Replace libspeexdsp with custom linear resampling (#26011)

cmake/FindSpeexDSP.cmake

@@ -1,40 +0,0 @@
-#
-# - Find speexdsp libraries
-#
-#  SPEEXDSP_INCLUDE_DIRS - where to find speexdsp headers.
-#  SPEEXDSP_LIBRARIES    - List of libraries when using speexdsp.
-#  SPEEXDSP_FOUND        - True if speexdsp is found.
-
-find_package(PkgConfig QUIET)
-pkg_search_module(PC_SPEEXDSP QUIET speexdsp)
-
-find_path(SPEEXDSP_INCLUDE_DIR
-  NAMES
-    speex/speex_resampler.h
-  HINTS
-    ${PC_SPEEXDSP_INCLUDE_DIRS}
-)
-
-find_library(SPEEXDSP_LIBRARY
-  NAMES
-    speexdsp
-  HINTS
-    ${PC_SPEEXDSP_LIBRARY_DIRS}
-)
-
-include(FindPackageHandleStandardArgs)
-find_package_handle_standard_args(SpeexDSP
-  REQUIRED_VARS   SPEEXDSP_LIBRARY SPEEXDSP_INCLUDE_DIR
-  VERSION_VAR     PC_SPEEXDSP_VERSION)
-
-if(SPEEXDSP_FOUND)
-  set(SPEEXDSP_LIBRARIES ${SPEEXDSP_LIBRARY})
-  set(SPEEXDSP_INCLUDE_DIRS ${SPEEXDSP_INCLUDE_DIR})
-  set(SPEEX_INCLUDE_DIRS ${SPEEXDSP_INCLUDE_DIR})
-else()
-  set(SPEEXDSP_LIBRARIES)
-  set(SPEEXDSP_INCLUDE_DIRS)
-  set(SPEEX_INCLUDE_DIRS)
-endif()
-
-mark_as_advanced(SPEEXDSP_LIBRARIES SPEEXDSP_INCLUDE_DIRS SPEEX_INCLUDE_DIRS)

debian/control

@@ -4,7 +4,7 @@ Section: misc
 Priority: optional
 Standards-Version: 3.9.2
 Multi-Arch: same
-Build-Depends: debhelper (>= 9), cmake (>= 3.8), libsdl2-dev, g++ (>= 4:10), pkg-config, nlohmann-json3-dev (>= 3.9.0), libspeex-dev, libspeexdsp-dev, libcurl4-openssl-dev, libcrypto++-dev, libfontconfig1-dev, libfreetype6-dev, libpng-dev, libssl-dev, libzip-dev (>= 1.0.0), libicu-dev (>= 59.0), libflac-dev, libvorbis-dev, libzstd-dev
+Build-Depends: debhelper (>= 9), cmake (>= 3.8), libsdl2-dev, g++ (>= 4:10), pkg-config, nlohmann-json3-dev (>= 3.9.0), libcurl4-openssl-dev, libcrypto++-dev, libfontconfig1-dev, libfreetype6-dev, libpng-dev, libssl-dev, libzip-dev (>= 1.0.0), libicu-dev (>= 59.0), libflac-dev, libvorbis-dev, libzstd-dev
 
 Package: openrct2
 Architecture: any

distribution/changelog.txt

@@ -4,6 +4,7 @@
 - Improved: [#21753] Tracked rides with cheated powered launch mode can change powered launch speed without extra cheats.
 - Improved: [#25526] When a shop item cannot be recoloured, show a preview of the building instead.
 - Improved: [#25941] The command line sprite build command is now faster.
+- Change: [#26011] Audio resampling no longer depends on the third-party library libspeexdsp.
 - Fix: [#14686, #23996, #25981] Preview images from different windows overwrite each other when using OpenGL.
 - Fix: [#15128, #15626, #16331, #17443, #18626, #21597, #24175, #24971, #25963] Crash when loading corrupted RCT2/RCT1 save files with duplicate entity indices.
 - Fix: [#25237] Wrong colours on the Knight costume.

