For best results your video camera should be calibrated. Record a video while moving the camera around the grid pausing at recommended camera positions and rotations (see Taking the Calibration Photos).
Then when setting up the calibration project type in the Wizard, select the calibration grid video file. The Manual Video Frame Extraction dialog will appear allowing you to navigate through the video and extract the appropriate frames. Be sure to include frames that show crisp coded targets (all 4 if a single sheet calibration), and have little or no blur.
In some cases, due to the lower resolution of the image frames, not all targets will be detected. See Camera Calibration Troubleshooting. Sometimes retaking the video can help but you may need to manually intervene to mark and/or reference targets as needed and then rerun the calibration process without the automarking stage (see Camera Calibration Options Dialog).