Skype for Business, Simultaneous Skype for Business video streams
How many video streams can I see in Skype for Business meetings?
Only 5 video streams are visible at any one time.
In video conferences that have more than two people, users can see
videos of participants in the conference. If the conference has more
than five participants, video of the most recently active participants
appears in the top row, and a picture appears for the other
participants.