distribution/readme.txt

@@ -1,4 +1,4 @@
-Last updated:    2025-08-04
+Last updated:    2026-02-15
 ------------------------------------------------------------------------
 
 
@@ -146,7 +146,6 @@ duktape          | MIT licence.
 libcURL          | MIT (or Modified BSD-style) licence.
 libicu           | Unicode licence.
 libpng           | libpng licence.
-libspeex         | BSD-style licence.
 libzip           | BSD 3 clause licence.
 nlohmann-json    | MIT licence.
 OpenSSL          | OpenSSL licence.

openrct2.common.props

@@ -88,7 +88,7 @@
       <GenerateDebugInformation>DebugFull</GenerateDebugInformation>
       <AdditionalDependencies>brotlicommon.lib;brotlidec.lib;brotlienc.lib;%(AdditionalDependencies)</AdditionalDependencies>
       <AdditionalDependencies Condition="'$(Breakpad)'=='true' and ('$(Platform)'=='Win32' or '$(Platform)'=='x64')">libbreakpadd.lib;libbreakpad_clientd.lib;%(AdditionalDependencies)</AdditionalDependencies>
-      <AdditionalDependencies>bz2d.lib;discord-rpc.lib;flac.lib;freetyped.lib;libpng16d.lib;ogg.lib;speexdsp.lib;SDL2-staticd.lib;vorbis.lib;vorbisfile.lib;zip.lib;zlibd.lib;zstd.lib;%(AdditionalDependencies)</AdditionalDependencies>
+      <AdditionalDependencies>bz2d.lib;discord-rpc.lib;flac.lib;freetyped.lib;libpng16d.lib;ogg.lib;SDL2-staticd.lib;vorbis.lib;vorbisfile.lib;zip.lib;zlibd.lib;zstd.lib;%(AdditionalDependencies)</AdditionalDependencies>
     </Link>
   </ItemDefinitionGroup>
   <ItemDefinitionGroup Condition="'$(Configuration)'=='Release' or '$(Configuration)'=='ReleaseLTCG'">
@@ -109,7 +109,7 @@
       <OptimizeReferences>true</OptimizeReferences>
       <AdditionalDependencies>brotlicommon.lib;brotlidec.lib;brotlienc.lib;%(AdditionalDependencies)</AdditionalDependencies>
       <AdditionalDependencies Condition="'$(Breakpad)'=='true' and ('$(Platform)'=='Win32' or '$(Platform)'=='x64')">libbreakpad.lib;libbreakpad_client.lib;%(AdditionalDependencies)</AdditionalDependencies>
-      <AdditionalDependencies>bz2.lib;discord-rpc.lib;flac.lib;freetype.lib;libpng16.lib;ogg.lib;speexdsp.lib;SDL2-static.lib;vorbis.lib;vorbisfile.lib;zip.lib;zlib.lib;zstd.lib;%(AdditionalDependencies)</AdditionalDependencies>
+      <AdditionalDependencies>bz2.lib;discord-rpc.lib;flac.lib;freetype.lib;libpng16.lib;ogg.lib;SDL2-static.lib;vorbis.lib;vorbisfile.lib;zip.lib;zlib.lib;zstd.lib;%(AdditionalDependencies)</AdditionalDependencies>
     </Link>
   </ItemDefinitionGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />

scripts/build-emscripten

@@ -6,7 +6,6 @@ mkdir -p build
 cd build
 
 START_DIR=$(pwd)
-SPEEXDSP_ROOT=/ext/speexdsp
 ICU_ROOT=/ext/icu/icu4c/source
 LIBZIP_ROOT=/ext/libzip
 ZSTD_ROOT=/ext/zstd
@@ -22,8 +21,6 @@ emcmake cmake ../ \
 	-DDISABLE_DISCORD_RPC=ON \
 	-DCMAKE_SYSTEM_NAME=Emscripten \
 	-DCMAKE_BUILD_TYPE=Release \
-	-DSPEEXDSP_INCLUDE_DIR="$SPEEXDSP_ROOT/include/" \
-	-DSPEEXDSP_LIBRARY="$SPEEXDSP_ROOT/libspeexdsp/.libs/libspeexdsp.a" \
 	-DICU_INCLUDE_DIR="$ICU_ROOT/common" \
 	-DICU_DATA_LIBRARIES=$ICU_ROOT/lib/libicuuc.so \
 	-DICU_DT_LIBRARY_RELEASE="$ICU_ROOT/stubdata/libicudata.so" \

