Motion capture by marker tracking
VideoTrack 2D is a motion capture software package for Windows. It tracks retroreflective markers placed on the analysed body and outputs their 2D coordinates.
How are markers detected in the video?
Through arbitrary chains of image processing filters. For example each video frame can be filtered with a color filter, then blurred to remove noise and finally thresholded. After processing the image only contains white marker pixels and black background. Marker pixel cluster-centers determine marker positions.
Starting from an initial manual marker assignment, each marker is tracked in the video sequence. Marker occlusions or bright spots in the video (ghost markers) can disturb the tracking process, as well as fast marker movements with non smooth trajectories. VideoTrack contains several tracking algorithms to improve tracking in these situations:
What about manual re-assignment?
VideoTrack 2D supports two editing modes for manual marker identification. Also particular markers can be exluded from analysis at frame intervals or set to constant positions.
How does deinterlacing work?
PAL video frames are saved in interlaced video format, which means 25Hz time resolution for a full video frame or 50Hz divided into odd and even video frames. VideoTrack's deinterlacing algorithm splits each frame in even and odd lines and linearly interpolates missing lines. It also supports batch deinterlacing for more than one file at a time.