Television manufacturers are moving toward ultra highdefinition — also known as “4K” — which offers four times the resolution of HD. It alsooffers greater depth of color and faster frame rate. That means moreinformation must travel through the cable from the video source to theTV.
The current de facto cable, HDMI (high-definition multimediainterface), solves some of the old problems of multiple cables,incompatible interfaces and bandwidth issues, but it could it be approaching the end of the line.
“There are currently two schools of thought,” Susan Schreiner, analystat C4 Trends, told TechNewsWorld. “Those that say that you don’t need a new HDMI cable for Ultra HD 4K — and those for whom it is a concern.”
Down This Pipe Before
Cable technology — as in the wired cables that deliver a signal to aTV — have evolved, but that evolution has been slow. Itwasn’t really an issue until the arrival of the VCR and, later, videogame consoles, which needed a connection to the TV. Remember when there were three cables that delivered the picture fromthe source to the TV?
That was the composite video era. Sound was sent on two analog stereocables that were red and white, while video was sent over ayellow cable. Composite technology is still around, even in today’sHD sets, as it allows for older devices to be connected.
“Composite video is basically the lowest common denominator for videocables,” Michael Heiss, consumer industry consultant, told TechNewsWorld. “It is a legacy cable that will still likely stickaround, as people might need to watch an old VHS tape.”
While composite never went away, it did start facing competition from S-Video,which separates the black-and-white and color signals, thusproviding better image quality than composite video. It became a “stepup” video cable in the late 1990s, offering an improvement in picturequality over composite.
S-Video does not carry an audio signal, andthat has to be delivered separately — either via an analog solutionsuch as the red/white cables, or via a digital option such as optical.As a result, S-Video actually doesn’t streamline the process much.Moreover, it is not able to carry an HD signal.
For HD, the industry adopted component video cables, which transmit video as three separate signals. Again, there were issues — notably,that audio is not carried in these cables, but also the factthat component cables provide no copyright protection for HD content.
The industry’s solution to these problems came in the form of HDMI,which was adopted in 2003. It carries a digital videosignal along with a digital audio signal over a single — albeit it big– cable. By its 10th anniversary, there were more than 3billion HDMI devices in use worldwide, according to the HDMILicensing Group. It had become the true industry standard.
With the arrival of 4K, are the days of HDMI already waning? Not exactly.
HDMI 2.0 — also referred to as “HDMI UHD” — which was released last year, allows for great throughput of data, which meant that it can carry 4K resolution at 60 frames per second (fps). It alsoincludes the options of the Rec. 2020 color space, provides Dual View,4:2:0 chroma subsampling, and supports 25 fps with 3D formats. It supports the 21:9 aspect ratio and offers improved 3D capability.
On the audio front, it carries up to 32 channels of audio, up to1536 kHz audio, and four audio streams. It offers dynamic auto lip-syncsupport. In other words, HDMI 2.0 should be more than enough for thenext generation of displays — but some aren’t convinced.
1.4 or 2.0 – That Is the Question
The problem is that the industry has tried to stick with HDMI 1.4, whichcan’t do all the magic of HDMI 2.0. The first 4K sets supported HDMI1.4, and that has created problems.
“The current HDMI 1.4 spec works with the initial wave of 4K sets,”noted C4’s Schreiner. “It can pass the maximum resolution with the currentgeneration of Ultra HD 4K TVs, which means it needs to pass3840 x 2160 pixels at up to 30 frames per second, and 4096 x 2160 at24 frames per second.
“That’s the maximum sending and receiving …available in this initial wave of 4K sets,” she added.
“We’re just atthe beginning of a new product cycle, so we expect that this willbecome of greater concern in the next generation of TVs — and newer 4Ksets are already starting to sport HDMI 2.0 ports,” Schreiner said.
“HDMI 1.4b, which is supported by systems now, provides UHD at 30frames per second and 24 bits color,” noted Craig Wiley, chair of the VESA(Video Electronics Standards Association) marketing task group.
