D-Link DCS-2000 Manual page 52

Channel number
Droppable Areas
The drag and drop can also apply to the change of videos. In the video area, if
you want to exchange the videos of different channel, you can drag the video
and drop to where you want to locate the video. If the destination video box is
empty, then video in the source video box will be shown on destination video
box, and the source video box will be empty. If the destination video box
contains video of some channel, then the videos in the source and destination
video box will be exchanged.
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