src/openrct2-android/app/src/main/CMakeLists.txt

@@ -40,7 +40,6 @@ ExternalProject_Add(libs
         ${CMAKE_BINARY_DIR}/libs/lib/${CMAKE_SHARED_LIBRARY_PREFIX}freetype${CMAKE_SHARED_LIBRARY_SUFFIX}
         ${CMAKE_BINARY_DIR}/libs/lib/${CMAKE_SHARED_LIBRARY_PREFIX}png16${CMAKE_SHARED_LIBRARY_SUFFIX}
         ${CMAKE_BINARY_DIR}/libs/lib/${CMAKE_SHARED_LIBRARY_PREFIX}SDL2${CMAKE_SHARED_LIBRARY_SUFFIX}
-        ${CMAKE_BINARY_DIR}/libs/lib/${CMAKE_SHARED_LIBRARY_PREFIX}speexdsp${CMAKE_SHARED_LIBRARY_SUFFIX}
         ${CMAKE_BINARY_DIR}/libs/lib/${CMAKE_SHARED_LIBRARY_PREFIX}ssl${CMAKE_SHARED_LIBRARY_SUFFIX}
         ${CMAKE_BINARY_DIR}/libs/lib/${CMAKE_SHARED_LIBRARY_PREFIX}icudata${CMAKE_SHARED_LIBRARY_SUFFIX}
         ${CMAKE_BINARY_DIR}/libs/lib/${CMAKE_SHARED_LIBRARY_PREFIX}icui18n${CMAKE_SHARED_LIBRARY_SUFFIX}
@@ -76,7 +75,6 @@ add_custom_command(TARGET libs POST_BUILD
     COMMAND ${CMAKE_COMMAND} -E copy "${CMAKE_BINARY_DIR}/libs/lib/libfreetype.so" ${CMAKE_LIBRARY_OUTPUT_DIRECTORY}
     COMMAND ${CMAKE_COMMAND} -E copy "${CMAKE_BINARY_DIR}/libs/lib/libpng16.so" ${CMAKE_LIBRARY_OUTPUT_DIRECTORY}
     COMMAND ${CMAKE_COMMAND} -E copy "${CMAKE_BINARY_DIR}/libs/lib/libSDL2.so" ${CMAKE_LIBRARY_OUTPUT_DIRECTORY}
-    COMMAND ${CMAKE_COMMAND} -E copy "${CMAKE_BINARY_DIR}/libs/lib/libspeexdsp.so" ${CMAKE_LIBRARY_OUTPUT_DIRECTORY}
     COMMAND ${CMAKE_COMMAND} -E copy "${CMAKE_BINARY_DIR}/libs/lib/libssl.so" ${CMAKE_LIBRARY_OUTPUT_DIRECTORY}
     COMMAND ${CMAKE_COMMAND} -E copy "${CMAKE_BINARY_DIR}/libs/lib/libz.so" ${CMAKE_LIBRARY_OUTPUT_DIRECTORY}
     COMMAND ${CMAKE_COMMAND} -E copy "${CMAKE_BINARY_DIR}/libs/lib/libzstd.so" ${CMAKE_LIBRARY_OUTPUT_DIRECTORY}
@@ -118,12 +116,6 @@ set_target_properties(SDL2main PROPERTIES IMPORTED_LOCATION
 )
 add_dependencies(SDL2main libs)
 
