Incorporating compatible code, under different license is perfectly OK and each work can have different license, while the whole combined work is under the terms of another.

I'm honestly quite confused what FFmpeg is objecting to here, if ILoveRockchip wrote code, under a compatible license (which Apache 2.0 is wrt. LGPLv2+ which FFmpeg is licensed under) -- then that seems perfectly fine.

The repository in question is of course gone. Is it that ILoveRockchip claims that they wrote code that was written FFmpeg? That is bad, and unrelated to any license terms, or license compatibility ... just outright plagiarism.