Switch SFX to Opus; use floating-point mixing

taisei-project · Akaricchi · May 11, 2019 · May 2, 2019 · May 4, 2019 · May 6, 2019
commit 4c815c8596c0783c4bae04ac63b4741d3436a0fe
diff --git a/README.rst b/README.rst
@@ -22,6 +22,7 @@ Dependencies
 -  libpng >= 1.5.0
 -  libwebpdecoder >= 0.5 or libwebp >= 0.5
 -  libzip >= 1.2
+-  opusfile
 -  zlib
 
 Optional:

diff --git a/meson.build b/meson.build
@@ -114,13 +114,14 @@ endif
 static = get_option('static') or (host_machine.system() == 'emscripten')
 
 dep_freetype    = dependency('freetype2',                           required : true,  static : static, fallback : ['freetype', 'freetype_dep'])
+dep_opusfile    = dependency('opusfile',                            required : false, static : static, fallback : ['opusfile', 'opusfile_dep'])
 dep_png         = dependency('libpng',         version : '>=1.5',   required : true,  static : static, fallback : ['libpng', 'png_dep'])
 dep_sdl2        = dependency('sdl2',           version : '>=2.0.5', required : true,  static : static, fallback : ['sdl2', 'sdl2_dep'])
 dep_sdl2_mixer  = dependency('SDL2_mixer',     version : '>=2.0.4', required : false, static : static, fallback : ['sdl2_mixer', 'sdl2_mixer_dep'])
 dep_webp        = dependency('libwebp',        version : '>=0.5',   required : false, static : static, fallback : ['libwebp', 'webp_dep'])
 dep_webpdecoder = dependency('libwebpdecoder', version : '>=0.5',   required : false, static : static, fallback : ['libwebp', 'webpdecoder_dep'])
-dep_zlib        = dependency('zlib',                                required : true,  static : static, fallback : ['zlib', 'zlib_dep'])
 dep_zip         = dependency('libzip',         version : '>=1.2',   required : false, static : static, fallback : ['libzip', 'libzip_dep'])
+dep_zlib        = dependency('zlib',                                required : true,  static : static, fallback : ['zlib', 'zlib_dep'])
 dep_crypto      = dependency('libcrypto',                           required : false, static : static)
 
 dep_m           = cc.find_library('m', required : false)

