Preview screenshot of recorded stream

I'm doing an application where people will be able to record a video message with their webcams and send invitations to friends to come and watch them. Once the friend reads the message and if the message's recorder agrees, the message goes to a public archives section. Is it possible to extract snapshots of the recorded streams in order to make a preview page of all posted messages ? You would first see a list of available videos with screenshots, then select the vid to see and then only the stream begins.

Something like youtube snapshots after you get your search results.

Thanks in advance