Only facebook messenger or also the camera program enabling the video? because that one might be a higher risk. i think facebook itself might record data, but will have good encryption because it is such a high profile company there is too much at stake when the encryption is inadequate. – johan vd Pluijm Dec 6 ’17 at 14:10.

https://security.stackexchange.com/questions/150342/how-private-is-fb-messenger-video-calling