GStreamer compilation with third party libraries

• 03 January 2023
• gstreamer

Suppose that you have to hack a GStreamer element which requires a library that is not (yet) packaged by your distribution, nor wrapped as a Meson’s subproject. How do you do?In our case, we needed the latest version of

• Vulkan-Headers
• Vulkan-Loader
• Vulkan-Tools

Which are interrelated CMake projects.

For these cases, GStreamer’s uninstalled development scripts can use a special directory: gstreamer/prefix. As the README.md says:

NOTE: In the development environment, a fully usable prefix is also configured in gstreamer/prefix where you can install any extra dependency/project.

This means that gstenv.py script (the responsible of setting up the uninstalled development environment) will add

• gstreamer/prefix/bin in PATH for executable files.
• gstreamer/prefix/lib and gstreamer/prefix/share/gstreamer-1.0 in GST_PLUGIN_PATH, for out-of-tree elements.
• gstreamer/prefix/lib in GI_TYPELIB_PATH for GObject Introspection metadata.
• gstreamer/prefix/lib/pkgconfig in PKG_CONFIG_PATH for third party dependencies (our case!)
• gstreamer/prefix/etc/xdg for XDG_CONFIG_DIRS for XDG compliant configuration files.
• gstreamer/prefix/lib and gstreamer/prefix/lib64 in LD_LIBRARY_PATH for third party libraries.

Therefore, the general idea, is to compile those third party libraries with their installation prefix as gstreamer/prefix.

In our case, Vulkan repositories are interrelated so they need to be compiled in certain order. Also, we decided, for self-containment, to clone them in gstreamer/subprojects.

Vulkan-Headers #

cd ~/gst/gstreamer/subprojects
git clone git@github.com:KhronosGroup/Vulkan-Headers.git
cd Vulkan-Headers
mkdir build
cd build
cmake -GNinja -DCMAKE_BUILD_TYPE=Debug -DCMAKE_INSTALL_PREFIX=/home/vjaquez/gst/gstreamer/prefix ..
cmake --build . --install

Vulkan-Loader #

cd ~/gst/gstreamer/subprojects
git clone git@github.com:KhronosGroup/Vulkan-Loader.git
cd Vulkan-Loader
mkdir build
cd build
cmake  -DCMAKE_BUILD_TYPE=Debug -DVULKAN_HEADERS_INSTALL_DIR=/home/vjaquez/gst/gstreamer/prefix DCMAKE_INSTALL_PREFIX=/home/vjaquez/gst/gstreamer/prefix ..
cmake --build . --install

Vulkan-Tools #

cd ~/gst/gstreamer/subprojects
git clone git@github.com:KhronosGroup/Vulkan-Tools.git
cd Vulkan-Tools
mkdir build
cd build
cmake  -DCMAKE_BUILD_TYPE=Debug -DVULKAN_HEADERS_INSTALL_DIR=/home/vjaquez/gst/gstreamer/prefix DCMAKE_INSTALL_PREFIX=/home/vjaquez/gst/gstreamer/prefix ..
cmake --build . --install

Right now we have the Vulkan headers and the Vulkan loader pkg-config file in place. And we should be able to compile GStreamer. Right?

Not exactly, because gstenv.py only sets the environment variables for the development environment, not for GStreamer compilation. But the solution is simple, because we have all set in the proper order: just to set PKG_CONFIG_PATH when executing meson setup:

PKG_CONFIG_PATH=/home/vjaquez/gst/gstreamer/prefix/lib/pkgconfig meson setup --buildtype=debug build

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