Interlaced video facts for kids

Interlaced video is a clever way to show pictures and videos on screens. Imagine a screen drawing a picture: instead of drawing every single line from top to bottom at once, interlacing draws the picture in two quick steps. First, it draws all the odd-numbered lines (like 1, 3, 5, etc.). Then, it goes back and fills in all the even-numbered lines (like 2, 4, 6, etc.).

This method makes the picture look smoother and clearer, almost like it's doubling the detail you see. Each of these two parts (the odd lines and the even lines) is called a field. They are sent one right after the other, so fast that your eyes see them as one complete, moving picture.

A company called Telefunken first came up with this idea in the 1920s. For many years, interlaced video was used everywhere, especially for older televisions and video recordings.

How Interlacing Works

Interlacing helps screens show a lot of information quickly. Instead of waiting for a full picture to be drawn line by line, you get half a picture very fast, then the other half fills in. This makes motion look more fluid, which was very important for older TV technology.

Think of it like drawing a picture with a pencil. If you draw all the main outlines first, then go back and add all the details, the picture appears faster than if you drew every single line perfectly from start to finish.

Fields: The Two Halves of a Picture

Each complete picture you see on an interlaced screen is made up of two fields. The first field contains all the odd-numbered lines of the image. The second field contains all the even-numbered lines. These two fields are shown one after the other, very quickly. For example, a TV might show 60 fields per second, which means it's showing 30 complete pictures per second (30 odd fields + 30 even fields).

This quick switching between fields helps create the illusion of smooth movement, especially when watching fast-paced action like sports.

Example

This gallery shows how an interlaced image is built up step by step. You can see how the odd lines appear first, followed by the even lines filling in the gaps.

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  First the odd-numbered lines are drawn,

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  one by one

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  the even lines

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  are drawn

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  Image composition as animation

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  The resulting image

Interlacing Today

While interlacing was very common for a long time, especially with older TVs and DVD players, newer technologies often use something called "progressive scan." Progressive scan draws every single line of the picture in order, from top to bottom, all at once. This is why you might see "1080p" on new TVs, where "p" stands for progressive.

However, interlaced video is still around, especially in older video recordings and some broadcast television. Devices like modern TVs and computers have special technology to "deinterlace" these older videos, making them look good on progressive screens.

Related Topics

• interpolation - This is a math idea about guessing missing data values. It's sometimes used in video to help fill in details.

Images for kids

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  Animation of an interlaced TV.

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  A screenshot from HandBrake, showing the difference between deinterlaced and interlaced images.

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  When someone watches interlaced video on a progressive monitor, they can sometimes see "combing" in movement.

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  A picture of a moving car tire, where "combing" has been reduced by adjusting the image.

See also

In Spanish: Exploración entrelazada para niños