Here is a script that downloads the source code of [FFmpeg](https://www.ffmpeg.org) library and assembles it for Android. The script produces shared libraries as well as header files. The output structure looks like this:
The actual content of all this directories depends on how the FFmpeg was configured before assembling. For my purpose I enabled only *libavcodec*, *libavformat* and *libavutil*, but you can set your own configuration to make the FFmpeg you need.
The version of FFmpeg here is **4.1.2**. And the script expects to use Android NDK **r19** (*b* and *c* also work as well as *r20-beta1*). Starting with FFmpeg 4.1 and NDK r19 the whole process became much simpler.
The x86 binary doesn't have assembler optimizations, since they bring text relocations. So it may encounter certain performance issues. The x86_64 doesn't have this problem though.