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The Dark Art Of HDMI

Hi All! Welcome to what will hopefully be the first of many tech discussions aimed to help everyone from experienced AV installers, to sparkies just starting to dabble in the world of AV and even the average Joe (Joanne) who want to better understand some of the tech wizardry that is going on in their home.

So, where to start? Well, with the boom of 4K TV's and media (physical and streaming) and 8K looming on the horizon, why not start with a detailed overview of 4K or as it is more commercially known, Ultra High Definition (UHD).


The easiest way to describe UHD is basically any resolution greater than Full HD, 4K all the way to 8K and above.......... that didn't help much, did it. Until not too long ago HD or Full HD was the best we could get, both at the movies and on our TVs at home. Any resolution between 720i and 1080P is considered High Definition or HD. These resolutions are a pixel count of 1280 x 720 pixels all the way up to 1920 x 1080 pixels, basically DVD to Blue ray quality. And for a while, these resolutions were great.....that is until we all started buying 65", 75", 85" and other monstrous sized TV's or Flat Panel Displays (FPD). These big screens brought the short comings of FULL HD front and center particularly when watching any image of great detail. So the creators of media, namely SONY and the like, needed a solution to give more detail to such large images. In short, we need more pixels!!

Along came 4K, and like HD there are many resolutions that fall within the 4K definition. The most common of these is 3840 x 2160 (what you would expect on your new TV) and DCI (Digital Cinema Initiatives) 4096 x 2160. Great, so now we have plenty of pixels to show all the detail we would ever need, right? Wrong. With this new detail came opportunities to further increase other spectrum of the viewing experience. First order of business, Colour. If we are going to have more pixels, lets broaden our depth of colour, and while we are at it more acronyms. HDR. High Dynamic Range! This basically, increases the sampling rate of the colour spectrum. Instead of 8 bits of colour sampling per second, lets do 12. Then was introduced WCG (Wide Colour Gamut) and then HDR10, and then HDR10+, and then DOLBY VISION. These are all levels of colour sampling and standards of colour with the purpose of further increasing the detail that 4K can give, particularly dark colours and yes black is a colour. Now, you may have seen on your new TV or input source, 4:4:4, 4:2:2, and 4:2:0, what is this and will it make a difference? The short answer is not really. Every pixel is broken up into 12 colour blocks, 4 red, 4 green and 4 blue. The way these blocks interact and with a little help of some trickery of the human eye we can get every colour of the rainbow. 4:4:4 uses every one of the 12 blocks, 4:2:2 uses 8, 4:2:0 uses 6. Along with the brightness processing of the TV you probably wouldn't notice which if the three you were seeing. So why do we have so many option to choose from? Time for a new paragraph....


High Definition Multi-Media Interface. In 2002 a new cable was born, designed to replace DVI and all the analogue cables before it (remember the Red, White, Yellow RCA). This cable is made up of 19 pins and some shielding. Back in 2002 all we asked of this cable is to give us HD picture and 5.1 or 7.1 channels of crisp audio. Then with revision HDMI 1.4 we starting throw ethernet, HDCP copyright encryption, now we are up to HDMI V2.0 and the same 19pin cable now has to give us 4K/UHD 60 frames per second, HDR10+, HDCP 2.2, high speed ethernet, CEC (consumer electronic control), 7.4.2 channels of ATMOS audio, and 5V standby power (and no, this 5V should not be used for anything but standby power). In data terms, we went from needing 1.5-3mps (megabytes per second) to 18mps. Thats alot of data, so in some cases compression trickery is used to bring this bandwidth down, but basically you need at last 11mps to get 4k on your screen. And here lies the problem.


All this extra strain on the HDMI cable is often the limiting factor when upgrading to 4K. Time and time again I get customers asking me if we can re-use their 15 year old HDMI cables, or if instead of using installer grade premium leads can we use these $10 cables we bought from the discount shop. Well, no, not if you really want to see 4K on your $2000+ new TV. Having high quality, Version 2, HDMI cables is imperative, if you get this right then most of the time everything else just works. I did say most of the time, didn't I:

To get 4K 4:4:4 HDR10+ with Dolby Atmos (Basically, the top of the top image and sound): - Must have high quality HDMI leads Version 2

- The leads should not be longer than 7-10m

- If using HDMI over CATX(hopefully shielded) extenders, make sure they are 4K HDR, ARC, Atmos ready

- Your TV must be 4K (it sounds silly, but more often than I would like to admit, I get asked "why doesn't my 10 year old Samsung TV play my 4K blue rays")

- All devices must be 4K, Blue Ray player, Apply TV 4K, Chromecast, Foxtel IQ4 (well its sort of 4K)

- Your home theater receiver must be 4K, if it doesn't have it plastered across the front then it probably isn't 4K

Its not impossible to get razor sharp UHD images on you screen, and it doesn't need to break the bank either. The key is a well thought out design and spending the money in the right place. Make sure any professional system designers or installers you engage are well aware of your expectations and if the first thing they do is head to google when you mention HDR, 4:4:4 or HDCP then maybe they aren't so professional.

Thanks again for being a part of our first blog, I may have bitten off more than I can chew but hopefully this brief (very brief) overview of UHD and what you need to get it, has informed an installer enough to deliver a better result to their client and has informed you, the end user, enough to maximize your experience at home.

If there is a topic you would love to hear more about, in the AV world, home automation space, or anything tech that you might find in your home, office or at work feel free to send us a nudge and we'll add it to our ever growing list of topics for upcoming blogs.

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