diff --git a/resources/00-taisei.pkgdir/sfx/bomb_marisa_a.ogg b/resources/00-taisei.pkgdir/sfx/bomb_marisa_a.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/bomb_marisa_a.opus b/resources/00-taisei.pkgdir/sfx/bomb_marisa_a.opus
diff --git a/resources/00-taisei.pkgdir/sfx/bomb_marisa_b.ogg b/resources/00-taisei.pkgdir/sfx/bomb_marisa_b.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/bomb_marisa_b.opus b/resources/00-taisei.pkgdir/sfx/bomb_marisa_b.opus
diff --git a/resources/00-taisei.pkgdir/sfx/bomb_reimu_a.ogg b/resources/00-taisei.pkgdir/sfx/bomb_reimu_a.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/bomb_reimu_a.opus b/resources/00-taisei.pkgdir/sfx/bomb_reimu_a.opus
diff --git a/resources/00-taisei.pkgdir/sfx/bomb_youmu_a.ogg b/resources/00-taisei.pkgdir/sfx/bomb_youmu_a.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/bomb_youmu_a.opus b/resources/00-taisei.pkgdir/sfx/bomb_youmu_a.opus
diff --git a/resources/00-taisei.pkgdir/sfx/bomb_youmu_b.ogg b/resources/00-taisei.pkgdir/sfx/bomb_youmu_b.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/bomb_youmu_b.opus b/resources/00-taisei.pkgdir/sfx/bomb_youmu_b.opus
diff --git a/resources/00-taisei.pkgdir/sfx/boom.ogg b/resources/00-taisei.pkgdir/sfx/boom.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/boom.opus b/resources/00-taisei.pkgdir/sfx/boom.opus
diff --git a/resources/00-taisei.pkgdir/sfx/boon.ogg b/resources/00-taisei.pkgdir/sfx/boon.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/boon.opus b/resources/00-taisei.pkgdir/sfx/boon.opus
diff --git a/resources/00-taisei.pkgdir/sfx/bossdeath.ogg b/resources/00-taisei.pkgdir/sfx/bossdeath.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/bossdeath.opus b/resources/00-taisei.pkgdir/sfx/bossdeath.opus
diff --git a/resources/00-taisei.pkgdir/sfx/charge_extra.ogg b/resources/00-taisei.pkgdir/sfx/charge_extra.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/charge_extra.opus b/resources/00-taisei.pkgdir/sfx/charge_extra.opus
diff --git a/resources/00-taisei.pkgdir/sfx/charge_generic.ogg b/resources/00-taisei.pkgdir/sfx/charge_generic.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/charge_generic.opus b/resources/00-taisei.pkgdir/sfx/charge_generic.opus
diff --git a/resources/00-taisei.pkgdir/sfx/death.ogg b/resources/00-taisei.pkgdir/sfx/death.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/death.opus b/resources/00-taisei.pkgdir/sfx/death.opus
diff --git a/resources/00-taisei.pkgdir/sfx/enemydeath.ogg b/resources/00-taisei.pkgdir/sfx/enemydeath.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/enemydeath.opus b/resources/00-taisei.pkgdir/sfx/enemydeath.opus
diff --git a/resources/00-taisei.pkgdir/sfx/extra_bomb.ogg b/resources/00-taisei.pkgdir/sfx/extra_bomb.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/extra_bomb.opus b/resources/00-taisei.pkgdir/sfx/extra_bomb.opus
diff --git a/resources/00-taisei.pkgdir/sfx/extra_life.ogg b/resources/00-taisei.pkgdir/sfx/extra_life.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/extra_life.opus b/resources/00-taisei.pkgdir/sfx/extra_life.opus
diff --git a/resources/00-taisei.pkgdir/sfx/generic_shot.ogg b/resources/00-taisei.pkgdir/sfx/generic_shot.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/generic_shot.opus b/resources/00-taisei.pkgdir/sfx/generic_shot.opus
diff --git a/resources/00-taisei.pkgdir/sfx/graze.ogg b/resources/00-taisei.pkgdir/sfx/graze.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/graze.opus b/resources/00-taisei.pkgdir/sfx/graze.opus
diff --git a/resources/00-taisei.pkgdir/sfx/hit.ogg b/resources/00-taisei.pkgdir/sfx/hit.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/hit.opus b/resources/00-taisei.pkgdir/sfx/hit.opus
diff --git a/resources/00-taisei.pkgdir/sfx/hit0.ogg b/resources/00-taisei.pkgdir/sfx/hit0.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/hit0.opus b/resources/00-taisei.pkgdir/sfx/hit0.opus
