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HDMI ARC and HDMI eARC: Everything you need to know

Submitted by Audiovision on Tue, 06/08/2021 - 15:03

The tried-and-true High-Definition Multimedia Interface (HDMI) has been the digital connexion for flat-panel TVs, projectors and other AV devices for more than 15 years. In that time, it has evolved into an all-round connexion that serves as a medium for various video and audio formats.


HDMI ARC (Audio Return Channel) is a clever protocol within the HDMI standard, and in theory can help simplify a complicated AV setup and reduce the number of cables needed.

But what's the point behind it? And where does the new eARC protocol fit into this picture? Read on for all the information you need (and more)...

What is HDMI and HDMI ARC?

HDMI hit the market back in 2002, and the first consumer kit with this high-tech connexion went on sale in 2004.

It was touted as a convenient way to send high-quality digital picture and sound data from a source to a TV, amplifier or soundbar. As HDMI has become the de facto connexion AV, traditional analogue connexions such as SCART and component video have gone into the spare parts bin.


The HDMI interface has evolved over the years, with new versions (HDMI 2.1 is the latest) bringing support for new audio and video technologies such as 3D, 4K, 8K, HDR and high frame rates, to name a few.

It wasn't until 2009 that the HDMI ARC protocol was added to the specifications. It was introduced as part of HDMI version 1.4 and has been part of the specification ever since.


When would you use HDMI ARC?


Or maybe your smart TV uses a built-in video app like Netflix or Amazon Prime Video. Either way, you don't want to use your TV 's speakers for sound - you want to hear everything through a soundbar or home theatre amplifier instead.

Until now, you've had to connect an optical cable from the back of your TV to an optical input on your audio device.

But that's a messy solution. In theory, HDMI ARC solves this problem.

HDMI ARC eliminates the need for an optical cable and allows you to send audio "downstream" from a compatible HDMI jack on your TV to a compatible HDMI ARC jack on a soundbar or AV receiver.


What do you need to use HDMI ARC?


To take advantage of HDMI ARC, you need a TV and an audio processor (AV receiver or soundbar) with matching ARC -enabled HDMI jacks.

Look around the back of your TV - if it has three or four HDMI jacks, you'll need to find the one labelled "(ARC)". The label is not mandatory, but as long as your TV is a late 2009 or newer model, there should be one. Cheque the TV owner's manual if you are unsure.

HDMI ARC may work automatically on some TVs. If it doesn't, you'll need to pick up a remote and make some adjustments at TV, such as disabling your TV 's built-in speakers and setting the TV to send sound to an external speaker or amplifier.

Using HDMI ARC does not require a new HDMI cable. Any HDMI cable should be able to do the trick - it's only when we move to eARC that this could (potentially) become a problem. But more on that later.

As part of the process, consider enabling HDMI CEC (Consumer Electronics Control) so you can turn on your TV and control the volume on your soundbar or amplifier without needing multiple remotes. A word of warning: turning on HDMI CEC can have some unwanted AV side effects - so experiment first.


Are there any problems with HDMI ARC?


Are you worried about potential lip sync issues? HDMI v1.3, introduced in 2006, added automatic audio sync, although it was only optional. This means that some ARC -enabled products will work well together, others may not.

The biggest problem for ARC in its current form is that it is up to manufacturers to decide which elements of the protocol they want to integrate.

Support for all relevant audio codecs is not mandatory, so you can't just assume that a TV will be able to send a 5.1 Dolby Digital or DTS audio track from a movie over ARC. Some manufacturers of TV only support Dolby Digital, while others only support two-channel stereo, which defeats the purpose.

It's worth noting that ARC doesn't allow you to bitstream the full-featured high-quality codecs like Dolby TrueHD, Dolby Atmos, DTS-HD Master Audio or DTS:X soundtracks that you find on Blu-rays and 4K Blu-rays. It simply takes out the core 5.1 stream. If you want this level of functionality, you'll need HDMI eARC.

However, with ARC, you can receive Dolby Atmos audio from streaming services that use this format, including Netflix and Amazon Prime Video. These services embed Dolby Atmos into a Dolby Digital Plus stream that ARC can handle.


What is HDMI eARC? What are the benefits?


Enhanced Audio Return Channel (also known as eARC) is the next generation of ARC. It is a feature implemented in the latest HDMI 2.1 specification.

The main benefit of eARC is a big increase in bandwidth and speed.This allows you to send higher quality audio from your TV to a soundbar or AV receiver.

There's scope for eARC to deliver up to 32 channels of audio, including eight-channel uncompressed streams at 24-bit/192 kHz at speeds up to 38 Mbps.

That means all the high-bit-rate formats currently available on Blu-ray discs, 4K Blu-rays and some streaming services - Dolby TrueHD, DTS-HD Master Audio and object-based formats like Dolby Atmos and DTS:X - will all be compatible.

But whether manufacturers will support them all remains to be seen.

On paper, HDMI eARC should also make handshaking between compatible devices much smoother and negate the need to enable HDMI CEC (which doesn't always work properly) - so running multiple products shouldn't require any extra steps to get everything working.

As for ARC, you need two devices with compatible HDMI eARC jacks for the protocol to work. Although a device doesn't have to be HDMI 2.1 certified, HDMI 2.1 certification pretty much guarantees eARC support.

Samsung offers one port on most models. 

Other products with eARC are also popping up with increasing frequency.

Denon launched its first eARC-compliant AV receivers in 2018, and then also began future-proofing its AV receivers in 2020 with models like the AVC-X3700H, which offers full HDMI 2.1 on one of its seven inputs and two of its three outputs, while the AVC-X6700H's eight inputs and two of its three outputs are HDMI 2.1 certified.

Recently, both the brilliant Sennheiser Ambeo Soundbar and award-winning Sonos Arc have eARC-compatible HDMI 2.1 outputs.


Do I need new HDMI cables to use eARC?


According to HDMI.org, if you currently use a standard HDMI cable with Ethernet or a High-Speed HDMI cable with Ethernet, you should have no problem. Ultra High-Speed HDMI cables with Ethernet will definitely work.

Due to the extra bandwidth needed for some audio formats over eARC, it's possible that very old cables could have issues. In January 2020, HDMI.org announced a mandatory certification programmeto ensure that any cable labelled Ultra High Speed supports all HDMI 2.1 features, including eARC.


Is eARC backwards compatible with ARC?


If your TV is HDMI eARC capable, but your AV amplifier or soundbar is only compatible with HDMI ARC, you'll probably get sound - but the bandwidth limitations of ARC mean you won't be able to experience the high bit rate that eARC can provide. So no, it's not backwards compatible.

Some AV receivers and soundbars (like those mentioned earlier) that don't have HDMI 2.1 chipsets can be upgraded to support eARC, but that varies from manufacturer to manufacturer and product to product. It depends on whether they are using compatible hardware that can accept the necessary firmware update.


Time will tell how well integrated eARC will be, but we hope that adoption becomes as ubiquitous as HDMI ARC seems to be now.