Interlaced video

Interlaced video is a method to display an image. Images are drawn line by line, and interlacing means that the odd lines are drawn first, and the even lines are "filled in" later. The two parts of the image are called fields, and are transmitted one after the other.

Telefunken invented the method in the 1920s. Today it is widely used for displaying images and video.

Example

First the odd-numbered lines are drawn,
one by one
the even lines
are drawn
Image composition as animation
The resulting image

Interlaced Video Media

Animation of the image construction for a cathode ray tube with interlacing method.
Interlacing artifacts. Note the lines protruding outwards from smooth surfaces due to the frames not lining up along the x-axis.
Interlaced scanning: display of odd (green) and even (red) scanlines, and line return blanking periods (dotted)
A GIF from HandBrake, demonstrating the difference between deinterlaced and interlaced images
When someone watches interlaced video on a progressive monitor with poor (or no) deinterlacing, they can see "combing" in movement between two fields of one frame.
Picture of a moving car tire, interlace combing reduced by realigning the even and odd field on the X axis. The other field has been moved 16 pixels right, reducing the combing on the bumper and the tire outline, but the hub cap that has turned between the fields has notable combing.