Working With Sync Groups
You can group of cameras into ad hoc Sync Group, which means that their playback is synchronised, and that you then control all those viewer together. This is extremely useful (actually, necessary) when you want to export video for evidentiary purposes and you require footage from different cameras.
Sync Groups are created on-the-fly by choosing the first one (it will be the one the others sync to), then clicking on the others you want in the group while holding down the Ctrl key on the keyboard. If you accidentally added a viewer, simply click on it again (while holding down Ctrl). The viewer borders will change to cyan to indicate that they are part of a sync group, while the most recently chosen one will have only its shortcut character highlighted in cyan.
Once you have created the group, you sync the cameras by clicking on the sync button on any of the viewers.
If the master viewer was recorded at a lower frame rate than others and you step forward one frame, the others will jump to the time that is displayed in the master.