This shim was made to compatibilize the Hantro x170 hardware codec OpenMAX library with ffmpeg on the Android KitKat version shipped with DJI Goggles.
You may need to tweak Makefile to achieve a successful build; you'll need to set the path to your Android NDK and have the toolchain executables in your PATH. You may also replace the libraries on ./lib by the ones extracted from your device, though that shouldn't be needed.