From fd9f4d3a7463e1612f9ad478ed15a2fd5cb99a18 Mon Sep 17 00:00:00 2001
From: David Racine <bass_dr@hotmail.com>
Date: Sun, 30 Aug 2026 23:15:29 -0400
Subject: [PATCH] Reopen the OPUS decoder when a note moves to another sample

The decoder cached on a note was keyed on nothing, so a note reused for a
different streamed sample carried on decoding the previous track. Audible as
the wrong custom music: the sequence and soundfont the audio editor reports
are correct, only the samples reaching the mixer are not.

Reproduced on the game-start cutscene chain with a streamed music pack in 4
of 6 runs; 0 of 6 after.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011Ex3z29fQzPEZgwH4EA641
---
 soh/include/z64audio.h         | 1 +
 soh/soh/mixer.h                | 1 +
 soh/src/code/audio_playback.c  | 3 ++-
 soh/src/code/audio_synthesis.c | 7 +++++++
 4 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/soh/include/z64audio.h b/soh/include/z64audio.h
index 6fed61399d6..026dffd684d 100644
--- a/soh/include/z64audio.h
+++ b/soh/include/z64audio.h
@@ -489,6 +489,7 @@ typedef struct {
     /* 0x1C */ u16 unk_1C;
     /* 0x1E */ u16 unk_1E;
     struct OggOpusFile* opusFile; // Only for streamed opus audio
+    uintptr_t opusSampleAddr;     // sample opusFile was opened for
 } NoteSynthesisState; // size = 0x20
 
 typedef struct {
diff --git a/soh/soh/mixer.h b/soh/soh/mixer.h
index 048135e4485..c4626cc2330 100644
--- a/soh/soh/mixer.h
+++ b/soh/soh/mixer.h
@@ -61,6 +61,7 @@ struct OggOpusFile;
 
 void aOPUSdecImpl(void* source_addr, uint16_t dest_addr, uint16_t nbytes, struct OggOpusFile** decState, int32_t pos,
                   uint32_t size);
+void aOPUSFree(struct OggOpusFile* opusFile);
 
 #define aSegment(pkt, s, b) \
     do {                    \
diff --git a/soh/src/code/audio_playback.c b/soh/src/code/audio_playback.c
index ce6c5d6f19b..e32a56306b0 100644
--- a/soh/src/code/audio_playback.c
+++ b/soh/src/code/audio_playback.c
@@ -1,5 +1,6 @@
 #include "global.h"
 #include "soh/ResourceManagerHelpers.h"
+#include "soh/mixer.h"
 
 extern bool gUseLegacySD;
 
@@ -150,7 +151,6 @@ void Audio_NoteInit(Note* note) {
     note->noteSubEu = gDefaultNoteSub;
 }
 
-extern void aOPUSFree(struct OggOpusFile* opusFile);
 void Audio_NoteDisable(Note* note) {
     if (note->noteSubEu.bitField0.needsInit == true) {
         note->noteSubEu.bitField0.needsInit = false;
@@ -166,6 +166,7 @@ void Audio_NoteDisable(Note* note) {
     if (note->synthesisState.opusFile != NULL) {
         aOPUSFree(note->synthesisState.opusFile);
         note->synthesisState.opusFile = NULL;
+        note->synthesisState.opusSampleAddr = 0;
     }
 }
 
diff --git a/soh/src/code/audio_synthesis.c b/soh/src/code/audio_synthesis.c
index 7b2db226799..c8cd068fc76 100644
--- a/soh/src/code/audio_synthesis.c
+++ b/soh/src/code/audio_synthesis.c
@@ -876,6 +876,13 @@ Acmd* AudioSynth_ProcessNote(s32 noteIndex, NoteSubEu* noteSubEu, NoteSynthesisS
 
                         // 2S2H [Port] [Custom audio] Handle decoding OPUS data
                         if (audioFontSample->codec == CODEC_OPUS) {
+                            // A note reused for another streamed sample keeps the decoder its predecessor opened,
+                            // so the previous track carries on playing under the new note.
+                            if (synthState->opusFile != NULL && synthState->opusSampleAddr != sampleAddr) {
+                                aOPUSFree(synthState->opusFile);
+                                synthState->opusFile = NULL;
+                            }
+                            synthState->opusSampleAddr = sampleAddr;
                             aOPUSdecImpl(sampleAddr, DMEM_UNCOMPRESSED_NOTE + s5, bytesToRead, &synthState->opusFile,
                                          synthState->samplePosInt, audioFontSample->fileSize);
                         } else {