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4K UHD: What Does it All Mean? p2

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Definitions and Guidelines for UHD: CTA (CEA) vs. Ultra HD Forum/UHD Alliance

The original CEA announcement in October of 2012 by the 4K Working Group defined Ultra HD TV as displays with the following characteristics:

  • At least 8 million pixels at 3840 pixels wide by 2160 pixels tall.
  • An aspect ratio of at least 16:9 or wider, length to width.
  • At least one input capable of displaying native 4K video without upscaling.

The remaining components necessary to the specifications such as color space (ITU-R Rec. 709), bit depth (8 bit) , and ATSC broadcast tuning would remain as they had with HDTV.

The CTA’s UHD requirements have since been updated several times to accommodate subsequent developments in available technology.  These updates have brought requirements for 4K upscaling by TVs in addition to the one input capable of native UHD resolution, High Frame Rate (HFR) up to 60 Hz, and HDCP 2.2 compatibility.  The updates also provide an allowance, but not a requirement, for WCG spaces greater than Rec. 709, additional bit depth, and the inclusion of HDR in the form of HDR10 per CTA and STMPE standards.  But remember that optional standards are not really standards, kind of by definition.

The newer Ultra HD Forum, an organization with a stated mission to further UHD deployment, seems to have taken their UHD definitions a step or two further.  They even have phases, but at present, only one phase, A, is in effect.  They are still working on B, as are those still working to develop the requisite technology.

Phase A UHD Recommendations:

The Ultra HD Forum’s current recommendations are at version 1.5, published in September of 2018, and include the following:

  • Display resolutions greater than or equal to 1080 and less than or equal to 2160p.
  • HFR up to 50/60 Hz with integer frame rates preferred.
  • Display bit depth of at least 10 bit.
  • High Efficiency Video Coding (HVEC) decoding capability.
  • WCG greater than Rec. 709 with colorimetry based on Rec. 2020 with conversion from Rec. 709.
  • HDR light output range of at least 13 f-stops supporting SMPTE ST 2084 Perceptual Quantizer (PQ10)/HDR10 or BBC Hybrid Log Gamma (HLG10).
  • One of two HDR brightness standards: 1000 nits peak brightness, 0.05 nits minimum brightness or 540 nits peak brightness, and 0.0005 nits minimum brightness, with the difference presumably to accommodate differences in LED and OLED light output capabilities.
  • Implementation of immersive audio such as Dolby Atmos in addition to legacy stereo and multi-channel (AC-3) 5.1 sound.
  • Support for live and prerecorded video production combing HDR and SDR along with conversion between Rec. 709 and Rec. 2020 color spaces and conversion between different HDR formats.
  • Recommendation to recognize 1080p resolution content with WCG and HDR to be UDH TV.

Makes the CTA UHD requirements seem a bit sparse, but they at least stick to 4K resolutions in their UHD.  It is the Ultra HD Forum specifications where UHD gets decoupled from a purely screen resolution definition and good old 1080p gets grouped into UHD as long as it supports HDR.  This does provide some justification for manufactures to keep the 4K branding on their UHD sets that the Forum is trying to discourage.

But the truth be told, even the guys coming up with the definitions and specifications don’t seem to have all of their terminology and facts straight.

There is a potential internal contradiction in the UHD Phase A specification which seems to require HDR to be considered UHD but then later says that SDR is acceptable for Phase A.  This contradiction occurs according to section 4.1, page 17/89, where it says pretty clearly that to be considered UHD that HDR is required, but then a couple of pages later it seems to say SDR is included in Phase A per Table 3, page 18/89.  See the circle there?  Along with some talk about HDR 1080p being UHD in the footnotes, it seems Ultra High Definition does not require higher definition than Full High Definition 1080p as long as the colors are richer and the screen brighter.

In another apparent bit of confusion, this time about color spaces, the Ultra HD Forum actually does not require full Rec. 2020 color space performance to satisfy Phase A requirements.  When reading through the numerous articles on UHD, a significant number of the third party commentary that I have seen seems to be taken in by the idea that the Rec. 2020 color gamut is what is being provided by TV manufacturers when claiming UHD Premium.  In reality they are not, nor are they required to.

