How is high definition differ from other formats?

Answer 1

High definition TV is the latest big thing in the television world and is an improvement in resolution over standard definition. Here are some numbers that explains it: Standard defintinion uses 480 lines (in the Americas) or 576 lines (Europe) to make up the television picture. The shape of SD pictures is normally 4 wide x 3 high although parts of Europe have now moved to 16 x 9 for standard definition (UK and Germany, primarily although other coutries are using 16 x 9 SD to a lesser extent) High definition uses 720 lines, 1035 lines or 1080 lines to make up the picture. All HD pictures are 16 x 9. The extra lines and the higher number of pixels that make up each image mean that about 5 times the amount of data is required compared to standard definition. This is where the better quality come in. Another difference is the way the picture is built up. SD signals use interlacing, a technique that delivers odd numbered lines in one pass, then even numbered lines in the next pass. Together, the two fields make a complete frame. Interlaced signals are identified with an "i" after the number. SD signals are therefore 480i and 576i. A complete image is shown 25 or 30 times each second. HD signals are currently 1035i, 1080i and 720p. The 720p signal is a progressive display, with the complete frame delivered in a single pass. There are 50 or 60 complete frames each second. Although the number of lines is less than the 1080i version, there are double the number of frames. 720p is therefore considered better for sports and fast moving images, while 1080i is preferred for movies - Broadcasters have varied opinions on the formats and applicaitons. Finally, 1080p is making an appearance. This is 1080 lines but with a full frame delivered 50 or 60 times each second. Broadcasters are looking at the technology but at present, they are a number of years away from adopting it as a standard.