How Video Works - pág.16

Synchronizing an image is a critical part of the video process.

Synchronizing Signals

As video moves from source to monitor, it is a series of electrical impulses. Whether analog or digital, by wire, fiber optic or through the air, the pulses that make up the picture follow each other one after the other. If you could freeze time then look at individual points along the signal path, you could measure individual voltages or find the bits to make pixels. The transmission medium then is a single dimension. It has only length, but not depth or width.

On the other hand, a single frame of video has both width and height. You can find a specific pixel from the signal path at some point between the left and right of the screen. It also is a measurable distance from the top and bottom. So a frame is a two-dimensional
image. Motion pictures are made of the two-dimensional frames being shown one after the other. You can think of this as a third dimension.

Synchronizing signals provide the information to drive the scanning that changes the three dimensional images to a serial form for transmission and storage. The same signals can then be used to rebuild the pictures so they can be viewed.

When mul TIP: le sources are used in the same system, like the cameras in a TV studio, each must start their scan at the same exact moment. While most of video process has transitioned to digital signals, analog sync is still commonly used throughout studio and remote production. Although digital devices process sync in a different manner, the same sync signals described below are still used to co-ordinate the process.