diff --git a/resources/00-taisei.pkgdir/sfx/hit1.ogg b/resources/00-taisei.pkgdir/sfx/hit1.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/hit1.opus b/resources/00-taisei.pkgdir/sfx/hit1.opus
diff --git a/resources/00-taisei.pkgdir/sfx/item_generic.ogg b/resources/00-taisei.pkgdir/sfx/item_generic.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/item_generic.opus b/resources/00-taisei.pkgdir/sfx/item_generic.opus
diff --git a/resources/00-taisei.pkgdir/sfx/laser1.ogg b/resources/00-taisei.pkgdir/sfx/laser1.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/laser1.opus b/resources/00-taisei.pkgdir/sfx/laser1.opus
diff --git a/resources/00-taisei.pkgdir/sfx/noise1.ogg b/resources/00-taisei.pkgdir/sfx/noise1.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/noise1.opus b/resources/00-taisei.pkgdir/sfx/noise1.opus
diff --git a/resources/00-taisei.pkgdir/sfx/powersurge_end.ogg b/resources/00-taisei.pkgdir/sfx/powersurge_end.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/powersurge_end.opus b/resources/00-taisei.pkgdir/sfx/powersurge_end.opus
diff --git a/resources/00-taisei.pkgdir/sfx/powersurge_start.ogg b/resources/00-taisei.pkgdir/sfx/powersurge_start.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/powersurge_start.opus b/resources/00-taisei.pkgdir/sfx/powersurge_start.opus
diff --git a/resources/00-taisei.pkgdir/sfx/powerup.ogg b/resources/00-taisei.pkgdir/sfx/powerup.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/powerup.opus b/resources/00-taisei.pkgdir/sfx/powerup.opus
diff --git a/resources/00-taisei.pkgdir/sfx/redirect.ogg b/resources/00-taisei.pkgdir/sfx/redirect.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/redirect.opus b/resources/00-taisei.pkgdir/sfx/redirect.opus
diff --git a/resources/00-taisei.pkgdir/sfx/shot1.ogg b/resources/00-taisei.pkgdir/sfx/shot1.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/shot1.opus b/resources/00-taisei.pkgdir/sfx/shot1.opus
diff --git a/resources/00-taisei.pkgdir/sfx/shot1_loop.ogg b/resources/00-taisei.pkgdir/sfx/shot1_loop.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/shot1_loop.opus b/resources/00-taisei.pkgdir/sfx/shot1_loop.opus
diff --git a/resources/00-taisei.pkgdir/sfx/shot2.ogg b/resources/00-taisei.pkgdir/sfx/shot2.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/shot2.opus b/resources/00-taisei.pkgdir/sfx/shot2.opus
diff --git a/resources/00-taisei.pkgdir/sfx/shot3.ogg b/resources/00-taisei.pkgdir/sfx/shot3.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/shot3.opus b/resources/00-taisei.pkgdir/sfx/shot3.opus
diff --git a/resources/00-taisei.pkgdir/sfx/shot_special1.ogg b/resources/00-taisei.pkgdir/sfx/shot_special1.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/shot_special1.opus b/resources/00-taisei.pkgdir/sfx/shot_special1.opus
diff --git a/resources/00-taisei.pkgdir/sfx/spellclear.ogg b/resources/00-taisei.pkgdir/sfx/spellclear.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/spellclear.opus b/resources/00-taisei.pkgdir/sfx/spellclear.opus
diff --git a/resources/00-taisei.pkgdir/sfx/spellend.ogg b/resources/00-taisei.pkgdir/sfx/spellend.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/spellend.opus b/resources/00-taisei.pkgdir/sfx/spellend.opus
diff --git a/resources/00-taisei.pkgdir/sfx/timeout1.ogg b/resources/00-taisei.pkgdir/sfx/timeout1.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/timeout1.opus b/resources/00-taisei.pkgdir/sfx/timeout1.opus
diff --git a/resources/00-taisei.pkgdir/sfx/timeout2.ogg b/resources/00-taisei.pkgdir/sfx/timeout2.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/timeout2.opus b/resources/00-taisei.pkgdir/sfx/timeout2.opus
diff --git a/resources/00-taisei.pkgdir/sfx/warp.ogg b/resources/00-taisei.pkgdir/sfx/warp.ogg
diff --git a/resources/00-taisei.pkgdir/sfx/warp.opus b/resources/00-taisei.pkgdir/sfx/warp.opus
diff --git a/src/audio/sdl2mixer/audio_sdl2mixer.c b/src/audio/sdl2mixer/audio_sdl2mixer.c
@@ -9,20 +9,32 @@
 #include "taisei.h"
 
