HDMI ARC/eARC: The One-Cable TV Audio Tech Fully Explained

If you’re unboxing a brand new 4K TV, A/V receiver, or soundbar, you’ve likely noticed a little symbol on at least one of the HDMI inputs that says “ARC,” “HDMI ARC,” or “ARC/eARC.” But what do these symbols mean? Hint: It has nothing to do with the reactor that fueled Iron Man’s suits. Rather, ARC stands for “audio return channel,” a protocol that started showing up on HDMI-equipped devices in 2009 and is now a ubiquitous standard.

But despite its nearly universal implementation, not everyone knows what ARC is or what it does. And since the technology is incredibly useful and has the potential to significantly simplify your entertainment system in a myriad of ways, we’re going to explain it all, including its most recent evolution, known as “eARC”: Enhanced audio return channel.

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The HDMI superhighwayHDMI cables held up.

Before we get into HDMI ARC/eARC, let’s quickly recap what an HDMI connection does: It can send digital video and audio from one device to another using a single cable. When it was introduced, that digital superhighway was limited to a single direction of flow. Audio and video traveled from a source device to a TV (or projector) and never the other way around.

The only exception to this is HDMI Consumer Electronics Control (CEC) — a very low-bandwidth set of commands that could be sent in both directions along an HDMI cable, so that a TV’s remote could control an A/V receiver’s volume, or the power button on an A/V receiver’s remote could turn off a TV. It wasn’t until a later revision of the HDMI standard (HDMI 1.4) that this began to change.

ARC: Audio return channel

As the name suggests, Audio Return Channel — which gives us the “ARC” in HDMI ARC/eARC — adds the ability for a TV to send audio backward along an HDMI cable to its source device. Why would you want to do that?

If you own an A/V receiver, and you plug in your Blu-ray players, game consoles, or streaming device into it, the receiver will play the audio portion through your home theater speakers and send the video portion along to your TV. So far, so good.

But not every source of video you might want to watch comes from an external device. Some TVs have their own streaming apps or TV tuners. Before the advent of HDMI ARC, if you wanted to hear these sources on your receiver’s speakers instead of the ones built into your TV, you needed to run a second cable (typically an optical cable) from your TV back to your receiver. That not only destroyed the simplicity of a single-cable connection, but it also meant you needed to press some additional buttons to get things working every time you switched to using your TV as the sound source.

HDMI ARC brings that simplicity back by letting you once again use a single cable for all your needs.

Better sound

Close-up of an A/V receiver display showing Dolby Atmos.
Denon

Optical cables are great for sending Dolby Digital 5.1 surround sound from device to device. However, throw a newer surround sound format at it, like Dolby Atmos or DTS:X, and it chokes. HDMI ARC, with its larger data capacity, can transmit these formats too, so if you’re using your TV to stream a Dolby Atmos title from Disney+, you’ll be able to send that signal to your compatible A/V receiver or soundbar.

There is a caveat here: Even though HDMI ARC has the capacity to transmit higher-bandwidth formats like Dolby Atmos, your TV still has to support these formats. For instance, some TVs will play Dolby Atmos using their built-in speakers, but they can’t pass along that same Dolby Atmos content via their HDMI ARC connection (known as Dolby Atmos passthrough). Always pay close attention to a product’s specifications to know what it can or can’t do.

Simpler switching

Normally, when using an optical connection from a TV to a receiver or soundbar, you need to manually switch to the optical input when you want to hear your TV’s sound, and then switch back to the HDMI inputs on the receiver or soundbar when you want to go back to watching an external source of content. You may also have to enable or disable your TV’s built-in speakers each time you switch.

With HDMI ARC, you can ditch your soundbar or receiver’s remotes — as soon as you start watching content that originates from your TV, your connected soundbar or receiver will automatically switch to the correct input.

eARC: Making ARC even better

LG SP9YA Dolby Atmos soundbar ports with HDMI eARC.
Simon Cohen / Tips Clear

HDMI ARC was a big improvement over optical audio connections, but the technology suffers from one limitation that audio purists have always bemoaned: It has the bandwidth to support Dolby Atmos, but only the lossy version of this format, which uses Dolby Digital Plus. If you’re only streaming Dolby Atmos (say from Netflix or Apple TV+), this is no big deal because that’s the same kind of Atmos that these services use.

But physical media, like Blu-ray discs or game discs for consoles, use a higher quality version of Dolby Atmos thanks to the lossless, hi-res capabilities of Dolby TrueHD. There’s also the possibility that streaming services will decide to offer lossless audio as an upgrade in the future.

As you might have already guessed, Dolby TrueHD requires more bandwidth than Dolby Digital Plus, and the HDMI ARC specification was never designed to handle it. That’s why we now have enhanced Audio Return Channel (eARC), which has plenty of capacity and can handle lossless hi-res audio up to 24-bit/192kHz, which should satisfy even the most demanding audiophile.

When would I use eARC?

Right now, eARC is going to be most useful for folks who connect all of their content devices to their TV’s HDMI inputs, instead of the inputs on a soundbar or A/V receiver. It’s especially handy for those who own a Dolby Atmos-capable soundbar, like the Sonos Arc or Bose Smart Soundbar 900 as these speakers don’t have their own HDMI inputs.

Without an eARC port on your TV, it won’t matter if you have the most expensive Blu-ray player connected to one of its other inputs — you won’t be able to transmit hi-res, lossless audio (whether Dolby Atmos or any other format) to your external audio devices.

