Tag Archives: HDMI Spec

First generation HDMI 1.4 spec UHD 4K, next-generation HDMI 2.0 spec UHD 4K and what integrators need to know.

An analysis of 4K Interim vs 4K Proper by Chris Pinder, Founder and MD of HDanywhere, June 2015.

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4K is a complicated subject matter. 4K isn’t one format, it’s an umbrella term for many combinations of resolutions, frame rates and colours. Talking about 4K in too generalised a way is dangerous. When I discuss 4K with anyone, in as non-patronising a way as possible to simplify and aid understanding, I refer to ‘i’ and ‘p’, (like 1080i and 1080p) but my ‘i’ and ‘p’ doesn’t mean interlaced and progressive, I mean first generation 4K and next-generation 4K, or in other words  ’interim’ and ‘proper’. P could also quite easily stand for ‘premium’.

This is my take on the two-speed world of 4K UHD devices at the moment. It may be labelled and marketed as 4K, it may even support HDCP 2.2 – but is it 4Ki or 4Kp?

Proper 4K (4Kp) is next-generation HDMI 2.0 spec 4K, it’s what Ultra HD Blu-ray is and what premium 4K content will be. Ultra HD video refreshes at a smooth 60 frames per second in amazing 10-bit 4:2:0 colour (or if your display doesn’t support 10-bit) 8-bit 4:4:4 colour – basically hugely superior colours than what we have seen before over HDMI. 4Kp can also support HDR content and runs at very high 18Gbps data rates and, as a result, will require all new high-bandwidth HDMI 2.0a* spec electronics.  4Kp will also have HDCP 2.2 copy protection encrypting the content, which I’ll touch on later.

What is most important from integrator perspective is that single-cable HDBaseT DOES NOT carry 4Kp. It will only carry 4Ki because HDBaseT is max 10.2Gbps and 4Kp requires 18Gbps.

Most devices out there today labelled as ’4K’ do not support 4Kp, they only support 4Ki. And by most, I mean over 95%. But this is improving, more and more displays are coming out now that support HDMI 2.0 and have a 10-bit panel. Ultra HD Blu-ray is likely going to be the first 4Kp source device we see. So what is 4Ki?

Interim 4K (4Ki) runs at a 9G data rate (half that of 4Kp) and doesn’t necessarily require new HDMI 2.0 electronics. It will work on older HDMI 1.4 spec devices. It may or may not have HDCP 2.2 encryption. And colour-wise if it’s running at 60fps it can only be the lesser 8-bit 4:2:0 quarter colours. For 4:4:4 a lower 30fps refresh rate is used instead and smooth panning shots are sacrificed. 10-bit colour content just flatly isn’t supported full stop.

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What is so important about colours?

4Kp/60 and 4Ki/60 if watched in black and white are EXACTLY the same. The same number of pixels wide and high, refreshing at 60 times per second, with the same pixel data for light and dark contrast. So no difference in sharpness, motion or contrast.

Where they differ is with a compromise on colour. The resolution of the colour layer that gets laid over the top of the black and white frame when combined to make the final image. With 8-bit 4:4:4 each pixel can choose a colour, whereas with 4:2:0 every 4 pixels have to share a single colour choice. Even though a cluster 4 pixels are sharing the same colour, the overlay of the black and white image creates different shades. The resulting 4:2:0 video content, although a lesser quality, is not as substantially different from 4:4:4 as you might think. In fact, when viewing the two from a couple of metres away, the human eye really struggles to differentiate them.

OK, now that you’re thinking is in tune with there being two primary types of 4K material and you understand the difference between the two.

You also NEED to be aware of a couple of associated meteors about to hit the AV side of the CI industry that relate to the facilitation of working 4K HDMI systems. (Remember HDMI is a system, NOT a cable) One is called ‘HDMI 2.0′ and the other is ‘HDCP 2.2′. The two meteors should really hit simultaneously, but not necessarily.

