheduler->active && !scheduler->resetPending &&

obs/frame_scheduler.h

@@ -29,6 +29,7 @@
 typedef struct LGFrameScheduler
 {
   bool     supported;
+  bool     sourceActive;
   bool     active;
   bool     resetPending;
   bool     immediatePending;
@@ -37,6 +38,7 @@ typedef struct LGFrameScheduler
   uint32_t generation;
   uint64_t period;
   uint64_t lastSend;
+  uint64_t lastTick;
 
   int64_t  phaseError;
   uint32_t feedbackFrameSerial;
@@ -54,8 +56,9 @@ LGFrameScheduler;
 
 void lgFrameSchedulerInit(LGFrameScheduler * scheduler, bool supported,
     uint32_t clientID);
+void lgFrameSchedulerSetActive(LGFrameScheduler * scheduler, bool active);
 void lgFrameSchedulerSetPeriod(LGFrameScheduler * scheduler,
-    uint64_t period);
+    uint64_t period, uint64_t tickTime);
 void lgFrameSchedulerRequestImmediate(LGFrameScheduler * scheduler);
 void lgFrameSchedulerObserveFrame(LGFrameScheduler * scheduler,
     uint32_t frameSerial, uint32_t generation, uint32_t scheduleEpoch,

obs/lg.c

@@ -135,6 +135,7 @@ typedef struct
   bool                 frameSerialValid;
   pthread_mutex_t      pointerLock;
   LGFrameScheduler     frameScheduler;
+  _Atomic(bool)        sourceActive;
 
   bool                 cursorMono;
   gs_texture_t       * cursorTex;
@@ -437,6 +438,7 @@ static void * lgCreate(obs_data_t * settings, obs_source_t * context)
   atomic_store(&this->cursorVer, 0);
   atomic_store(&this->cursorTransformVer, 0);
   atomic_store(&this->sdrWhiteLevel, KVMFR_SDR_WHITE_LEVEL_DEFAULT);
+  atomic_store(&this->sourceActive, obs_source_active(context));
   lgUpdate(this, settings);
   return this;
 }
@@ -723,6 +725,8 @@ static void * frameThread(void * data)
     }
 
     pthread_mutex_lock(&this->pointerLock);
+    lgFrameSchedulerSetActive(&this->frameScheduler,
+      atomic_load_explicit(&this->sourceActive, memory_order_acquire));
     lgFrameSchedulerUpdate(&this->frameScheduler,
       this->pointerQueue, now);
     pthread_mutex_unlock(&this->pointerLock);
@@ -970,7 +974,6 @@ static void lgUpdate(void * data, obs_data_t * settings)
 
   lgFrameSchedulerInit(&this->frameScheduler,
     udata->features & KVMFR_FEATURE_FRAME_SCHEDULE, clientID);
-  lgFrameSchedulerSetPeriod(&this->frameScheduler, lgFramePeriod());
 
   this->state = STATE_STARTING;
   createThreads(this);
@@ -1443,7 +1446,12 @@ static void lgVideoTick(void * data, float seconds)
     return;
   }
 
-  lgFrameSchedulerSetPeriod(&this->frameScheduler, framePeriod);
+  const bool sourceActive = atomic_load_explicit(
+    &this->sourceActive, memory_order_acquire);
+  lgFrameSchedulerSetActive(&this->frameScheduler, sourceActive);
+  if (sourceActive)
+    lgFrameSchedulerSetPeriod(
+      &this->frameScheduler, framePeriod, tickTime);
 
   this->cursorRect.x = this->cursor.x;
   this->cursorRect.y = this->cursor.y;
@@ -1724,6 +1732,20 @@ static void lgVideoTick(void * data, float seconds)
   obs_leave_graphics();
 }
 
+static void lgActivate(void * data)
+{
+  LGPlugin * this = (LGPlugin *)data;
+  atomic_store_explicit(
+    &this->sourceActive, true, memory_order_release);
+}
+
+static void lgDeactivate(void * data)
+{
+  LGPlugin * this = (LGPlugin *)data;
+  atomic_store_explicit(
+    &this->sourceActive, false, memory_order_release);
+}
+
 static void lgSetupCursorEffect(LGPlugin * this, int outputTransfer)
 {
   const KVMFRColorTransform * transform = &this->activeCursorTransform;
@@ -1916,6 +1938,8 @@ struct obs_source_info lg_source =
   .update                = lgUpdate,
   .get_defaults          = lgGetDefaults,
   .get_properties        = lgGetProperties,
+  .activate              = lgActivate,
+  .deactivate            = lgDeactivate,
   .video_tick            = lgVideoTick,
   .video_render          = lgVideoRender,
 #if LIBOBS_API_MAJOR_VER >= 28