The Video Preview window manages the video stream immediately received from the webcam. This is a “private” window that allows you to control your settings before be enabled (or also when you're enabled) on a Full-Duplex channel.
The function is activated/deactivated through the main horizontal menu -> Windows -> Preview or by clicking on this toolbar button.
PC & Mac: Preview button
This is an example of preview window:
PC & Mac: Preview window
Please note that if in this window there’s no video and it is written “no video”, your webcam is not connected or not working properly (for example, it happens when the webcam is configured to be working in the same moment on other programs or the drivers are not installed yet).
PC & Mac: Preview with No Video
If the window display an hear, it means that you have been set as an “only audio” user: so, other users can only listening at you while you will see all the other videos.
PC & Mac: Preview for an Only Audio user
If you use a PC, by clicking on the window background with the right mouse button the preview window contextual menu will appear, which functions are similar to the Client Configurator -> Audio & Video setup.
Once you have selected another device, remember to enable again this contextual menu and to click on Apply settings to make real your changes.
PC: Preview window with his contextual menu
Mac users have not the contextual menu on the Preview because they can not change their default audio/video devices to be used in the conference.