The Current State of HDMI -
It's now been more than three years since the HDMI 2.0 standard was released and more than 2 years since the first 4K/UHD consumer products showed up with HDMI 2.0 inputs/outputs. There were subsequent enhancements/extensions (e.g., support for High Dynamic Range) to that standard in the form of HDMI version 2.0a. The introduction and transition from HDMI 1.4 to HDMI 2.0, along with the transition to HDCP 2.2 and its copyright protection mechanisms, resulted in a number of compatibility issues among 4K/UHD source devices, displays and intermediate devices, such as audio/video receivers (AVRs). Many of those issues have been slowly worked out to the point that most currently available hardware seems to be compatible, but there are still certain makes and models of devices that when connected to other HDMI 2.0 equipped devices may have issues.
The other 'component' in the signal distribution chain that has been a issue, especially for home theater owners that are using a 4K/UHD projector, has been the HDMI cables. HDMI 2.0 allows for data rates up to 18 Gbps while HDMI 1.4 max'ed out at 10.2 Gbps. When moving to HDMI 2.0 the fact is that most "high speed" HDMI cables simply cannot pass the highest data rates allowed by the HDMI 2.0 standard when the cable is more than a few feet long. This can be a real problem since home theater video projectors are frequently ceiling mounted and located some distance (e.g., 25 ft. or more) from the 'equipment rack' when you take into account running the cable, from the equipment rack to the wall, up the inside of the wall, above the room's ceiling, and then down to the projector.
In 2016 the HDMI Licensing Organization came out with standards, including testing requirements, for certifying cables to support the maximum HDMI 2.0 bandwidth requirements. More information on the Premium High Speed HDMI Cable Certification program can be found
HERE. HDMI cables that pass these certification tests are allowed to be labelled as "Premium Certified" HDMI high speed cables and carry the official certification label as shown below.
So if you have, or plan to, upgrade your home theater to fully support 4K/UHD, I strongly encourage you to use HDMI cables that carry the Premium Certification sticker. While taking this step should make your home theater wiring 'future proof' for the next few years, there is whole new generation of HDMI coming along within a few years (see below), and this will also require a new generation of HDMI cables.
Next Generation HDMI -
Just when it appears the consumer electronics industry is starting to get the HDMI 2.0 compatibility issues worked out, the HDMI Organization has released the HDMI 2.1 standard. This next generation version of HDMI substantially increases the capability of HDMI to handle Ultra HD signals and video formats.
As background, the current HDMI 2.0 can support 4K/UHD signals, with refresh rates up to 60Hz. However, at that resolution and refresh rate the bit depth is limited to just 8-bits when the chroma (color) format is either in 4:4:4 or RGB format (i.e., providing full 4K resolution for color information in the image). Alternatively when the lower resolution chroma 4:2:0 format is used, the bit depth can go upto as high as 16-bits. The current HDMI 2.0 standard does not support resolutions beyond 4K/UHD (2160P) nor are refresh rates above 60 Hz.
The recently announced HDMI 2.1 standard substantially increases the capability of HDMI well beyond what's possible with HDMI 2.0. More specific (the following is directly quoted from the press release):
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"HDMI Specification 2.1 is the most recent update of the HDMI specification featuring advanced features for the HDMI eco-system. It supports a range of Higher Video Resolutions and refresh rates including 8K60 and 4K120, Dynamic HDR, and increased bandwidth with a new 48G cable. Version 2.1 of the HDMI Specification is backward compatible with earlier versions of the Specification.
HDMI Specification 2.1 Feature Highlights Include:
- Higher Video Resolutions support a range of higher resolutions and faster refresh rates including 8K60Hz and 4K120Hz for immersive viewing and smooth fast-action detail.
- Dynamic HDR ensures every moment of a video is displayed at its ideal values for depth, detail, brightness, contrast, and wider color gamuts—on a scene-by-scene or even a frame-by-frame basis.
- 48G cables enable up to 48Gbps bandwidth for uncompressed HDMI 2.1 feature support including 8K video with HDR. The cable is backwards compatible with earlier versions of the HDMI Specification and can be used with existing HDMI devices.
- eARC supports the most advanced audio formats such as object-based audio, and enables advanced audio signal control capabilities including device auto-detect.
- Game Mode VRR features variable refresh rate, which enables a 3D graphics processor to display the image at the moment it is rendered for more fluid and better detailed gameplay, and for reducing or eliminating lag, stutter, and frame tearing"
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The big news technically is the maximum supported data rates are increasing from the 18 Gbps of HDMI 2.0 up to a maximum of 48 Gbps with HDMI 2.1. This will require a whole new generation of HDMI transmitter and receiver chips (ICs) to be developed for use in such future electronic devices as TVs, projectors, AVRs, disc players, streaming players, etc. Also a new generation of HDMI cables will be required.
This increased bandwidth for HDMI is needed to support advanced video and audio formats, such as:
- support for 8K/UHD (4320p resolution) video format at up to 60 Hz refresh rate
- support enhancements for 4K/UHD such as refresh rates up to 120 Hz and support for 4:4:4 and RGB chroma formats at increased bit depth when operating at 60Hz
- support for enhanced High Dynamic Range (HDR) formats that dynamically adjust the picture brightness level frame-by-frame
- support for advanced object-oriented audio formats (i.e., beyond the already supported versions of Dolby ATMOS and DTS-X)
So when will consumer electronics start showing up on store shelves that include HDMI 2.1 support? My best guess is we won't see the first products until at least sometime in 2018 and then widespread use won't begin until perhaps, at least, in 2020. Also, the earliest implementations may be a limited versions of HDMI 2.1 with only support for certain specific features. These limited versions may appear well before products become available that support the full 48 Gbps max. data rate as well as the full feature set defined by the HDMI 2.1 standard. I say this based on the history for the roll out of HDMI 2.0 where many early implementations of HDMI 2.0 only supported 10.2 Gbps data rates (i.e., the same as HDMI 1.4) while supporting only a subset of the 4K/UHD features defined by that standard. In fact, there are still some 4K/UHD products being sold today with only a limited version of HDMI 2.0 and we are now nearly 3 1/2 years since the HDMI 2.0 standard was released.
