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Originally Posted by beardtm Ok , this may be a noob question but id like to know the answer.
Can a tv show both interlace and progressive pictures?
If this TV can do 480p and 1080i, why cant it do 1080p? |
If we assume we're talking about a UK TV, then it might be capable of displaying 576p at 50Hz or 1080i at 50Hz, but not 720p at 50Hz.
576p at 50Hz means 28,800 lines per second. 1080i at 50Hz means 27,000 lines per second, so it's actually slightly easier in some ways. 720p would require 36,000 lines per second. 1080p would be 54,000 lines per second.
In fact, the numbers tend to be based on american or Japanese requirements, so you're looking at 480p rather than 576p, with 60Hz refresh rates. 480p is therefore 28,800 lines per second. 1080i is 32,400 lines per second (pushing it) and 720 is 43,200 lines per second - much harder. TVs are primarily designed for 60Hz areas, which makes 720p even tougher. 1080p would be an impossible 64,800 lines per second.
It's also to do with whether you can adjust the vertical position of the beam accurately enough. In 1080i mode the scanlines from each field will probably overlap slightly with those from the previous field. This isn't a problem in interlaced mode, because each line has already dimmed down almost to zero by the time the next field is drawn, but in 1080p mode each scan-line has to be distinct from the one next to it, otherwise the overlapping area gets excited twice, making it overbright and likely to burn.