From the Ultra HD Forum Guidelines, version 1.3:

6.1 HDR/WCG Technologies

There  are many terms  in  use  in  the  field  of  HDR  television.  This  section  explains  the  existing terminology and how terms are used in these Guidelines.

Note that currently some UHD displays are capable of accepting BT.2020 [4] content, but as of this publication, no direct view display is available that is capable of rendering the full gamut of colors in the BT.2020 [4] color space.  It is assumed that in these cases, the device employs “best effort” gamut mapping tailored to its particular display characteristics, and thus these devices are considered BT.2020 [4]-compatible.

Color space and gamut are related, overlapping concepts, but they are not fully synonymous in a very subtle way.  In practice, using the Rec. 2020 color space really means fitting the available gamut inside the primaries from the Rec. 2020 color space, it does not mean that the full available gamut from that space can be reproduced.  This is also tacitly acknowledged in several other sections such as:

6.2.1.2 Imaging Devices: Resolution, Dynamic Range and Spectral Characteristics

In the area of color space and spectral characteristics, the more advanced sensing devices will exhibit characteristics approaching the color gamut of BT.2020 [4], while more typical devices will produce acceptable color performance approximating the DCI-P3 gamut or just beyond the gamut of BT.709 [3].

6.2.2 Reference Monitor

For UHD Phase A, a reference monitor can ideally render at least the following: resolutions up to 3840x2160, frame rates up to 60p, BT.2020 [4] color space (ideally at least the P3 gamut), and HDR (i.e., greater than or equal to the contrast ratio that could be derived from 13 f-stops of dynamic range).

9.3.1 Bit Depths (under Table 14, Existing Practices for Real-Time Program Service Distribution Formats)

In Cases 3 and 4, SMPTE ST 2086 can be used to signal Peak White. It should also be noted that in Cases 3 and 4, the color gamut can be up to BT.2020 color primaries; however, in current practice the gamut does not exceed DCI P3 primaries.

Actually, UHD Premium branded TVs are only required to display 90% of the much smaller DCI-P3 color space, which happens to fit inside the Rec. 2020 color space.  This is because the best current UHD TVs cannot display full Rec. 2020 colors, but it is better for marketing to keep citing the more impressive Rec. 2020 in the specifications.  More on that to come.

Rec 2020 v P3 v 709


The Future: Phase B Recommendations:

Phase B is presently in flux with many of the technologies need still in development, but consists, at present, of a list of candidate technologies expected to launch in 2018 and later including:

  • Implementation of UHD 8K resolution.
  • Increased HFR exceeding Phase A 50/60 Hz.
  • Increased color bit depth to 12 bits.
  • ICtCp color space per Rec. 2100.
  • Color remapping information (CRI)
  • Scalable coding of spatial, temporal, color gamut, dynamic range information.
  • Dynamic metadata for HDR with per scene metadata coding per STMPE 2094 in addition to HDR single layer (HDR10) and HDR dual layer (Dolby Vision).
  • Next generation object based audio codecs including Dolby AC-4, DTS:X, and MPEG-H.

Phase B is made up of technologies that are not yet practical enough to deploy, but are on the horizon.  The goal is to have single program streams that are backwards compatible based on scalable video coding that embeds multiple resolutions, 1080p/2K, 2160p/4K, and 4320p/8K at different frame rates, color encoding, i.e. Rec. 709 and 2020, and mixed SDR and HDR content all with shiny new audio codecs.

For those paying attention, Phase B will include Dynamic High Dynamic Range, DHDR.  Using the associative property, this becomes: DHDR = HDDR = HD^2R, which just has to be better because they have Dynamic to the second power in the name, right?  Who comes up with these crap naming schemes anyways?  Oh, that’s right... the marketing guys.

UHDTV Specifications

So now that we have discussed several versions of UHD guidelines from the various manufacturer’s organizations that produce them, we are onto the actual technical standards to which the guidelines refer.

Keep in mind that this list is in no way comprehensive as I am quite sure there are more standards lurking about.  I have, however, included links to the actual documents where they are available for viewing or download, if one is so inclined.

Warning: a significant number of acronyms to follow.

