Hi,
First of all you should check you have created video CFBs on your GWs.
Then,you should enable "Video Capabilities" on each of your 8941 phones.
Without dedicated MCU with your Video Conference you will get switching video stream from active phone.
Like,if phone A is talking at this moment,another phones "B"and "C" will see phone "A" only.
When phone "B" will begin talk, phones "A" and "C" will see stream from phone "B"