feat: add support for STEM

The soundsource will ensure the file is a valid STEM file and load
manifest. It will however only expose the main mix to the sound engine

CMakeLists.txt

@@ -2191,32 +2191,6 @@ target_link_libraries(mixxx-test PRIVATE mixxx-lib mixxx-gitinfostore GTest::gte
 find_package(benchmark)
 target_link_libraries(mixxx-test PRIVATE benchmark::benchmark)
 
-# Test Suite
-include(CTest)
-include(GoogleTest)
-enable_testing()
-gtest_add_tests(
-  TARGET mixxx-test
-  EXTRA_ARGS --logLevel info
-  WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"
-  TEST_LIST testsuite
-)
-if (NOT WIN32)
-  # Default to offscreen rendering during tests.
-  # This is required if the build system like Fedora koji/mock does not
-  # allow to pass environment variables into the ctest macro expansion.
-  set_tests_properties(${testsuite} PROPERTIES ENVIRONMENT "QT_QPA_PLATFORM=offscreen")
-endif()
-
-# Benchmarking
-add_custom_target(mixxx-benchmark
-  COMMAND $<TARGET_FILE:mixxx-test> --benchmark
-  WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"
-  COMMENT "Mixxx Benchmarks"
-  VERBATIM
-)
-add_dependencies(mixxx-benchmark mixxx-test)
-
 #
 # Resources
 #
@@ -3458,6 +3432,51 @@ if(FFMPEG)
   target_include_directories(mixxx-lib PUBLIC "${FFMPEG_INCLUDE_DIRS}")
 endif()
 
+# STEM file support
+default_option(STEM "STEM file support" "FFMPEG_FOUND;FFMPEG")
+if (STEM)
+  if(NOT FFMPEG)
+    message(FATAL_ERROR "FFMPEG was not enabled")
+  endif()
+  target_compile_definitions(mixxx-lib PUBLIC __STEM__)
+  target_compile_definitions(mixxx-test PUBLIC __STEM__)
+  target_sources(mixxx-test PUBLIC
+    src/test/stemtest.cpp
+    src/test/steminfotest.cpp
+  )
+  target_sources(mixxx-lib PRIVATE
+    src/sources/soundsourcestem.cpp
+    src/track/steminfoimporter.cpp
+    src/track/steminfo.cpp # TODO precompiled header?
+  )
+endif()
+
+# Test Suite
+include(CTest)
+include(GoogleTest)
+enable_testing()
+gtest_add_tests(
+  TARGET mixxx-test
+  EXTRA_ARGS --logLevel info
+  WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"
+  TEST_LIST testsuite
+)
+if (NOT WIN32)
+  # Default to offscreen rendering during tests.
+  # This is required if the build system like Fedora koji/mock does not
+  # allow to pass environment variables into the ctest macro expansion.
+  set_tests_properties(${testsuite} PROPERTIES ENVIRONMENT "QT_QPA_PLATFORM=offscreen")
+endif()
+
+# Benchmarking
+add_custom_target(mixxx-benchmark
+  COMMAND $<TARGET_FILE:mixxx-test> --benchmark
+  WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"
+  COMMENT "Mixxx Benchmarks"
+  VERBATIM
+)
+add_dependencies(mixxx-benchmark mixxx-test)
+
 # Google PerfTools
 option(GPERFTOOLS "Google PerfTools libtcmalloc linkage" OFF)
 option(GPERFTOOLSPROFILER "Google PerfTools libprofiler linkage" OFF)
@@ -3565,8 +3584,8 @@ if(OPUS)
     src/encoder/encoderopussettings.cpp
   )
   target_compile_definitions(mixxx-lib PUBLIC __OPUS__)
-  target_link_libraries(mixxx-lib PRIVATE OpusFile::OpusFile)
-  target_link_libraries(mixxx-lib PRIVATE Opus::Opus)
+  target_link_libraries(mixxx-lib PRIVATE OpusFile::OpusFile Opus::Opus)
+  target_link_libraries(mixxx-test PRIVATE OpusFile::OpusFile Opus::Opus)
 endif()
 
 # MAD MP3 Decoder

src/sources/soundsource.cpp

@@ -32,7 +32,7 @@ QString SoundSource::getTypeFromUrl(const QUrl& url) {
 
 //static
 QString SoundSource::getTypeFromFile(const QFileInfo& fileInfo) {
-    const QString fileSuffix = fileInfo.suffix().toLower().trimmed();
+    const QString fileSuffix = fileInfo.completeSuffix().toLower().trimmed();
 
     if (fileSuffix == QLatin1String("opus")) {
         // Bypass the insufficient mime type lookup from content for opus files
@@ -52,6 +52,14 @@ QString SoundSource::getTypeFromFile(const QFileInfo& fileInfo) {
         // https://mixxx.zulipchat.com/#narrow/stream/109171-development/topic/mimetype.20sometimes.20wrong
         return fileSuffix;
     }
+    if (fileSuffix == QLatin1String("stem.mp4")) {
+        // STEM suffix extends the ".mp4" suffix. This is because stem files are
+        // meant to fall back to MP4 decoder, in case a player doesn't have the
+        // capability to extract the different stem track. However, we need to
+        // detect that early as the file natively looks like a traditional MP4
+        // with multiple tracks (audio and video)
+        return fileSuffix;
+    }
 
     QMimeType mimeType = QMimeDatabase().mimeTypeForFile(
             fileInfo, QMimeDatabase::MatchContent);

src/sources/soundsourceproxy.cpp

@@ -36,6 +36,9 @@
 #ifdef __MEDIAFOUNDATION__
 #include "sources/soundsourcemediafoundation.h"
 #endif
+#ifdef __STEM__
+#include "sources/soundsourcestem.h"
+#endif
 
 #include "library/coverartutils.h"
 #include "track/globaltrackcache.h"
@@ -177,6 +180,13 @@ QList<QMimeType> mimeTypesForFileType(const QString& fileType) {
             }
         }
     }
+    if (fileType == "stem.mp4") {
+        // *.stem.mp4 suffix doesn't not have a specific MIME type associated
+        // with it, and simply falls back to MP4. To prevent conflicts with the
+        // MP4 decoder able to decode arbitrary MP4 file (such as video,
+        // extracting just the audio track), we don't return any MIME here
+        return {};
+    }
     return mimeTypes;
 }
 
@@ -223,6 +233,11 @@ bool SoundSourceProxy::registerProviders() {
     registerSoundSourceProvider(
             &s_soundSourceProviders,
             std::make_shared<mixxx::SoundSourceProviderSndFile>());
+#endif
+#ifdef __STEM__
+    registerSoundSourceProvider(
+            &s_soundSourceProviders,
+            std::make_shared<mixxx::SoundSourceProviderSTEM>());
 #endif
     // Register the high-priority reference providers AFTER all other
     // providers to verify that their priorities are correct.