Video Fundamentals
Interlaced Scanning

All composite video systems display the video image on a TV screen using an interlaced scanning technique. The following figure shows the interlaced scanning concept.

The analog video signal includes synchronization pulses that control the scanning line-by-line from left to right and field-by-field from top to bottom. The pulses that control the line-by-line scanning are called the horizontal synchronization pulses (Hsync). The pulses that control the vertical scanning are called the vertical synchronization pulses (Vsync).

Two interlaced fields compose a complete frame. The first field, called the odd field, scans the odd lines of the video image. The second field, called the even field, scans the even lines of the video image. The process repeats for every frame.