Add 'Use Alternative Audio Hook' option, enable by default

src/core/settings.cpp

@@ -143,6 +143,8 @@ void Settings::Load(SettingsInterface& si)
   apply_game_settings = si.GetBoolValue("Main", "ApplyGameSettings", true);
   runahead_frames = static_cast<u32>(si.GetIntValue("Main", "RunaheadFrameCount", 0));
 
+  audio_fast_hook = si.GetBoolValue("Audio", "FastHook", true);
+
   cpu_execution_mode =
     ParseCPUExecutionMode(
       si.GetStringValue("CPU", "ExecutionMode", GetCPUExecutionModeName(DEFAULT_CPU_EXECUTION_MODE)).c_str())

src/core/settings.h

@@ -58,6 +58,8 @@ struct Settings
 
   ConsoleRegion region = ConsoleRegion::Auto;
 
+  bool audio_fast_hook = true;
+
   CPUExecutionMode cpu_execution_mode = CPUExecutionMode::Interpreter;
   u32 cpu_overclock_numerator = 1;
   u32 cpu_overclock_denominator = 1;

src/libretro/libretro_audio_stream.cpp

@@ -11,16 +11,32 @@ LibretroAudioStream::LibretroAudioStream() = default;
 
 LibretroAudioStream::~LibretroAudioStream() = default;
 
+void LibretroAudioStream::UploadToFrontend()
+{
+  std::array<SampleType, MaxSamples> output_buffer;
+  u32 total_samples = 0;
+  while (const auto num_samples = m_buffer.GetContiguousSize()) {
+    const auto write_pos = output_buffer.begin() + total_samples;
+    std::copy_n(m_buffer.GetReadPointer(), num_samples, write_pos);
+    m_buffer.Remove(num_samples);
+    total_samples += num_samples;
+  }
+  g_retro_audio_sample_batch_callback(output_buffer.data(), total_samples / AUDIO_CHANNELS);
+}
+
 void LibretroAudioStream::FramesAvailable()
 {
-  for (;;)
+  if (!g_settings.audio_fast_hook)
   {
-    const u32 num_samples = m_buffer.GetContiguousSize();
-    if (num_samples == 0)
-      break;
+    for (;;)
+    {
+      const u32 num_samples = m_buffer.GetContiguousSize();
+      if (num_samples == 0)
+        break;
 
-    const u32 num_frames = num_samples / AUDIO_CHANNELS;
-    g_retro_audio_sample_batch_callback(m_buffer.GetReadPointer(), num_frames);
-    m_buffer.Remove(num_samples);
+      const u32 num_frames = num_samples / AUDIO_CHANNELS;
+      g_retro_audio_sample_batch_callback(m_buffer.GetReadPointer(), num_frames);
+      m_buffer.Remove(num_samples);
+    }
   }
-}
+}

src/libretro/libretro_audio_stream.h

@@ -9,6 +9,8 @@ class LibretroAudioStream final : public AudioStream
   LibretroAudioStream();
   ~LibretroAudioStream();
 
+  void UploadToFrontend();
+
 protected:
   void FramesAvailable() override;
 };

src/libretro/libretro_core_options.h

@@ -2034,6 +2034,19 @@ struct retro_core_option_v2_definition option_defs_us[] = {
      {NULL, NULL},
    },
    "false"},
+  {"swanstation_Audio_FastHook",
+   "Use Alternative Audio Hook (Restart)",
+   NULL,
+   "Use a faster and more efficient to submit audio samples to the frontend. Mostly safe to enable, but may hang "
+   "for a select few games that rely on the old method to function. Requires the core to be restarted to apply.",
+   NULL,
+   "advanced",
+   {
+     {"true", "Enabled"},
+     {"false", "Disabled"},
+     {NULL, NULL},
+   },
+   "true"},
   {NULL, NULL, NULL, NULL, NULL, NULL, {{NULL, NULL}}, NULL},
 };
 

src/libretro/libretro_host_interface.cpp

@@ -697,6 +697,12 @@ void LibretroHostInterface::retro_run_frame()
     UpdateGeometry();
 
   m_display->Render();
+
+  if (g_settings.audio_fast_hook)
+  {
+    auto* const audio_stream = dynamic_cast<LibretroAudioStream*>(m_audio_stream.get());
+    audio_stream->UploadToFrontend();
+  }
 }
 
 unsigned LibretroHostInterface::retro_get_region()
@@ -1153,6 +1159,12 @@ void LibretroHostInterface::UpdateSettings()
 
       g_settings.gpu_use_software_renderer_for_readbacks = old_settings.gpu_use_software_renderer_for_readbacks;
     }
+
+    if (g_settings.audio_fast_hook != old_settings.audio_fast_hook)
+    {
+      ReportFormattedMessage("Changing audio hook will apply on core reload.");
+      g_settings.audio_fast_hook = old_settings.audio_fast_hook;
+    }
   }
 
   CheckForSettingsChanges(old_settings);