Nepedia
Back to Discover
Advanced Reader
💻

High-definition television

technology Maturity 9-11 Next article →

High-definition television, or HDTV, is a video system designed to provide much higher image resolution than older technologies. Resolution refers to the amount of detail visible in a picture. By using a much larger number of pixels, HDTV creates a clearer and more detailed image for the viewer. This technology is now the standard format for most broadcasts. It is used in terrestrial broadcast television, cable television, and satellite television.

Digital broadcast standards
Digital broadcast standards

The quality of an HDTV image depends on how the pixels are arranged and scanned. One common format is 720p, which contains 921,600 pixels. Another format is 1080i, which uses an interlaced scan to show approximately 1,040,000 pixels. Interlaced scanning draws the image in specific patterns to manage data. A more advanced format is 1080p, which uses a progressive scan. Progressive scan draws the entire image at once, resulting in about 2,073,600 pixels. This method provides better rendering of fast motion and reduces screen flicker. When transmitting at two megapixels per frame, HDTV offers about five times the pixel count of standard-definition television (SDTV).

Different parts of the world utilize various digital television standards to transmit these signals. These standards ensure that devices can correctly receive and display the video data. In North America, the primary standard is ATSC. Much of Europe, Asia, Africa, and Australia use the DVB standard. China and some neighboring countries use the DTMB standard. In South America and Japan, the ISDB standard is used, though it exists in two incompatible variations. In South Korea, mobile devices often use the DMB standard.

Digital broadcast standards
Digital broadcast standards

The history of high definition began much earlier than most people realize. The term was used as early as 1933 to describe new television systems. In 1936, the British launched high-definition trials using the Baird 240 line sequential scan and the Marconi-EMI 405 line interlaced system. The Baird system was discontinued in 1937. In 1938, France introduced a 441-line system. By 1941, the United States adopted the NTSC 525-line system. France even introduced an 819-line system in 1949, which was very high resolution for its time. However, this system required significant bandwidth for color versions, which limited the number of available channels.

Modern analog HDTV development was led significantly by Japan. The Japan Broadcasting Corporation, known as NHK, began researching video and sound interactions in 1964. By 1972, they developed the NHK Color system, which featured 1,125 lines and a 60 Hz refresh rate. In 1979, NHK developed the Hi-Vision consumer system. This used a method called MUSE, or multiple sub-Nyquist sampling encoding, to transmit the signal. While MUSE required twice the bandwidth of the older NTSC system, it provided four times the resolution. Japan began the world's first daily high-definition satellite test broadcasts on June 4, 1989.

The transition to digital HDTV in the United States involved many different organizations. In 1982, the Advanced Television Systems Committee (ATSC) was formed to develop new standards. By 1993, the Digital HDTV Grand Alliance was established to finalize these systems. This group included companies like AT&T Bell Labs, Philips, and Zenith, as well as the Massachusetts Institute of Technology. The first public HDTV broadcast in the U.S. occurred on July 23, 1996, in Raleigh, North Carolina. A major milestone happened on October 29, 1998, when the ATSC system had its public launch during astronaut John Glenn's return to space.

High-definition technology has evolved through constant competition between companies and nations. Throughout the 20th century, engineers worked to create systems that were higher definition than the last. This race has moved into the 21st century with the development of 4K, 5K, and 8K systems. These newer technologies continue to increase the number of pixels and the clarity of the image. As digital standards like DVB and ATSC continue to manage how we receive video, the quest for even higher resolution remains a central goal in media technology.

661 words

Where will your curiosity go next?

Keep exploring at your chosen reading level.

🖼️ Images & Media (1)
File:Digital broadcast standards.svg
Digital broadcast standards.svg
More to explore

What is Nepedia?

A free, ad-free encyclopedia for children. Every article is written at five reading levels, so the same page works for a five-year-old and a fifteen-year-old — use the level switcher above to see this one change. No account needed to read.