International Telecommunications Union

ITU

The ITU is broken into three sectors responsible for different areas of overall ITU responsibility.  The Radiocommunication division, known as the ITU-R, handles broadcast spectrum communications and satellite orbital resources.  The Standardization division, ITU-T handles all non-broadcast telecommunications.  The third section, Development, ITU-D, promotes development and access to communications technologies.
Standards developed by the ITU for UHD TV span across the ITU-R and ITU-T and are developed jointly with several other standards bodies.

ITU-R Approved Standards

Standards for TV themselves have traditionally fallen under the ITU-R as originally, before the advent of home video cassettes and subsequent developments in home video, TV was principally a broadcast medium.

  • Rec. ITU-R BT.1201-1 (2008) Extremely High Resolution Imagery
  • Rec. ITU-R BT.1769-0 (2008) Parameter values for an expanded hierarchy of LSDI image formats for production and international programme exchange (Withdrawn)
  • Rec. ITU-R BT.2020-2 (2015) Parameter values for ultra-high definition television systems for production and international programme exchange
  • Rec. ITU-R BT.2035-0 (2013) A reference viewing environment for evaluation of HDTV program material or completed programmes
  • Rec. ITU-R BS.2051-0 (2014) Advanced sound system for programme production
  • Rec. ITU-R BT.2100-0 (2016) Image parameter values for high dynamic range television for use in production and international programme exchange
  • Report ITU-R BT.2390-2 (2017) High Dynamic range television for production and international programme exchange

Other ITU-R Reports and In Progress

ITU-T Standards

Standards produced by the ITU-T that relate to UHD TV have been in video encoding schemes through the Video Coding Experts Group (VCEG, ITU-T Q.6/SG 16) in conjunction with the International Standards Organization (ISO) Moving Pictures Experts Group (MPEG, ISO/IEC JTC 1/SC 29/WG 11).  The combined efforts of the two organizations has resulted in the H.26x series of video encoding standards.

Standards developed by the  ITU-T VCEG and ISO/IEC JTC1 MPEG used in support of UHD TV concern video encoding and include:

You may recall H.264 from the early days of HDTV, but it has now been supplanted by the newer H.265, also known as MPEG-H.  The MPEG-H standard is actually more comprehensive than the portion listed above, which relates specifically to video.  Known as ISO/IEC 230008 – High efficiency coding and media delivery in heterogeneous environments is broken into a number of parts representing different aspects of digital content delivery:

  • Part 1: MPEG Media Transport (MMT) - a network adaptable media streaming format.
  • Part 2: High Efficiency Video Coding – a data compression standard that doubles the compression performance of the previous standard, MPEG-4, and support up to 8192 x 4320 (8K) resolutions that is jointly developed with the ITU-T VCEG.
  • Part 3: 3D Audio – an audio compression standard supporting 3D multichannel audio.
  • Parts 4-6: Reference software corresponding to parts 1-3.
  • Parts 7-9: Conformance testing standards corresponding to parts 1-3.
  • Part 10: MMT FEC Coding.
  • Part 11: MMT Composition Coding.
  • Part 12: High Efficiency Image File Format developed from the ISO base media file format.
  • Part 13:  MMT Implementation Guidelines.

As can be seen above, the full standard describes encoding/decoding for both video and audio along with defining a transmission medium, implementation guidelines, reference software, and a conformance testing regimen.

In theory, H.265 has a 2:1 compression ratio advantage over the older H.264 for the supposed same picture quality.  In practice, that is likely to be somewhat less when used with real world video content and not theoretical calculations and idealized test files.  Regardless, it is a significant jump.

