Beyond HDMI 1.4
The current generation of the HDMI (High Definition Multimedia Interface) specification was issued in early 2010, in the same time frame as the specification for Blu-ray 3D players (which specifies a HDMI 1.4a output). The latest version of the HDMI Specification is v1.4b which is functionally the same as v1.4a, but with the addition of testing requirements to be used by manufacturers to certify compliance with the specification. Most current consumer video devices include support for the HDMI v.1.4a. I provided an overview of the HDMI v1.4a provisions related to 3D video in my very first blog (HERE) for Projector Reviews.
The HDMI Founder’s Group has been superceded by the “HDMI Forum Organization” which was created in October 2011. The idea was to bring additional companies into the process of defining the next generation HDMI standard. A new technical working group, under the HDMI Forum, has been tasked to develop the next generation of the HDMI specification. For this blog I am offering some background as well as speculation for some of the new capabilities that might be enabled by this next generation HDMI specification.
Membership in the HDMI Forum is required in order to participate in the development of the new HDMI specification and that membership is limited to companies willing to pay the $15,000 annual membership fee. Only members of the HDMI Forum have access to the working papers and draft versions of the new HDMI specification, as it is being developed. Therefore, we cannot expect to hear anything official as to what new capabilities/features are being included in the next version of HDMI until the new specification is finalized and approved by the HDMI Forum board of directors later this year.
I’ll start off by describing what we do know about the plans related to the HDMI Forum and the next generation HDMI standard. The following summary is taken directly from information released last fall (2011) and a January 2012 update published by the HDMI Forum Organization on their web site.
“The HDMI Forum expects to release the next version of the HDMI Specification in the second half of this year.”
While the next version of the HDMI Specification will be a new specification it will “…refer to the HDMI Specification v 1.4b and be backward compatible to it.”
There will no more development to the HDMI Specification v1.4b “…and the future versions of the HDMI Specification will build upon all functions and features of the HDMI Specification v1.4b.”
“The next version, which is focused on meeting immediate market needs, will include increased bandwidth to accommodate higher resolutions as well as address new video timings and other features. In parallel, the HDMI Forum expects to develop a longer-term roadmap that will define the next generation of the HDMI interface.”
At the time of the October 2011 announcement the HDMI Forum expected “…to hold Technical Working Group meetings in November and December”  to begin the development of the next generation HDMI specification and a January 2012 update reported: “Current activities include ongoing meetings with the Technical Working Group as well as the Marketing Task Group.”
The January update from the HDMI forum reported “We are very pleased that in just over 2 months, 43 leading consumer electronics, PC and mobile products companies have joined the HDMI Forum”
Steve Venuti, president of HDMI Licensing, along with other members of that organization participated in a press conference during the International Consumer Electronics Show (CES) in January 2012. From their presentation (available for download HERE) it was stated the goals for the HDMI specification update include:
“Display and Receiver Ecosystems Improvements” for “higher resolutions”, “higher refresh rates” and “deeper more lifelike colors.”
For “immediate spec needs” the items “increased bandwidth to accommodate resolutions” and “broader video timing support” were listed.
For “long terms goals” the items “improved connectivity with mobile devices” and “improved command and control” were listed.
Also from a statement made during the same press conference at CES 2012, the new specification is expected to address such things as the needed support for higher resolution video and would “for example”address support for “4K by 2K at 60 Hz.”
The above information is about all that has been made public about the plans for the next generation HDMI Specification, however given what is happening in the consumer electronics industry, we can speculate on some enhancements and support for new capabilities that may be included in this next generation HDMI specification. I want to make it clear this is only speculation on my part, as I have no direct insight on what is going on behind the closed doors of the HDMI Forum or its Technical Working Group. Rather, I am basing my speculation on those technical areas where the limitations of the current HDMI v1.4b specification is starting to become a limiting factor for enabling the next generation of Audio/Video electronics, including the next generation of video projectors.
