I am currently writing a video project using FFMPEG shared library with other license abiding projects (like libass and freetype2). I have a script that compiles FFMPEG and the other libraries as a single .so file (Android) and then my actual code just imports/dynamic links the library and use its functions. I have FFMPEG code released the way I compiled it with the libraries on an open source platform (like Github) which I assume abides to the license.
FFMPEG is compiled without the "non-free" and "gpl" flags so everything together (including the other 3rd party libraries compiled with it) should be LGPL 2.1 (not GPL3). I plan to have it as a submodule to my video player project.
For my video player library, I do not planning on open sourcing (for reasons out of my control). If my video player is just loading the shared library at runtime can it be treated as its own license, can I can have my video player closed source and have different license? Supposedly anyone can take the library and compile their own shared library and load it into the app.