This step intends to separate the objects to track from the background. The background will become black, while the objects to track will appear in white. Most of the time, this step follows a preprocessing method like background subtraction.
A threshold value (between 0 and 256). If the objects to track don't appear in the image, try to reduce the value. If parts of the background become white, the value need to be increased.
Whether the threshold must be inverted or not.