The current HDMI specification (i.e., HDMI v1.4b) defines support for various video, audio and networking (Ethernet) signal formats. The current HDMI standard includes a shopping list of different video resolutions and refresh rates and specifics the technical details for how each of these signal formats is to be supported via HDMI. While many different video formats are defined, many of these are optional formats while a smaller set of video formats are required to be supported by any display device certified as being HDMI v1.4a (or 1.4b) compliant. The bandwidth supported by the currently HDMI ports and HDMI cables certified as “High Speed” is 340 MHz supporting a maximum data rate of 10.2 Gbps.
AUDIO – For audio the current HDMI standard supports various audio signal format with the most capable being the lossless 7.1 channel audio formats, i.e., Dolby TrueHD and DTS HD-MA, provided by Blu-ray discs, as well as support for multi-channel PCM audio. While it can not be ruled out, I doubt the next generation HDMI specification will add support for additional audio formats, such as support for advanced 9.1 or 11.1 channel audio formats that have recently been proposed for future use in commercial cinemas.
NETWORK – The HDMI 1.4a specification added support for up to 100 Mbps Ethernet networking between connected devices. While most A/V devices are still using dedicated Ethernet networks (using CAT5 or CAT6 wiring) or Wi-Fi for streaming video or transferring video files between devices, perhaps the HDMI connection for networking will gain support in future consumer Audio/Video (A/V) products. It is possible the next generation HDMI specification will add support for 1 Gbps Ethernet. This might prove useful for the transfer of ultra high resolution (especially beyond HD) video between connected devices (e.g., media server and display).
We may also see upgrades to HDMI networking in support of home automation and networking/control of Audio/Video equipment, but some of these enhancements may not make it into the next HDMI specification update (i.e., into a subsequent update to the HDMI spec.).
SUPPORT for HANDHELD and MOBILE DEVICES – This probably refers, at least in part, to adding support for HML (Mobile High Definition Link) that lets mobile devices connect to HDTV’s via HDMI and supports passing power and control signals, along with HD video and audio, across the HDMI connection.
VIDEO – Within the past two years 3D HD video sources and displays have become commonplace and earlier this year the first consumer video display (actually the Sony VPL-VW1000 projector) supporting 4K resolution became available. LG has announced plans to market 4K flat panel TVs late in 2012. The current HDMI specification, as well as the current Blu-ray standard, both have reached their limit as to 3D video capability. While the current HDMI specification supports 4K resolution video, it does not support 3D at 4K resolution. Finally neither 3D or 4K video are supported by the current HDMI standard at high refresh rates or at high color bit depth. I’ll discuss each of these limitations below.
Support for 4K video – The term “4K” comes from the commercial digital cinema world where it corresponds to a projected image with a maximum resolution of 4096 x 2160 pixels (i.e., a total of 8.8 Mpixels with each pixel being square). 4K for consumer use is sometimes being called Ultra High Definition (UHD). The 4K digital cinema format, when all 8.8 Mpixels are used, has an aspect ratio of image is approx. 1.9:1 while fewer pixels (i.e., 3996 x 2160) are used for displaying the more common 1.85:1 aspect ratio used for many commercial movies. HDTV uses an aspect ratio of 1.78:1 and a similar industry 4K standard for “Quad Full High Definition” (QFHD) has been defined with a resolution of 3840 x 2160 pixels (exactly double the vertical and double the horizontal resolution of Full HD 1080p).
Most commercial cinemas equipping with new digital projectors appear to now be installing models supporting the 4K standard (while many older 2K projectors, with 2048 x 1080 resolution, can be found in existing installations). Christie and Sony appear to be the largest suppliers of 4K projectors for digital cinema. Commercial digital projectors are based on the standards set by the “Digital Cinema Initiatives” (DCI). Also the Society of Motion Picture and Television Engineers (SMPTE) has established digital cinema standards for the formating of the digital information. These standards that cover commercial digital projectors include both 2K and 4K resolutions with a bit depth of 12 bits per color (36-bits per pixel) for 2D video. The DCI 4K standard supports 2D video at 24 Hz with no support for 3D at 4K resolution (only at 2K resolution). Digital Cinema projectors do not currently use HDMI for their signal input.