Meteor 1: HDMI 2.0 is the new twice-as-big digital pipeline to accommodate the higher data rates of proper 4K jumping from 9G to 18G bandwidth. Its not a new cable design, its new electronics at either end of the existing (short) HDMI cable we use. So that is new source devices (Ultra HD Blu-ray players for example) and new displays (10-bit SUHD Samsung panels for example). However for longish cable distances, say 3m and over, current passive cables may struggle with the higher data rates. We’ll begin to see some new breeds of HDMI cable types appear to solve this. Some will use integrated active/powered boosting chips and others are likely to be a copper/fibre hybrid cable. Existing long length HDMI cables, that may be buried in walls for example will be able to be utilised through the use of restorative dongles that can be placed at the start and end of the cable run. I expect to see this HDMI cable rescue/fixer market grow over the coming years sharply.

Meteor 2: HDCP 2.2 is the new 128 bit encryption designed to secure 4K content from being pirated. It is the same level of security encryption as credit card issuers use for internet transactions. Unless every device in the signal path is HDCP 2.2-capable, theoretically the content will not be shown. Source, matrix, AVR, balun, display, projector must all support HDCP 2.2. One weak link means black screen. The thing about HDCP 2.2 support is that it’s essential to ensure the best chance of displaying 4K content from your favourite content providers (i.e Hollywood and sports). The HDCP 2.2 event horizon will largely be determined by the release of Ultra-HD 4K Blu-ray and 4K content being delivered via our set-top-boxes.

Conclusion

In summary, until more next-gen 4Kp source devices, like Ultra HD Blu-ray, set-top-boxes, and media players are released we live in a kind of interim 4K limbo land, a phoney, interim 4K world with no proper, premium 4K content to enjoy. In addition to this, more displays with HDMI 2.0, HDCP 2.2 and 10-bit panels need to be released so that users can take full advantage of the advancements in picture quality offered by 4Kp. Month-on-month this situation improves.

From an integrator perspective, quite rightly there is a lot of emphasis currently on HDCP 2.2 support within matrixes. But even when HDCP 2.2 compliant, single-cable HDBaseT is a bottleneck in many video distribution systems, which will result in premium 4K content video quality being downgraded when distributed. There is a quality compromise currently in order to deliver a distributed solution over a single network cable.

SIDELINE RED HERRING: What about 4K streaming like Netflix?

Well it’s not 4Kp and it’s not 4Ki… It’s dynamically compressed, streamed 4K content using AVC H.264 and HEVC H.265 codecs with varying quality from home to home according primarily to the speed and quality of their network. For the purposes of this article, I am talking about uncompressed 4K content.

More info here: http://www.dailytech.com/Netflix+to+Stream+House+of+Cards+in+4K+via+HEVC+H265+Compression/article33962.htm

 

HDMI 2.0 – key features of the new specification.

HDMI 2.0 was unveiled to the world at IFA Berlin in September.  Following this, Aussie company Kordz, stocked in the UK by HD Connectivity, became the first approved HDMI 2.0 Adopter in the world, outside of the HDMI Forum, and is the only HDMI 2.0 Adopter in Australia.  Founder David Meyer lifts the lid on the key features, inner workings and potential pitfalls of this new specification.

Each time a new version of HDMI is announced, there follows a buzz of new features and formats, but also a groan from the custom installation community as to what the implications may be.  HDMI 2.0 paves the way for some fantastic new video and audio capabilities, but no need to panic – the changes may not run as deep as you might think.  Ultimately HDMI 2.0 will settle into a place of normality, as has happened with every iteration before it.

So what does HDMI 2.0 offer, how is it different, and what are the headline features that you need to know about?  Let’s take a look.

