Note that you cannot active NDI while a Skype call is active. This setting will remain on until manually turned off.
If you haven’t already, turn on NDI in Skype: See also the Remote Guests in Your Live Broadcast Tutorial for a step-by-step guide to remote guests via Skype. This bit of magic requires activating Skype’s NDI® for Content Creators feature. One of the most popular features of Ecamm Live is the ability to have as many as five remote guests appear in your broadcast.
