Add sf2 (soundfont) support to wildmidi

CMakeLists.txt

@@ -66,6 +66,12 @@ OPTION(WANT_OPENAL "Include OpenAL (Cross Platform) support" OFF)
 
 OPTION(WANT_DEVTEST "Build WildMIDI DevTest file to check files" OFF)
 
+OPTION(WANT_SF2 "SoundFont2 (SF2) support via TinySoundFont" ON)
+IF (WANT_SF2 AND CMAKE_VERSION VERSION_LESS 3.14)
+    MESSAGE(WARNING "WANT_SF2 requires CMake 3.14+ (FetchContent); disabling SF2 support")
+    SET(WANT_SF2 OFF)
+ENDIF()
+
 CMAKE_DEPENDENT_OPTION(WANT_MP_BUILD "Build with Multiple Processes (/MP)" OFF "WIN32;MSVC" OFF)
 CMAKE_DEPENDENT_OPTION(WANT_OSX_DEPLOYMENT "OSX Deployment" OFF "APPLE" OFF)
 
@@ -299,6 +305,17 @@ IF(WANT_PLAYER OR WANT_PLAYERSTATIC)
     MESSAGE(STATUS "Enabled audio output backends: ${ENABLED_OUTPUT}")
 ENDIF()
 
+IF (WANT_SF2)
+    INCLUDE(FetchContent)
+    FetchContent_Declare(tinysoundfont
+        GIT_REPOSITORY https://github.com/schellingb/TinySoundFont.git
+        GIT_TAG fbc913531b85f5707f49115110bb86b1cd583885 # 2025-07-19
+    )
+    FetchContent_MakeAvailable(tinysoundfont)
+    INCLUDE_DIRECTORIES(SYSTEM "${tinysoundfont_SOURCE_DIR}")
+    SET(WILDMIDI_SF2 1)
+ENDIF()
+
 # Setup up our config file
 CONFIGURE_FILE("${PROJECT_SOURCE_DIR}/include/config.h.cmake" "${PROJECT_BINARY_DIR}/include/config.h")
 

docs/SF2.md

@@ -0,0 +1,69 @@
+# SoundFont2 (SF2) Support
+
+Implementation plan and design notes for [issue #8](https://github.com/Mindwerks/wildmidi/issues/8).
+
+## Approach
+
+WildMIDI gains SF2 rendering via [TinySoundFont](https://github.com/schellingb/TinySoundFont)
+(`tsf.h`, MIT licensed, single-header, pure C), fetched at configure time with CMake
+`FetchContent` and pinned to a known-good commit.
+
+The key insight: WildMIDI's format parsers (MID, XMI, MUS, HMP, HMI) already convert
+everything into a single time-stamped event list (`struct _event`), and the renderer is
+just the stage that consumes that list. SF2 support swaps the *rendering* stage while
+keeping every parser, the timing engine, and the public API untouched. No other MIDI
+library renders XMI/MUS/HMP/HMI through SoundFonts — this is WildMIDI's niche.
+
+TinySoundFont's common criticism — "you must do your own MIDI parsing" — is exactly
+what makes it the right fit here: its `tsf_channel_*` API maps 1:1 onto WildMIDI's
+already-decoded event types.
+
+## How it works
+
+1. **Loading** — `WildMidi_Init()` / `WildMidi_InitVIO()` sniff the config file for the
+   RIFF/`sfbk` magic (not the file extension). An `.sf2` file given directly as the
+   "config file" is loaded through the existing VIO buffer callbacks into one global
+   `tsf*` instance. Additionally, the timidity.cfg parser understands a
+   `soundfont <file>` directive (relative paths resolved against the config dir, same
+   as `source`), so `/etc/timidity/fluidr3_gm.cfg` works as-is.
+2. **Per-song synth** — each opened midi (`struct _mdi`) gets its own `tsf_copy()` of
+   the global instance (sample data shared, voices private), created in `_WM_initMDI()`
+   and freed in `_WM_freeMDI()`. Concurrent handles stay safe.
+3. **Rendering** — `WM_GetOutput_SF2()` mirrors the scheduling loop of
+   `WM_GetOutput_Linear()`. Every event still runs its normal `do_event` (tempo, lyrics,
+   channel state; GUS note-ons no-op safely since no GUS patches are loaded) and is
+   additionally translated to the corresponding `tsf_channel_*` call. Audio is rendered
+   by `tsf_render_short()` into the 32-bit mix buffer, so `WM_MO_REVERB` and the rest of
+   the output pipeline behave exactly like the GUS path.
+4. **Release tails** — when the event list ends, rendering continues while
+   `tsf_active_voice_count() > 0`, so SF2 release envelopes aren't clipped at
+   end-of-song.
+
+## Event translation
+
+| WildMIDI event | TSF call |
+|---|---|
+| note on/off | `tsf_channel_note_on` / `_off` |
+| patch change | `tsf_channel_set_presetnumber(..., isdrum)` |
+| pitch wheel | `tsf_channel_set_pitchwheel` |
+| all controllers (bank, volume, pan, expression, hold, RPN/NRPN, sound/notes off, …) | `tsf_channel_midi_control` (TSF implements the full CC map) |
+| Roland drum-track sysex | `tsf_channel_set_bank_preset(ch, 128, 0)` |
+
+Channel 9 defaults to bank 128 (drums) at synth creation, per GM convention.
+
+## Build
+
+* `WANT_SF2` CMake option, default `ON`; requires CMake >= 3.14 (auto-disables with a
+  warning on older CMake so legacy platforms keep building).
+* Offline/distro builds: point `FETCHCONTENT_SOURCE_DIR_TINYSOUNDFONT` at a local
+  checkout — standard CMake, no extra plumbing.
+* License: `tsf.h` is MIT, compatible with linking into the LGPLv3 library.
+
+## Non-goals (first pass)
+
+* Mixing GUS patches and SF2 in one config — if a soundfont is loaded it takes over
+  rendering entirely.
+* SF3 (ogg-compressed) soundfonts — one `#define TSF_SF3` + stb_vorbis away if wanted.
+* timidity per-soundfont options (`amp=`, `order=`, `remove`) — parsed token is the
+  filename only.
+* `WildMidi_MasterVolume()` does not affect the SF2 path yet (TSF has its own gain).

