Surround support

src/audio/effects.c

@@ -542,3 +542,30 @@ s32 adsr_update(struct AdsrState *adsr) {
     return 0;
 #endif
 }
+
+/**
+ * Compute comb filter gain based on Y position (height relative to camera).
+ * Used for creating height-based audio effects in surround sound.
+ * 
+ * Returns:
+ *   -32 to -1 (0xE0-0xFF): Sound is below camera (negative Y)
+ *   0 to 127: Sound is above camera (positive Y)
+ *   Bit 0 is always set (odd number)
+ */
+s8 audio_compute_comb_filter(f32 posY) {
+    s8 combFilterGain;
+
+    if (posY < 0.0f) {
+        // Below camera
+        if (posY < -625.0f) {
+            combFilterGain = -32; // Very far below
+        } else {
+            combFilterGain = (s8)(((625.0f + posY) / 625.0f) * 31.0f) + 0xE0;
+        }
+    } else if (posY > 1250.0f) {
+        combFilterGain = 127; // Very far above
+    } else {
+        combFilterGain = (s8)((posY / 1250.0f) * 126.0f);
+    }
+    return combFilterGain | 1;
+}

src/audio/effects.h

@@ -43,4 +43,6 @@ f32 adsr_update(struct AdsrState *adsr);
 s32 adsr_update(struct AdsrState *adsr);
 #endif
 
+s8 audio_compute_comb_filter(f32 posY);
+
 #endif // AUDIO_EFFECTS_H

src/audio/external.c

@@ -7,12 +7,14 @@
 #include "external.h"
 #include "playback.h"
 #include "synthesis.h"
+#include "effects.h"
 #include "game/level_update.h"
 #include "game/object_list_processor.h"
 #include "game/camera.h"
 #include "seq_ids.h"
 #include "dialog_ids.h"
 #include <lib/src/osAi.h>
+#include <stdio.h>
 
 #if defined(VERSION_EU) || defined(VERSION_SH)
 #define EU_FLOAT(x) x##f
@@ -1045,6 +1047,45 @@ static f32 get_sound_pan(f32 x, f32 z) {
     return pan;
 }
 
+/**
+ * Calculate surround effect index from Z position (depth relative to camera).
+ * In SM64's coordinate system, positive Z is behind the camera, negative Z is in front.
+ * Uses AUDIO_MAX_DISTANCE for scaling, matching pan and volume distance calculations.
+ * 
+ * Returns:
+ *   0x00 - 0x3F: Sound is in front of camera (0 = far front, 0x3F = at camera)
+ *   0x40 - 0x7F: Sound is behind camera (0x40 = at camera, 0x7F = far behind)
+ *
+ * Called from threads: thread4_sound, thread5_game_loop (EU only)
+ */
+static u8 get_sound_surround_effect_index(f32 z) {
+    f32 absZ;
+    s32 surroundEffectIndex;
+    f32 maxZ = 1000.f;
+
+    absZ = (z < 0 ? -z : z);
+    if (absZ > maxZ) {
+        absZ = maxZ;
+    }
+
+    // In SM64, positive z means behind the camera
+    if (z > 0.0f) {
+        // Behind camera - surround effect index 0x3F (at camera) to 0x7F (far behind)
+        surroundEffectIndex = (s32)((absZ / maxZ) * 64.0f) + 0x3F;
+        if (surroundEffectIndex > 0x7F) {
+            surroundEffectIndex = 0x7F;
+        }
+    } else {
+        // In front of camera - surround effect index 0x3F (at camera) to 0x00 (far front)
+        surroundEffectIndex = 0x3F - (s32)((absZ / maxZ) * 63.0f);
+        if (surroundEffectIndex < 0) {
+            surroundEffectIndex = 0;
+        }
+    }
+
+    return (u8)surroundEffectIndex;
+}
+
 /**
  * Called from threads: thread4_sound, thread5_game_loop (EU only)
  */
@@ -1225,6 +1266,16 @@ static void update_game_sound(void) {
                     gSequencePlayers[SEQ_PLAYER_SFX].channels[channelIndex]->soundScriptIO[4] = soundId;
                     gSequencePlayers[SEQ_PLAYER_SFX].channels[channelIndex]->soundScriptIO[0] = 1;
 
