Comparison of 4K and 8K HDMI cables

A little challenge to begin with: spot the error in the following sentence:


Just about anyone who’s bought a new high-resolution games console, sound bar, computer monitor or TV set knows that the humble HDMI cable is a necessity for connecting each.


Let’s leave aside the impertinence of referring to the HDMI (High-Definition Multimedia Interface) standard as ‘humble’ (it’s a game-changer). The real error resides in referring to these cables in the singular. If you’re looking for the right HDMI cable for your devices, you need to know from the get-go that there are a number of different types. They’ve evolved over the years since they were first introduced in 2003.


In this guide, we’ll focus on the two newest: 4K and 8K.


What’s unique about HDMI cables?


HDMI is a ‘pure-digital’ interface that has fast become not only the best but also the only way to connect HDMI-equipped television sets, home theatre receivers and sound bars to a raft of high-resolution devices such as HD-DVD and Blu-ray players, new-generation games consoles, and HD-capable satellite and cable TV set-top boxes.


It’s a lot more than a port on the back of a TV set or the cable that fits into it – it’s a set of rules that enable high-resolution devices to communicate.


Unlike older ‘analogue’ TVs, which used a continually fluctuating (analogue) electrical, which produced a compromised picture by today’s standards, modern HDTVs use information in the form of ones and zeroes that travel along specially developed cables as distinct electrical pulses (hence the term ‘digital’). The end result is a far sharper and more colour-rich picture.


Some manufacturers will seek a competitive edge by promoting their HDMI cables as nylon-braided or with other minor benefits. It’s probably wise to regard these as superficial bells and whistles. It’s the cable inside that does the digital donkey work.


In a nutshell, that’s basically what HDMI cables share in common. However, as we mentioned earlier, there have been several different iterations of the HDMI cable over the years to keep up with rapidly changing video standards.


The two latest versions of HDMI cables are those compatible with the latest video standards known as ‘High Speed’ HDMI 2.0 (capable of supporting up to 4K resolution) and ‘Ultra High Speed’ HDMI 2.1 (capable of supporting up to 8K resolution).


Let’s take a deeper dive into the compatible HDMI cables next.


High Speed HDMI 2.0 (4K) cables


The most crucial consideration when selecting an HDMI cable capable of supporting 4K resolution TV pictures is its speed. If it can’t convey digital signals fast enough for the requirements of your high-resolution equipment and your media sources, it simply won’t work properly.


The speed at which data travels along an HDMI cable is measured in gigabits per second (Gbps). To spare you the headache of memorising a raft of different numbers, (the group of leading tech companies that presides over the standards for HDMI devices and cables) has simplified cable speeds into four kinds.


If you’re not yet the proud owner of a 4K resolution TV and you don’t intend on becoming one any time soon, the ‘Standard HDMI’ cable will almost certainly suffice. It’ll work well with standard HD games consoles, Blu-ray and standard DVD players, streaming media players, and AV sound bars and receivers.


However, if you decide to upgrade above standard HD, you may well find that you need a ‘faster’ cable to keep up with the new device’s input requirements. This is when the High Speed HDMI 2.0 cable becomes a worthwhile investment. Released in September 2013, it’s capable of conveying digital signals fast enough to deliver glorious video images on a 4K TV at 30Hz.


A word of caution before proceeding. 4K-compatible HDMI cables are noticeably more expensive than their predecessor (HDMI 1.4), so if you’re not investing in a 4K-capable video display device, it’s simply an added expense that will not deliver any further improvement to your viewing experience. The technology that it’s designed to enable is packed into the device. Without the device, you’re simply spending extra money needlessly.


If you possess a very high-quality version of the earlier standard (and your cable is still relatively new), you may find that you don’t need to buy a 4K-compatible cable at all. The best advice is to try it and see – if your display image flashes and flickers, you’ll need to upgrade to the 4K-compatiable HDMI 2.0 standard.


With that said, if you are ‘going full 4K’, the benefits don’t end with the wonderfully enhanced visuals. High Speed 4K-compatible HDMI cables can support as many as 32 audio channels, with dynamic lip synch thrown in for good measure so that you never experience any irritating lags between sound and image.


