Surround sound support

mm/2s2h/BenPort.cpp

@@ -37,7 +37,7 @@
 #endif
 #include "Extractor/Extract.h"
 // OTRTODO
-//#include <functions.h>
+// #include <functions.h>
 #include "2s2h/Enhancements/FrameInterpolation/FrameInterpolation.h"
 
 #ifdef ENABLE_CROWD_CONTROL
@@ -211,7 +211,10 @@ OTRGlobals::OTRGlobals() {
     overlay->LoadFont("Fipps", 32.0f, "fonts/Fipps-Regular.otf");
     overlay->SetCurrentFont(CVarGetString(CVAR_GAME_OVERLAY_FONT, "Press Start 2P"));
 
-    context->InitAudio({ .SampleRate = 32000, .SampleLength = 1024, .DesiredBuffered = 1680 });
+    AudioChannelsSetting channelSetting =
+        static_cast<AudioChannelsSetting>(CVarGetInteger("gAudioChannelsSetting", audioStereo));
+    context->InitAudio(
+        { .SampleRate = 32000, .SampleLength = 1024, .DesiredBuffered = 1680, .ChannelSetting = channelSetting });
 
     SPDLOG_INFO("Starting 2 Ship 2 Harkinian version {} (Branch: {} | Commit: {})", (char*)gBuildVersion,
                 (char*)gGitBranch, (char*)gGitCommitHash);

mm/src/audio/code_8019AF00.c

@@ -4,6 +4,7 @@
 #include "GameInteractor/GameInteractor.h"
 #include "2s2h/Enhancements/Audio/AudioEditor.h"
 #include <libultraship/bridge/consolevariablebridge.h>
+#include <libultraship/bridge/audiobridge.h>
 
 typedef struct {
     /* 0x0 */ s8 x;
@@ -6080,32 +6081,44 @@ void Audio_PlaySfx_SurroundSoundTest(void) {
 
 void Audio_SetFileSelectSettings(s8 audioSetting) {
     s8 soundMode;
+    AudioChannelsSetting channelsSetting = audioStereo;
 
     switch (audioSetting) {
         case SAVE_AUDIO_STEREO:
             soundMode = SOUNDMODE_STEREO;
             sSoundMode = SOUNDMODE_STEREO;
+            channelsSetting = audioStereo;
             break;
 
         case SAVE_AUDIO_MONO:
             soundMode = SOUNDMODE_MONO;
             sSoundMode = SOUNDMODE_MONO;
+            channelsSetting = audioStereo;
             break;
 
         case SAVE_AUDIO_HEADSET:
             soundMode = SOUNDMODE_HEADSET;
             sSoundMode = SOUNDMODE_HEADSET;
+            channelsSetting = audioStereo;
             break;
 
         case SAVE_AUDIO_SURROUND:
             soundMode = SOUNDMODE_SURROUND;
             sSoundMode = SOUNDMODE_SURROUND_EXTERNAL;
+            channelsSetting = audioMatrix51;
             break;
 
         default:
             break;
     }
 
+    // Dynamically switch audio backend between stereo and 5.1 surround
+    SetAudioChannels(channelsSetting);
+
+    // Save audio channel setting so it persists across game launches
+    CVarSetInteger("gAudioChannelsSetting", channelsSetting);
+    CVarSave();
+
     SEQCMD_SET_SOUND_MODE(soundMode);
 }
 

mm/src/audio/lib/synthesis.c

@@ -1484,13 +1484,32 @@ Acmd* AudioSynth_ApplySurroundEffect(Acmd* cmd, NoteSampleState* sampleState, No
     } else {
         aLoadBuffer(cmd++, synthState->synthesisBuffers->surroundEffectState, dmem,
                     sizeof(synthState->synthesisBuffers->surroundEffectState));
-        aMix(cmd++, (numSamplesPerUpdate * (s32)SAMPLE_SIZE) >> 4, dryGain, dmem, DMEM_LEFT_CH);
-        aMix(cmd++, (numSamplesPerUpdate * (s32)SAMPLE_SIZE) >> 4, (dryGain ^ 0xFFFF), dmem, DMEM_RIGHT_CH);
+
+        // === Matrix surround encoding: steer surround to RL or RR based on pan ===
+        // Calculate pan position: 0.0 = full left, 0.5 = center, 1.0 = full right
+        f32 sumVol = sampleState->targetVolLeft + sampleState->targetVolRight;
+        f32 panPosition = 0.5f; // default: center (mono surround)
+        if (sumVol > 0.0f) {
+            panPosition = (f32)sampleState->targetVolRight / sumVol;
+        }
+
+        // The L/R balance determines RL vs RR steering:
+        // - L dominant (leftGain > rightGain): surround goes more to Rear Left
+        // - R dominant (rightGain > leftGain): surround goes more to Rear Right
+        // - Equal: mono surround to both
+        s16 leftGain = (s16)(dryGain * (1.0f - panPosition));
+        s16 rightGain = (s16)(dryGain * panPosition);
+
+        aMix(cmd++, (numSamplesPerUpdate * (s32)SAMPLE_SIZE) >> 4, leftGain, dmem, DMEM_LEFT_CH);
+        aMix(cmd++, (numSamplesPerUpdate * (s32)SAMPLE_SIZE) >> 4, (rightGain ^ 0xFFFF), dmem, DMEM_RIGHT_CH);
 