-add_library(speexdsp SHARED IMPORTED)
-set_target_properties(speexdsp PROPERTIES IMPORTED_LOCATION
-    ${CMAKE_BINARY_DIR}/libs/lib/${CMAKE_SHARED_LIBRARY_PREFIX}speexdsp${CMAKE_SHARED_LIBRARY_SUFFIX}
-)
-add_dependencies(speexdsp libs)
-
 add_library(icu STATIC IMPORTED)
 set_target_properties(icu PROPERTIES IMPORTED_LOCATION
     ${CMAKE_BINARY_DIR}/libs/lib/${CMAKE_SHARED_LIBRARY_PREFIX}icui18n${CMAKE_SHARED_LIBRARY_SUFFIX}
@@ -207,9 +199,6 @@ add_definitions(-DDISABLE_DISCORD_RPC -DDISABLE_OPENGL -DGL_GLEXT_PROTOTYPES -D_
 # Enable scripting
 add_definitions(-DENABLE_SCRIPTING)
 
-# Fix SpeexDSP compilation
-add_definitions(-DHAVE_STDINT_H)
-
 # -Werror -Wall
 set(COMMON_COMPILE_OPTIONS "${COMMON_COMPILE_OPTIONS} -fstrict-aliasing -Wundef -Wmissing-declarations -Winit-self  -Wno-unknown-pragmas -Wno-unused-function -Wno-missing-braces ")
 set(COMMON_COMPILE_OPTIONS "${COMMON_COMPILE_OPTIONS} -Wno-comment -Wshadow  -Wmissing-declarations -Wnonnull")
@@ -261,7 +250,7 @@ add_library(openrct2 SHARED ${LIBOPENRCT2_SOURCES})
 target_link_libraries(openrct2 android stdc++ log dl SDL2 png z zstd icu icuuc icudata crypto ssl freetype)
 
 add_library(openrct2-ui SHARED ${OPENRCT2_GUI_SOURCES})
-target_link_libraries(openrct2-ui openrct2 android stdc++ GLESv1_CM GLESv2 SDL2main speexdsp brotlicommon brotlidec bz2 freetype ogg vorbis vorbisfile FLAC)
+target_link_libraries(openrct2-ui openrct2 android stdc++ GLESv1_CM GLESv2 SDL2main brotlicommon brotlidec bz2 freetype ogg vorbis vorbisfile FLAC)
 
 add_executable(openrct2-cli ${OPENRCT2_CLI_SOURCES})
 target_link_libraries(openrct2-cli openrct2 android stdc++ GLESv1_CM GLESv2)

src/openrct2-android/app/src/main/java/io/openrct2/GameActivity.java

@@ -76,7 +76,6 @@ public class GameActivity extends SDLActivity {
     protected String[] getLibraries() {
         return new String[]{
                 "c++_shared",
-                "speexdsp",
                 "bz2",
                 "freetype",
                 "z",

src/openrct2-ui/CMakeLists.txt

@@ -13,20 +13,10 @@ if (EMSCRIPTEN)
     set(SHARED_FLAGS "-fexceptions")
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${USE_FLAGS} ${SHARED_FLAGS}")
     set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} ${EMSCRIPTEN_LDFLAGS} --bind ${SHARED_FLAGS} -sEXPORTED_FUNCTIONS=${EMSCRIPTEN_EXPORTED_FUNCTIONS} --js-library ${ROOT_DIR}/emscripten/deps.js")
-    find_package(SpeexDSP REQUIRED)
 elseif (MSVC)
     find_package(SDL2 REQUIRED)
-    find_library(SPEEX_LDFLAGS libspeexdsp)
-    if (NOT DISABLE_FLAC)
-        find_library(SPEEX_LDFLAGS libflac)
-    endif ()
-    if (NOT DISABLE_VORBIS)
-        find_library(SPEEX_LDFLAGS libogg)
-        find_library(SPEEX_LDFLAGS libvorbis)
-    endif ()
 else ()
     PKG_CHECK_MODULES(SDL2 REQUIRED IMPORTED_TARGET sdl2)
-    PKG_CHECK_MODULES(SPEEX REQUIRED IMPORTED_TARGET speexdsp)
     if (NOT DISABLE_FLAC)
         PKG_CHECK_MODULES(FLAC REQUIRED IMPORTED_TARGET flac)
     endif ()
@@ -67,17 +57,14 @@ ipo_set_target_properties(openrct2)
 # mingw builds cannot use the PkgConfig imported targets
 if (EMSCRIPTEN)
     target_link_libraries(openrct2 "libopenrct2"
-                                    ${SPEEXDSP_LIBRARIES}
                                     ${ICU_DATA_LIBRARIES}
                                     ${ICU_DT_LIBRARY_RELEASE})
 elseif (NOT MSVC AND NOT WIN32)
     target_link_libraries(openrct2 "libopenrct2"
-                                    PkgConfig::SDL2
+                                    PkgConfig::SDL2)
-                                    PkgConfig::SPEEX)
 else ()
     target_link_libraries(openrct2 "libopenrct2"
-                                    ${SDL2_LDFLAGS}
+                                    ${SDL2_LDFLAGS})
-                                    ${SPEEX_LDFLAGS})
 endif ()
 target_link_platform_libraries(openrct2)
 