+                    // Set surround effect index based on Z depth when starting sound
+                    if (gSoundMode == SOUND_MODE_SURROUND) {
+                        gSequencePlayers[SEQ_PLAYER_SFX].channels[channelIndex]->surroundEffectIndex =
+                            get_sound_surround_effect_index(*sSoundBanks[bank][soundIndex].z);
+                        // Set comb filter gain based on Y height for vertical positioning
+                        gSequencePlayers[SEQ_PLAYER_SFX].channels[channelIndex]->combFilterGain =
+                            audio_compute_comb_filter(*sSoundBanks[bank][soundIndex].y);
+                        gSequencePlayers[SEQ_PLAYER_SFX].channels[channelIndex]->combFilterSize = 16;
+                    }
+
                     switch (bank) {
                         case SOUND_BANK_MOVING:
                             if (!(sSoundBanks[bank][soundIndex].soundBits & SOUND_CONSTANT_FREQUENCY)) {
@@ -1409,6 +1460,17 @@ static void update_game_sound(void) {
                     // on the same line after preprocessing, and the compiler,
                     // somehow caring about line numbers, makes it not match (it
                     // computes function arguments in the wrong order).
+
+                    // Update surround effect index based on Z depth during playback
+                    if (gSoundMode == SOUND_MODE_SURROUND) {
+                        gSequencePlayers[SEQ_PLAYER_SFX].channels[channelIndex]->surroundEffectIndex =
+                            get_sound_surround_effect_index(*sSoundBanks[bank][soundIndex].z);
+                        // Update comb filter gain based on Y height for vertical positioning
+                        gSequencePlayers[SEQ_PLAYER_SFX].channels[channelIndex]->combFilterGain =
+                            audio_compute_comb_filter(*sSoundBanks[bank][soundIndex].y);
+                        gSequencePlayers[SEQ_PLAYER_SFX].channels[channelIndex]->combFilterSize = 0x28;
+                    }
+
                     switch (bank) {
                         case SOUND_BANK_MOVING:
                             if (!(sSoundBanks[bank][soundIndex].soundBits & SOUND_CONSTANT_FREQUENCY)) {

src/audio/external.h

@@ -13,6 +13,7 @@
 #define SOUND_MODE_STEREO           0
 #define SOUND_MODE_MONO             3
 #define SOUND_MODE_HEADSET          1
+#define SOUND_MODE_SURROUND         2
 
 #define SEQ_PLAYER_LEVEL            0  // Level background music
 #define SEQ_PLAYER_ENV              1  // Misc music like the puzzle jingle

