HDMI (High-Definition Multimedia Interface) is a set of hardware and software standards designed to support the transmission of audio and video. Unlike older standards, which required separate cables for audio and video, HDMI can handle both though a single connection.
It's now the de facto standard for connecting external devices to TVs, linking external displays to computers (although that often requires an adaptor) and even adding smart TV functions to regular TVs through devices like the Google Chromecast, Apple TV and Amazon Fire TV Stick. Let's take a walk down HDMI Lane to see what makes it tick and how to make informed buying decisions.
HDMI began its life 15 years ago as the standard's founders - Hitachi, Panasonic, Philips, RCA, Silicon Image, Sony, Thomson and Toshiba - sought to have a single cable interface for connecting peripherals and TVs. It's now supported by thousands of companies making everything from TVs to adapters.
Over the years, HDMI has evolved from being a one-way protocol - like sending from a Blu-ray player to a TV - to a bidirectional standard that allows you to connect soundbars, like the Sonos Beam, so sound can be sent out from your TV.
However, if you buy a new device that supports HDMI 2.0, the shift from HDMI 1.4 to 2.0 wasn't as massive as the version numbers suggest. So it's unlikely you'll need to buy a bunch of new cables. If your cables were really HDMI 1.4 complaint, you shouldn't have any trouble with them working with HDMI 2.0 devices.
The most recently ratified release of HDMI is HDMI 2.1. It added better support for 4K video at 120 frames per second, tripling HDMI's bandwidth to 48Gbps, High Dynamic Range (HDR) video and support for 10K video should our eyeballs need it and TV producers ever release content that can take advantage of the higher resolutions.
It's worth noting that HDMI 2.1 is a pretty big improvement on its predecessor and will require new hardware to adopt. So, don't expect a firmware update for your gear to support the new standard.
What About HDCP?
There may be times when you connect some HDMI-complaint gear and get a message about HDCP protection.
High-bandwidth Digital Content Protection (HDCP) is a digital right management (DRM) application developed by Intel that is design to prevent the transmission of unauthorised copies of audio and video.
Interestingly, HDCP's protections are almost useless in stopping content piracy and the encryption and supporting protocols have been broken and the workarounds made public. As a copy-protection mechanism it has proved pretty useless but can be a pain in the butt.
ARC, CEC and HEC
With HDMI being a bi-directional protocol, it's possible to both send and receive data across it. For example, you can connect a Blu-ray player to your TV and the sound and video from the disk will be received by the TV. The audio can then be sent from the TV, out to a HDMI-enabled speaker system.
Or, you can use the remote control unit for one device, control another if the two devices are connected over HDMI.
ARC: Audio Return Channel lets you connect audio devices. For example, the Sonos Beam I mentioned earlier, receives audio from a TV over ARC.
It's worth noting that the support for ARC may not be enabled on every TV or one every HDMI port on a TV. For example, on my Hisense set, there are four HDMI ports but only one is labeled as supporting ARC. So, if you're planning to connect a device you may need to to check which port you want to use.
CEC: The Consumer Electronics Control is all about controlling different connected devices. With the right combination of equipment, it's possible to use one remote control to manage multiple devices.
For example, you could use the volume control for your TV to manage the output from your sounder. In the past, you'd either have two remotes or you'd purchase a universal remote and program it to understand each of your peripheral devices.
HEC: HDMI Ethernet Channel brings together CEC and HEC so a single cable can be used to connect peripherals and allow audio, for example, to be redirected and for a single remote control to be used to control each device. HEC also supports 100Mbps data connections between devices.
Are Expensive Cables Better?
In the early days of HDMI, there were companies selling 1m cables for over $200. Frankly, I always thought that was close to highway robbery.
A discussion on the Choice Community website offers some helpful advice.
For shorter cable runs, paying between $5 and $10 per metre is reasonable but a staff member commenting on that forum notes that guideline is less suitable for longer cables and to pay particular attention to the plugs saying for moulded plugs are better as found that modular plugs fall apart with heavy use.
In other words, as long as the cables are at least HDMI 1.4 compliant and you stick to shorter runs of under 3m, there's little value in spending a small fortune on cables.
Eventually, standards change and new ways of doing things are invented. In larger AV projects I've been involved with, we've deployed HDBaseT which uses CAT6 cable for transmitting all sorts of different data.
The stand supports uncompressed ultra-high-definition digital video and audio, Ethernet, control signals, USB 2.0, and up to 100W of power over a single CAT6 cable at distances of up to 100m.
At the moment, the main application of HDBaseT is in commercial environments where it's easier to deploy networking cable. For example, in boardroom fit-outs I've seen the contractors run multiple lengths of ethernet cable without having to assign them to specific functions. That means you can use one type of cable for multiple applications, thus making future-proofing easier.
Whether this makes it's way to the consumer market is debatable but it's a development worth keeping an eye on.