third_party_libsnd/README.md

libsndfile

libsndfile is a C library for reading and writing files containing sampled audio data.

Authors

The libsndfile project was originally developed and maintained by Erik de Castro Lopo erikd@mega-nerd.com aka @erikd. The project was developed on Github at https://github.com/erikd/libsndfile.

After the release of version 1.0.30, @erikd transferred the project to the libsndfile team, see AUTHORS for details.

Hacking

The canonical source code repository for libsndfile is at http://libsndfile.github.io/libsndfile/.

You can grab the source code using:

git clone https://github.com/libsndfile/libsndfile.git

For building for Android see BuildingForAndroid.

There are currently two build systems: the traditional GNU autotool based one and modern CMake based build system. Use of the CMake build system is documented below.

Setting up a build environment for libsndfile on Debian or Ubuntu is as simple as:

sudo apt install autoconf autogen automake build-essential libasound2-dev \
  libflac-dev libogg-dev libtool libvorbis-dev libopus-dev pkg-config python

For other Linux distributions or any of the *BSDs, the setup should be similar although the package install tools and package names may be slightly different.

Similarly on Mac OS X, assuming brew is already installed:

brew install autoconf autogen automake flac libogg libtool libvorbis opus pkg-config

Once the build environment has been set up, building and testing libsndfile is as simple as:

./autogen.sh
./configure --enable-werror
make
make check

The CMake build system

Although Autotools is the primary and recommended build toolchain, CMake meta build generator is also available. The build process with CMake takes place in two stages. First, standard build files are created from configuration scripts. Then the platform's native build tools are used for the actual building. CMake can produce Microsoft Visual Studio project and solution files, Unix Makefiles, Xcode projects and many more.

Some IDE support CMake natively or with plugins, check you IDE documentation for details.

Requirements

1. C99-compliant compiler toolchain (tested with GCC, Clang and Visual Studio 2015)
2. CMake 3.1.3 or newer

There are some recommended packages to enable all features of libsndfile:

1. Ogg, Vorbis and FLAC libraries and headers to enable these formats support
2. ALSA development package under Linux to build sndfile-play utility
3. Sndio development package under BSD to build sndfile-play utility

Building from command line

CMake can handle out-of-place builds, enabling several builds from the same source tree, and cross-compilation. The ability to build a directory tree outside the source tree is a key feature, ensuring that if a build directory is removed, the source files remain unaffected.

mkdir CMakeBuild
cd CMakeBuild

Then run cmake command with directory where CMakeLists.txt script is located as argument (relative paths are supported):

cmake ..

This command will configure and write build script or solution to CMakeBuild directory. CMake is smart enough to create Unix makefiles under Linux or Visual Studio solution if you have Visual Studio installed, but you can configure generator with -G command line parameter:

cmake .. -G"Unix Makefiles"

The build procedure depends on the selected generator. With "Unix Makefiles" you can type:

make & make install

With "Visual Studio" and some other generators you can open solution or project from CMakeBuild directory and build using IDE.

Finally, you can use unified command:

cmake --build .

CMake also provides Qt-based cross platform GUI, cmake-gui. Using it is trivial and does not require detailed explanations.

Configuring CMake

You can pass additional options with /D<parameter>=<value> when you run cmake command. Some useful system options:

• CMAKE_C_FLAGS - additional C compiler flags
• CMAKE_BUILD_TYPE - configuration type, DEBUG, RELEASE, RELWITHDEBINFO or MINSIZEREL. DEBUG is default
• CMAKE_INSTALL_PREFIX - build install location, the same as --prefix option of configure script

Useful libsndfile options:

• BUILD_SHARED_LIBS - build shared library (DLL under Windows) when ON, build static library othervise. This option is OFF by default.

• BUILD_PROGRAMS - build libsndfile's utilities from programs/ directory, ON by default.

• BUILD_EXAMPLES - build examples, ON by default.

• BUILD_TESTING - build tests. Then you can run tests with ctest command, ON by default. Setting BUILD_SHARED_LIBS to ON disables this option.

• ENABLE_EXTERNAL_LIBS - enable Ogg, Vorbis, FLAC and Opus support. This option is available and set to ON if all dependency libraries were found.

• ENABLE_CPU_CLIP - enable tricky cpu specific clipper. Enabled and set to ON when CPU clips negative\positive. Don't touch it if you are not sure

• ENABLE_BOW_DOCS - enable black-on-white documentation theme, OFF by default.

• ENABLE_EXPERIMENTAL - enable experimental code. Don't use it if you are not sure. This option is OFF by default.

• ENABLE_CPACK - enable CPack support. This option is ON by default.

• ENABLE_PACKAGE_CONFIG - generate and install package config file.

• INSTALL_PKGCONFIG_MODULE - generate and install pkg-config module.

• INSTALL_MANPAGES - install man pages for programs. This option is ON by default

• ENABLE_STATIC_RUNTIME - enable static runtime on Windows platform (MSVC and MinGW), OFF by default.

  Note: For MSVC compiler this option is deprecated for CMake >= 3.15, see policy CMP0091. Use CMAKE_MSVC_RUNTIME_LIBRARY option instead.

