ROI is region of interest. In a given scene, it's probable that some of the image is not of interest, yet it takes up view space. By specifying an ROI you can increase the area of interest by not showing the area in which you have no interest. For instance, you may have a camera that only has a 1280 x 960 view. Much of the height is sky, or ground. By using ROI you could show that as a 1280 x 720 view instead. This has more of what you want by showing you less of what you don't want.
Set ROI enable to yes. Set the desired width (cx) and height (cy) of the image as a percentage of the original, incoming view. For examples, if you want that 960 px height to be 720, and if it is the sky you want to remove, set the ROI cy to 75% and ROI y to 25%. If it is the ground you want to remove, set ROI cy to 75% and ROI y to 0%. You can do the same to the width.Percent is used instead of pixels since the image a camera sends can change dimension depending on, for example, profile, or if you decide to stream in a different resolution. By using percent as the unit basis, you won't have to come back and update the ROI each time the image resolution changes. And it doesn't have to be exact: y at 33% and cy at 67% works well for removing much of the sky, and it's simple.
The ROI sums (x + cx and y + cy) must not exceed 100%. The change won't be accepted if that happens. Generally, setting the lengths (cx and cy) before the x and y is the way to go. The lengths must be at least 20%.
Using an ROI effectively zooms the image. The ePTZ considers the ROI image as being 1x no matter how much zoom it effectively has.
Also on the ROI panel is ePTZ. This is sometimes known as digital zoom. If you want this, and the only reason you might not is if the camera has optical zoom, set ePTZ enable to yes.
To perform ePTZ, first set keyboard focus to the main view (or peel view) by clicking in its window. Using a mouse with a scroll wheel, turn the wheel forward to zoom in, and turn it backward to zoom out. To scroll within the zoomed view, point the mouse cursor in the view, hold down the left-mouse button (LMB) while you move the mouse to move the view port within the zoomed view. If you have a horizontal action to the wheel, pushing it right zooms 2x, and pushing it left restores to 1x.A mouse/trackpad without a scroll wheel/gesture cannot adjust the e-zoom and so ePT would not be available.
For touch screens, pinch-zoom and dragging will do about the same as a mouse/scroll wheel.