Digitized video, also known as motion pictures, is a sequence of still images consisting of a set of several frames that are constantly changing on a timeline. Moving images can be divided into two categories: video and animation. If each frame is a real image of a natural scene obtained in real time it is called video; while each frame is a computer or manually produced graphics with a sense of reality is called animation.

The realization of moving images is based on the foundation of visual transience. Visual retention is a biological phenomenon in which the image of an object is retained on the retina of the human eye for a short period of time (01 second) after the object is observed. When the position and shape of an object are changed continuously, slightly at a time, at a sufficiently rapid rate, the visual retention effect of the human eye senses that the object is in continuous motion.

If a series of static images arranged in a certain order are played continuously at a certain speed, the human eye will feel the continuous dynamic effect. For example, the movie is shown at a rate of 24 frames / second, and the use of masking plate blocking 24 times / second to achieve to overcome visual transience, so that people see a continuous smooth and flicker-free picture.

Motion pictures are characterized by continuity, time delay, and correlation.

(1) continuity: in the time axis of the frame as the unit of movement, belongs to the discrete media category. Dynamic images represent a wider range than static images and are more expressive.

(2) time-delay: moving images have a large amount of data, which must be compressed before they can be used in computers. The capacity and speed of the computer directly affects the image quality.

(3) correlation: the correlation between frames is the basis for the formation of continuous action of moving images, and the conditions for compression and other processing. Motion pictures are less sensitive to errors.