 #include <SDL_mixer.h>
+#include <opusfile.h>
 
 #include "../backend.h"
 #include "global.h"
 #include "list.h"
+#include "util/opuscruft.h"
 
 #define B (_a_backend.funcs)
 
-#define AUDIO_FREQ 44800
-#define AUDIO_FORMAT MIX_DEFAULT_FORMAT
+#define AUDIO_FREQ 48000
+#define AUDIO_FORMAT AUDIO_F32SYS
 #define AUDIO_CHANNELS 32
 #define UI_CHANNELS 4
 #define UI_CHANNEL_GROUP 0
 #define MAIN_CHANNEL_GROUP 1
 
+#if AUDIO_FORMAT == AUDIO_S16SYS
+typedef int16_t sample_t;
+#define OPUS_READ_SAMPLES_STEREO op_read_stereo
+#elif AUDIO_FORMAT == AUDIO_F32SYS
+typedef float sample_t;
+#define OPUS_READ_SAMPLES_STEREO op_read_float_stereo
+#else
+#error Audio format not recognized
+#endif
+
 // I needed to add this for supporting loop sounds since Mixer doesn’t remember
 // what channel a sound is playing on.  - laochailan
 
@@ -71,7 +83,7 @@ static bool audio_sdl2mixer_init(void) {
 		return false;
 	}
 
-	if(!(Mix_Init(MIX_INIT_OGG) & MIX_INIT_OGG)) {
+	if(!(Mix_Init(MIX_INIT_OPUS) & MIX_INIT_OPUS)) {
 		log_error("Mix_Init() failed: %s", Mix_GetError());
 		Mix_Quit();
 		return false;
@@ -346,10 +358,9 @@ static void custom_fadeout_free(int chan, void *udata) {
 static void custom_fadeout_proc(int chan, void *stream, int len, void *udata) {
 	CustomFadeout *e = udata;
 
-	assert(AUDIO_FORMAT == AUDIO_S16SYS); // if you wanna change the format, you get to implement it here. This is the hardcoded default format in SDL_Mixer by the way
+	sample_t *data = stream;
+	len /= sizeof(sample_t);
 
-	int16_t *data = stream;
-	len /= 2;
 	for(int i = 0; i < len; i++) {
 		e->counter++;
 		data[i]*=1.-min(1,(double)e->counter/(double)e->duration);
@@ -416,13 +427,7 @@ static bool audio_sdl2mixer_sound_stop_all(AudioBackendSoundGroup group) {
 	return true;
 }
 
-static const char *const *audio_sdl2mixer_get_supported_sfx_exts(uint *numexts) {
-	static const char *const exts[] = { ".ogg", ".wav" };
-	*numexts = ARRAY_SIZE(exts);
-	return exts;
-}
-
-static const char *const *audio_sdl2mixer_get_supported_bgm_exts(uint *numexts) {
+static const char *const *audio_sdl2mixer_get_supported_exts(uint *numexts) {
 	static const char *const exts[] = { ".opus", ".ogg", ".wav" };
 	*numexts = ARRAY_SIZE(exts);
 	return exts;
@@ -455,6 +460,92 @@ static void audio_sdl2mixer_music_unload(MusicImpl *imus) {
 	free(imus);
 }
 
+static OggOpusFile *try_load_opus(SDL_RWops *rw) {
+	uint8_t buf[128];
+	SDL_RWread(rw, buf, 1, sizeof(buf));
+	int error = op_test(NULL, buf, sizeof(buf));
+
+	if(error != 0) {
+		log_debug("op_test() failed: %i", error);
+		goto fail;
+	}
+
+	OggOpusFile *opus = op_open_callbacks(rw, &opusutil_rwops_callbacks, buf, sizeof(buf), &error);
+
+	if(opus == NULL) {
+		log_debug("op_open_callbacks() failed: %i", error);
+		goto fail;
+	}
+
+	return opus;
+
+fail:
+	SDL_RWseek(rw, 0, RW_SEEK_SET);
+	return NULL;
+}
+
+static Mix_Chunk *read_opus_chunk(OggOpusFile *opus, const char *vfspath) {
+	// WARNING: it's important to use the SDL_* allocation functions here for the pcm buffer,
+	// so that SDL_mixer can free it properly later.
+
+	const size_t read_size = 1920;
+	size_t buf_size = read_size * 4;
+	size_t samples = 0;
+	sample_t *pcm = SDL_malloc(buf_size * sizeof(*pcm)), *pcm_ptr = pcm;
+
+	for(;;) {
+		ptrdiff_t ofs = (ptrdiff_t)(pcm_ptr - pcm);
+
+		if(buf_size - ofs < read_size) {
+			buf_size *= 2;
+			pcm = SDL_realloc(pcm, buf_size * sizeof(*pcm));
+			pcm_ptr = pcm + ofs;
+		}
+
+		int r = OPUS_READ_SAMPLES_STEREO(opus, pcm_ptr, read_size);
+
+		if(r == OP_HOLE) {
+			continue;
+		}
+
+		if(r < 0) {
+			log_error("Opus decode error %i after %zu samples (%s)", r, samples, vfspath);
+			SDL_free(pcm);
+			op_free(opus);
+			return NULL;
+		}
+
+		// r is the number of samples read !!PER CHANNEL!!
+		// since we tell Opusfile to downmix to stereo, exactly 2 channels are guaranteed.
+		int read = r * 2;
+		samples += read;
+
+		if(read == 0) {
+			op_free(opus);
+
+			// try to avoid wasting memory
+			pcm = SDL_realloc(pcm, samples * sizeof(*pcm));
+
+			Mix_Chunk *snd = Mix_QuickLoad_RAW((void*)pcm, samples * sizeof(*pcm));
+
+			if(!snd) {
+				log_error("Mix_QuickLoad_RAW() failed: %s (%s)", Mix_GetError(), vfspath);
+				SDL_free(pcm);
+				return NULL;
+			}
+
+			// hack to make SDL_mixer free the buffer for us
+			snd->allocated = true;
+
+			return snd;
+		}
+
+		pcm_ptr += read;
+	}
+
+	UNREACHABLE;
+}
+
 static SoundImpl *audio_sdl2mixer_sound_load(const char *vfspath) {
 	SDL_RWops *rw = vfs_open(vfspath, VFS_MODE_READ | VFS_MODE_SEEKABLE);
 