@@ -109,7 +96,6 @@ endif ()
 
 # Includes
 target_include_directories(openrct2 PRIVATE "${CMAKE_CURRENT_LIST_DIR}/.."
-                                              ${SPEEX_INCLUDE_DIRS}
                                               ${OGG_INCLUDE_DIRS}
                                               ${VORBIS_INCLUDE_DIRS}
                                               ${FLAC_INCLUDE_DIRS})

src/openrct2-ui/audio/AudioChannel.cpp

@@ -14,7 +14,6 @@
 #include <algorithm>
 #include <cmath>
 #include <openrct2/audio/AudioSource.h>
-#include <speex/speex_resampler.h>
 
 namespace OpenRCT2::Audio
 {
@@ -25,7 +24,6 @@ namespace OpenRCT2::Audio
 
     private:
         AudioSource_* _source = nullptr;
-        SpeexResamplerState* _resampler = nullptr;
 
         MixerGroup _group = MixerGroup::Sound;
         double _rate = 0;
@@ -52,30 +50,11 @@ namespace OpenRCT2::Audio
             AudioChannelImpl::SetPan(0.5f);
         }
 
-        ~AudioChannelImpl() override
-        {
-            if (_resampler != nullptr)
-            {
-                speex_resampler_destroy(_resampler);
-                _resampler = nullptr;
-            }
-        }
-
         [[nodiscard]] IAudioSource* GetSource() const override
         {
             return _source;
         }
 
-        [[nodiscard]] SpeexResamplerState* GetResampler() const override
-        {
-            return _resampler;
-        }
-
-        void SetResampler(SpeexResamplerState* value) override
-        {
-            _resampler = value;
-        }
-
         [[nodiscard]] MixerGroup GetGroup() const override
         {
             return _group;

src/openrct2-ui/audio/AudioContext.h

@@ -15,7 +15,6 @@
 #include <string>
 
 struct SDL_RWops;
-using SpeexResamplerState = struct SpeexResamplerState_;
 
 namespace OpenRCT2::Audio
 {
@@ -25,8 +24,6 @@ namespace OpenRCT2::Audio
     struct ISDLAudioChannel : public IAudioChannel
     {
         [[nodiscard]] virtual AudioFormat GetFormat() const = 0;
-        [[nodiscard]] virtual SpeexResamplerState* GetResampler() const = 0;
-        virtual void SetResampler(SpeexResamplerState* value) = 0;
     };
 
     namespace AudioChannel

src/openrct2-ui/audio/AudioMixer.cpp

@@ -13,7 +13,6 @@
 #include <iterator>
 #include <openrct2/OpenRCT2.h>
 #include <openrct2/config/Config.h>
-#include <speex/speex_resampler.h>
 
 using namespace OpenRCT2::Audio;
 
@@ -124,6 +123,7 @@ const AudioFormat& AudioMixer::GetFormat() const
     return _outputFormat;
 }
 
+// TODO: investigate replacing this with OpenAL (#26035)
 void AudioMixer::GetNextAudioChunk(uint8_t* dst, size_t length)
 {
     UpdateAdjustedSound();
@@ -156,6 +156,7 @@ void AudioMixer::GetNextAudioChunk(uint8_t* dst, size_t length)
     }
 }
 
