[obs] report video cadence over LGMP

obs/CMakeLists.txt

@@ -104,6 +104,7 @@ link_libraries(
 
 set(SOURCES
   ${CMAKE_BINARY_DIR}/version.c
+  frame_scheduler.c
   main.c
   lg.c
 )

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;
+}

obs/frame_scheduler.h

@@ -0,0 +1,61 @@
+/**
+ * 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

obs/lg.c

@@ -23,6 +23,7 @@
 #include <obs/obs-config.h>
 #include <obs/obs-module.h>
 #include <obs/util/threading.h>
+#include <obs/util/platform.h>
 #include <obs/graphics/graphics.h>
 #include <obs/graphics/matrix4.h>
 
@@ -40,6 +41,7 @@
 #include "rgb24.effect.h"
 #include "hdrpq.effect.h"
 #include "cursor.effect.h"
+#include "frame_scheduler.h"
 
 /* scRGB reference white in cd/m² (OBS GS_CS_709_SCRGB is defined as
  * 1.0 = 80 cd/m²). PQ encodes an absolute 0..10000 cd/m² range, so linear
@@ -122,6 +124,8 @@ typedef struct
 
   pthread_t            frameThread, pointerThread;
   os_sem_t           * frameSem;
+  pthread_mutex_t      pointerLock;
+  LGFrameScheduler     frameScheduler;
 
   bool                 cursorMono;
   gs_texture_t       * cursorTex;
@@ -169,6 +173,16 @@ static void * frameThread(void * data);
 static void * pointerThread(void * data);
 static void lgUpdate(void * data, obs_data_t * settings);
 
+static uint64_t lgFramePeriod(void)
+{
+  struct obs_video_info videoInfo;
+  if (!obs_get_video_info(&videoInfo) ||
+      !videoInfo.fps_num || !videoInfo.fps_den)
+    return 0;
+
+  return 1000000000ULL * videoInfo.fps_den / videoInfo.fps_num;
+}
+
 static const char * lgGetName(void * unused)
 {
   return obs_module_text("Looking Glass Client");
@@ -266,6 +280,7 @@ static void * lgCreate(obs_data_t * settings, obs_source_t * context)
 
   os_sem_init (&this->frameSem , 0);
   os_sem_init (&this->cursorSem, 1);
+  pthread_mutex_init(&this->pointerLock, NULL);
   atomic_store(&this->cursorVer, 0);
   atomic_store(&this->cursorTransformVer, 0);
   atomic_store(&this->sdrWhiteLevel, KVMFR_SDR_WHITE_LEVEL_DEFAULT);
@@ -422,6 +437,7 @@ static void lgDestroy(void * data)
   deinit(this);
   os_sem_destroy(this->frameSem );
   os_sem_destroy(this->cursorSem);
+  pthread_mutex_destroy(&this->pointerLock);
 
   obs_enter_graphics();
   gs_effect_destroy(this->unpackEffect);
@@ -488,6 +504,23 @@ static void * frameThread(void * data)
         break;
       }
     }
+
+    const uint64_t now = os_gettime_ns();
+    if (status == LGMP_OK)
+    {
+      LGMPMessage msg;
+      if (lgmpClientProcess(this->frameQueue, &msg) == LGMP_OK)
+      {
+        const KVMFRFrame * frame = (const KVMFRFrame *)msg.mem;
+        lgFrameSchedulerObserveFrame(&this->frameScheduler,
+          frame->frameSerial, msg.udata, now);
+      }
+    }
+
+    pthread_mutex_lock(&this->pointerLock);
+    lgFrameSchedulerUpdate(&this->frameScheduler,
+      this->pointerQueue, now);
+    pthread_mutex_unlock(&this->pointerLock);
     os_sem_post(this->frameSem);
     usleep(1000);
   }
@@ -511,8 +544,11 @@ static void * pointerThread(void * data)
 {
   LGPlugin * this = (LGPlugin *)data;
 
