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Question
Can I configure camera’s calibration using recorded video (Measure-based calibration explained)?
Answer
The calibration can be done by using already recorded videos, as is demonstrated in the video below. Either video recorded on the camera's SD card or on a recorder can be used. This can save calibration time and can be done by a single person.
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Access the calibration menu and choose Measure.
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By default, live video is selected as the video source, but other choices are available (1):
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Replay: replay either locally recorded video (on SD card) or from a configured recorder
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Local clip: record video based on the live video stream on the fly
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Snapshots: make still images based on the live stream
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If Replay is chosen, a video timeline will show under the video pane, which can be searched for an appropriate time, as well as paused when needed (2).
Grey lines when measuring people
The grey lines beside the blue measuring elements show the calculated sizes and orientations. Make sure they are similar enough to the measured elements.
Wrong orientation
Right orientation
Video showing how to use measured calibration:
Measured calibration tips
- Draw at least one element per value to be estimated
- Focus on those areas of the image where you want to detect, track and alarm
- Draw at least one element at the point farthest away from the camera that is still needed
- Distribute the elements well over the focus areas
- Use vertical lines to mark humans in the image
- Check for all elements whether the entered height / length / angle is correct
Measured calibration is the classic way to calibrate. Any known positioning variables are copied from the Positioning tab and remaining variables are calculated based on manually sketched vertical and ground lines as well as ground angles to determine perspective, which let the camera deduce fitting values for unknown tilt, roll, height and focal length values on demand.
Similar measuring elements are also available to verify the calibration. Note that vertical lines can also be used to measure height of standing persons. Best practice is to distribute the measuring elements well in the image, e.g. one to the front, one to the rear and one to the side.