@@ -463,11 +554,27 @@ static SoundImpl *audio_sdl2mixer_sound_load(const char *vfspath) {
 		return NULL;
 	}
 
-	Mix_Chunk *snd = Mix_LoadWAV_RW(rw, true);
+	// SDL2_Mixer as of 2.0.4 is too dumb to actually try to load Opus chunks,
+	// even if it was compiled with Opus support (which only works for music apparently /facepalm)
+	// So we'll try to load them via opusfile manually.
 
-	if(!snd) {
-		log_error("Mix_LoadWAV_RW() failed: %s (%s)", Mix_GetError(), vfspath);
-		return NULL;
+	Mix_Chunk *snd = NULL;
+	OggOpusFile *opus = try_load_opus(rw);
+
+	if(opus) {
+		snd = read_opus_chunk(opus, vfspath);
+
+		if(!snd) {
+			// error message printed by read_opus_chunk
+			return NULL;
+		}
+	} else {
+		snd = Mix_LoadWAV_RW(rw, true);
+
+		if(!snd) {
+			log_error("Mix_LoadWAV_RW() failed: %s (%s)", Mix_GetError(), vfspath);
+			return NULL;
+		}
 	}
 
 	SoundImpl *isnd = calloc(1, sizeof(*isnd));
@@ -492,8 +599,8 @@ static bool audio_sdl2mixer_sound_set_volume(SoundImpl *isnd, double gain) {
 AudioBackend _a_backend_sdl2mixer = {
 	.name = "sdl2mixer",
 	.funcs = {
-		.get_supported_music_exts = audio_sdl2mixer_get_supported_bgm_exts,
-		.get_supported_sound_exts = audio_sdl2mixer_get_supported_sfx_exts,
+		.get_supported_music_exts = audio_sdl2mixer_get_supported_exts,
+		.get_supported_sound_exts = audio_sdl2mixer_get_supported_exts,
 		.init = audio_sdl2mixer_init,
 		.music_fade = audio_sdl2mixer_music_fade,
 		.music_is_paused = audio_sdl2mixer_music_is_paused,

diff --git a/src/audio/sdl2mixer/meson.build b/src/audio/sdl2mixer/meson.build
@@ -4,8 +4,9 @@ a_sdl2mixer_src = files(
 )
 
 a_sdl2mixer_deps = []
-a_sdl2mixer_libdeps = [dep_sdl2_mixer]
+a_sdl2mixer_libdeps = [dep_sdl2_mixer, dep_opusfile]
 
