get build image: ovidiudragoi/ffmpeg-build-ubuntu-20.04
ref: https://chowdera.com/2022/129/202205091526046812.html
For compilers to find ffmpeg@4 you may need to set: export LDFLAGS="-L/opt/homebrew/opt/ffmpeg@4/lib" export CPPFLAGS="-I/opt/homebrew/opt/ffmpeg@4/include"