How to build your version of javaCV for Android?

Question

Android

Hello!
For a week now I have been struggling with the task of how to build and use the opencv, ffmpeg libraries on android.
As a result, I found a javacv project, which is based on javacpp. Found samples on github. But in one sample, the ffmpeg library was built without the h264 codec. The second without rtmp protocol.
Accordingly, there is a task to create your own assembly, but this raises many questions and errors. Or at the assembly stage or at the stage of embedding in an Android project.
Can someone suggest how to do it right. Or maybe someone already had assembly experience?