My scons output looks like that
Configuring FFMPEG
Checking for libavcodec (53.35.0 or higher)... 	yes
Checking for libavformat (53.21.0 or higher)... 	yes
Checking for libavresample (0.0.3 or higher)... 	no
Checking for libswresample (0.0.1 or higher)... 	no

As a non native speaker I cannot understand you comment. Have I worry about this situation? Can you add massage to scons for clarification? Thank you.