Polycom 1500 Administrator's Manual page 1083

RealPresence Collaboration Server (RMX) 1500/1800/2000/4000 Administrator's Guide
The participants Video Protocol in the New Participant or Participant Properties - Advanced tab should be left
at (or set to) its default value: Auto.
The Auto setting allows the video protocol to be negotiated according to the endpoint's capabilities:
● OCS endpoints and Lync Server clients connect to the conference using the RTV protocol.
● Other endpoints negotiate the video protocol in the following sequence: H.264, followed by RTV,
followed by H.263 and finally H.261.
Protocol Forcing
Selecting H.264, RTV, H.263 or H.261 as the Video Protocol results in endpoints that do not support the
selected Video Protocol connecting as Secondary (audio only).
Polycom®, Inc. 1051