From d53425e3bf9cf41162f03aafdb0564721f40a240 Mon Sep 17 00:00:00 2001
From: OpenSauce04 <opensauce04@gmail.com>
Date: Thu, 7 Nov 2024 16:33:28 +0000
Subject: [PATCH] Improved playback consistency of realtime audio option during
 inconsistent framerates

---
 src/audio_core/hle/hle.cpp |  2 +-
 src/core/core.cpp          |  4 ++--
 src/core/core.h            |  2 +-
 src/core/perf_stats.cpp    | 11 +++++++++++
 src/core/perf_stats.h      |  6 ++++++
 5 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/src/audio_core/hle/hle.cpp b/src/audio_core/hle/hle.cpp
index 108d5e2ca..bd27ce7b2 100644
--- a/src/audio_core/hle/hle.cpp
+++ b/src/audio_core/hle/hle.cpp
@@ -419,7 +419,7 @@ void DspHle::Impl::AudioTickCallback(s64 cycles_late) {
     // Reschedule recurrent event
     const double time_scale =
         Settings::values.enable_realtime_audio
-            ? std::clamp(Core::System::GetInstance().GetLastFrameTimeScale(), 1.0, 3.0)
+            ? std::clamp(Core::System::GetInstance().GetStableFrameTimeScale(), 1.0, 3.0)
             : 1.0;
     s64 adjusted_ticks = static_cast<s64>(audio_frame_ticks / time_scale - cycles_late);
     core_timing.ScheduleEvent(adjusted_ticks, tick_event);
diff --git a/src/core/core.cpp b/src/core/core.cpp
index 747393fd7..bf8aca7e6 100644
--- a/src/core/core.cpp
+++ b/src/core/core.cpp
@@ -391,8 +391,8 @@ PerfStats::Results System::GetLastPerfStats() {
     return perf_stats ? perf_stats->GetLastStats() : PerfStats::Results{};
 }
 
-double System::GetLastFrameTimeScale() {
-    return perf_stats->GetLastFrameTimeScale();
+double System::GetStableFrameTimeScale() {
+    return perf_stats->GetStableFrameTimeScale();
 }
 
 void System::Reschedule() {
diff --git a/src/core/core.h b/src/core/core.h
index 85bc79276..60f7605dd 100644
--- a/src/core/core.h
+++ b/src/core/core.h
@@ -184,7 +184,7 @@ public:
 
     [[nodiscard]] PerfStats::Results GetLastPerfStats();
 
-    double GetLastFrameTimeScale();
+    double GetStableFrameTimeScale();
 
     /**
      * Gets a reference to the emulated CPU.
diff --git a/src/core/perf_stats.cpp b/src/core/perf_stats.cpp
index c05cf80e5..ea7f01ca6 100644
--- a/src/core/perf_stats.cpp
+++ b/src/core/perf_stats.cpp
@@ -129,6 +129,17 @@ double PerfStats::GetLastFrameTimeScale() const {
     return duration_cast<DoubleSecs>(previous_frame_length).count() / FRAME_LENGTH;
 }
 
+double PerfStats::GetStableFrameTimeScale() const {
+    std::scoped_lock lock{object_mutex};
+
+    constexpr double FRAME_LENGTH_MILLIS = (1.0 / SCREEN_REFRESH_RATE) * 1000;
+    const size_t num_frames = std::min<size_t>(50UL, current_index + 1);
+    const double sum = std::accumulate(perf_history.begin() + current_index - num_frames,
+                                       perf_history.begin() + current_index, 0.0);
+    const double stable_frame_length = sum / num_frames;
+    return stable_frame_length / FRAME_LENGTH_MILLIS;
+}
+
 void FrameLimiter::WaitOnce() {
     if (frame_advancing_enabled) {
         // Frame advancing is enabled: wait on event instead of doing framelimiting
diff --git a/src/core/perf_stats.h b/src/core/perf_stats.h
index d68ff4dda..ce289592f 100644
--- a/src/core/perf_stats.h
+++ b/src/core/perf_stats.h
@@ -83,6 +83,12 @@ public:
      */
     double GetLastFrameTimeScale() const;
 
+    /**
+     * Has the same functionality as GetLastFrameTimeScale, but uses the mean frame time over the
+     * last 50 frames rather than only the frame time of the previous frame.
+     */
+    double GetStableFrameTimeScale() const;
+
     void AddArticBaseTraffic(u32 bytes) {
         artic_transmitted += bytes;
     }