Comelit MT COMELIT VSC IP START SERIES - Manual (Page 13)

Set the right window selected channel’s brightness, contrast, saturation and
tone, click default value to make the parameters restore default. It only
support brightness and contrast setting for our protocol.
2.1.7 Preview interface electronic zoom
As select the channel preview window, it support electrical smooth zoom in by
mouse middle button wheel operation.
2.2 Video playback
Click Playback to go to video playback module, as figure below: