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High Definition, Blu-Ray & 4K Ultra-HD
This guide will explain everything about High Definition, Blu-Ray, HDMI and anything else related.

What is High Definition?
HD is a TV display format that offers 5 times more picture quality than regular TV broadcasts, Standard Definition (regular TV broadcasting) has a resolution of 720x576 in the UK (720x480 in the US), this means the image on screen is made up of 576 horizontal lines and each of those lines is 720 pixels (dots) wide, so the image on screen is made up of 720 X 576 pixels = 414,720 pixels (0.4 Megapixels). High Definition has a max resolution of 1920 x 1080 (worldwide) which results in 2,073,600 pixels (2 Megapixels), its this extra 'definition' that makes the picture quality look much clearer and sharper than regular SD. The max resolution is referred to as 1080p (as it has 1080 lines in progressive scan) or Full-HD , HD can also be broadcast at a lower resolution called 720p (720 lines in progressive scan) which is 1280x720 which has 921,600 pixels (0.9 Megapixels) and while it has half the definition of 1080p it is still twice as good as regular SD.

1080i vs 1080p vs 720p - Interlaced / Progressive
Most Terrestial/Satellite broadcasters use the 1080i format over the 1080p format, the i and p letters on the end of the numbers refers to Interlaced scanning and Progressive scanning, Interlaced video is 50 fields per second in the UK (60 in the US), the first field displays all the odd lines of the video (1,3,5,7 etc) and the next field alternately displays all the even lines (2,4,6,8 etc) and that repeats for the other 48 fields all in quick succession which to the naked eye makes up one image on screen (although digital LCD/Plasma TV sets have to 'de-interlace' to Progressive before displaying due to nature of digital/LCD panels), Progressive means all the lines are displayed at the same time, usually at 25 frames per second in the UK (this is how you end up with 50i on 'Interlaced' as each single frame has two fields on an interlaced signal). Interlacing video can introduce artifacts especially when its de-interlaced.

 

Here we see an example of interlacing artifacts:
photo credit: wikipedia

interlacing

When video is 'De-interlaced' the CPU needs to work what should be in the picture and what shouldnt frame to frame, this is ok when theres no movement, but when the camera pans or theres lots of movement in the video then the picture quality will not be as good as it would be if it were Progressive.

Blu-Ray
When High Defintion displays came about, manufacturers were quick to release a new disc format that could play these high resolution movies, Toshiba's HD-DVD and Sony's Blu-Ray were born (the name 'Blu-Ray' comes from the color of the lazer used in the player), and just like that there was a format war on, just like the VHS and Betamax format war in the 80's (where VHS won) - needless to say that Blu-Ray won and HD-DVD was removed from production, this was mostly because Blu-Ray discs could hold twice as much data (50Gb) than that of HD-DVD (25Gb) so it was a no-brainer when it come to the big movie company's choosing a format to release their productions on.

 

4K - Ultra-HD
As time goes on newer technologies emerge, 4K (or Ultra-HD / UHD) is the latest 'Hi-Resolution' technology and is still quite new (as of Summer 2013) with only a handfull of 4K ready TV's available, all this is (using the same explanations above) is 'doubling' the width and height pixels of Full-HD 1080p which effectively 'quadruples' the picture quality again giving it a resolution of 3840 x 2160 which is 8.3 megapixels, this is 2160p or Ultra-HD / UHD.


HDMI - High Definition Multimedia Interface
HDMI is the industry standard interface for connecting High Definition devices to HD TV's - such as connecting a Blu-Ray player, HD Satellite Receiver, HD Mediaplayer or HD gaming console to an HD-Television.

HDMI

The cable is used to carry digital data and therefore is not affected by interference (over short/regular length cables) like many analogous video cables, so if you see any selling for high prices offering suprerior picture quality or interference protection please dont buy them as this is a lie, digital data transmission is completely different from analogue data transmission, it is hard to force errors into digital data transmission and even if you do it is protected with error correction which repairs/replaces missing data (destroyed by interference) at the other end, a 1.99 HDMI cable will work exactly the same as a 500 HDMI cable, the only difference there can be is 'build quality' - a better built one may last longer but its unlikely to be the case unless your constantly tearing out cables from behind sets, ive only ever used cheap 3 cables and never had any problems yet 5 years on! The only real time you need to consider any sort of 'decent quality' HDMI cable is when your going to use really long runs of it...such as 5-10 meters or more (which most people dont), if you do then I recommend you look up for Bonded-Pair HDMI cable by the Blue Jeans Cable Company as they have a thorough explanation why their patented cable is suprerior to regular twisted pair for long runs, longer runs can be susceptible to a few things like Interference, Impedance issues & return loss - see HERE for more details

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