For people who connect their devices to an A/V receiver (or a soundbar with at least one HDMI input), the need for eARC is a little less. Typical sources of high-quality audio (Blu-ray players mainly) can be plugged into this gear directly, without relying on the TV’s audio capabilities. But there’s still the chance that you’ll have a high-end audio source plugged into your TV, and at these times eARC would be handy.

So eARC just about getting better Dolby Atmos?

TV dialog sync settings for Sonos Beam.

No, not entirely. HDMI eARC has been designed to allow up to 37Mbits per second of bandwidth for the audio return channel, whereas HDMI ARC was never designed for more than 1Mbits per second. That’s a huge difference and it gives eARC the ability to pass a variety of hi-res audio formats. For instance, while Dolby TrueHD gives Atmos its best showing, TrueHD can also be used to deliver lossless versions of less exotic audio content like 5.1, 7.1, or plain-old two-channel stereo. The same thing goes for formats like DTS:X, DTS-HD, and DTS-HD Master Audio.

eARC has an automated lip-sync feature, so theoretically, you’ll no longer need to jump into delay settings on your TV or audio gear to get a perfect match of sound and picture, the way you sometimes need to do when using HDMI ARC or optical connections.

There are also some potential non-audio benefits to eARC. ARC requires HDMI-CEC to be enabled on your gear — the two work in tandem. eARC has its own built-in mechanism for device detection, which doesn’t require CEC. So while it’s still recommended to keep CEC enabled (turning it off means you won’t be able to send device commands over HDMI), if it’s causing you headaches, it might be possible to use eARC without CEC.

I’ve also heard about HDMI 2.1 — is this the same thing?

That’s the million-dollar question. And the answer is, yes. And no. It’s complicated.

HDMI 2.1 is the most recent version of the HDMI specification — the technical list of requirements that any manufacturer wishing to implement HDMI 2.1 on their devices must adhere to. And yes, HDMI eARC is included among the many features of HDMI 2.1. But here’s where it gets weird.

Manufacturers can, to a certain degree, pick and choose which of HDMI 2.1’s features they want to support. They can support them all or just a few, and either way, they’re still allowed to claim that they offer you HDMI 2.1, which is, quite frankly, messed up. Believe it or not, eARC is considered an optional feature, much as ARC was optional under previous HDMI versions.

To make matters even more complicated, it’s possible to enable HDMI eARC using non-HDMI 2.1 chipsets, which means that a TV could offer eARC, yet possess no other HDMI 2.1 features.

We’ve got a great HDMI 2.1 explainer if you want to do a deeper dive into what this new specification offers (hint: It’s mostly for gamers and people with 8K TVs) but for our purposes, here’s what you need to know: If you’re looking for a device that supports HDMI eARC, look for that exact label on the product box, or in the specs, or on the HDMI port labels.

What equipment do I need for HDMI ARC or eARC?

The Zeskit Ultra High Speed 8K HDMI cable.
Zeskit

For HDMI ARC, you’ll need a TV with an HDMI ARC port, and a soundbar, A/V receiver, or other audio device with a corresponding HDMI ARC port. You’ll also need an HDMI cable to connect these two devices — virtually any HDMI cable will do the job as HDMI ARC is not especially demanding when it comes to bandwidth.

For HDMI eARC, it’s the same thing — both devices need an eARC port, but you’ll also need an HDMI cable that has Ethernet support, like a High-Speed HDMI cable with Ethernet, or an Ultra-High-Speed HDMI cable. As we noted above, eARC places more demands on bandwidth than ARC.

Wondering if your current gear supports HDMI ARC or eARC? If it does, there should be an “ARC” or “ARC/eARC” label on the HDMI port that supports these features.

There’s one important thing you need to be aware of: Even though newer HDMI devices are designed to be backward compatible with older HDMI devices, this is not always true of eARC. Most of the time, if you connect say, an eARC TV to an ARC soundbar, you’ll still get audio from the TV — you’ll be restricted to ARC’s lower-quality audio capabilities, but it should work. But the eARC specification does not require that eARC devices are backward compatible, so there may be some instances where this doesn’t work at all. As with all technical specifications, it’s best to read the fine print and double-check with a manufacturer before buying.

Apple TV 4K 2021

Image showing HDMI eARC settings on an Apple TV 4K (2021).
Apple

The vast majority of folks will use ARC/eARC between their TVs and soundbars or A/V receivers, but there is one unusual case that’s worth mentioning. The Apple TV 4K 2021 model also has HDMI eARC (even though the HDMI port isn’t labeled with eARC), which is bizarre if you think of it just as a streaming media device. But because you can wirelessly connect Apple’s discontinued HomePods or HomePod Minis to this Apple TV to act as your home theater speakers, Apple’s little black box can now act as a kind of hybrid streamer/receiver, letting you listen to any content the Apple TV can play as well as any audio your TV can generate.

Should my next TV, soundbar, or A/V receiver be equipped with HDMI eARC?

In general, we’d say absolutely. HDMI 2.1 (along with HDMI eARC) are the latest standards for connecting audio and video equipment. Even if you don’t plan to take advantage of their benefits immediately, most A/V purchases are going to be around for at least 10 years. That’s a long time to be stuck with something that isn’t current.

However, if you’re buying a small TV for a kitchen or bedroom, and you have no intention of ever connecting it to an external soundbar or receiver, you can probably stick with HDMI ARC (or indeed, no HDMI ARC). And if you’re buying an inexpensive soundbar for improving your TV’s sound, and you don’t care about Dolby Atmos, hi-res audio, or future-proofing, then that device is probably fine without ARC or eARC too.

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