System: Add "Skip Duplicate Frame Display" option

Skips the presentation/display of frames that are not unique.
Can be combined with driver-level frame generation to increase
perceptible frame rate. Can result in worse frame pacing, and is
not compatible with syncing to host refresh.

src/core/fullscreen_ui.cpp

@@ -3454,6 +3454,14 @@ void FullscreenUI::DrawEmulationSettingsPage()
     bsi, FSUI_ICONSTR(ICON_FA_STOPWATCH_20, "Reduce Input Latency"),
     FSUI_CSTR("Reduces input latency by delaying the start of frame until closer to the presentation time."), "Display",
     "PreFrameSleep", false, optimal_frame_pacing_active);
+
+  DrawToggleSetting(
+    bsi, FSUI_ICONSTR(ICON_FA_CHARGING_STATION, "Skip Duplicate Frame Display"),
+    FSUI_CSTR("Skips the presentation/display of frames that are not unique. Can result in worse frame pacing."),
+    "Display", "SkipPresentingDuplicateFrames", false,
+    !(GetEffectiveBoolSetting(bsi, "Display", "VSync", false) &&
+      GetEffectiveBoolSetting(bsi, "Main", "SyncToHostRefreshRate", false)));
+
   const bool pre_frame_sleep_active =
     (optimal_frame_pacing_active && GetEffectiveBoolSetting(bsi, "Display", "PreFrameSleep", false));
   DrawFloatRangeSetting(
@@ -7652,6 +7660,8 @@ TRANSLATE_NOOP("FullscreenUI", "Shows the number of frames (or v-syncs) displaye
 TRANSLATE_NOOP("FullscreenUI", "Simulates the CPU's instruction cache in the recompiler. Can help with games running too fast.");
 TRANSLATE_NOOP("FullscreenUI", "Simulates the region check present in original, unmodified consoles.");
 TRANSLATE_NOOP("FullscreenUI", "Simulates the system ahead of time and rolls back/replays to reduce input lag. Very high system requirements.");
+TRANSLATE_NOOP("FullscreenUI", "Skip Duplicate Frame Display");
+TRANSLATE_NOOP("FullscreenUI", "Skips the presentation/display of frames that are not unique. Can result in worse frame pacing.");
 TRANSLATE_NOOP("FullscreenUI", "Slow Boot");
 TRANSLATE_NOOP("FullscreenUI", "Smooths out blockyness between colour transitions in 24-bit content, usually FMVs. Only applies to the hardware renderers.");
 TRANSLATE_NOOP("FullscreenUI", "Smooths out the blockiness of magnified textures on 3D objects.");

src/core/settings.cpp

@@ -271,6 +271,7 @@ void Settings::Load(SettingsInterface& si)
   display_pre_frame_sleep = si.GetBoolValue("Display", "PreFrameSleep", false);
   display_pre_frame_sleep_buffer =
     si.GetFloatValue("Display", "PreFrameSleepBuffer", DEFAULT_DISPLAY_PRE_FRAME_SLEEP_BUFFER);
+  display_skip_presenting_duplicate_frames = si.GetBoolValue("Display", "SkipPresentingDuplicateFrames", false);
   display_vsync = si.GetBoolValue("Display", "VSync", false);
   display_force_4_3_for_24bit = si.GetBoolValue("Display", "Force4_3For24Bit", false);
   display_active_start_offset = static_cast<s16>(si.GetIntValue("Display", "ActiveStartOffset", 0));
@@ -519,6 +520,7 @@ void Settings::Save(SettingsInterface& si, bool ignore_base) const
   si.SetStringValue("Display", "Scaling", GetDisplayScalingName(display_scaling));
   si.SetBoolValue("Display", "OptimalFramePacing", display_optimal_frame_pacing);
   si.SetBoolValue("Display", "PreFrameSleep", display_pre_frame_sleep);
+  si.SetBoolValue("Display", "SkipPresentingDuplicateFrames", display_skip_presenting_duplicate_frames);
   si.SetFloatValue("Display", "PreFrameSleepBuffer", display_pre_frame_sleep_buffer);
   si.SetBoolValue("Display", "VSync", display_vsync);
   si.SetStringValue("Display", "ExclusiveFullscreenControl",

