HDMI is the most favored method of connecting consumer audio and video devices across the world. It may look like an ordinary cable, but it is one of the few universal interfaces of its kind that is designed to carry everything from audio, video, Ethernet, and additional digital signals at the same time.
HDMI eARC is the enhanced version of the ARC (Audio Return Channel) protocol that has already existed in the HDMI standard. However, this nifty feature implemented within the HDMI standard is instrumental in simplifying home theater setups further by obviating the need for additional cables. To understand what separates eARC from ARC, it is vital to know the significance of HDMI and what role ARC plays in the home theater ecosystem.
HDMI: Decluttering Your Entertainment Room
The dawn of the digital era in home entertainment space saw different brands introducing their own proprietary formats, each with their own cables, interconnects, and digital standards of communication between devices. It didn’t take long for the rear I/O panel of an AV receiver in the average home theater setup to have nearly as much cable spaghetti as a poorly maintained data center. The major home theater players soon realized that it would be impossible to make their products appeal to consumers without slaying the cable spaghetti monster their fragmented connectivity standards had created.
Their answer was yet another proprietary connectivity standard called HDMI. The HDMI specification is the fruit of seven founding companies joining forces and involving a forum of 83 electronics stakeholders to create a single cable that is truly capable of decluttering and simplifying the home theater ecosystem.
This new interface has enough bandwidth to carry high-resolution video, uncompressed multi-channel audio, Ethernet, and additional digital data (including digital handshake data pertaining to anti-piracy measures) both upstream and downstream. HDMI primarily serves as the single cable that interfaces with virtually every single piece of equipment in your home theater setup while eliminating the need for several different interconnects.
What is HDMI ARC?
Although HDMI appeared in consumers’ homes in 2004, the Audio Return Channel (ARC) protocol wasn’t introduced until 2009 with version 1.4 of the HDMI specification. An HDMI cable connected to a TV usually receives video and audio signals from a source such as a video game console, Blu-ray player, AV receiver, or set-top box. The ARC protocol allows the TV to send audio data “upstream” to the source device over the HDMI cable.
Do I even need HDMI ARC?
If you own a flatscreen TV, you probably have invested in an aftermarket speaker system. The speaker system can range from a simple soundbar to an elaborate AV receiver hooked up to a massive 5.1 channel surround-sound setup. Most consumers use a separate optical or coaxial cable to carry sound signals from the TV to such speaker systems. This is especially true if they want the external speaker system to play the audio stream from the set-top box connected to the TV or onboard video streaming apps such as Netflix, Amazon Prime Video, and Hulu.
HDMI ARC removes the extra optical or coaxial cables needed to carry the digital audio signal from the TV to the AV receiver (or soundbar). The same HDMI cable that carries the video signal from the AV receiver to your TV can now be used to send the audio signal from the devices connected to the TV (and built-in streaming apps) to your external speaker setup. Anyone who owns an external speaker setup will benefit from HDMI ARC because it is the most convenient and clutter-free means to relay audio signals from the TV.
Enter HDMI eARC: Bringing ARC Up to Speed
Although the HDMI standard had the automatic lip sync correction feature a good three years prior to the introduction of HDMI ARC, its implementation was left optional. Not surprisingly, the processing delays between connected devices caused lip sync issues if the interconnected devices hadn’t implemented automatic lip sync correction. This has changed with HDMI eARC, which makes it mandatory for all devices to implement this feature in order to receive the eARC certification. Therefore, watching movies will not be a hit-or-miss affair with eARC.
HDMI eARC also happens to be implemented in the latest HDMI 2.1 specification. That means it also benefits from the high bandwidth capability of the new standard. The older HMDI ARC protocol had enough bandwidth to carry a compressed 5.1 channel audio signal. However, modern uncompressed multi-channel audio formats such as DTS-HD Master Audio and Dolby TrueHD, in addition to even more complicated object-based formats such as Dolby Atmos and DTS:X, cannot be transmitted over the limited bandwidth capability of the existing ARC protocol.
This is where the massive 48Gbps bandwidth of the HDMI 2.1 specification is leveraged to allow HDMI eARC to deliver uncompressed audio data with an impressive (and overkill) resolution of 24-bit/192HKz at 38Mbps. On top of that, it also extends the channel cap all the way up to 32 discrete audio channels. The new eARC protocol will not only handle the uncompressed digital audio formats supported by streaming video apps but also the most bandwidth-heavy formats found on 4K Blu-ray discs and upcoming next-generation video game consoles.
Another lesser known HDMI feature is the Consumer Electronics Control (CEC), which allows different devices connected by HDMI cables to achieve a digital handshake. This in turn allows these devices to communicate with one another and enables cool features such as letting users control basic functions of multiple devices with a single remote controller. This feature was a hit-or-miss affair due to the fragmentation caused by different manufacturers using their own implementation. With HDMI eARC, this digital handshake promises to be more solid and seamless.
What do I need to use HDMI eARC?
At the bare minimum, you will need two devices supporting the new HDMI 2.1 standard, which also includes the eARC protocol. For most average consumers, this will involve a TV and AV receiver (or soundbar) supporting the new HDMI 2.1 specification. Furthermore, you will also need Ultra High Speed HDMI cables to support all features of the new eARC protocol, especially if you also intend to use the highest resolution video modes supported in the new HDMI 2.1 specification. However, existing High Speed HDMI cables with Ethernet capability will also support all eARC features.
Will my new TV (with eARC support) work with my old ARC-capable soundbar?
The official answer from the HDMI forum, unfortunately, is a big maybe. The HDMI 2.1 specification doesn’t impose any restriction on manufacturers to ensure backwards compatibility with the HDMI ARC protocol before giving out eARC certification. Technically, eARC isn’t defined to be backwards compatible with ARC.
Future-Proof with HDMI 2.1
However, since only a handful of new devices have eARC support at the moment, it only makes sense for manufacturers to make the new eARC devices capable of at least talking with existing ARC hardware. In all probability, your eARC-enabled TV will pass audio signals onto your ARC-compatible soundbar. But definitely don’t expect to pass eARC-only high-resolution audio signals through older ARC hardware.
As the HDMI 2.1 standard is newly ratified, devices such as TVs, soundbars, and AV receivers supporting it are slowly being introduced. The upcoming PS5 and Xbox Series X video game consoles are also expected to ship with HDMI 2.1 capability considering their output resolution capability. If you are in the market for new TV and audio/video gear, you might want to make sure to buy HDMI 2.1 capable devices to be ready for the future.