Ok, just to finalize this. Instead of the cmake code I attached above to link FFmpeg libraries, I used the same FindFFmpeg.cmake file that used by OBS Studio project on GitHub, and it worked as expected!
I don't know what is the difference yet, I need to read through it carefully and find the differences.
I'm hoping for an answer on this. Here is a screenshot of the QT Maintenance Tool.
Shouldn't I see a way to install the QT Multimedia component here? I have a red arrow where I would have assumed I'd see it (I've seen examples on the web with screenshots showing it.) I have 6.3.1 installed.
@Christian-Ehrlicher True it is a taste thing. We did this long long ago and have got used to it.
I rechecked the usage of file. If all file names are explicitly added, GLOB is not needed.
It is also true that GLOB is not recommended. However, since we have a lot of files, it was simply applied. One problem is that some files are not used and will be included automatically in the project