NTSC vs. PAL: Difference & Explanation

Instructor: Lonny Meinecke

Lonny teaches psychology classes at King University, and has a bachelor's degree in IT and a doctorate in psychology.

In this lesson, we'll describe the differences between NTSC and PAL. We'll also explain some of the concepts beneath these two similar ways to deliver a video signal from one place to another in various parts of the world.

What are NTSC and PAL?

NTSC and PAL as two ways to deliver a moving picture to a display device, such as an old-fashioned television. A moving picture is composed of a series of frames, with each frame functioning like a still life painting. Since our mind wants to make sense of what the eye sees, we need to deliver the frames faster than the mind can separate them: around 24 frames per second. Since our mind doesn't like the idea of missing anything, it would rather mix these frames into one continuous motion than admit it can't keep up.

NTSC and PAL also deliver color information, along with the definition of a moving picture. You can think of this process as the ability to separate the shapes, or what we call luminance or brightness, from the color content, or chrominance, usually hue and saturation.

How Video Signals Get from Place to Place

One way we can deliver a moving picture to people is through television. In this medium, someone transmits the moving images as a signal, and the television's receiver accepts them as a series of horizontal lines. But as you might suspect, a signal and a picture are not the same thing. The signal is more like a code we can send through the air or across a wire, and at the far end, a device turns that signal into a meaningful sequence of pictures and sounds, which fool the eyes and ears.

But as there's a limit to how much information can be transmitted and processed each second, we usually have to split up the signal in clever ways - typically in half. In a progressive signal, we display all the picture lines at once. But in an interlaced signal, we only display every other picture line. Just like frames, interlacing fools the brain into thinking there aren't any gaps in the lines, even when there are.

Another way we can deliver a moving picture to people is from a storage device, like an optical DVD player or magnetic video tape. Usually, we can do this across a wire, such as a USB cable or similar piece of equipment; we can also use Wi-Fi or a Bluetooth system to transmit images through the air.

Differences between NTSC and PAL

First off, it's important to understand that the terms NTSC and PAL refer to analog video signals, not digital signals. An analog signal is a continuous wave that varies over time. An electrical digital signal is one in which bits of information are converted into a pattern.

The standard definition televisions from the good old days used analog signals. But, if we're talking about computers and high definition televisions, the new digital signals don't really use NTSC or PAL. For example, most computer DVD players can display either an NTSC or PAL movie. However, some DVDs may have a region code, meaning it can only be played on a DVD player that supports that geographic region, or one that is region-free.

Okay, that said, why NTSC and PAL? Well, NTSC is a way of delivering a color television signal in certain parts of the world, mainly in North America, parts of South America, and Japan. These areas use a similar electrical system; it's called 60 hertz, or 60 times a second. PAL is another way of delivering a color television signal, which along with SECAM, is used by the rest of the world. Those areas often use an electrical system based on 50 hertz (50 times a second). The main differences are summarized in the following table:

NTSC vs. PAL
NTSC vs PAL table

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