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Digital video

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Digital video is an electronic representation of moving images. It uses encoded digital data to represent visual information. This is different from analog video, which uses analog signals. Digital video works by displaying a series of digital images in rapid succession. These individual images are called frames. The speed at which these frames appear is the frame rate. It is usually measured in frames per second. Common frame rates include 24, 25, 30, or 60 frames per second.

Each frame in a digital video is made of tiny dots called pixels. The color of every pixel is represented by a fixed number of bits. For example, 8-bit color captures 256 different levels of a color. Digital video offers many advantages over analog systems. It is easy to copy, multicast, share, and store. One major benefit is that digital video can be reproduced with no degradation in quality. When analog sources are copied, they experience something called generation loss. This means the quality drops each time a copy is made.

Blu-ray disc2
Blu-ray disc2

To create digital video, cameras use specialized image sensors. The basis for these cameras is the metal–oxide–semiconductor, or MOS, image sensor. The first practical semiconductor image sensor was the charge-coupled device, or CCD. Willard S. Boyle invented the CCD in 1969. His work in physics was so important that he won a Nobel Prize. In the 1990s, the CCD was followed by the CMOS active-pixel sensor. These sensors allow cameras to turn light into the digital data needed for video.

Pavek Museum - TV Camera
Pavek Museum - TV Camera

Developing digital video required new ways to handle large amounts of data. In the 1970s, pulse-code modulation, or PCM, helped start digital video coding. However, standard-definition content required very high bit rates of 45 to 140 Mbit/s. By the 1980s, the discrete cosine transform, or DCT, became the standard for compression. Compression is a way to make video files smaller. The first coding standard was H.120, created by the CCITT in 1984. This was not very practical because it used an inefficient algorithm called differential pulse-code modulation, or DPCM.

Sony logo
Sony logo

The H.261 standard was the first practical video coding standard because it used DCT compression. Since then, DCT has been used in all major video coding standards. In 1991, the Motion Picture Experts Group developed MPEG-1 to compress VHS-quality video. This was followed in 1994 by MPEG-2, which became the standard for DVDs and standard-definition digital television. In 2003, H.264/MPEG-4 AVC was released. This is currently the most widely used video coding standard. It is used by 91% of video developers. The current generation is HEVC, also known as H.265, introduced in 2013. HEVC is used by 43% of developers.

Digital video history includes important commercial milestones. Sony introduced the D1 format in 1986. This format recorded uncompressed standard-definition component video. Because it required three cables, it was mostly used by large television networks. In 1988, Sony and Ampex co-developed the D2 format. D2 recorded video in ITU-601 format without compression. The main difference was that D2 used composite encoding. This meant it only needed a single cable. This made D2 a perfect fit for many television facilities. D2 was also used to master laserdiscs.

Betacam SP camera
Betacam SP camera

The shift to digital has changed the entire film industry. In 2013, major films shot on digital overtook those shot on film. Since 2016, over 90% of major films have been shot on digital video. In 2018, only 24 major films were released using 35mm film. Today, companies like Sony, Panasonic, Canon, and Arri offer many choices. Some cameras are designed specifically for the digital cinema market. These high-end cameras offer more resolution and dynamic range than standard broadcast cameras.

Cinemascope 4 perf 35 mm film
Cinemascope 4 perf 35 mm film

Digital video is now part of many different systems. It is used in digital television (DTV) to transmit video from networks to consumers. DTV is faster and offers more options than the analog methods used before the 1950s. Digital video is also used in healthcare to track infant heart rates and oxygen levels. In schools, students and teachers use it for many different purposes. Even security systems have changed. Closed circuit television (CCTV) now uses digital video recorders, or DVRs, to store evidence.

Sony Handycam DCR-VX700E MiniDV camcorder
Sony Handycam DCR-VX700E MiniDV camcorder
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File:Betacam_SP_camera.jpg
Betacam_SP_camera.jpg
File:A_todo_o_nada_Chile_Studio_(20200130_194157).jpg
A_todo_o_nada_Chile_Studio_(20200130_194157).jpg
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Sony_logo.svg
File:Pavek_Museum_-_TV_Camera.jpg
Pavek_Museum_-_TV_Camera.jpg
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File:Cinemascope_4_perf_35_mm_film.svg
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File:Video_tape_B-Format_(6498660779).jpg
Video_tape_B-Format_(6498660779).jpg
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Blu-ray_disc2.png
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