How can I create video from raw images in C++ using libav?

I'm developing a network camera that outputs raw gray scaled images at a very high frame rate.

So, I need to store these images quickly and with a reasonable compression level, because otherwise, I could quickly run out of memory and disk space.

I have tried OpenCV for creating the video, but a 10 second video consumes more than 3GB, due to lack of or lower compression rate.

My idea is to use libav to deliver the array that comes from the network and then stores the final video at the end of the stream.

Could someone help me finding a piece of C++ code for doing that?