  Note: For MinGW toolchain this option is experimental. If you enabled it and then disabled again, you need to clear CMake cache (delete CMakeCache.txt).

• ENABLE_COMPATIBLE_LIBSNDFILE_NAME - set DLL name to libsndfile-1.dll (canonical name) on Windows platform, sndfile.dll otherwise, OFF by default. Library name can be different depending on platform. The well known DLL name on Windows platform is libsndfile-1.dll, because the only way to build Windows library before was MinGW toolchain with Autotools. This name is native for MinGW ecosystem, Autotools constructs it using MinGW platform rules from sndfile target. But when you build with CMake using native Windows compiler, the name is sndfile.dll. This is name for native Windows platform, because Windows has no library naming rules. It is preffered because you can search library using package manager or CMake's find_library command on any platform using the same sndfile name.

• ENABLE_SSE2 - add compiler flag to enable SSE2 if required, ON by default.

  This option is for X86 and GCC compatible compilers configurations only.

  If you compile for other SIMD set, e.g. AVX2, you may want to set ENABLE_SSE2 to OFF.

  Note: This option is not active for X64 configuration, because SSE2 is always available in this mode and all optimizations are enabled by default.

Deprecated options:

• DISABLE_EXTERNAL_LIBS - disable Ogg, Vorbis and FLAC support. Replaced by ENABLE_EXTERNAL_LIBS
• DISABLE_CPU_CLIP - disable tricky cpu specific clipper. Replaced by ENABLE_CPU_CLIP
• BUILD_STATIC_LIBS - build static library. Use BUILD_SHARED_LIBS instead

Linking from CMake projects

First you need to add FindOgg.cmake, FindVorbis.cmake, FindFLAC.cmake and FindOpus.cmake files to some directory inside your CMake project (usually cmake) and add it to CMAKE_MODULE_PATH:

project(SomeApplication)

list(APPEND CMAKE_MODULE_PATH ${CMAKE_CURRENT_SOURCE_DIR}/cmake)

Now you can search libsndfile library from your CMakeLists.txt with this command:

find_package(SndFile)

SndFile_FOUND is set to ON when library is found.

If libsndfile dependency is critical, you can add REQUIRED to find_package:

find_package(SndFile REQUIRED)

With with option find_package will terminate configuration process if libsndfile is not found.

You can also add version check:

find_package(SndFile 1.0.29)

find_package will report error, if libsndfile version is < 1.0.29.

You can combine REQUIRED and version if you need.

To link libsndfile library use:

target_link_libraries(my_application PRIVATE SndFile::sndfile)

Notes for Windows users

System CRT library

First advice about Visual Studio system CRT libraries, it is system code linked as static or dynamic library to every C application.

You can find related option in Visual Studio project properties:

C/C++ -> Code Generation -> Runtime Library

Dynamic version of system CRT library is defaut and it means that end user needs to have the same runtime library installed on his system. Most likely it is so, but if it is not, the user will see this error message using libsndfile DLL:

"The program can't start because <crt-dll-name>.dll is missing from your computer. Try reinstalling the program to fix this problem. "

To avoid this, you may want to enable static CRT library linking. In this case the size of your DLL will increase slightly the size will increase slightly, but you can redistribute the libsndfile DLL without having to install the correct version of the system CRT library.

CMake project will use dynamic system CRT libraries by default, just like Visual Studio does. But you can change it using ENABLE_STATIC_RUNTIME or CMAKE_MSVC_RUNTIME_LIBRARY options.

Note: You cannot use both options at the same time, it will lead to a configuration error.

If you have CMake >= 3.15 you should use CMAKE_MSVC_RUNTIME_LIBRARY option.

This will enable static linking:

cmake .. -D"MultiThreaded$<$<CONFIG:Debug>:Debug>"

You can use libsndfile ENABLE_STATIC_RUNTIME option to to control CRT library linking for CMake project: OFF or unset (default) for dynamic, and ON for static linking:

cmake .. -DENABLE_STATIC_RUNTIME=ON

Note: This option is deprecated and may be removed in far future because we have standard option CMAKE_MSVC_RUNTIME_LIBRARY now.

Using Vcpkg package manager

Second advice is about Ogg, Vorbis FLAC and Opus support. Searching external libraries under Windows is a little bit tricky. The best way is to use Vcpkg. You need to install static libogg, libvorbis, libflac and libopus libraries:

vcpkg install libogg:x64-windows-static libvorbis:x64-windows-static
libflac:x64-windows-static opus:x64-windows-static libogg:x86-windows-static
libvorbis:x86-windows-static libflac:x86-windows-static opus:x86-windows-static

Then and add this parameter to cmake command line:

-DCMAKE_TOOLCHAIN_FILE=<path-to-vcpkg>/scripts/buildsystems/vcpkg.cmake

You also need to set VCPKG_TARGET_TRIPLET because you use static libraries:

-DVCPKG_TARGET_TRIPLET=x64-windows-static

Note: Use must use the same CRT library for external libraries and the libsndfile library itself. For *-static triplets Vcpkg uses static CRT.

Submitting Patches

See CONTRIBUTING.md for details.