The most common 3D projection technique used in digital cinemas is the RealD system which displays a 2K image using a “triple flash” technique where the projected image alternates between the right and left images of the stereographic image pair. Each right and left image is displayed 3 times (i.e., triple flashed) by the projector. For such a system the input to the projector is 2K resolution video at 48 Hz (24 Hz per each the right and left images). Recently Sony has been demonstrating a dual lens 4K projector where the input to the projector is a 4K image at 24 Hz with the right and left images (each with 2K resolution) placed one above the other within the same 4K resolution video frame. This new type of Sony 3D projector displays both images simultaneously through its dual lenses/filters, rather than alternating the images, as with the RealD approach. In either case the displayed resolution in 3D mode is only 2K rather than full 4K. However, there seems to be some desire to support full 4K resolution in 3D mode and there is a push from some movie producers, notably James Cameron and Peter Jackson to go to a 48 Hz frame rate (per eye) for 3D presentations. Peter Jackson’s “The Hobbit” as well as James Cameron’s upcoming features “Avatar 2” and “Avatar 3” are reportedly being shot at the increased frame rate. Also there are now digital cinema projectors being introduced that support these higher frame rates.
It has been reported (or strongly hinted is perhaps more accurate) that the Blu-ray Disc Association (BDA) is, or will be, working on the specification for a Blu-ray 4K format. No specific time table for finalization of this specification, nor what 4K modes are to be supported, has been announced by the BDA. However, as was done with the introduction of Blu-ray 3D two and half years ago, it can be anticipated that an update to the HDMI specification may also be necessary. Since many of the same consumer electronics manufacturers are represented in both the BDA and HDMI Forum, I would expect the upcoming HDMI next generation specification to be coordinated with the BDA to ensure compatibility with the anticipated Blu-ray 4K specification. It is in this context that I speculate that the update to the HDMI specification may include 4K related options for:
4K resolution video at up to 60 Hz for 2D video (instead of the current 24 Hz limit for 4096 x 2160 resolution and the 30 Hz limit for 3840 x 2160 resolution video). This was already a stated, as an example of the goals, for the next generation HDMI specification, so this not really speculation on my part.
4K resolution video at 24 Hz per eye (48 Hz total) for 3D video sourced from 24 Hz material and perhaps also support provided at 30 Hz per eye for 3D video sourced from 30 Hz material. Perhaps even higher 4K 3D frame rates will be supported (e.g., 4K 3D at 48 Hz per eye), but I doubt they will be for the next HDMI update.
4K resolution video with up to at least 12-bit color depth (instead of the current HDMI 8-bit limit)
4K resolution video with specific support for the DCI Color Space (with expanded color gamut over the HDTV standard) as used for 4K digital cinema.
In addition to the expanded support for 4K video, I suspect there may be a few enhancements also coming for 1080p 3D video support. Specifically, I speculate that the update to the HDMI specification may include options for:
Full resolution 1080p 3D video at frame rates up to 60 Hz (per eye) – (instead of the current limit of 24 Hz)
While the current Blu-ray Disc standard for both 2D and 3D recordings is limited to 8-bit color depth (24-bits total for all 3 primary colors), the current HDMI specification does support “deep color”, with increased color bit depth, for 2D video and the next generation HDMI specification may add support for deep color with 1080p 3D video. Note that many existing Blu-ray players will internally process the source 8-bit per color and (when operating in 2D mode) offer the option to provide the output with artificially created deep color bit-depth.
Since several of the new features/capabilities, that I have speculated may appear with the next generation HDMI specification, will require more bandwidth with higher data rates between the connected A/V devices, a new generation of HDMI cables will be required to support these more demanding requirements.
The next generation HDMI specification is expected to be issued within the next few months and perhaps some more information on the new capabilities enabled by this HDMI update will be available at the CEDIA Expo 2012 trade show in Sept. 2012. If fact, some products announced at the CEDIA Expo may incorporate features enabled by the next generation HDMI specification, especially if those new products are not scheduled to begin shipping until after the first of the year.
My next Blog (expected later in August) will be a CEDIA Expo 2012 preview, then I will be blogging each day from the CEDIA Expo, that starts September 5th (the trade show exhibits open on Sept. 6th) in Indianapolis, Indiana.