Video conferencing

i am a newbie.

i have 3 parties (eg. a,b,c) with voice conferencing. if a, b have video, could they have video conference along with voice conferencing with c?

if all three parties are using sip/iax clients that support video and asterisk is set to pass video, and all 3 are going through asterisk then yes

Asterisk (at least up to 1.6) doesn’t have video conference bridges, so video will only work point to point.

What would a video conference bridge do? Would it generate a split screen display?

Obviously the phones could handle this and only present simple calls to Asterisk.

all parties have sip phones but only A and C have video.

i would like to achieve below:
A dials B (voice only).
B dials C and all parties engage in voice conferencing,
A and C see each other in video.

pls advise.