If you’re unboxing a brand new 4K TV, AV 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.” Some of your current components may have these labels, too! If you’re not sure what they mean, you aren’t alone — but it could be good news for simpler or higher-quality audio connections. ARC stands for “audio return channel,” an HDMI protocol introduced in 2009.
While ARC capabilities are common on at least one HDMI port on devices like TVs and soundbars, not everyone is using this advanced standard to improve their entertainment setup. So we’re a closer look at what ARC is, how it works, and what the upgraded version, known as “eARC,” offers. Let’s start with some important HDMI basics.
See more The HDMI superhighway
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 was 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 AV receiver’s volume or the power button on an AV 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 AV 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 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 AV receiver or soundbar.
There is a caveat here: Even though HDMI ARC can 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.
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 Simon Cohen / Digital Trends
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, along with certain downloaded music files, 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 AV receiver. It’s especially handy for those who own a Dolby Atmos-capable soundbar, like the Sonos Beam (gen-2), 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 AV 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 is eARC just about getting better Dolby Atmos?
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 auto