On HDTV

Published:2011/3/1 1:10:00 Author:LiuQiaoyan From:SeekIC

High-definition television refers to TV owning resolution virtually higher than traditional television systems . HD has one or two million pixels per frame , almost five times that of SD . Early HDTV broadcasting used analog techniques , but today it is digitally broadcasting by using video compression . Some personal video recorders with hard disk storage but without high-definition tuners are described as HD reasonably , which can be a cause of confusion .
The term high definition was used to describe a series of television systems originated from the late 1930s , however , these systems were only high definition when compared to earlier systems that were based on mechanical systems having as few as 30 lines of resolution . In the 1990s , because of technical and economic reasons , HDTV was not allowed to use more bandwidths than normal television ,that’s the reason why it didn’t enter the global market then .Early high-definition television commercial experiments required over four times the bandwidth of a standard-definition broadcast . Though great efforts had been made to decrease analog HDTV to about 2 times of the bandwidth of SDTV ,the television formats were still only assignable by satellite .In addition , in the early years , the record and reproduce of HDTV signal was a huge technical challenge . Japan remained the only country with successful public broadcast analog HDTV at that time , with seven broadcasters sharing a single channel . Digital HDTV broadcasting started in Japan since 2000 , and the analog service ended in 2007 .
At a minimum , the linear resolution of high-definition television is two times greater than that of standard-definition television , thus delivering clearer details than either analog television or regular DVD. The technical standards for broadcasting HDTV also handle the 16:9 aspect ratio images without using letterboxing or anamorphic stretching , thus increasing the effective image resolution .
The least form of HDTV that can be achieved is a 720p resolution matched with an HD-Converter DVD player together with component cables rather than an HDMI cable , which would provide bandwidth and include the audio all in one cable . Refresh rate refers the rate at which the screen refreshes every second . For example , 60 hertz would mean the TV screen is refreshed 60 times every second . Compare this to the highest form of HDTV . The true HD would be able to obtain 1080p resolution paired with a Blu-ray player or a HD-DVD player . Besides an HD-ready television set , other equipment may be needed to view HD television . For more information about LM3485MM .

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