audacity/lib-src/libsndfile

libsndfile

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

Hacking

The canonical source code repository for libsndfile is at https://github.com/erikd/libsndfile/.

You can grab the source code using:

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

For building for Android see BuildingForAndroid.

There are currently two build systems; the official GNU autotool based one and a more limited and experimental 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 libopus 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, experimental 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. This option is ON by default.

• ENABLE_STATIC_RUNTIME - enable static runtime on Windows platform, OFF by default.

  Note: For MSVC compiler this option is depecated. Use CMAKE_MSVC_RUNTIME_LIBRARY option instead (CMake >= 3.15).

• 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.

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, FindVorbisEnc.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

First advice - set ENABLE_STATIC_RUNTIME to ON. This will remove dependencies on runtime DLLs.

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

Submitting Patches

See CONTRIBUTING.md for details.