         wetGain = (dryGain * synthState->curReverbVol) >> 7;
+        s16 wetLeftGain = (s16)(wetGain * (1.0f - panPosition));
+        s16 wetRightGain = (s16)(wetGain * panPosition);
 
-        aMix(cmd++, (numSamplesPerUpdate * (s32)SAMPLE_SIZE) >> 4, wetGain, dmem, DMEM_WET_LEFT_CH);
-        aMix(cmd++, (numSamplesPerUpdate * (s32)SAMPLE_SIZE) >> 4, (wetGain ^ 0xFFFF), dmem, DMEM_WET_RIGHT_CH);
+        aMix(cmd++, (numSamplesPerUpdate * (s32)SAMPLE_SIZE) >> 4, wetLeftGain, dmem, DMEM_WET_LEFT_CH);
+        aMix(cmd++, (numSamplesPerUpdate * (s32)SAMPLE_SIZE) >> 4, (wetRightGain ^ 0xFFFF), dmem, DMEM_WET_RIGHT_CH);
+        // === End matrix surround encoding ===
     }
 
     aSaveBuffer(cmd++, DMEM_SURROUND_TEMP + (numSamplesPerUpdate * SAMPLE_SIZE),

mm/src/code/z_common_data.c

@@ -6,6 +6,7 @@
 #include "z64environment.h"
 #include "z64transition.h"
 #include <string.h>
+#include <libultraship/bridge/audiobridge.h>
 
 SaveContext gSaveContext ALIGNED(16);
 
@@ -26,6 +27,6 @@ void SaveContext_Init(void) {
     gSaveContext.prevHudVisibility = HUD_VISIBILITY_ALL;
 
     gSaveContext.options.language = LANGUAGE_ENG;
-    gSaveContext.options.audioSetting = SAVE_AUDIO_STEREO;
+    gSaveContext.options.audioSetting = (GetAudioChannels() == audioMatrix51) ? SAVE_AUDIO_SURROUND : SAVE_AUDIO_STEREO;
     gSaveContext.options.zTargetSetting = 0;
 }

mm/src/code/z_sram_NES.c

@@ -8,6 +8,7 @@
 #include "2s2h/Enhancements/Saving/SavingEnhancements.h"
 #include "2s2h/GameInteractor/GameInteractor.h"
 #include <libultraship/bridge/consolevariablebridge.h>
+#include <libultraship/bridge/audiobridge.h>
 
 void Sram_SyncWriteToFlash(SramContext* sramCtx, s32 curPage, s32 numPages);
 void func_80147414(SramContext* sramCtx, s32 fileNum, s32 arg2);
@@ -1774,18 +1775,22 @@ void func_801457CC(GameState* gameState, SramContext* sramCtx) {
                                           gFlashSaveNumPages[sp64 + FLASH_SAVE_BACKUP_OFFSET]);
                 }
             } else {
+                // Get default audio setting from config
+                s8 defaultAudioSetting =
+                    (GetAudioChannels() == audioMatrix51) ? SAVE_AUDIO_SURROUND : SAVE_AUDIO_STEREO;
+
                 if (phi_s2) {
                     gSaveContext.options.optionId = 0xA51D;
                     gSaveContext.options.language = LANGUAGE_ENG;
-                    gSaveContext.options.audioSetting = SAVE_AUDIO_STEREO;
+                    gSaveContext.options.audioSetting = defaultAudioSetting;
                     gSaveContext.options.languageSetting = 0;
                     gSaveContext.options.zTargetSetting = 0;
                 } else {
                     memcpy(&gSaveContext.options, sramCtx->saveBuf, sizeof(SaveOptions));
                     if (gSaveContext.options.optionId != 0xA51D) {
                         gSaveContext.options.optionId = 0xA51D;
                         gSaveContext.options.language = LANGUAGE_ENG;
-                        gSaveContext.options.audioSetting = SAVE_AUDIO_STEREO;
+                        gSaveContext.options.audioSetting = defaultAudioSetting;
                         gSaveContext.options.languageSetting = 0;
                         gSaveContext.options.zTargetSetting = 0;
                     }