1080p HDTV is the holy grail of high definition television. Most
fans of HDTV are aware of the 1080i and 720p formats, but fewer
are aware that a third specification, 1080p exists.
You may know that 1080i refers to 1080 lines of vertical
resolution interlaced. This means that instead of 30 frames a
second, the TV displays 60 fields per second, where each field
contains alternate lines of the picture. Because the fields are
refreshed so quickly, your brain interprets the signal as 30
full frames per second. 720p means 720 vertical lines of
progressive scan video where every frame of the signal is
displayed in its entirety, giving a higher-quality, film-like
appearance to the picture. Most HDTVs or HDTV-ready TVs support
either 720p or both 1080i and 720p, very few support 1080p HDTV.
Part of the reason for this is that very few broadcasters want
to broadcast 1080p signals. The reason for that is that 1080p
requires significantly higher bandwidth than either 1080i or
720p. And for broadcasters, bandwidth is a precious commodity.
Using up more bandwidth for one signal means that there is less
room for other channels. So in many cases, opting for a 1080p
signal would mean dropping or degrading other channels. Is 1080p
HDTV important? Well, yes and no. Not all video footage benefits
greatly from progressive scan. Sports broadcasts and action
movies look better at 720p than 1080i because there is lots of
fast movement and the interlacing in 1080i is sometimes
noticeable, reducing the quality of the picture. Movies and TV
shows where there is not a great deal of fast action look better
at 1080i than 720p because the higher resolution has a greater
impact on quality than the progressive scan, which has little
effect where there is only a small difference in the image
between frames. So, while 1080p HDTV is the best of both worlds,
the cost in terms of bandwidth, is very high compared to the
benefit for most people most of the time.
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