You dont need to compile avidemux yourself to write your own plugins.
What you need is :

• Avidemux installed on your system , the version built with visual c++
• CMake > 3.x
• Optionnaly MSys installed, it's just simpler
• Visual c++ 2015 or 2017, Community edition is fine
• A demo/sample video filter, available here videofilterdemo_2.7.zip

You will need to install cmake version 3.x
Make sure the cmake “bin” folder is in your path

Start a command prompt Call the vcvars64.bat from visual c++ binary dir, that will set up things Then start msys bash.exe shell

Go to the source folder of the demo and create the sln file

mkdir build
cd build
cmake  -G "Visual Studio 14 2015 Win64" -DCMAKE_INSTALL_PREFIX="c:/Program Files/Avidemux 2.7 - 64bits"  -DVERBOSE=True -DCMAKE_BUILD_TYPE=Release ..

If you just unzipped the files in a folder, use that folder. For example if you unzipped avidemux in Z:/avidemux the command becomes

cmake  -G "Visual Studio 14 2015 Win64" -DCMAKE_INSTALL_PREFIX="z:/avidemux"  -DVERBOSE=True -DCMAKE_BUILD_TYPE=Release ..

Look for error, it should go without problem.

If you dont want to use visual C++ ide , you can just

  
cmake --build . --target INSTALL

If you want ot use the visual C++ ide, you can also load the generated .sln into visual c++

When the build is over, either copy the resulting dll file into the plugin subfolder of avidemux install or, alternatively, run the install target in Visual C++

Important/Common problem

You cannot mix binaries built with Visual C++ and built with Mingw/g++ It will *NOT* work. Don't even try.