src/core/settings.h

@@ -148,6 +148,7 @@ struct Settings
   s8 display_line_end_offset = 0;
   bool display_optimal_frame_pacing : 1 = false;
   bool display_pre_frame_sleep : 1 = false;
+  bool display_skip_presenting_duplicate_frames : 1 = false;
   bool display_vsync : 1 = false;
   bool display_force_4_3_for_24bit : 1 = false;
   bool gpu_24bit_chroma_smoothing : 1 = false;

src/core/system.cpp

@@ -150,6 +150,7 @@ static void PollDiscordPresence();
 
 static constexpr const float PERFORMANCE_COUNTER_UPDATE_INTERVAL = 1.0f;
 static constexpr const char FALLBACK_EXE_NAME[] = "PSX.EXE";
+static constexpr u32 MAX_SKIPPED_FRAME_COUNT = 2; // 20fps minimum
 
 static std::unique_ptr<INISettingsInterface> s_game_settings_interface;
 static std::unique_ptr<INISettingsInterface> s_input_settings_interface;
@@ -183,7 +184,10 @@ static bool s_throttler_enabled = false;
 static bool s_optimal_frame_pacing = false;
 static bool s_pre_frame_sleep = false;
 static bool s_syncing_to_host = false;
-static bool s_last_frame_skipped = false;
+static bool s_syncing_to_host_with_vsync = false;
+static bool s_skip_presenting_duplicate_frames = false;
+static u32 s_skipped_frame_count = 0;
+static u32 s_last_presented_internal_frame_number = 0;
 
 static float s_throttle_frequency = 0.0f;
 static float s_target_speed = 0.0f;
@@ -1963,32 +1967,43 @@ void System::FrameDone()
     AccumulatePreFrameSleepTime();
 
   // explicit present (frame pacing)
-  if (current_time < s_next_frame_time || s_syncing_to_host || s_optimal_frame_pacing || s_last_frame_skipped)
+  const bool is_unique_frame = (s_last_presented_internal_frame_number != s_internal_frame_number);
+  s_last_presented_internal_frame_number = s_internal_frame_number;
+
+  const bool skip_this_frame =
+    (((s_skip_presenting_duplicate_frames && !is_unique_frame) ||
+      (!s_optimal_frame_pacing && (current_time > s_next_frame_time || g_gpu_device->ShouldSkipDisplayingFrame()))) &&
+     !s_syncing_to_host_with_vsync && (s_skipped_frame_count < MAX_SKIPPED_FRAME_COUNT) && !IsExecutionInterrupted());
+  if (!skip_this_frame)
   {
+    s_skipped_frame_count = 0;
+
     const bool throttle_before_present = (s_optimal_frame_pacing && s_throttler_enabled && !IsExecutionInterrupted());
     const bool explicit_present = (throttle_before_present && g_gpu_device->GetFeatures().explicit_present);
     if (explicit_present)
     {
-      s_last_frame_skipped = !PresentDisplay(!throttle_before_present, true);
+      const bool do_present = PresentDisplay(false, true);
       Throttle(current_time);
-      g_gpu_device->SubmitPresent();
+      if (do_present)
+        g_gpu_device->SubmitPresent();
     }
     else
     {
       if (throttle_before_present)
         Throttle(current_time);
 
-      s_last_frame_skipped = !PresentDisplay(!throttle_before_present, false);
+      PresentDisplay(false, false);
 
       if (!throttle_before_present && s_throttler_enabled && !IsExecutionInterrupted())
         Throttle(current_time);
     }
   }
-  else if (current_time >= s_next_frame_time)
+  else
   {
-    Log_DebugPrintf("Skipping displaying frame");
-    s_last_frame_skipped = true;
-    Throttle(current_time);
+    Log_DebugPrint("Skipping displaying frame");
+    s_skipped_frame_count++;
+    if (s_throttler_enabled)
+      Throttle(current_time);
   }
 
