add cmake config option to allow build video module with mit license retained.

[eebssk1]

You can add a definition so video module will only look for bsd/lgpl licensed encoders like kvazaar/svt-av1/openh264.
Which make your video module lgpl. Thus keeps your project as mit since lgpl does not effect the whole code,only the one that modify the lgpl-ed code.

Also i think the video module can also be mit because it only effect code that modify lgpl code. It's clearly that you are just using it instead of modifying.

[TianZerL]

I cannot control witch pre-build ffmpeg libs user will use to build video module. And I simply pass the user specified encoder to ffmpeg.
I think GPL3 is the safest option.