include/config.h.cmake

@@ -55,6 +55,9 @@
 /* define this if building for AmigaOS variants */
 #cmakedefine WILDMIDI_AMIGA 1
 
+/* define this to enable SoundFont2 support via TinySoundFont */
+#cmakedefine WILDMIDI_SF2 1
+
 /* Define if you have the <stdint.h> header file. */
 #cmakedefine HAVE_STDINT_H
 

include/internal_midi.h

@@ -161,6 +161,8 @@ struct _mdi {
     uint8_t is_type2;
 
     char *lyric;
+
+    void *sf2_synth; /* per-mdi TinySoundFont instance, NULL unless a soundfont is loaded */
 };
 
 

include/sf2.h

@@ -0,0 +1,52 @@
+/*
+ * sf2.h -- SoundFont2 rendering via TinySoundFont
+ *
+ * Copyright (C) WildMIDI Developers 2026
+ *
+ * This file is part of WildMIDI.
+ *
+ * WildMIDI is free software: you can redistribute and/or modify the player
+ * under the terms of the GNU General Public License and you can redistribute
+ * and/or modify the library under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation, either version 3 of
+ * the licenses, or(at your option) any later version.
+ *
+ * WildMIDI is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License and
+ * the GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License and the
+ * GNU Lesser General Public License along with WildMIDI.  If not,  see
+ * <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __SF2_H
+#define __SF2_H
+
+struct _mdi;
+struct _event;
+
+/* returns 1 if the buffer looks like a RIFF sfbk (SoundFont2) file */
+extern int _WM_SF2_Magic(const uint8_t *data, uint32_t size);
+
+/* load/free the global soundfont instance */
+extern int _WM_SF2_Load(const uint8_t *data, uint32_t size);
+extern void _WM_SF2_Unload(void);
+extern int _WM_SF2_Active(void);
+
+/* per-mdi synth instances (voices private, sample data shared) */
+extern void *_WM_SF2_NewSynth(uint16_t rate);
+extern void _WM_SF2_FreeSynth(void *synth);
+extern void _WM_SF2_Reset(void *synth);
+
+/* translate a wildmidi event to the synth */
+extern void _WM_SF2_Event(void *synth, struct _mdi *mdi, struct _event *event);
+
+/* returns nonzero while notes are still sounding (release tails) */
+extern int _WM_SF2_ActiveVoices(void *synth);
+
+/* render stereo frames into the 32bit mix buffer */
+extern void _WM_SF2_Render(void *synth, int32_t *out, uint32_t frames);
+
+#endif /* __SF2_H */

src/CMakeLists.txt

@@ -41,6 +41,11 @@ SET(wildmidi_library_HDRS
  ../include/wildplay.h
 )
 
+IF (WANT_SF2)
+    LIST(APPEND wildmidi_library_SRCS sf2.c)
+    LIST(APPEND wildmidi_library_HDRS ../include/sf2.h)
+ENDIF()
+
 # set our library names
 IF (MSVC) # windows uses *.lib for both static and dynamic, workaround
     SET(LIBRARY_DYN_NAME "libWildMidi")

src/internal_midi.c

@@ -37,6 +37,9 @@
 #include "wildmidi_lib.h"
 #include "patches.h"
 #include "internal_midi.h"
+#ifdef WILDMIDI_SF2
+#include "sf2.h"
+#endif
 
 #define HOLD_OFF 0x02
 
@@ -1946,6 +1949,12 @@ _WM_initMDI(void) {
 
     mdi->lyric = NULL;
 
+#ifdef WILDMIDI_SF2
+    if (_WM_SF2_Active()) {
+        mdi->sf2_synth = _WM_SF2_NewSynth(_WM_SampleRate);
+    }
+#endif
+
     _WM_do_sysex_gm_reset(mdi, NULL);
 
     return (mdi);
@@ -1996,6 +2005,9 @@ void _WM_freeMDI(struct _mdi *mdi) {
     free(mdi->events);
     _WM_free_reverb(mdi->reverb);
     free(mdi->mix_buffer);
+#ifdef WILDMIDI_SF2
+    _WM_SF2_FreeSynth(mdi->sf2_synth);
+#endif
     if (mdi->tmp_info) {
         free(mdi->tmp_info->copyright);
         free(mdi->tmp_info);