   // pre-frame sleep (input lag reduction)
@@ -2810,15 +2825,20 @@ void System::FormatLatencyStats(SmallStringBase& str)
 
 void System::UpdateSpeedLimiterState()
 {
+  DebugAssert(IsValid());
+
   const float old_target_speed = s_target_speed;
   s_target_speed = s_turbo_enabled ?
                      g_settings.turbo_speed :
                      (s_fast_forward_enabled ? g_settings.fast_forward_speed : g_settings.emulation_speed);
   s_throttler_enabled = (s_target_speed != 0.0f);
-  s_optimal_frame_pacing = s_throttler_enabled && g_settings.display_optimal_frame_pacing;
-  s_pre_frame_sleep = s_throttler_enabled && g_settings.display_pre_frame_sleep;
+  s_optimal_frame_pacing = (s_throttler_enabled && g_settings.display_optimal_frame_pacing) ||
+                           g_gpu_device->GetWindowInfo().IsSurfaceless(); // surfaceless check for regtest
+  s_skip_presenting_duplicate_frames = s_throttler_enabled && g_settings.display_skip_presenting_duplicate_frames;
+  s_pre_frame_sleep = s_optimal_frame_pacing && g_settings.display_pre_frame_sleep;
 
   s_syncing_to_host = false;
+  s_syncing_to_host_with_vsync = false;
   if (g_settings.sync_to_host_refresh_rate &&
       (g_settings.audio_stream_parameters.stretch_mode != AudioStretchMode::Off) && s_target_speed == 1.0f && IsValid())
   {
@@ -2835,7 +2855,8 @@ void System::UpdateSpeedLimiterState()
   }
 
   // When syncing to host and using vsync, we don't need to sleep.
-  if (s_syncing_to_host && IsVSyncEffectivelyEnabled())
+  s_syncing_to_host_with_vsync = (s_syncing_to_host && IsVSyncEffectivelyEnabled());
+  if (s_syncing_to_host_with_vsync)
   {
     Log_InfoPrintf("Using host vsync for throttling.");
     s_throttler_enabled = false;
@@ -2843,25 +2864,21 @@ void System::UpdateSpeedLimiterState()
 
   Log_VerbosePrintf("Target speed: %f%%", s_target_speed * 100.0f);
 
-  if (IsValid())
-  {
-    // Update audio output.
-    AudioStream* stream = SPU::GetOutputStream();
-    stream->SetOutputVolume(GetAudioOutputVolume());
+  // Update audio output.
+  AudioStream* stream = SPU::GetOutputStream();
+  stream->SetOutputVolume(GetAudioOutputVolume());
 
-    // Adjust nominal rate when resampling, or syncing to host.
-    const bool rate_adjust =
-      (s_syncing_to_host || g_settings.audio_stream_parameters.stretch_mode == AudioStretchMode::Resample) &&
-      s_target_speed > 0.0f;
-    stream->SetNominalRate(rate_adjust ? s_target_speed : 1.0f);
+  // Adjust nominal rate when resampling, or syncing to host.
+  const bool rate_adjust =
+    (s_syncing_to_host || g_settings.audio_stream_parameters.stretch_mode == AudioStretchMode::Resample) &&
+    s_target_speed > 0.0f;
+  stream->SetNominalRate(rate_adjust ? s_target_speed : 1.0f);
 
-    if (old_target_speed < s_target_speed)
-      stream->UpdateTargetTempo(s_target_speed);
-
-    UpdateThrottlePeriod();
-    ResetThrottler();
-  }
+  if (old_target_speed < s_target_speed)
+    stream->UpdateTargetTempo(s_target_speed);
 
+  UpdateThrottlePeriod();
+  ResetThrottler();
   UpdateDisplaySync();
 
   if (g_settings.increase_timer_resolution)
@@ -3959,6 +3976,7 @@ void System::CheckForSettingsChanges(const Settings& old_settings)
         g_settings.fast_forward_speed != old_settings.fast_forward_speed ||
         g_settings.display_max_fps != old_settings.display_max_fps ||
         g_settings.display_optimal_frame_pacing != old_settings.display_optimal_frame_pacing ||
+        g_settings.display_skip_presenting_duplicate_frames != old_settings.display_skip_presenting_duplicate_frames ||
         g_settings.display_pre_frame_sleep != old_settings.display_pre_frame_sleep ||
         g_settings.display_pre_frame_sleep_buffer != old_settings.display_pre_frame_sleep_buffer ||
         g_settings.display_vsync != old_settings.display_vsync ||
@@ -5082,10 +5100,8 @@ void System::HostDisplayResized()
   g_gpu->UpdateResolutionScale();
 }
 