-if get_option('a_sdl2mixer') and not dep_sdl2_mixer.found()
-    error('sdl2mixer backend enabled, but SDL2_mixer was not found. Install SDL2_mixer or disable a_sdl2mixer')
+if get_option('a_sdl2mixer')
+    assert(dep_sdl2_mixer.found(), 'sdl2mixer backend enabled, but SDL2_mixer was not found. Install SDL2_mixer or disable a_sdl2mixer')
+    assert(dep_opusfile.found(), 'sdl2mixer backend enabled, but opusfile was not found. Install opusfile or disable a_sdl2mixer')
 endif
diff --git a/src/credits.c b/src/credits.c
@@ -125,8 +125,8 @@ static void credits_fill(void) {
 		"https://zlib.net/\n\n"
 		"libpng\n"
 		"http://www.libpng.org/\n\n"
-		"Ogg Vorbis\n"
-		"https://xiph.org/vorbis/"
+		"Ogg Opus\n"
+		"https://www.opus-codec.org/"
 	), 350);
 
 	credits_add((

diff --git a/src/meson.build b/src/meson.build
@@ -149,6 +149,10 @@ taisei_deps += [
     util_deps,
 ]
 
+if taisei_deps.contains(dep_opusfile)
+    taisei_src += util_opus_src
+endif
+
 taisei_basename = (macos_app_bundle ? 'Taisei' : 'taisei')
 
 if host_machine.system() == 'emscripten'

diff --git a/src/util/meson.build b/src/util/meson.build
@@ -17,6 +17,10 @@ util_src = files(
     'stringops.c',
 )
 
+util_opus_src = files(
+    'opuscruft.c',
+)
+
 sse42_src += files(
     'sse42.c',
 )

diff --git a/src/util/opuscruft.c b/src/util/opuscruft.c
@@ -0,0 +1,41 @@
+/*
+ * This software is licensed under the terms of the MIT-License
+ * See COPYING for further information.
+ * ---
+ * Copyright (c) 2011-2019, Lukas Weber <laochailan@web.de>.
+ * Copyright (c) 2012-2019, Andrei Alexeyev <akari@alienslab.net>.
+ */
+
+#include "taisei.h"
+
+#include "opuscruft.h"
+
+#include <SDL.h>
+#include <opusfile.h>
+
+static int opusutil_rwops_read(void *_stream, unsigned char *_ptr, int _nbytes) {
+	SDL_RWops *rw = _stream;
+	return SDL_RWread(rw, _ptr, 1, _nbytes);
+}
+
+static int opusutil_rwops_seek(void *_stream, opus_int64 _offset, int _whence) {
+	SDL_RWops *rw = _stream;
+	return SDL_RWseek(rw, _offset, _whence) < 0 ? -1 : 0;
+}
+
+static opus_int64 opusutil_rwops_tell(void *_stream) {
+	SDL_RWops *rw = _stream;
+	return SDL_RWtell(rw);
+}
+
+static int opusutil_rwops_close(void *_stream) {
+	SDL_RWops *rw = _stream;
+	return SDL_RWclose(rw) < 0 ? EOF : 0;
+}
+
+OpusFileCallbacks opusutil_rwops_callbacks = {
+	.read = opusutil_rwops_read,
+	.seek = opusutil_rwops_seek,
+	.tell = opusutil_rwops_tell,
+	.close = opusutil_rwops_close,
+};
diff --git a/src/util/opuscruft.h b/src/util/opuscruft.h
@@ -0,0 +1,18 @@
+/*
+ * This software is licensed under the terms of the MIT-License
+ * See COPYING for further information.
+ * ---
+ * Copyright (c) 2011-2019, Lukas Weber <laochailan@web.de>.
+ * Copyright (c) 2012-2019, Andrei Alexeyev <akari@alienslab.net>.
+ */
+
+#ifndef IGUARD_util_opuscruft_h
+#define IGUARD_util_opuscruft_h
+
+#include "taisei.h"
+
+#include <opusfile.h>
+
+extern OpusFileCallbacks opusutil_rwops_callbacks;
+
+#endif // IGUARD_util_opuscruft_h