-  if (lgmpClientSubscribe(
-        this->lgmp, LGMP_Q_POINTER, &this->pointerQueue) != LGMP_OK)
+  pthread_mutex_lock(&this->pointerLock);
+  const LGMP_STATUS subscribeStatus = lgmpClientSubscribe(
+    this->lgmp, LGMP_Q_POINTER, &this->pointerQueue);
+  pthread_mutex_unlock(&this->pointerLock);
+  if (subscribeStatus != LGMP_OK)
   {
     this->state = STATE_STOPPING;
     return NULL;
@@ -523,8 +559,10 @@ static void * pointerThread(void * data)
     LGMP_STATUS status;
     LGMPMessage msg;
 
+    pthread_mutex_lock(&this->pointerLock);
     if ((status = lgmpClientProcess(this->pointerQueue, &msg)) != LGMP_OK)
     {
+      pthread_mutex_unlock(&this->pointerLock);
       if (status != LGMP_ERR_QUEUE_EMPTY)
       {
         printf("lgmpClientProcess: %s\n", lgmpStatusString(status));
@@ -651,9 +689,12 @@ static void * pointerThread(void * data)
     }
 
     lgmpClientMessageDone(this->pointerQueue);
+    pthread_mutex_unlock(&this->pointerLock);
   }
 
+  pthread_mutex_lock(&this->pointerLock);
   lgmpClientUnsubscribe(&this->pointerQueue);
+  pthread_mutex_unlock(&this->pointerLock);
 
   bfree(this->cursorData);
   this->cursorData = NULL;
@@ -693,9 +734,10 @@ static void lgUpdate(void * data, obs_data_t * settings)
 
   usleep(200000);
 
+  uint32_t clientID;
   uint32_t remoteVersion;
   if ((status = lgmpClientSessionInit(this->lgmp, &udataSize,
-      (uint8_t **)&udata, NULL, &remoteVersion)) != LGMP_OK)
+      (uint8_t **)&udata, &clientID, &remoteVersion)) != LGMP_OK)
   {
     printf("lgmpClientSessionInit: %s", lgmpStatusString(status));
     if (status == LGMP_ERR_INVALID_VERSION)
@@ -719,6 +761,10 @@ static void lgUpdate(void * data, obs_data_t * settings)
     return;
   }
 
+  lgFrameSchedulerInit(&this->frameScheduler,
+    udata->features & KVMFR_FEATURE_FRAME_SCHEDULE, clientID);
+  lgFrameSchedulerSetPeriod(&this->frameScheduler, lgFramePeriod());
+
   this->state = STATE_STARTING;
   createThreads(this);
 }
@@ -1075,6 +1121,7 @@ static void lgFormatInit(LGPlugin * this, const KVMFRFrame * frame,
 static void lgVideoTick(void * data, float seconds)
 {
   LGPlugin * this = (LGPlugin *)data;
+  (void)seconds;
 
   if (this->state == STATE_RESTARTING)
   {
@@ -1086,6 +1133,8 @@ static void lgVideoTick(void * data, float seconds)
   if (this->state != STATE_RUNNING)
     return;
 
+  const uint64_t tickTime    = os_gettime_ns();
+  const uint64_t framePeriod = lgFramePeriod();
   LGMP_STATUS status;
   LGMPMessage msg;
 
@@ -1096,6 +1145,8 @@ static void lgVideoTick(void * data, float seconds)
     return;
   }
 
+  lgFrameSchedulerSetPeriod(&this->frameScheduler, framePeriod);
+
   this->cursorRect.x = this->cursor.x;
   this->cursorRect.y = this->cursor.y;
 
@@ -1236,6 +1287,10 @@ static void lgVideoTick(void * data, float seconds)
   }
 
   const KVMFRFrame * frame = (KVMFRFrame *)msg.mem;
+  lgFrameSchedulerObserveFrame(&this->frameScheduler,
+    frame->frameSerial, msg.udata, tickTime);
+  lgFrameSchedulerFeedback(&this->frameScheduler,
+    frame->frameSerial, msg.udata, tickTime);
 
   bool textureValid = (this->dmabufTested && this->dmabuf) || this->texture;
   if (!textureValid || this->formatVer != frame->formatVer)