src/audio/internal.h

@@ -446,6 +446,9 @@ struct SequenceChannel {
                    u8 unkSH06; // some priority
 #endif
     /*0x05, 0x06*/ u8 bankId;
+    /*          */ u8 surroundEffectIndex; // Surround depth: 0 = front, 0x7F = behind
+    /*          */ u8 combFilterSize;      // Comb filter size (delay in bytes, typically 0x28)
+    /*          */ u16 combFilterGain;     // Comb filter gain for surround height effect
 #if defined(VERSION_EU) || defined(VERSION_SH)
     /*    , 0x07*/ u8 reverbIndex;
     /*    , 0x08, 0x09*/ u8 bookOffset;
@@ -567,6 +570,7 @@ struct NoteSynthesisState {
     /*      0x04*/ u8 reverbVol;
     /*      0x05*/ u8 unk5;
 #endif
+    /*    */ u8 combFilterNeedsInit; // TRUE if comb filter state needs to be cleared
     /*0x04, 0x06*/ u16 samplePosFrac;
     /*0x08*/ s32 samplePosInt;
     /*0x0C*/ struct NoteSynthesisBuffers *synthesisBuffers;
@@ -641,6 +645,10 @@ struct Note {
     /*0x04, 0x30, 0x30*/ u8 priority;
     /*      0x31, 0x31*/ u8 waveId;
     /*      0x32, 0x32*/ u8 sampleCountIndex;
+    /*                */ u8 surroundEffectIndex; // Index for surround effect pan position
+    /*                */ u8 pan;                 // Pan position: 0 = left, 128 = center, 255 = right
+    /*                */ u8 combFilterSize;      // Comb filter size (delay in bytes)
+    /*                */ u16 combFilterGain;     // Comb filter gain for surround height effect
 #ifdef VERSION_SH
     /*            0x33*/ u8 bankId;
     /*            0x34*/ u8 unkSH34;
@@ -701,7 +709,11 @@ struct Note {
     /*0x3C*/ u16 targetVolLeft; // Q1.15, but will always be non-negative
     /*0x3E*/ u16 targetVolRight; // Q1.15, but will always be non-negative
     /*0x40*/ u8 reverbVol; // Q1.7
-    /*0x41*/ u8 unused1; // never read, set to 0x3f
+    /*0x41*/ u8 surroundEffectIndex; // Index for surround effect pan position
+    /*0x42*/ u8 pan; // Pan position: 0 = left, 128 = center, 255 = right
+    /*    */ u8 combFilterSize;      // Comb filter size (delay in bytes, typically 0x28)
+    /*    */ u8 combFilterNeedsInit; // TRUE if comb filter state needs to be cleared
+    /*    */ u16 combFilterGain;     // Comb filter gain for surround height effect
     /*0x44*/ struct NoteAttributes attributes;
     /*0x54, 0x58*/ struct AdsrState adsr;
     /*0x74, 0x7C*/ struct Portamento portamento;
@@ -731,6 +743,7 @@ struct NoteSynthesisBuffers {
     s16 samples[0x40];
 #endif
 #endif
+    s16 combFilterState[0x40]; // State buffer for comb filter (stores previous samples for delay)
 };
 
 #ifdef VERSION_EU

src/audio/mixer.c

@@ -35,7 +35,7 @@
 #define BUF_U8(a) (rspa.buf.as_u8 + ((a) - 0x450))
 #define BUF_S16(a) (rspa.buf.as_s16 + ((a) - 0x450) / sizeof(int16_t))
 #else
-#define BUF_SIZE 2512
+#define BUF_SIZE 2816 // extended to accommodate Surround mode
 #define BUF_U8(a) (rspa.buf.as_u8 + (a))
 #define BUF_S16(a) (rspa.buf.as_s16 + (a) / sizeof(int16_t))
 #endif

src/audio/playback.c

@@ -9,6 +9,7 @@
 #include "synthesis.h"
 #include "effects.h"
 #include "external.h"
+#include <stdio.h>
 
 void note_set_resampling_rate(struct Note *note, f32 resamplingRateInput);
 
@@ -46,6 +47,10 @@ void note_set_vel_pan_reverb(struct Note *note, f32 velocity, u8 pan, u8 reverbV
     pan &= unkMask;
 #endif
 
