Kdenlive/Development

Kdenlive is rather easy to build (at least on supported platforms), and this page should show you the simple steps to get there. If you encounter any problem during the process or spot any information that should be added/updated, please don't hesitate to reach out to the Developer's mailing list, on the Telegram Kdenlive Developers' group or the Developers' Matrix room.

Pre-requisites and Supported Platforms

Kdenlive is primarily developed on GNU/Linux. There is an effort to build Kdenlive on Microsoft Windows, but it's still a work in progress.

Currently supported distributions are:

• Ubuntu 20.04 LTS Focal Fossa and derivatives
• Arch Linux

You should be able to build it on any platform that provides up to date versions of the following dependencies Qt >= 5.7, KF5 >= 5.50,MLT >= 6.20.0.

To get a recent enough version fo MLT on Ubuntu, you have to add Kdenlive's ppa

sudo add-apt-repository ppa:kdenlive/kdenlive-master
sudo apt update

It is recommended to uninstall the official kdenlive packages to avoid potential conflicts.

sudo apt remove kdenlive kdenlive-data

Installing dependencies

Development tooling

You will need classical development tools (like git, gcc ...) but also cmake :

sudo apt install build-essential git cmake extra-cmake-modules libsm-dev

KDE Frameworks 5, based on Qt5

On Ubuntu the following packages will pull all the necessary dependencies:

sudo apt install libkf5archive-dev libkf5bookmarks-dev libkf5coreaddons-dev libkf5config-dev \
libkf5configwidgets-dev libkf5dbusaddons-dev libkf5kio-dev libkf5widgetsaddons-dev \
libkf5notifyconfig-dev libkf5newstuff-dev libkf5xmlgui-dev libkf5declarative-dev \
libkf5notifications-dev libkf5guiaddons-dev libkf5textwidgets-dev libkf5purpose-dev \
libkf5iconthemes-dev kdoctools-dev libkf5crash-dev libkf5filemetadata-dev kio \
kinit qtdeclarative5-dev libqt5svg5-dev qml-module-qtquick-controls libqt5networkauth5-dev \
qtmultimedia5-dev qtquickcontrols2-5-dev breeze-icon-theme

Multimedia stack

If your distribution packages a recent enough version of MLT (>= 6.20.0), you can install it directly along with ffmpeg and frei0r plug-ins. Otherwise, you'll have to add our ppa or compile it yourself (see above)

sudo apt install libmlt++-dev libmlt-dev melt frei0r-plugins ffmpeg

Dependencies for localization

There are some additional dependencies required by the specific script to fetch the translations:

sudo apt install ruby subversion gnupg2 gettext

Getting the source code

Cloning the git repo

The easiest way to get Kdenlive source code is to clone the git repo:

git clone https://invent.kde.org/multimedia/kdenlive.git

Selecting the branch

You should generally base your developments on the master branch

cd kdenlive
git checkout master

or if you want to get the code for a given release

cd kdenlive
git checkout release/20.04

Building Kdenlive

Create a directory for the build inside the kdenlive directory:

mkdir build
cd build

To avoid problems with plugins and libraries, it is easier to install Kdenlive in /usr:

cmake .. -DKDE_INSTALL_USE_QT_SYS_PATHS=ON -DCMAKE_INSTALL_PREFIX=/usr -DRELEASE_BUILD=OFF

Alternately you can build it with debug flags (advanced users only ;-) and you need to have clang installed ) :

cmake .. -DKDE_INSTALL_USE_QT_SYS_PATHS=ON \
-DCMAKE_INSTALL_PREFIX=/usr -DCMAKE_BUILD_TYPE=Debug \
-DCMAKE_CXX_COMPILER=/usr/bin/clang++ \
-DECM_ENABLE_SANITIZERS='address' \
-DBUILD_TESTING=ON -DBUILD_FUZZING=ON -DBUILD_COVERAGE=OFF \
-DRELEASE_BUILD=OFF

You may get a warning "Qt5 WebEngineWidgets not found. You cannot use your Freesound.org credentials, only preview files can be downloaded from the Online Resources Widget": as this is a very specific feature requiring a rather large dependency, you can just ignore it. But if you want to use that feature, you must install qtwebengine5-dev.

To compile the translations of the application, you need KDE Frameworks >= 5.76, make sure to delete the "po" subdirectory from your build folder if it exists, and use this cmake command to configure the project :

cmake .. -DKDE_INSTALL_USE_QT_SYS_PATHS=ON -DCMAKE_INSTALL_PREFIX=/usr -DKDE_L10N_SYNC_TRANSLATIONS=ON -DRELEASE_BUILD=OFF

Then build and install:

make -j5
sudo make install

You can then start your compiled version by simply entering:

kdenlive

If you have compiled it in debug mode, you may encounter errors like

SUMMARY: AddressSanitizer: new-delete-type-mismatch (/usr/bin/kdenlive+0x643020) 
==6982==HINT: if you don't care about these errors you may set ASAN_OPTIONS=new_delete_type_mismatch=0
==6982==ABORTING

As the hint says, the you can solve this with

export ASAN_OPTIONS=new_delete_type_mismatch=0

Next Steps

Now that you've got a working dev environment, you can find some nice first issues to solve.

A instruction of the workflow with KDE's GitLab can be found here. You can also gain more general knowledge by exploring the tutorials on TechBase.

IDE Setup

Pick your favourite!

Setting up KDevelop

Open KDevelop and go to Project > Open/Import project Then select the CMakeLists.txt file in the kdenlive source folder. You can now start hacking on Kdenlive!

Setting up QtCreator

After checking out Kdenlive from git—when working on refactoring, you may want to clone two copies, one with the next branch and another one on the refactoring branch—, you can open the CMakeLists.txt in QtCreator, which will load the project if cmake succeeds. If you run/debug Kdenlive, make sure that kdenlive and not kdenlive_render is selected as an active project.

If you let QtCreator restore the previous session (File > Session manager), it will remember the open documents. Environment variables (see below) can be set in Projects > Build Environment.

MLT documentation

Kdenlive uses MLT’s C++ API called mlt++. This API is not documented as it is simply a wrapper to C functions. For example, the documentation of Mlt::Consumer::position() can be found in framework/mlt_consumer.c:mlt_consumer_position(). The actual C function name is usually a combination of the class name and the function name, but can also be found by consulting mlt++/MltConsumer.cpp:position().

Environment variables

If kdenlive crashes on startup (e.g. in QtCreator) and shows a message like:

   kdenlive(24309) KXMLGUIClient::setXMLFile: cannot find .rc file "kdenliveui.rc" for component "kdenlive"

then you have to ensure the .rc file is found. If CMake is configured to install Kdenlive to /usr/local, the .rc file is put there, but when kdenlive is then run from the build directory, the KXMLGUIClient will not search there. Solution: Set the environment variable KDEDIRS to $KDEDIRS:/usr/local.

You can get more information about the paths that are checked by running kdenlive like this:

   strace build/src/kdenlive 2>&1 | grep kdenliveui.rc

Wayland

To avoid flickering here are some Kdenlive envvars that work with Sway?

QT_QPA_PLATFORM=wayland-egl
SDL_VIDEODRIVER=wayland
XDG_SESSION_TYPE=wayland

Contact

Chat

There are several chat groups on Telegram and Matrix. The groups existing on both services are bridged via a bot so you can choose your preferred one. Not all groups exist an all services.

Telegram

• Main group
• Developer group
• Manual Contributors group

Matrix

• Main group
• Developer group

Mailing List

The kdenlive developer mailing list archives can be found here

A searchable archive of the kdenlive developer mailing list can be found here

Information on how to subscribe can be found here