Evolution of HDTV
After years of research, NHK of Japan first developed the modern system of HDTV, and wide screen sweep of 1,125 lines 60 Hz image, making even the film quality of 35mm film.
With increasing interest in high definition, in 1987 the Federal Communications Commission FCC in the USA led to the formation of the Advisory Committee on Advanced Television Service (ACATS, for its acronym in English), responsible for selecting a single standard advanced television terrestrial broadcasting for the U.S., a system standard for high definition television can be transmitted simultaneously with the current NTSC signal, and therefore restricted the scheme to use 6 MHz channel bandwidth.
On 1 June 1990, General Instruments Company of San Diego, California, proposed a land-based HDTV digital HDTV, thus marking a watershed in the history of television. The digital era began, marking the end of analog television and imposing huge industrial challenge to completely reinvent television.
In a concerted effort and adherence to national strategies for market dominance, the U.S. government proposed major manufacturers working each in its proposal to pool their efforts in a "Grand Alliance" to propose a single television system digital HD, with "best of the best-in terms of technologies for each of the participants: AT & T (Lucent), MIT, General Instrument, Zenith Electronics Corporation, North American Philips, David Sarnoff Research Center (RCA), and Thompson Consumer Electronics.
The system of HDTV HDTV proposed would have two main modalities: 1,080 active lines with 1,920 pixels per line square, with interlaced scanning of 59.94 and 60 frames per second, and 720 active lines, with 1.280 pixels per line, with progressive scan 59.94 and 60 frames per second. Both formats also operate with progressive scan 30 and 24 frames per second for the transmission of programs filmed.
The Grand Alliance system employs video compression and transport systems MPEG-2, Dolby Digital (AC-3), and modulation 8-VSB vestigial side band. With this, we developed a widescreen system, relative width / height ratio of 16:9, with five times more picture quality than standard definition television than 480 active lines and relation width / height ratio of 4:3. All this squeezed into a narrow channel TV 6 MHz bandwidth.
Despite having achieved this feat of electronic engineering, the FCC bowed to the interests of the computer industry, and asked in 1995 to include digital standard in various formats under standard definition television (SDTV for short in English) of 480 lines with progressive scanning and interlaced (see Table 5).
Available formats for digital television, according to Table III of the ATSC standard.
Finally, on 24 December 1996, the U.S. government adopted as mandatory standard for terrestrial transmission of digital television and HDTV, the SDTV and HDTV standard for the ACATS, documented by the Committee on Advanced Television Systems (ATSC, by its initials in English). This standard, known as the ATSC standard, left out as regards the imposition of the scanning type (only progressive or interlaced only) in order to achieve, once again, the consensus with the group of interest in the industry computing.
Since the adoption of the ATSC standard, the government body responsible for spectrum allocation in the U.S. agreed to start free allocation of digital channels to all dealers of analog TV channels, in order to stimulate the simultaneous digital transmission programming. Also, set the major goal in this transition to digital transmission, which returns the NTSC analog channel at the end of the transition period, a goal that was set the year 2006 reasonable date for completion of transmission service NTSC .
With the ATSC standard, you will need to make decisions about the quality of the image to be transmitted to the user, ie, if you send a certain standard definition SDTV program, using the digital channel for simultaneous transmission of multiple programs at all "SDTV multiplex," or whether you will be sent with the highest quality available high-definition HDTV, thus becoming more competitive. The high-definition broadcast HDTV would be the preferred medium for sports events and programming in PrimeTime. In this regard, several U.S. television networks, cable operators and DBS programmers have announced their intention to provide programming services to HDTV HDTV by the end of 1998, and at least in the top ten markets in the country (including DirecTV and HBO).Today, the limiting factor for achieving high definition at home, is the lack of television screens can handle. Month to month announced improvements, including the recently offered by Fujitsu, have developed around a flat screen 42-inch wide-screen 16:9 ratio with 1.024 pixels per line, only one step of full high definition. However, the full potential of the standard for HDTV HDTV requires more than they can deliver the best television screens today, so this revolution in digital television technology is triggering the start of a technological niche research and industrial development in television display manufacturers.
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