HDTV Receivers, Tuners

High-definition video generally refers to any video system of higher resolution than standard-definition (SD), i.e. NTSC, PAL and SECAM. more...

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It is important to note the difference between general purpose high-definition video as discussed in this article, and its specific applications in television (HDTV), professional acquisition (HDCAM, HDCAM-SR, DVCPRO-HD & D5-HD), consumer acquisition (HDV) and optical disc systems (Blu-ray and HD-DVD).

History

Original HD specifications date back to the early 1980s, when Japan developed an 1125-line TV standard operating at 30 frames per second (fps). Japan presented their standard at an international meeting of television engineers in Algiers in 1981 and Japan's NHK presented its analog HDTV system at Swiss conference in 1983. The NHK system was standardized in the United States as SMPTE (Society of Motion Picture and Television Engineers) standard #240M in the early 1990s.

Historically, the term high-definition television was used to refer to television standards developed in the late 1930s to replace the early experimental mechanically-scanned systems that ranged from 15 lines to about 220 lines of resolution. John Logie Baird of the UK was a major proponent of these early mechanically scanned systems, but they were quickly replaced by all-electronic systems developed by engineers such as Philo T. Farnsworth, Vladimir Zworykin and the EMI team including Alan Blumlein under Isaac Shoenberg.

The United Kingdom was the first to start regular broadcast television - the BBC Television Service - in 1936 from Alexandra Palace, initially with a 240-line, 25 frames-per-second (fps) mechanically-scanned system by Baird Television Limited alternating with a 405-line Marconi-EMI interlaced system at 50 fields per second (each frame consisting of two fields). The Baird system was dropped after the end of 1936. This was referred to as the world's first scheduled 'high definition' television service, and thus the term must be regarded as originally identifying systems offering 240-line resolution or better. The Marconi-EMI specification went on to be adopted across Europe as CCIR System A.

In the United States, the National Television System Committee (for which the NTSC standard is named) standardized on 525 lines at 30 fps in 1940, with regular broadcasts starting on July 1, 1941. The NTSC standard was updated to include first a non-compatible 441-line color standard in 1950, which was then replaced by a compatible 525-line, 29.97fps color standard approved in 1953 and used to this day. PAL (Phase Alternating Line) was developed in the late 1950s with 625 lines at 25fps and went on the air in 1964. SECAM (SEquential Colour Avec Memoir) was developed by the French as a competitor to PAL, also using 625 lines and 25fps. SECAM was adopted by France and its colonial territories, as well as the Soviet Union, the Peoples' Republic of China, and their satellite communist governments.

Read more at Wikipedia.org