Development of HDMI 2.0

HDMI 2.0 is the first major HDMI specification release since version 1.4 back in 2009, so it’s fair to say a lot has changed, and it needs to.  There are now two HDMI organisations;

  • HDMI Licensing, LLC, with its seven founder companies.  Developers and managers of the HDMI 1.x generations, and now also appointed licensing, marketing and compliance managers of HDMI 2.0,
  • HDMI Forum, Inc., a non-profit corporation founded in 2011, with more than 80 member companies for broader market development of future versions of HDMI,

An important point to note is that HDMI 1.4b remains as an ongoing specification, with HDMI 2.0 running concurrently with its subset of additional optional features and enhancements.  Existing HDMI Adopters do not automatically get an upgrade; they must sign an addendum and be accepted before they can become adopters of HDMI 2.0.

Key Features of HDMI 2.0

Here’s a summary of some of the key new features of HDMI 2.0;

Video

  • 2160p/60 (4K) 8-bit 4:2:0 in the existing 9Gbps data rate (previously 30fps limited),
  • 2160p/60 (4K) 10 or 12-bit 4:2:2 colour at a new higher speed of 18Gbps,
  • Anamorphic video modes for 2.37:1 picture,
  • New ‘Dual View’ video mode for two simultaneous full screen 1080p images (on 3D backbone),

Audio

  • Up to 32 channels of One Bit audio to 192kHz, and up to 1536kHz sampling in 2-channel mode,
  • New 10.2, 22.2 and 30.2 channel modes for ‘3D Audio’ speaker placement,
  • Up to 4 simultaneous audio streams to accompany Dual View video or multi-language,

Other

  • New 2.0 clock mode, EQs and data scrambling for transmission robustness,
  • New improved CEC 2.0, HDCP 2.2 support, and expanded applications for DDC.

In this article we’ll focus on 2160p, touching on anamorphic, but coming back to explore audio some other day.

Emerging Trends – 4K TV Firmware upgrade to “HDMI 2.0”

The first key new feature of HDMI 2.0 out of the gate is the upgrade of 2160p (4K) to 60 frames per second within the existing defined HDMI bandwidth, where previously it was limited (under HDMI 1.4) to 30fps.  Both Sony and Panasonic have recently announced firmware updates for their existing 4K TVs to enable this feature, indicating that there is no new hardware (aka ‘speed’) required.  As an aside, they tend to tout this upgrade as “HDMI 2.0”, but that’s a non-compliant practice as it’s actually just one of a multitude of new features of HDMI 2.0 that they’re talking about.  What they really mean is that the firmware just adds newly defined support 2160p/60, 8-bit 4:2:0… assuming the existence of content.

So how is it possible to double the frame rate without doubling the bandwidth?  The answer lies in the ‘…8-bit 4:2:0’ reference; save on colour data, give back in frame rate.

Chroma subsampling and pixel data packing

Chroma subsampling is a process of compressing, or rather stripping out colour data to reduce file size &/or video transmission bandwidth load.  The premise is that the human eye is far less sensitive to colour than in is to brightness and grayscale, by a factor of 20, in fact.  As such, the amount of colour information in video can potentially be reduced without us really noticing… or that’s the plan.

The trick is to leave the resolution and gray scale untouched, which is why it’s only applicable to Component video (YCbCr) signalling, where the separate luminance (Y) channel can be left intact.  The most common chroma subsampling methodologies are 4:2:2 with half colour data when compared to 4:4:4 original, and then there’s 4:2:0 (as used with DVD & Blu-ray) with just one quarter of the original colour data.

The sampling commonly occurs over a 2×2 pixel array, where each pixel comprises a Luminance channel (Y) and two Chrominance channels (Cb & Cr).  Fig.1 below shows a simplified depiction of the uncompressed array before any subsampling, called 4:4:4.  Fig.2 shows how HDMI 1.4 (and prior) handles YCbCr, where everything from 8-bit 4:2:0 to 12-bit 4:2:2 produces precisely the same bandwidth at a constant 96 bits per array (same as 8-bit 4:4:4).  Fig.3 depicts 4:2:0 as it really should be, being how HDMI 2.0 handles it; with 8 bits of ‘Y’ per pixel, and just one of each 8-bit colour component Cb & Cr across the whole 2×2 array.

