From 11ba75f843bb573e43dfe26ba7befede223ddbf2 Mon Sep 17 00:00:00 2001
From: Chris Dixon <meischris39@hotmail.com>
Date: Tue, 27 Oct 2026 10:47:43 +0000
Subject: [PATCH] libretro: add a Vblank Pacing option (#2562)

Without threaded rendering a run ends when a frame is presented, or
after 50 ms of emulated time without one. Frontends that pace retro_run
by the frame rate instead of blocking on audio, Kodi among them, then
get several vblanks per run through loading screens and have to drop
the extra audio. With the option on, every run ends at the next vblank.
[ci skip]
---
 core/cfg/option.cpp                    |  1 +
 core/cfg/option.h                      |  1 +
 core/emulator.cpp                      |  2 +-
 core/hw/pvr/Renderer_if.cpp            |  2 +-
 shell/libretro/libretro_core_options.h | 14 ++++++++++++++
 shell/libretro/option.cpp              |  1 +
 6 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/core/cfg/option.cpp b/core/cfg/option.cpp
index 82f3994f6..575622c99 100644
--- a/core/cfg/option.cpp
+++ b/core/cfg/option.cpp
@@ -110,6 +110,7 @@ Option<int64_t> PixelBufferSize("rend.PixelBufferSize", 512_MB);
 Option<int> AnisotropicFiltering("rend.AnisotropicFiltering", 1);
 Option<int> TextureFiltering("rend.TextureFiltering", 0); // Default
 Option<bool> ThreadedRendering("rend.ThreadedRendering", true);
+Option<bool> VblankPacing("");
 Option<bool> DupeFrames("rend.DupeFrames", false);
 Option<int> PerPixelLayers("rend.PerPixelLayers", 32);
 #ifdef TARGET_UWP
diff --git a/core/cfg/option.h b/core/cfg/option.h
index 267c90b00..05f948935 100644
--- a/core/cfg/option.h
+++ b/core/cfg/option.h
@@ -471,6 +471,7 @@ extern Option<int64_t> PixelBufferSize;
 extern Option<int> AnisotropicFiltering;
 extern Option<int> TextureFiltering; // 0: default, 1: force nearest, 2: force linear
 extern Option<bool> ThreadedRendering;
+extern Option<bool> VblankPacing;
 extern Option<bool> DupeFrames;
 extern Option<bool> NativeDepthInterpolation;
 extern Option<bool> EmulateFramebuffer;
diff --git a/core/emulator.cpp b/core/emulator.cpp
index 25e685bcc..9026f72af 100644
--- a/core/emulator.cpp
+++ b/core/emulator.cpp
@@ -1088,7 +1088,7 @@ void Emulator::vblank()
 	EventManager::event(Event::VBlank);
 	runner.execTasks();
 	// Time out if a frame hasn't been rendered for 50 ms
-	if (sh4_sched_now64() - startTime <= 50_sh4ms)
+	if (!config::VblankPacing && sh4_sched_now64() - startTime <= 50_sh4ms)
 		return;
 	if (ggpo::active())
 		ggpo::endOfFrame();
diff --git a/core/hw/pvr/Renderer_if.cpp b/core/hw/pvr/Renderer_if.cpp
index 49c3f720f..3d4c0a47e 100644
--- a/core/hw/pvr/Renderer_if.cpp
+++ b/core/hw/pvr/Renderer_if.cpp
@@ -268,7 +268,7 @@ private:
 		if (renderer->Present())
 		{
 			presented = true;
-			if (!config::ThreadedRendering && !ggpo::active())
+			if (!config::ThreadedRendering && !config::VblankPacing && !ggpo::active())
 				emu.getSh4Executor()->Stop();
 #ifdef LIBRETRO
 			retro_rend_present();
diff --git a/shell/libretro/libretro_core_options.h b/shell/libretro/libretro_core_options.h
index 2cb2cb222..81c631fbb 100644
--- a/shell/libretro/libretro_core_options.h
+++ b/shell/libretro/libretro_core_options.h
@@ -644,6 +644,20 @@ struct retro_core_option_v2_definition option_defs_us[] = {
       },
       "enabled",
    },
+   {
+      CORE_OPTION_NAME "_vblank_pacing",
+      "Vblank Pacing",
+      NULL,
+      "Each frame the frontend runs emulates exactly one vblank, whether or not the game drew. For frontends that pace the core by its frame rate rather than by blocking on audio; without it, loading screens that draw nothing run several vblanks per frame and their sound arrives in bursts. Needs Threaded Rendering disabled.",
+      NULL,
+      "performance",
+      {
+         { "disabled", NULL },
+         { "enabled",  NULL },
+         { NULL, NULL },
+      },
+      "disabled",
+   },
    {
       CORE_OPTION_NAME "_auto_skip_frame",
       "Auto Skip Frame",
diff --git a/shell/libretro/option.cpp b/shell/libretro/option.cpp
index 6d317df65..ee041d7fb 100644
--- a/shell/libretro/option.cpp
+++ b/shell/libretro/option.cpp
@@ -89,6 +89,7 @@ Option<bool> IntegerScale("");
 Option<bool> LinearInterpolation("", true);
 Option<bool> VSync("", true);
 Option<bool> ThreadedRendering(CORE_OPTION_NAME "_threaded_rendering", true);
+Option<bool> VblankPacing(CORE_OPTION_NAME "_vblank_pacing");
 Option<int> AnisotropicFiltering(CORE_OPTION_NAME "_anisotropic_filtering");
 Option<int> TextureFiltering(CORE_OPTION_NAME "_texture_filtering");
 Option<bool> PowerVR2Filter(CORE_OPTION_NAME "_pvr2_filtering");