解决方案：
1. 执行如下安装
sudo apt-get install libsdl2-dev
sudo apt-get install libsdl2-2.0-0
sudo apt-get install libsdl2-image-dev
sudo apt-get install libsdl2-image-2.0-0
sudo apt-get install libsdl2-mixer-dev
sudo apt-get install libsdl2-mixer-2.0-0
sudo apt-get install libsdl2-net-dev
sudo apt-get install libsdl2-net-2.0-0
2. 重新配置编译安装SDL2：
./configure --prefix=/usr/local --enable-shared --disable-static && make -j 4 && sudo make install
3.重新配置编译安装ffmpeg：
./configure --prefix=/usr/local/ --enable-debug=3 --enable-sdl2 --enable-libfdk-aac --enable-libx264 --enable-gpl --enable-nonfree && make -j 4 && sudo make install