AN2483

Video signal standards

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Video signal standards

The visual resolution of a video signal or display is the amount of detail that can be seen.

This is different from the resolution format of a signal or display. For example, in a computer

application, an XGA (seeTable 1) resolution has a format resolution of 1024 horizontal pixels

and 768 vertical pixels (lines), and is the implied visual resolution.

There are many different kinds of video signals, which can be divided into either television or

computer types. The format of signals varies from country to country. In the United States

and Japan, the NTSC format is used. HDTV/SDTV are the High Definition TV and Standard

Definition TV. VGA and XGA are PC video resolutions. In Europe, the PAL format is

common. PAL stands for Phase Alternating Line. PAL is an improvement on NTSC format.

SECAM is used in France and stands for sequential coleur avec memoire (with memory).

Although all the above standards use the same basic scanning system and represent colour

with a type of phase modulation, they differ in several ways, including specific scanning

frequencies, number of scan lines, and colour modulation techniques.

The three basic video signal formats in order of decreasing quality are:

1.

Composite or CVBS Interface(Colour, Video, Blanking, and Synchronization/also called

Composite Video Baseband Signal), which uses one wire pair.

2.

Y/C or S-video Interface, which uses two wire pairs.

3.

Component Interface, which uses three wire pairs. In order of increasing quality, the

composite (or CVBS) which uses one wire pair;

In order of increasing quality, the composite (or CVBS) which uses one wire pair; Y/C (or

Svideo), which uses 2 wire pairs; and component, which uses 3 wire pairs are the 3 basic

video signal formats. Each wire pair consists of a signal and ground. The three Interfaces

differ in the level of information they can combine (encode). More encoding typically

degrades the quality but allows the signal to be carried on fewer wires. Component has the

least amount of encoding, whilst composite has the most.

Table 1.

Video signal comparison

Video format

NTSC

PAL

HDTV/SDTV

VGA

XGA

Description

Television format for

North America and

Japan

Television format for

most of Europe and

South America

High definition TV

/standard definition

TV

PC video

resolutions

PC video

resolutions

Vertical resolution

format (visible

lines/frame)

Approx 480 (525

total lines)

Approx 575 (625

total lines)

1080 or 720 or 480;

18 different formats

480

768

Horizontal

resolution format

(visible pixels/line)

Determined by

bandwidth, ranges

from 320 to 650

Determined by

bandwidth, ranges

from 320 to 720

1920 or 704 or 640;

18 different formats

640

1024

Horizontal rate

(KHz)

15.734

15.625

33.75-45

31.5

60

Vertical frame

rate(Hz)

29.97

25

30-60

60-80

60-80

Highest frequency

(MHz)

4.2

5.5

25

15.3

40.7