When a point-to-point call is placed between two HD terminals, the main video protocol on the terminals is set to Auto. A message indicating that The loopback test cannot be performed due to protocol inconsistency. is displayed when a remote video loopback is performed.
The audio and video codecs on the two terminals are different, though the main video protocol on the terminals is set to Auto.
Solution: set the main video protocol and formats on the two terminals to consistent values.