+// TODO: investigate replacing this with OpenAL (#26035)
 void AudioMixer::UpdateAdjustedSound()
 {
     // Did the volume level get changed? Recalculate level in this case.
@@ -171,6 +172,7 @@ void AudioMixer::UpdateAdjustedSound()
     }
 }
 
+// TODO: investigate replacing this with OpenAL (#26035)
 void AudioMixer::MixChannel(ISDLAudioChannel* channel, uint8_t* data, size_t length)
 {
     int32_t outputByteRate = _outputFormat.GetByteRate();
@@ -236,8 +238,7 @@ void AudioMixer::MixChannel(ISDLAudioChannel* channel, uint8_t* data, size_t len
             outRate = _outputFormat.freq * (1 / rate);
         }
         _effectBuffer.resize(length);
-        bufferLen = ApplyResample(
+        bufferLen = ApplyResample(buffer, static_cast<int32_t>(bufferLen / outputByteRate), numSamples, inRate, outRate);
-            channel, buffer, static_cast<int32_t>(bufferLen / outputByteRate), numSamples, inRate, outRate);
         buffer = _effectBuffer.data();
     }
 
@@ -256,30 +257,60 @@ void AudioMixer::MixChannel(ISDLAudioChannel* channel, uint8_t* data, size_t len
 /**
  * Resample the given buffer into _effectBuffer.
  * Assumes that srcBuffer is the same format as _outputFormat.
+ *
+ * TODO: investigate replacing this with OpenAL (#26035)
  */
-size_t AudioMixer::ApplyResample(
+size_t AudioMixer::ApplyResample(const void* srcBuffer, int32_t srcSamples, int32_t dstSamples, int32_t inRate, int32_t outRate)
-    ISDLAudioChannel* channel, const void* srcBuffer, int32_t srcSamples, int32_t dstSamples, int32_t inRate, int32_t outRate)
 {
-    int32_t outputByteRate = _outputFormat.GetByteRate();
+    // Prevent buffer underread in inner loop
+    if (srcSamples < 2)
+        return 0;
 
-    // Create resampler
+    const int channels = _outputFormat.channels;
-    SpeexResamplerState* resampler = channel->GetResampler();
+    const int bytesPerFrame = channels * sizeof(int16_t);
-    if (resampler == nullptr)
+
+    const int16_t* src = static_cast<const int16_t*>(srcBuffer);
+    int16_t* dst = reinterpret_cast<int16_t*>(_effectBuffer.data());
+
+    double ratio = static_cast<double>(inRate) / static_cast<double>(outRate);
+
+    for (int32_t i = 0; i < dstSamples; ++i)
     {
-        resampler = speex_resampler_init(_outputFormat.channels, _outputFormat.freq, _outputFormat.freq, 0, nullptr);
+        double srcPos = i * ratio;
-        channel->SetResampler(resampler);
+        int32_t index = static_cast<int32_t>(srcPos);
+        double frac = srcPos - index;
+
+        // Clamp to avoid reading past end
+        if (index >= srcSamples - 1)
+        {
+            index = srcSamples - 2;
+            frac = 1.0;
+        }
+
+        for (int ch = 0; ch < channels; ++ch)
+        {
+            int32_t baseIndex = index * channels + ch;
+
+            int16_t s1 = src[baseIndex];
+            int16_t s2 = src[baseIndex + channels];
+
+            // Linear interpolation
+            double sample = (1.0 - frac) * s1 + frac * s2;
+
+            // Clamp to int16 range
+            if (sample > 32767.0)
+                sample = 32767.0;
+            if (sample < -32768.0)
+                sample = -32768.0;
+
+            dst[i * channels + ch] = static_cast<int16_t>(sample);
+        }
     }
-    speex_resampler_set_rate(resampler, inRate, outRate);
 
-    uint32_t inLen = srcSamples;
+    return dstSamples * bytesPerFrame;
-    uint32_t outLen = dstSamples;
-    speex_resampler_process_interleaved_int(
-        resampler, static_cast<const spx_int16_t*>(srcBuffer), &inLen, reinterpret_cast<spx_int16_t*>(_effectBuffer.data()),
-        &outLen);
-
-    return outLen * outputByteRate;
 }
 
