To build FFmpeg library for BSPlayer you need Linux or Windows with MSYS2 and Android NDK. Build system is designed to work with NDK standalone toolchain (read NDK documentation). Unpack FFmpeg source bellow, edit 'build-ffmpeg.sh' script and set NDK toolcahin path and FFmpeg options. Then just run: ./build-ffmpeg.sh [param], where param is one of: armeabi-v7a, arm64-v8a, x86, x86-64 for. ex for ARMv7: ./build-ffmpeg.sh armeabi-v7a Or You can also use scripts build_arm, build_arm64... If everything went ok, libffmpeg.so should be in lib folder or in current folder under Windows.
You can also download all-in-one packages bellow, where everything is included. Nothing else is needed just run one of build scripts.
There are packages for each CPU separately and for all CPU architectures. You can check which CPU you need in Preferences->Playback preferences->Custom codec under "Select custom codec"