+    // Store pan as u8 (0=left, 128=center, 255=right) for surround effect
+    // EU pan is 0-127, scale to 0-255
+    note->pan = pan * 2;
+
     if (note->noteSubEu.stereoHeadsetEffects && gSoundMode == SOUND_MODE_HEADSET) {
 #ifdef VERSION_SH
         smallPanIndex = pan >> 1;
@@ -114,6 +119,24 @@ void note_set_vel_pan_reverb(struct Note *note, f32 velocity, u8 pan, u8 reverbV
     } else if (gSoundMode == SOUND_MODE_MONO) {
         volLeft = 0.707f;
         volRight = 0.707f;
+    } else if (sub->stereoHeadsetEffects && gSoundMode == SOUND_MODE_SURROUND) {
+        // TEMPORARY: Surround mode behaves like stereo to test if glitch persists
+        sub->headsetPanLeft = 0;
+        sub->headsetPanRight = 0;
+        sub->usesHeadsetPanEffects = FALSE;
+        volLeft = gStereoPanVolume[pan];
+        volRight = gStereoPanVolume[127 - pan];
+        // Use same thresholds as stereo (0x20/0x60)
+        if (pan < 0x20) {
+            sub->stereoStrongLeft = TRUE;
+            sub->stereoStrongRight = FALSE;
+        } else if (pan > 0x60) {
+            sub->stereoStrongRight = TRUE;
+            sub->stereoStrongLeft = FALSE;
+        } else {
+            sub->stereoStrongLeft = FALSE;
+            sub->stereoStrongRight = FALSE;
+        }
     } else {
         volLeft = gDefaultPanVolume[pan];
         volRight = gDefaultPanVolume[127 - pan];
@@ -1151,6 +1174,11 @@ void note_init_for_layer(struct Note *note, struct SequenceChannelLayer *seqLaye
 #endif
     sub->stereoHeadsetEffects = seqLayer->seqChannel->stereoHeadsetEffects;
     sub->reverbIndex = seqLayer->seqChannel->reverbIndex & 3;
+    note->surroundEffectIndex = seqLayer->seqChannel->surroundEffectIndex;
+    note->combFilterGain = seqLayer->seqChannel->combFilterGain;
+    note->combFilterSize = seqLayer->seqChannel->combFilterSize;
+    // EU pan is s32 0-127, scale to u8 0-254
+    note->pan = (u8)(seqLayer->seqChannel->pan * 2);
 }
 #else
 s32 note_init_for_layer(struct Note *note, struct SequenceChannelLayer *seqLayer) {
@@ -1172,6 +1200,13 @@ s32 note_init_for_layer(struct Note *note, struct SequenceChannelLayer *seqLayer
         build_synthetic_wave(note, seqLayer);
     }
     note_init(note);
+    // Copy surround index after note_init to avoid being reset by note_init_volume
+    note->surroundEffectIndex = seqLayer->seqChannel->surroundEffectIndex;
+    // Copy comb filter settings for height-based surround effect
+    note->combFilterGain = seqLayer->seqChannel->combFilterGain;
+    note->combFilterSize = seqLayer->seqChannel->combFilterSize;
+    // Non-EU pan is f32 0.0-1.0, scale to u8 0-255
+    note->pan = (u8)(seqLayer->seqChannel->pan * 255.0f);
     return FALSE;
 }
 #endif
@@ -1414,6 +1449,9 @@ void note_init_all(void) {
         note = &gNotes[i];
 #if defined(VERSION_EU) || defined(VERSION_SH)
         note->noteSubEu = gZeroNoteSub;
+        note->combFilterGain = 0;
+        note->combFilterSize = 0;
+        note->synthesisState.combFilterNeedsInit = TRUE;
 #else
         note->enabled = FALSE;
         note->stereoStrongRight = FALSE;
@@ -1437,7 +1475,10 @@ void note_init_all(void) {
         note->targetVolLeft = 0;
         note->targetVolRight = 0;
         note->frequency = 0.0f;
-        note->unused1 = 0x3f;
+        note->surroundEffectIndex = 0;
+        note->combFilterGain = 0;
+        note->combFilterSize = 0;
+        note->combFilterNeedsInit = TRUE;
 #endif
         note->attributes.velocity = 0.0f;
         note->adsrVolScale = 0;

src/audio/seqplayer.c

@@ -37,6 +37,9 @@ void sequence_channel_init(struct SequenceChannel *seqChannel) {
     seqChannel->stopSomething2 = FALSE;
     seqChannel->hasInstrument = FALSE;
     seqChannel->stereoHeadsetEffects = FALSE;
+    seqChannel->surroundEffectIndex = 0;
+    seqChannel->combFilterGain = 0;
+    seqChannel->combFilterSize = 0;
     seqChannel->transposition = 0;
     seqChannel->largeNotes = FALSE;
 #if defined(VERSION_EU) || defined(VERSION_SH)