Problem scenario
You do not want to use pip or pip3 to install opencv. How do you install opencv (with the -DWITH_FFMPEG=ON flag)?
Solution
Prerequisite
This assumes that cmake has been installed. If you are running Ubuntu/Debian, run this: sudo apt -y install cmake
If you are running CentOS/RHEL/Fedora (some RedHat derivative), run this: sudo yum -y install cmake
If you are running SUSE, run this: sudo zypper -n install cmake
Procedures
Run these commands:
wget -O opencv.zip https://github.com/opencv/opencv/archive/master.zip
sudo cp -i opencv.zip /bin/
cd /bin
sudo unzip /bin/opencv.zip
sudo mkdir build && cd build
sudo cmake ../opencv-master -DWITH_FFMPEG=ON