A small but significant upgrade to the HDMI 2.0 cable standard was released in April 2015. Known as ‘HDMI 2.0a’, these cables include additional support for High Dynamic Range (HDR) video displays. This delivers appreciably improved picture quality by enhancing the detail in the bright and dark regions of the image, and also throws a more multifaceted range of colours into the mix.


The information needed for the added HDR quality comes in the form of extra metadata in the HDR content itself, such as that streamed from 4K video sources via services such as Netflix or Ultra HD Blu-ray discs. HDMI 2.0a High Speed 4K-compatible cables essentially make it possible for devices to transmit and receive this quality-enhancing metadata.


Shortly after HDMI 2.0a, and still included in the general HDMI 2.0 4K-compatible cable standard, a further minor update was released. Known as HDMI 2.0b, it added support for Hybrid Log Gamma or ‘HGL’ versions of HDR video displays.


We’ve concentrated so far mostly on the ‘pros’ of buying a 4K-compatible HDMI 2.0. We’d be a little remiss if we didn’t also alert you to any ‘cons’.


One of them is that these cables will usually deliver poorer-quality end results if they have to traverse distances over three metres. If you need to run a cable over a greater length than that, you’re better advised to opt for an ‘active’ HDMI cable with an integral processing chip that sees to it that the signal gets smoothly from source to display without any interruption or loss of quality.


The next question is, what about upcoming 8K devices, and will you need an 8K-compatible HDMI 2.1 cable?


Ultra High Speed HDMI 2.1 (8K-compatible) cables


There’s no disputing the fact that the new HDMI 2.1 standard, which was released in October 2017, constitutes a major upgrade – it packs in a colossal bandwidth capacity of 48 Gbps compared to its predecessor.


The question is, given that many new-generation 8K devices are still in the pipeline and haven’t yet reached the retail shelves, do you need an 8K-comatible cable yet?


These are still mainly future technologies. However, even so, there may be some reasons why purchasing one of these high-end HDMI cables now is worth the investment. These include the following.


Your 4K Apple TV flashes or flickers. Complaints have arisen from some owners of these high-end TV sets that they keep having their viewing experience impaired by intermittent flickering or flashes of brightness – glitches that seem to occur more frequently when they’re using Dolby Vision or related HDR1O formats. Apple now advises that users can eliminate these problems by connecting to their TV sets with an 8K-compatible cable.


You play video games in 4K. The Xbox One S 4K console, for example, has a hefty output of 60Hz. If you’re using an earlier HDMI standard such as HDMI 1.4, you’re simply not going to enjoy the benefits of 4K video quality (these cables only support 4K with 30Hz outputs). Because Ultra High Speed HDMI 8K compatible cables support refresh rates of as much as 120Hz, they can comfortably support such a high-end games console without the merest hint of a freeze or a glitch.


You’ve invested in Dolby Atmos or DTS:X audio equipment. The latest generation of top-drawer surround-sound formats such as Dolby Atmos, DTS:X, Dolby True HD, and DTS Master) all employ HDMI eARC, or ‘Enhanced Audio Return Channel’. The earlier ARC technology (introduced in 2009) dispensed with a separate audio cable so that you could listen to your sound bar simply with an HDMI cable. The newer eARC improves on this standard with much larger bandwidth that permits high-quality, uncompressed sound formats, mandatory lip-synch correction so that picture and sound always match perfectly with no lag, and much better HDMI link-ups between devices. However, if you own this high-end equipment, the only cable capable of doing the job is the new 8K-compatible HDMI.


You’re wiring a home theatre. By investing in next-generation 8K-compatible HDMI cables now, you’ll be saving yourself the cost, mess and inconvenience of doing so later when 8K devices are more ubiquitous.


You own a Dolby Vision TV that includes 4:4:4 chroma subsampling. This is a 4K signal with a hefty 60Hz uncompressed Dolby Vision HDR that needs a massive 24.06 Gbps of bandwidth. It’ll grant you the most spectacularly detailed picture quality – but not with an HMDI 1.4 or HDMI 2.0 cable, because neither can handle that requirement.


If you know that you’ll be investing in next-generation 8K equipment, the 8K-compatible Ultra High Speed 2.1 HDMI cable is for you.

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