-bool System::PresentDisplay(bool allow_skip_present, bool explicit_present)
+bool System::PresentDisplay(bool skip_present, bool explicit_present)
 {
-  const bool skip_present = allow_skip_present && g_gpu_device->ShouldSkipDisplayingFrame();
-
   Host::BeginPresentFrame();
 
   // acquire for IO.MousePos.

src/core/system.h

@@ -478,7 +478,7 @@ void RequestDisplaySize(float scale = 0.0f);
 void HostDisplayResized();
 
 /// Renders the display.
-bool PresentDisplay(bool allow_skip_present, bool explicit_present);
+bool PresentDisplay(bool skip_present, bool explicit_present);
 void InvalidateDisplay();
 
 //////////////////////////////////////////////////////////////////////////

src/duckstation-qt/emulationsettingswidget.cpp

@@ -20,6 +20,8 @@ EmulationSettingsWidget::EmulationSettingsWidget(SettingsWindow* dialog, QWidget
   SettingWidgetBinder::BindWidgetToBoolSetting(sif, m_ui.syncToHostRefreshRate, "Main", "SyncToHostRefreshRate", false);
   SettingWidgetBinder::BindWidgetToBoolSetting(sif, m_ui.optimalFramePacing, "Display", "OptimalFramePacing", false);
   SettingWidgetBinder::BindWidgetToBoolSetting(sif, m_ui.preFrameSleep, "Display", "PreFrameSleep", false);
+  SettingWidgetBinder::BindWidgetToBoolSetting(sif, m_ui.skipPresentingDuplicateFrames, "Display",
+                                               "SkipPresentingDuplicateFrames", false);
   SettingWidgetBinder::BindWidgetToFloatSetting(sif, m_ui.preFrameSleepBuffer, "Display", "PreFrameSleepBuffer",
                                                 Settings::DEFAULT_DISPLAY_PRE_FRAME_SLEEP_BUFFER);
   SettingWidgetBinder::BindWidgetToBoolSetting(sif, m_ui.rewindEnable, "Main", "RewindEnable", false);
@@ -71,7 +73,9 @@ EmulationSettingsWidget::EmulationSettingsWidget(SettingsWindow* dialog, QWidget
   }
   connect(m_ui.turboSpeed, QOverload<int>::of(&QComboBox::currentIndexChanged), this,
           &EmulationSettingsWidget::onTurboSpeedIndexChanged);
-  connect(m_ui.vsync, &QCheckBox::checkStateChanged, this, &EmulationSettingsWidget::onVSyncChanged);
+  connect(m_ui.vsync, &QCheckBox::checkStateChanged, this, &EmulationSettingsWidget::updateSkipDuplicateFramesEnabled);
+  connect(m_ui.syncToHostRefreshRate, &QCheckBox::checkStateChanged, this,
+          &EmulationSettingsWidget::updateSkipDuplicateFramesEnabled);
   connect(m_ui.optimalFramePacing, &QCheckBox::checkStateChanged, this,
           &EmulationSettingsWidget::onOptimalFramePacingChanged);
   connect(m_ui.preFrameSleep, &QCheckBox::checkStateChanged, this, &EmulationSettingsWidget::onPreFrameSleepChanged);
@@ -121,6 +125,11 @@ EmulationSettingsWidget::EmulationSettingsWidget(SettingsWindow* dialog, QWidget
                              tr("Specifies the amount of buffer time added, which reduces the additional sleep time "
                                 "introduced. Higher values increase input latency, but decrease the risk of overrun, "
                                 "or missed frames. Lower values require faster hardware."));
+  dialog->registerWidgetHelp(
+    m_ui.skipPresentingDuplicateFrames, tr("Skip Duplicate Frame Display"), tr("Unchecked"),
+    tr("Skips the presentation/display of frames that are not unique. Can be combined with driver-level frame "
+       "generation to increase perceptible frame rate. Can result in worse frame pacing, and is not compatible with "
+       "syncing to host refresh."));
   dialog->registerWidgetHelp(
     m_ui.rewindEnable, tr("Rewinding"), tr("Unchecked"),
     tr("<b>Enable Rewinding:</b> Saves state periodically so you can rewind any mistakes while playing.<br> "
@@ -133,8 +142,8 @@ EmulationSettingsWidget::EmulationSettingsWidget(SettingsWindow* dialog, QWidget
     tr(
       "Simulates the system ahead of time and rolls back/replays to reduce input lag. Very high system requirements."));
 
