You can download a calibration pattern at the following link:
To capture a good calibration video, print out your calibration pattern and place it on a planar surface and capture it using your camera from diferent angles and distances. To achieve good results, the calibration pattern must be as planar as possible.
- Use the same camera settings (resolution, framerate, lens configuration) as in the videos that are to be analysed.
- Make sure that the calibration pattern is planar. To achieve this, place it on a solid planar surface that does not bend easily. Make sure, that the paper is not fold or scrapped. Additionally, you may flatten the paper, or fix it using a sticky tape.
- Use good lightning conditions.
- Make sure that during the video the calibration pattern positions cover the whole camera frame, including corners - i.e. you have captured the calibration patter at its top-most position, bottom-most position, left-most position and right-most position, and also in corners of the camera frame.
- You should also capture the calibration pattern as close to the borders of camera frame as possible. The calibration pattern can be partially out of field of view - just make sure that all the inner points of calibration pattern are visible. Inner points are the ones, that are at the point of touching of any two black squares.
- If the calibration pattern may go obscured or out of field of view during the calibration video, the calibration does not fail - it just skips over the frames that does not contain all inner points of the calibration pattern.
- Make sure, that you will capture the calibration pattern from as many view angles as possible. More is better - do not be afraid! :)