Standardization in SMPTE

SMPTE

The Society of Motion Picture and Television Engineers (SMPTE) produces standards and engineering guidance for motion imaging including the obvious film and television production industries, as well as in digital cinema, audio recording, information technologies, and even medical imaging.  These standards include film and broadcast formats, storage media, physical transmission interfaces, video test patterns, and data exchange formats.  The pertinent contributions related to UHD TV include:

  • ST 2036-1:2014 - Ultra High Definition Television — Image Parameter Values for Program Production

  • ST 2036-2-2008 - Ultra High Definition Television1 — Audio Characteristics and Audio Channel Mapping for Program Production

  • ST 2036-3:2015 - Ultra High Definition Television — Mapping into Single-link or Multi-link 10 Gb/s Serial Signal/Data Interface

  • ST 2036-4:2015 - Ultra High Definition Television — Multi-link 10 Gb/s Signal/Data Interface Using 12-Bit Width Container

  • ST 2084:2014 - Dynamic Range Electro-Optical Transfer Function of Mastering Reference Displays

  • ST 2086:2014 - SMPTE Standard - Mastering Display Color Volume Metadata Supporting High Luminance and Wide Color Gamut Images

  • OV 2094-0:2017 -  SMPTE Overview Document - Dynamic Metadata for Color Volume Transformation — Overview for the SMPTE ST 2094 Document Suite

  • RP 431-2:2011 - SMPTE Recommended Practice - D-Cinema Quality — Reference Projector and Environment

Note that the links are not to the actual documents, as is the case in some of the other sections, as STMPE is looking for some cash to allow you to see these.

The last item included describes the characteristics of the reference digital projector, which plays into the next section, the Digital Cinema Initiative specifications and is a limiting metric on colorimetry for cinema and, incidentally, the Ultra HD Forum.

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Recent Forum Posts:

BoredSysAdmin posts on March 22, 2019 11:43
Stanton, post: 1306509, member: 14012
Which is a good thing, because (trying not to get “political”) Net Neutrality (as previously defined) was another example of un-necessary regulation over an adequately performing free-market…but that is a discussion for another time/article.
Adding a dump rating to your post would be a childish thing to do, but consider that I exactly did that.
There are so many things factually wrong in your short comment.
Stanton posts on March 22, 2019 11:41
TankTop5, post: 1305140, member: 87285
Would I be wrong in assuming an average or almost cheap 4K is as good or better than a couple year old very high 2k?

If that “cheap” 4k TV also supports WCG and (some form of) HDR, then most likely yes. The flat-panel TV revolution has finally given us “affordable” large-screen (>40") TVs, which are more likely to display the benefits of 4k resolution. Now 8k is a different story…and that doesn't even address (the lack of) 8k content.
Stanton posts on March 22, 2019 11:35
BoredSysAdmin, post: 1305184, member: 28046
Federal net neutrality is currently dead, and I doubt that despite currently ongoing states lawsuits it would be reenacted during this administration term.

Which is a good thing, because (trying not to get “political”) Net Neutrality (as previously defined) was another example of un-necessary regulation over an adequately performing free-market…but that is a discussion for another time/article.
Auditor55 posts on March 17, 2019 16:18
I'm glad they are using UHD. 4K is and was always marketing hype. UHD is more appropriate terminology. From my experience the difference between 4K and 1080p is hardly noticeable if at all. TV manufactures know that most people think resolution means better, not considering the point of diminishing returns. Today we see the big 3 TV manufacturers, Sony, Samsung and LG already pushing 8K resolution TV's to the public when 4K has barely taken hold. They know that resolution sells and they know there will be those that feel their current 4K TV is already obsolete with really explaining to them the benefit of purchasing an 8K TV.
VonMagnum posts on March 16, 2019 07:23
What bugs me is that they're planning to allow broadcasters to charge for service, ending huge chunks of “free” airwaves for the public. I got rid of cable precisely because I had to endure so much advertising (ever increasing amounts to the point where it averaged 22 minutes of ads per hour compared to 10 minutes in the 1960s and 1970s on free TV no less) and I STILL paid $123 a month for 2 HD boxes that were constantly plagued by hard drive failures (the cable boxes got so hot and yet were so slow in the GUI it was absurd) and for that I paid a $10 a month “rental” fee for each year after year plus anothe 99 cents per remote? Awful. Just awful.

I had enough. $12 a month on Netflix gets me up to 4K shows with zero advertising and yet Netflix can still afford to make their own shows and movies to boot on top of tons of older ones. Prime does the same for a similar price per month and I got it for free shipping reasons, not TV , music and movies, but I get those too yet they think I'm going to pay for over the air TV with advertising and spotty reception??? No thanks.
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