opencv requires C++11 support, while ffmpeg builds using C.
Building libavformat/vf_libopencv.c with C++ does not work at all.
%bcond_without omx # OpenMAX IL support
%bcond_without openal # OpenAL 1.1 capture support
%bcond_without opencl # OpenCL 1.2 code
-%bcond_without opencv # OpenCV video filtering
+%bcond_with opencv # OpenCV video filtering
%bcond_without opengl # OpenGL rendering support
%bcond_with openh264 # OpenH264 H.264 encoder
%bcond_without openmpt # OpenMPT module decoder