Using and calibrating Qualisys video cameras

Video capture with Qualisys cameras involves the following steps:

  1. Make sure that the cameras that will be used for recording video are in video mode.

  2. Choice of video settings (capture rate, exposure, compression, etc.). The available video settings and the interface for changing them in QTM depends on the camera model. The video capture rate can be set individually per camera and may be different from the capture rate of the cameras in marker mode. Some camera models have the option to use in-camera MJPEG compression. This allows a longer capture, however, at a reduced maximum capture rate, see chapter Qualisys video sensor specifications (in-camera MJPEG).

  3. Calibration of Qualisys video cameras is optional, but required for 3D overlay. Qualisys video cameras can be calibrated together with the marker cameras in the system. During the calibration, the Qualisys video camera will be automatically switched to marker mode, so it is important to make sure that the marker settings are correct. If you do not want to include a video camera in the calibration, you can uncheck it in the linearization options, see chapter Linearization.

  4. Start a new capture. Depending on the camera model and settings, video is streamed to QTM during the measurement or buffered on the camera and fetched after the capture is finished.

    Depending on the capture frequency streaming video cameras might store some frames during the capture. These frames are fetched after the capture is finished.

  5. The video from each camera will be stored in a separate AVI file and can be played back in QTM, see chapter Qualisys video files. You can then for example activate the 3D overlay on the video, see chapter 3D data overlay on video, and export the view with the Export to AVI feature on the File menu.

Calibrating Qualisys video cameras

Qualisys video cameras are calibrated in the same way as Qualisys marker cameras. During the calibration, the video cameras will be automatically switched to marker mode. Follow these steps to calibrate Qualisys video cameras.

  1. First, you need to set the marker settings. Switch to Marker intensity mode and adjust the exposure and threshold so that the markers are red, and the background is dark blue.

  2. Make sure that the cameras have enough overlap with other cameras within the system. Preferably, the L-frame is visible, but this is not required.

  3. Start a calibration. The video cameras will be calibrated together with the marker cameras in the system.