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*, *libavutil* and *libswscale*, but you can set your own configuration to make the FFmpeg you need.