+// TODO: investigate replacing this with OpenAL (#26035)
 void AudioMixer::ApplyPan(const IAudioChannel* channel, void* buffer, size_t len, size_t sampleSize)
 {
     if (channel->GetPan() != 0.5f && _outputFormat.channels == 2)
@@ -296,6 +327,7 @@ void AudioMixer::ApplyPan(const IAudioChannel* channel, void* buffer, size_t len
     }
 }
 
+// TODO: investigate replacing this with OpenAL (#26035)
 int32_t AudioMixer::ApplyVolume(const IAudioChannel* channel, void* buffer, size_t len)
 {
     float volumeAdjust = _volume;
@@ -347,6 +379,7 @@ int32_t AudioMixer::ApplyVolume(const IAudioChannel* channel, void* buffer, size
     return mixVolume;
 }
 
+// TODO: investigate replacing this with OpenAL (#26035)
 void AudioMixer::EffectPanS16(const IAudioChannel* channel, int16_t* data, int32_t length)
 {
     const float dt = 1.0f / static_cast<float>(length * 2.0f);
@@ -364,6 +397,7 @@ void AudioMixer::EffectPanS16(const IAudioChannel* channel, int16_t* data, int32
     }
 }
 
+// TODO: investigate replacing this with OpenAL (#26035)
 void AudioMixer::EffectPanU8(const IAudioChannel* channel, uint8_t* data, int32_t length)
 {
     float volumeL = channel->GetVolumeL();
@@ -379,6 +413,7 @@ void AudioMixer::EffectPanU8(const IAudioChannel* channel, uint8_t* data, int32_
     }
 }
 
+// TODO: investigate replacing this with OpenAL (#26035)
 void AudioMixer::EffectFadeS16(int16_t* data, int32_t length, int32_t startvolume, int32_t endvolume)
 {
     static_assert(SDL_MIX_MAXVOLUME == kMixerVolumeMax, "Max volume differs between OpenRCT2 and SDL2");
@@ -392,6 +427,7 @@ void AudioMixer::EffectFadeS16(int16_t* data, int32_t length, int32_t startvolum
     }
 }
 
+// TODO: investigate replacing this with OpenAL (#26035)
 void AudioMixer::EffectFadeU8(uint8_t* data, int32_t length, int32_t startvolume, int32_t endvolume)
 {
     static_assert(SDL_MIX_MAXVOLUME == kMixerVolumeMax, "Max volume differs between OpenRCT2 and SDL2");

src/openrct2-ui/audio/AudioMixer.h

@@ -69,9 +69,7 @@ namespace OpenRCT2::Audio
          * Resample the given buffer into _effectBuffer.
          * Assumes that srcBuffer is the same format as _outputFormat.
          */
-        size_t ApplyResample(
+        size_t ApplyResample(const void* srcBuffer, int32_t srcSamples, int32_t dstSamples, int32_t inRate, int32_t outRate);
-            ISDLAudioChannel* channel, const void* srcBuffer, int32_t srcSamples, int32_t dstSamples, int32_t inRate,
-            int32_t outRate);
         void ApplyPan(const IAudioChannel* channel, void* buffer, size_t len, size_t sampleSize);
         int32_t ApplyVolume(const IAudioChannel* channel, void* buffer, size_t len);
         static void EffectPanS16(const IAudioChannel* channel, int16_t* data, int32_t length);

src/openrct2/CMakeLists.txt

@@ -126,7 +126,6 @@ if (EMSCRIPTEN)
     set(SHARED_FLAGS "-fexceptions")
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${USE_FLAGS} ${SHARED_FLAGS}")
     set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} ${EMSCRIPTEN_LDFLAGS} --bind ${SHARED_FLAGS}")
-    find_package(SpeexDSP REQUIRED)
 elseif (MSVC)
     find_package(png 1.6 REQUIRED)
     find_package(zlib REQUIRED)