HDTV (high definition television)
HDTV (high definition television) is a television display technology that provides picture quality similar to 35 mm. movies with sound quality similar to that of today's compact disc. Some television stations have begun transmitting HDTV broadcasts to users on a limited number of channels. HDTV generally uses digital rather than analog signal transmission. However, in Japan, the first analog HDTV program was broadcast on June 3, 1989. The first image to appear was the Statue of Liberty and the New York Harbor. It required a 20 Mhz channel, which is why analog HDTV broadcasting is not feasible in most countries.
HDTV and standard definition television (SDTV) are the two categories of display formats for digital television (DTV) transmissions, which are becoming the standard. HDTV provides a higher quality display with a vertical resolution display from 720p to 1080i. The p stands for progressive scanning, which means that each scan includes every line for a complete picture, and the i stands for interlaced scanning which means that each scan includes alternate lines for half a picture. These rates translate into a frame rate of up to 60 frames per second, twice that of conventional television. One of HDTV's most prominent features is its wider aspect ratio (the width to height ratio of the screen) of 16:9, a development based on research showing that the viewer's experience is enhanced by screens that are wider. HDTV pixel numbers range from one to two million, compared to SDTV's range of 300,000 to one million. New television sets will be either HDTV-capable or SDTV-capable, with receivers that can convert the signal to their native display format.
In terms of audio quality, HDTV receives, reproduces, and outputs Dolby Digital 5.1.
In the United States, the FCC has assigned broadcast channels for DTV transmissions. In SDTV formats, DTV makes it possible to use the designated channels for multiple signals at current quality levels instead of single signals at HDTV levels, which would allow more programming with the same bandwidth usage. Commercial and public broadcast stations are currently deciding exactly how they will implement their use of HDTV.
HDTV uses the MPEG-2 file format and compression standard.
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- You may also find information at the official Advanced Television Systems Committee (ATSC) Web site .
- For additional information about HDTV, see Public TV and the transition to digital HDTV on the Current Online Web site.