After getting the overview camera and the PTZ camera to work, we have to calibrate the system so that the two can work together correctly.


LectureSight uses 3 co-ordinate systems:

  • Video Analysis uses the dimensions of the overview camera image (for example 640x360). Pixel counts and movement thresholds defined for object tracking therefore refer to these dimensions.

  • The Camera Operator uses a normalized co-ordinate system from -1 to 1 on both the horizontal and vertical axes, where the top-left is (-1, -1), centre is (0,0) and bottom-right is (1,1). Zoom is mapped from 0 (wide) to 1 (close).

  • The Steering Worker uses the co-ordinate system of the PTZ camera.

    VAPIX cameras use degrees as co-ordinates. As LectureSight manages PTZ co-ordinates as integers, VAPIX co-ordinates are scaled up by 100 by the camera driver to preserve precision, so 37.65 degrees is represented as 3765.

Inverted cameras

If the Overview Camera is mounted inverted (up-side down), you can invert the overview image using:


If the PTZ Camera is mounted inverted, you may need to add these properties for some VISCA cameras:


and this property for VAPIX cameras:

Scene Profile

Create a new Scene Profile to restrict the area in which the system tracks objects.

Scene Limits

These 4 configuration properties map the overview image to the camera PTZ co-ordinates.


Initially these values are not set, and thus the limits of the camera’s co-ordinates are used as the scene limits.

Manual Calibration

To set values for the four scene limits, disable camera steering by using the following command on the console


Move the production camera (using the PTZ Camera’s remote control or web interface) first so that the PTZ Camera is centred on the top-left point of the overview image, and then on the bottom-right point.

Note the camera’s co-ordinates at those points in the PTZ Camera Control window. Update the configuration with those values, and restart LectureSight.

Marker Calibration

!!! info “Automatic marker calibration is only supported for VAPIX cameras.”

Marker calibration maps overview co-ordinates to camera pan and tilt values by matching positions on the overview image with camera preset positions.

The calibration process creates horizontal and vertical conversion models using spline interpolation inside the range of the marker points, and linear extrapolation outside the range, to convert between overview image co-ordinates and camera positions. This will in general provide more accurate results than setting the scene limits manually.

To set up marker calibration:

  • In the Scene Profile Editor, identify 3 or more fixed points on the image (for example the corner of a fixed blackboard, or a light switch). The set of points should cover most of the horizontal and vertical range of the presentation area.
  • Create calibration markers at each point. Give each marker a name, for example m1, m2, m3, m4, m5, and save the profile.
  • In the camera web interface, create a set of presets with the same names as the calibration markers. At each preset, the camera should be centred on the venue feature identified by the matching calibration marker.
  • Restart LectureSight, or use the console command cs:calibrate to trigger marker calibration:
g! cs:calibrate
Automatic calibration completed

The calibration process discovers the pan and tilt co-ordinates of each preset by moving the camera in turn to each position, with a pause time of 2.5s between presets.

On subsequent startup, the Steering Worker will report whether automatic calibration has been used, and if successful, the values of the calculated pan and tilt thresholds:

Automatic calibration, camera pan/tilt limits: pan -3673 to 3649, tilt -2596 to 2348

Once automatic calibration has successfully run, changes to the configured scene limits will have no effect, as the calculated values will be used.

If no calibration markers have been created or there are too few matching markers and presets, the log will include:

Automatic calibration not possible

This can be caused by markers that are too close together in the x or y axes. Try to adjust the marker positions so they are distributed across the field of view, both horizontally and vertically.

Initial position

Set the initial position of the PTZ camera


Frame width

Set the frame width of the PTZ camera at the configured zoom position, relative to the width of the overview image, which is 2 in normalized co-ordinates (-1 to 1).

For example a frame.width of 0.5 means that the PTZ Camera’s image is 25% of the width of the overview image (0.5 / 2).


You can verify visually that the frame width is correct by looking at the frame boundary guides on the PTZ Camera Control window.