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Many analysis tasks identify regions in video. In some cases you might want to encode a video with an overlay that identifies these regions. For example, you can produce a video where detected faces are surrounded by an ellipse or number plates are surrounded by a polygon.
Creating an overlay produces similar results to drawing on the video with the draw transform engine. However, the overlay is written to the subtitle track so the video frames are not modified and the overlay can be turned on and off when you play the video in the HPE MMAP Media Player.
Overlays are supported only for video. If you want to draw on images, use the draw transform engine.