What is NTSC (National Television Standards Committee)?

NTSC (National Television Standards Committee) is an encoding/transmission system for analog color television, which was developed in the United States in the 1940s and is widely used in the United States and Japan.

What is NTSC (National Television Standards Committee)?

What is the NTSC Video Format?

A variant of NTSC is the PAL video system used in Europe and some countries in South America.

The NTSC television system consists of an extension of the North American monochrome system, its development started in the late 1930s by CBS (Columbia Broadcasting System). However, this development was approved by the FCC in the 1950s.

This system consists of the transmission of approximately 30 images per second consisting of 486 visible horizontal lines, each up to 648 pixels.

To make better use of bandwidth, the video uses an interlaced mode at 60 areas per second. This mode is a 4.25 MHz band that converts to a resolution of 30 frames and approximately 270 vertical lines with a total of 525 horizontal lines.

Features

The NTSC format consists of the transmission of 29.97 frames of video in interlaced mode with a total resolution of 525 lines and a video refresh rate of 30 frames per second and 60 fields of alternate lines.

To understand and properly assess the current challenges in an electronic color TV system such as NTSC, it is important to consider the different drawbacks that were originally proposed to overcome when building this system.

The current black and white receivers must receive the signals in color and reproduce them in black and white. Color receivers must pick up black and white signals and accurately reproduce them in black and white.

Color receptors must pick up color signals and accurately reproduce them in color.

The bandwidth of the system must be the same in both versions, and the picture tube used must be able to reproduce images alternately in color and black and white.

To obtain compatibility, the color components and black/white split of the signals had to be studied.

Both components are modulated on the same RF carrier of the channel, and then the luminance signal generates components such as the chrominance signal, the audio signal, and the reference signal to reconstruct the suppressed subcarrier in phase and in a very tightly controlled amplitude in a quadrature modulation process in a single suppressed subcarrier.

It is also important to note that for the highest color accuracy, the chrominance signal is transmitted in two components, (R-Y) and (A-Y).

Both are in quadrature and are transmitted with a 90-degree phase shift. They are modulated on the same chrominance subcarrier.

All these signals must be transmitted and received on a single 6Mhz channel at the same time, and the video carrier should be spaced 1.25 MHz above the lower limit for the channel and 0.25 MHz above the audio carrier upper limit. As a result, the image and sound carriers are always 4.5 MHz.

The color subcarrier is located 3.579545 MHz above the image carrier. Commercial television broadcasting now uses a sideband transmission for image information. The lower sideband is 0.75 MHz wide and the upper sideband is 4 MHz.

As a result, the lower frequencies of the video are associated with the higher frequencies of the video. The bandwidth of the FM voice carrier is approximately 75 kHz.

Amplitude and phase modulation is used to encode color information on the 3.579545 MHz color subcarrier.

To ensure compatibility with the black and white system, the two chrominance components are configured with a quadrature modulation on the 3.579545 MHz subcarrier, while maintaining the black and white monochrome signal as the luminance component of the color image.

Since the demodulation of the chrominance components is synchronous, a color shift is sent at the beginning of each line, so it is known as a phase reference sinusoidal signal.

Sometimes the color burst level is used to correct for variations in chrominance amplitude in the same way as using the sync level to correct the quality of the entire video signal.

Advantage and Disadvantage

NTSC systems work at 60Hz, preventing the classic flickering of the PAL system operating at 50Hz/25FPS, making eyes less tired.

Transmission and interference problems tend to degrade the quality of the picture on the NTSC system. This problem shifts the phase of the color signal and sometimes it loses color balance as soon as the frame is captured.

This issue makes it necessary to include a shade control. This is not necessary for PAL or SECAM systems.

Another of its drawbacks is it’s limited to only 525 lines of vertical resolution, which is the lowest of all television systems.

This resolution limit gives a lower quality image than can be sent on the same bandwidth as other systems.

Digital System

Since the importance of color coding used in devices such as digital televisions, modern video game consoles and DVDs decreased, there is no longer any difference between systems.

The meaning of NTSC is reduced to a number of lines equal to 480 horizontal lines, with a refresh rate of 29,970 images per second, or double per second for interlaced images.

Broadcast System

A television channel broadcasting with the American standard NTSC-M uses 6 MHz bandwidth to contain the video signal, audio signal, and some guard bands.

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