“Released in September 2013, HDMI 2.0 extends this capability to 60frames per second, but the difficulty has been in delivering HDMI 2.0, since it extendsthe data rate on a legacy signal format that is difficult to support,” he told TechNewsWorld.
The Argument for DisplayPort
Because the move to HDMI 2.0 could require a radical shift, interest has arisen in adoptingDisplayPort 1.3 as the next-generation cable interface for TV displays.
“VESA published the DisplayPort v1.2 standard in January 2010, whichprovided support for 4K up to 60 frames per second and 30 bit color,and there have been systems available now for a few years,” Wiley pointed out.
“DisplayPort uses the common high-speed signal technologyshared by USB, PCI Express, and other high-speed interface standards,” he said.
“DisplayPort 1.3, the latest version of the DisplayPort standard,delivers a higher data rate, which is sufficient to support 4K videoat 120 Hz, multiple 4K video streams, or 5K video. [It] is used by the latestcomputer monitors in the marketplace,” continued Wiley.
“The emergence of 4K video resolutions and beyond may spark areassessment of video interconnect technologies,” he suggested.”DisplayPort is based on a more modern packetized data structure thatuses all four lanes for data transmission with an embedded clock,and it’s easily implementable in today’s submicron processtechnologies — meaning the DP interface can be integrated.”
However, to move to DisplayPort would require a complete replacement ofthe existing HDMI cables. It is unlikely consumers or the industryare ready to unplug one cable for another. It also would meanthat a new port would be required in future set-top boxes, Blu-rayplayers and game consoles. That would require a lot of updating ofequipment.
“DisplayPort has its champions,” said Schreiner.
“We are at acrossroads of sorts, moving towards terrific resolution with greatersimplicity, and I’m not sure that the market could bear a transition toDisplayPort as yet another format,” she added.
“In general, there seems to be enough confusion by consumers — and theyare just getting their heads around 1080p,” noted Schreiner. “TVmanufacturers are also wary as profit margins are squeezed, andinvestments have been made in HDMI designs and manufacturing for theforeseeable future.”
Further, there is the issue that perhaps more can be put through the nextgeneration of HDMI to keep it plugged in for years to come.
“DisplayPort is a pipe, just like HDMI is a pipe,” observed Heiss.
“You canput in what you want, up to the bandwidth limit. Yes, DisplayPort canhandle all this stuff, but what isn’t so visible is the copyprotection — and that is another issue that will have to be resolved,” he said.
“Sure, some people like DisplayPort because it has greater bandwidthand it has higher resolution,” acknowledged Heiss. “Apple and Panasonic use it –but most TV sets don’t have DisplayPort. That is not a knock on thetechnology. It is just that HDMI has billions and billions served.”
I’m surprised that you went to the trouble to talk about 4:2:0 color space, but did not describe 4:4:4 color space at 60Hz, and the higher bandwidth required for it. Moving forward into FY2016, there are two requirements for the maximum picture information to be displayed of native 4K material. 1) HDMI 2.0 with 18Gbps bandwidth, and 2) source and sink devices which are 4:4:4 compliant, not merely 4:2:0 compliant (which is equivalent to current Blu-ray color space). Unfortunately there are no regulations which dictate that manufacturers must adhere to only the 4:4:4 certification OR that they must label their devices as being 4:2:0 or 4:4:4 compliant. This means that even if you have 4K content (which natively is 4:4:4) and have a 4K display (ADP, UltraHD FPD or FPJ), if there is anything in between, such as a receiver or switch which is only 4:2:0 compliant, then the display will only show 4:2:0, not 4:4:4.
On a side note, Sony has thrown a big monkey wrench into the mix by mandating HDCP 2.2 compliance in the digital chain of devices in order to show 4K theatrical releases (at least Sony/Columbia-TriStar titles). Otherwise the resolution will be downgraded, as will the color space.