HDTV stands for High Definition Television. It is a digital format
that provides an extremely high-resolution picture, accompanied
by amazing digitally enhanced sound, all presented in glorious widescreen.
Simply HDTV contains approximately five times more information or
detail on screen than standard definition TV.
In the past, we have had no reason to be concerned with lines of
resolution, because all televisions displayed the same resolution.
This standard is known as PAL broadcasting system and was capable
of showing 576 lines on screen. In comparison, High Definition TV
increases those standard 576 lines to either 720 or 1080. Adding
almost twice the amount of lines multiplies the amount of pixels
(the small dots that create the picture). Having more pixels on
your screen greatly improve the sharpness of your pictures.
What are the benefits of High Definition?
With HDTV, pictures look much sharper and clearer than ever before.
Colours are richer and the image appears to have more depth, as
if you were looking out of a window into "real life".
In addition, HDTV screens use an aspect ratio of 16:9 – that is,
16 units wide for every nine units deep. This is proportionally
much wider than the traditional screen aspect ratio of 4:3, making
it particularly suited to the viewing of movies, which are shot
in a much wider aspect ratio to suit cinema screens.
HD formats in the UK
The main HDTV standards used by broadcasters are 720p,
1080i and 1080p. The number refers
to the number of lines that make up each frame, whilst the letter
represents how those lines are displayed on screen. The 'P' stands
for Progressive and 'I' stands for Interlaced.
- 720p will show 50 frames per second (fps) each with 1280 by
1024 pixels
- 1080i has a 1920 by 1080 pixel resolution and is transmitted
at 50 half frames per second (25 frames split over 50 fields)
- 1080p will show 50 frames per second (fps) each with 1920 by
1080 pixels
Interlaced - means the image comprises of two
different parts that 'interlace' or flash rapidly between each other
to form a complete image. Because the interlacing happens so fast,
the eyes don't register the fact that only field is on-screen at
any given time and the brain fills in the missing data.
Progressive - with progressive scan, the entire
frame is painted onto the display all at once - essentially creating
one continuous field. In the time it takes an interlaced display
to scan each of its two fields once, a progressive display will
scan the complete frame twice. When watching video that contains
a great deal of movement, a progressive scan display does a good
job of rendering that movement seamlessly without creating motion
errors or glitches.
What does 'HD ready' actually mean?
Whenever you see the HD ready badge, you can be sure that the TV
meets the standard criteria outlined by EICTA. They have defined
a basic set of requirements for 'HD ready' displays. The requirements
demanded to meet the standard are:
- A native resolution of at least 720 lines in widescreen format
- The ability to accept HD input via DVI or HDMI and Component
- Must accept 720p 50, 720p 60, 1080i 25 and 1080i 30 input signals
- The DVI or HDMI input supports HDCP content protection
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