Video signal standards

AN2483

4/6

1.1

Composite/CVBS Interface

Composite video signals, which are also referred to as CVBS, are the most commonly used

analog video Interface. They combine brightness information (luma), colour information

(chroma), and synchronizing signals on just one cable. The connector is typically an RCA

jack.

Note:

brightness information in the signal is the instantaneous amplitude at any point in time. The

amplitude of the modulation is proportional to the amount of colour.

1.2

Y/C Interface

Y/C signals, which are often referred to as 'S-video' signals are less encoded than those of

Composite signals. The Y signal represents brightness and the C signal represents color. .

They are both carried over 2 separate wire pairs.

1.3

Computer signal Interfaces

Virtually all computer Interfaces use RGB format signals. Picture information is carried

separately by the three base components Red, Green and Blue. Synchronizing information

is typically carried as separate horizontal (H) and vertical (V) signals. The five signals, R, G,

B, H and V, are carried on one cable consisting of a shielded bundle of wires. Sometimes

the H and V synchronizes information is merged with one of the RGB signals, typically the

Green component, but this is becoming less common. This is referred to as "sync-on-

Green". In rarer cases, the sync information is on the Red or the Blue signal.

1.4

Component Interface

The component signal Interface is the best performer as it contains the least encoding. The

signals exist in a nearly native format. They use three pairs of wires that typically include a

luma (Y) and two color-difference format signals on an RGB format signal. Color-difference

formats are normally used in TV applications, whereas an RGB format is almost always

used in computer applications. In addition to the brightness, the Y signal also contains

synchronizing information. The color-difference signals contain R (Red) minus the Y signal

and B (Blue) minus the Y signal. The theory behind this combination is that each of the

basic R, G and B components can be derived from the color-difference signals. Common

variations of color-difference signals include:

●

Y, B-Y, R-Y: Luma and colour-difference signals

●

Y, Pr, Pb: Pr and Pb are scaled versions of B-Y and R-Y. Commonly found in high end

consumer equipment.

●

Y, Cr, Cb: Digital-signal equivalent to Y, Pr and Pb.

●

Y, U, V: Not an Interface standard. These are intermediate, quadrature signals used in

the formation of composite and Y/C signals. Sometimes, they are incorrectly referred to

as "component Interface".