What they’ve done with HDMI 2.0 is recognise that 8-bit 4:2:0 natively nets 48 bits per sample array, and they’ve actually passed on the savings.  That is, they halve the bandwidth, which enables them to then double it again with frame rate.  Voila, 30fps goes to 60fps in the same bandwidth as before.  Note this is ONLY applicable to 8-bit 4:2:0.  This is not where HDMI 2.0 stops – there’s even better formats on the horizon.

HDMI 2.0 Need for speed

There are several formats of 2160p (4K) that are included in the HDMI 1.4 specification, all of which run at 8.91Gbps, the specification then capping out at 10.2Gbps.   HDMI 2.0 introduces some more at this legacy level, and several superior combinations at double this rate, being 17.82Gbps (rounded to 18Gbps, 6Gbps/ch).  This is well beyond the limits of HDMI 1.4, and defines the top end of HDMI 2.0.  The range above 10.2Gbps is referred to as “HDMI 2.0 mode”, whereby the TMDS Clock is slowed to 1/40th of the data rate to counter the effects of EMI at such high speeds.  Other techniques like data scrambling are also employed to improve stability.

HDMI 2.0 Cables

Right off the bat – THERE IS NO SUCH THING!  If anyone offers you so-called “HDMI 2.0 cables”, turn and run.  It will be either a marketing tactic, or expression of ignorance.  Either way it’s non-compliant.  When the HDMI 2.0 specification was first announced, it was accompanied by this statement;

“..Current High Speed cables (category 2 cables) are capable of carrying the increased bandwidth.”
– HDMI Licensing, LLC, Press Release, 4 Sep 2013
http://www.hdmi.org/press/press_release.aspx?prid=133

There is no new speed, no new cable.  Does it make sense that a cable rated to 10.2Gbps can then carry up to 18Gbps?  Logically no, but they have some tricks up their sleeve.  2.0 introduces a parametric-like new sink EQ system which supposed to make a 10.2Gbps tested cable perform up to 18Gbps.  It can’t however fully compensate for the collapsing effect of cable length, and will be expected to cap out at around 3m with a decent cable.  Beyond that, it’s all bets off and there is no new cable spec, speed or directive.  My prediction – HDMI cables will have to turn active, as some already have.

2.37:1 Cinemascope

Another fantastic feature of HDM I 2.0 is the ability for it to support different pixel aspect ratios, namely 4:3 (nothing to do with 4:3 TV, by the way).  Eg; a 1080p image is comprised of 1,920 pixels wide and 1,080 pixels high.  Every pixel is square, so content is fed to each pixel in 1:1 ratio.  The array of 1:1 pixels then determines overall image aspect ratio, being 1.78:1, or 16:9.

What HDMI 2.0 has introduced is the ability for content to be formatted using 4:3 pixel ratio.  Every pixel in a supporting display could potentially be fed 4:3 anamorphic content, even though the pixel is still 1:1 square.  In practice, a projector with a matching anamorphic lens will horizontally stretch the image by 1/3 (4:3).  The result is 2.37:1 picture aspect ratio (1.78/3)x4 = 2.37.

No more encoded black bars.  It means we can look forward to maximising image resolution for cinemascope 2.37:1 in a standardised format.

Summary

HDMI 2.0 brings many benefits and some exciting new features, paving the way for a level of AV immersion the likes of which we’ve never seen.  Yes it means new hardware, but that points to opportunity for the custom AV dealer/installer.  HDMI speeds are ever increasing, and that means more demand on quality infrastructure to ensure everything works as planned.

Imagine a premium 2160p/60 2.37:1 aspect home cinema projection system with brilliant 12-bit 4:2:2 colour and 10.2 audio system.  How about dual-view gaming with 2 players each experiencing their own full screen 1080p image on the same TV, with separate audio tracks being fed to their headphones?   Or to really make your head spin, imagine an IMAX Private Theater ™ with 30.2 channel 3D digital sound.  Phwoah!