What is HDTV?Written by Gary Davis
What is HDTV? By Gary Davis Dish-Network-Satellite-TV.wsWebmasters: You may reprint this article in its entirety, providing you leave Byline and About Author sections intact, including links to Dish Network Satellite TV. High Definition TeleVision is what HDTV literally means. But high definition compared to what? In order to answer this question, we need to know a bit about original analog TV system. Analog TV 30 images per second (in Europe 25) are shown by normal analog TV sets. It does this by writing image lines horizontally, 525 lines in one image (In Europe 625) on screen. The number of pixels on one line is about 500. This would be a definition of 500 pixels per line by 525 (or 625) lines. Compared to modern computer monitors this is really bad. Even lowest resolutions monitors have higher resolutions (640 x 480) than an analog TV. HDTV - High Definition TeleVision HDTV is high resolution Digital TeleVision (DTV) combined with Dolby Digital Surround Sound (AC-3). There are 18 different formats defined for Digital TV of which 6 are considered to be HDTV: | Active Lines Per Picture | Pixels Per Line | Aspect Ratio | Frame Rate | Scanning Approach | The difference between Progressive and Interlaced is not difficult. It has to do with how one image is built up. With interlaced technology odd lines are shown first and then even lines are shown. The lines are shown in this order: 1,3,5,….521, 523, 525, 2, 4, 6,…. 522, 524, 1, 3, etc. This means that every 1/60 of a second a half image is shown. This often results in flickering, which can be tiring for eyes. Progressive technology manages to show a whole image every 1/60 of a second, resulting in a much smoother picture. How Is HDTV Better? - Normal TV has a resolution of about 210.000 pixels. An HDTV screen has a resolution of upto 2.000.000 pixels, which gives up to 10 times more picture detail.
| | Analog vs Digital Transmission Written by Gary Davis
Analog vs Digital Transmission By Gary DavisDish-Network-Satellite-TV.ws Webmasters: You may reprint this article in its entirety, providing you leave Byline and About Author sections intact, including links to Dish Network Satellite TV. Remember old days of analog TV, radio, etc. Most of us do unless you’re really young. And still today there are plenty of analog systems in use. Normal radio still uses analog transmission. But digital age has begun and more and more we will use digital systems rather than analog systems. Digital transmission systems have many advantages over analog transmission systems, like higher quality of audio and video. How come digital systems can transmit higher quality signals than analog systems? The truth is that they don’t. They just use some tricks to eliminate noise. Analog Transmission Systems When something like video and audio, is recorded by an analog system, recording has a certain quality. This recording (when done professionally) has a very high quality. When recording is transmitted it is modulated directly to a carrier wave, which is then transmitted through air, cable, via satellite, etc. During this transmission, carrier and modulated signal will loose amplitude (power) and due to interference noise is introduced to carrier and its modulated signal. The result will always be a received signal that has a lower quality than transmitted signal. Hence, modulated signal, recording, will also be of lower quality than original. Analog transmission systems are unable to maintain quality original has. Digital Transmission Systems In digital world recording can be transmitted to another place without loosing any quality. An exact copy of original recording is transmitted. So how come that digital transmission systems don’t loose quality when transmitting a signal?
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