-  onVSyncChanged();
   onOptimalFramePacingChanged();
+  updateSkipDuplicateFramesEnabled();
   updateRewind();
 }
 
@@ -200,12 +209,6 @@ void EmulationSettingsWidget::onTurboSpeedIndexChanged(int index)
   m_dialog->setFloatSettingValue("Main", "TurboSpeed", okay ? value : 0.0f);
 }
 
-void EmulationSettingsWidget::onVSyncChanged()
-{
-  const bool vsync = m_dialog->getEffectiveBoolValue("Display", "VSync", false);
-  m_ui.syncToHostRefreshRate->setEnabled(vsync);
-}
-
 void EmulationSettingsWidget::onOptimalFramePacingChanged()
 {
   const bool optimal_frame_pacing_enabled = m_dialog->getEffectiveBoolValue("Display", "OptimalFramePacing", false);
@@ -221,6 +224,13 @@ void EmulationSettingsWidget::onPreFrameSleepChanged()
   m_ui.preFrameSleepBufferLabel->setVisible(show_buffer_size);
 }
 
+void EmulationSettingsWidget::updateSkipDuplicateFramesEnabled()
+{
+  const bool vsync = m_dialog->getEffectiveBoolValue("Display", "VSync", false);
+  const bool sync_to_host = m_dialog->getEffectiveBoolValue("Main", "SyncToHostRefreshRate", false) && vsync;
+  m_ui.skipPresentingDuplicateFrames->setEnabled(!sync_to_host);
+}
+
 void EmulationSettingsWidget::updateRewind()
 {
   const bool rewind_enabled = m_dialog->getEffectiveBoolValue("Main", "RewindEnable", false);

src/duckstation-qt/emulationsettingswidget.h

@@ -21,9 +21,9 @@ private Q_SLOTS:
   void onEmulationSpeedIndexChanged(int index);
   void onFastForwardSpeedIndexChanged(int index);
   void onTurboSpeedIndexChanged(int index);
-  void onVSyncChanged();
   void onOptimalFramePacingChanged();
   void onPreFrameSleepChanged();
+  void updateSkipDuplicateFramesEnabled();
   void updateRewind();
 
 private:

src/duckstation-qt/emulationsettingswidget.ui

@@ -68,10 +68,10 @@
       <string>Latency Control</string>
      </property>
      <layout class="QGridLayout" name="gridLayout">
-      <item row="0" column="0">
-       <widget class="QCheckBox" name="vsync">
+      <item row="1" column="1">
+       <widget class="QCheckBox" name="preFrameSleep">
         <property name="text">
-         <string>Vertical Sync (VSync)</string>
+         <string>Reduce Input Latency</string>
         </property>
        </widget>
       </item>
@@ -82,6 +82,13 @@
         </property>
        </widget>
       </item>
+      <item row="0" column="0">
+       <widget class="QCheckBox" name="vsync">
+        <property name="text">
+         <string>Vertical Sync (VSync)</string>
+        </property>
+       </widget>
+      </item>
       <item row="1" column="0">
        <widget class="QCheckBox" name="optimalFramePacing">
         <property name="text">
@@ -89,23 +96,23 @@
         </property>
        </widget>
       </item>
-      <item row="1" column="1">
-       <widget class="QCheckBox" name="preFrameSleep">
+      <item row="2" column="0">
+       <widget class="QCheckBox" name="skipPresentingDuplicateFrames">
         <property name="text">
-         <string>Reduce Input Latency</string>
+         <string>Skip Duplicate Frame Display</string>
         </property>
        </widget>
       </item>
-      <item row="2" column="0" colspan="2">
-       <layout class="QHBoxLayout" name="preFrameSleepBufferLayout" stretch="0,1">
-        <item>
+      <item row="2" column="1">
+       <layout class="QFormLayout" name="formLayout_3">
+        <item row="0" column="0">
          <widget class="QLabel" name="preFrameSleepBufferLabel">
           <property name="text">
            <string>Frame Time Buffer:</string>
           </property>
          </widget>
         </item>
-        <item>
+        <item row="0" column="1">
          <widget class="QDoubleSpinBox" name="preFrameSleepBuffer">
           <property name="suffix">
            <string> Milliseconds</string>