When we have to embed a video or post an image in Compass 2g (AKA Blackboard Learn) or in a website, we try to follow the 640x480 or lower.
This website provides sizing for those types of embeds that can be used in social media but in course embeds as well. I am happy to have this information, i will be using it a lot!
http://www.lunametrics.com/blog/2012/11/12/final-social-media-sizing-cheat-sheet/?goback=.gde_4640982_member_204443721
