Hdtv (high Definition Television ) & Digital Tv Introduction

HDTV (high definition television ) & Digital TV Introduction

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HDTV (high definition television ) & Digital TV Introduction By Diego Villa Created 09/21/2008 - 18:21

Technology aspect ratio digital tv modulation video compression High-Definition Television (HDTV) is a digital television system with greater resolution than analog television systems (NTSC, PAL/SECAM) and standard-definition television (SDTV) and Digital TV is more flexible and efficient than analog television. The big bandwidth requirement for HDTV necessitates the development of video compression techniques like MPEG-1, MPEG-2 and MPEG-4. With MPEG-2 compression, a typical 6MHz TV bandwidth can contain up to 4 SDTV channels or 1 HDTV channel. Early Developments: Before HDTV was developed, there were two major analog TV standards. One is NTSC developed in the US which runs at 525 lines at 60 Hz. The other is PAL/ SECAM developed in Europe which runs at 625 lines at 50 Hz. Both standards use interlacing and 4:3 aspect ratio. There were early attempts to develop analog HDTV. The most succesful was Japan’s MUSE which was launched in the 1990s. It has an aspect ratio of 5:3 and 1125 interlaced lines at 60fps. It requires bandwidth greater than the traditional systems and was eventually turned off in 2007. Digital TV: The big bandwidth requirement for HDTV necessitates the development of digital video compression. MPEG-1 was initially developed and later MPEG-2 which became the defined transport stream in the DVB standard. Later developments in compression technology saw the rise of MPEG-4 with many variants, the most popular of which is the H.264 standard. With MPEG-2 compression, a typical 6MHz TV bandwidth can contain up to 4 SDTV channels or 1 HDTV channel. Aside from the developments in video compression, different digital TV transmission standards were also developed. In the US, the ATSC standard was developed based on 8-VSB modulation. In Europe, it was DVB-T and in Japan, ISDB-T. The two latter standards are both based on COFDM modulation. In 1983, the ITU set up a working group to come up with a common standard for HDTV. There were thorny issues especially on the frame rate which is 25 fps for countries with 50Hz AC mains and 30 fps for those with 60Hz AC mains. There was agreement however on the aspect ratio which became 16:9, the mean between the traditional TV 4:3 aspect ratio and

21.09.2008 11:34

HDTV (high definition television ) & Digital TV Introduction

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cinema’s 2.35:1. Popular HDTV and SDTV Formats:

The above three formats are available in different variants according to frame rate used – 24fps, 25fps, 30fps, 50fps and 60fps. Future Developments: NHK of Japan started development of Super Hi-Vision technology and showed prototype in 2002. Its resolution is far better than HDTV at 7680 x 4320 or around 16x greater. But because of the huge amount of data involved in this format, along came the requirement for cameras, transmission technology and display media that can handle such content. It will take some time before commercial deployment of this format takes place. Trademarks

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21.09.2008 11:34