What is HDMI eARC exactly? For that, we must first talk about its predecessor, HDMI-ARC. This standard has been around for a while and as the name indicates, this technology is part of the broader HDMI standard. Version 1.4 to be exact, which was introduced over eleven years ago. HDMI-ARC meant a breakthrough in ease of use, because the ARC connection allowed the sound from your TV to be sent to an audio device via the HDMI cable. Actually, we should write ‘returned’, not ‘sent’, because ARC means Audio Return Channel. The idea was that the audio went against the grain, as it were, because an HDMI cable, according to original HDMI thinking, only served to bring video to the television. Not to route audio to another device. You only had to use a separate optical cable for that.
Perhaps that is why ARC was only added to the very first HDMI standard much later, which was already established around 2002. Why did it take seven years for this useful technology to arrive? Possibly because the HDMI creators initially did not think there would be a reason to bring the audio from a television ‘outside’. Now that seems strange, but in the early 2000s the soundbar was still a relatively new invention. Anyone who wanted better sound for their image at that time had to use an AV receiver to bundle video sources and control speakers. In that view, the TV was just a ‘dumb’ screen.
Trend 1: AV receivers are becoming less popular
After its introduction in 2009, HDMI-ARC quickly became indispensable, thanks to the steep rise of the soundbar and the collapse of the AV receiver segment. One’s death turned out to be the other’s bread. There was no escape: more and more people simply wanted an audio device that they could quickly and easily connect to their TV set. Complicated receivers with their own video switching options and extensive speaker setups, hardly anyone wanted to. As home theater fans, we would say, “They are wrong.” But that is an other story.
Trend 2: Streaming is displacing discs
At the same time, there is another trend that has emerged especially in recent years: external video sources (such as a Blu-ray player or digicorder) are being used less and less. Instead, the apps from streaming services (such as Netflix) that are on the TV itself became extremely popular. In short, television itself became the source of content – and therefore also of the accompanying sound. Nowadays, if there is an external device hanging on a television screen, it is a console.
Trend 3: Surround goes for 3D
Recently, a third trend was added: the breakthrough of surround sound with height channels. Think of DTS: X and Auro3D, but especially Dolby Atmos. This is by far the most popular surround codec of the latest generation, both for physical carriers and for streaming services. Initially, Atmos seemed like something for the avid home theater builder and not relevant for people who ‘only’ bought a soundbar. However, technology is not standing still, making an increasingly accurate reproduction of surround (including height channels) by a soundbar possible. In 2020 such a device can still not match a good set-up with discrete speakers. But it cannot be denied that placing eleven speakers in a room and connecting to an AV receiver takes a lot more effort than installing and connecting a soundbar. And then we will not mention the price difference: a top-level soundbar with Atmos costs approximately 1,000 to 1,500 euros, with the occasional outlier such as the 2.Sennheiser Ambeo Bar . For a setup with receiver and speakers that offers 5.1.4, you will quickly lose 4,000 – 5,000 euros. Or much more. Few would like to spend 2.5 to four times more for better quality, but less convenience.
The same, but different
So HDMI-ARC has proven to be very useful, but for several reasons the standard has run into its limitations. Time for an update: eARC. It is only one letter more, but it is a serious evolution. Make no mistake, apparently ARC and eARC do about the same thing, but technically eARC is completely different. Where ARC the CEC channel used for the communication between TV and audio device, eARC uses the data channel that was provided to send a network connection over an HDMI cable. That Ethernet-over-HDMI channel has been around for a long time, but is hardly used in practice. The step to this channel is significant, because HDMI-CEC often proved to perform fickle. This is not so bad for reporting a volume change (and with eARC that will therefore continue to be done via CEC). More importantly, eARC must prevent errors during a so-called discovery moment (in which the TV and audio device tell each other what they can do). Because that is very problematic and can cause silences if, for example, you click on a certain piece of content with a surround encoding in a streaming service app.
A plus of eARC is therefore that fewer problems may occur with the interplay between audio device and television. In addition, this data channel is also used to control lip sync. So eARC audio devices should play sound in perfect sync with the image.
More bandwidth
The biggest advantage everyone points out is that the eARC connection has more bandwidth than HDMI-ARC. The latter was limited to maximally compressed 5.1 streams, such as Dolby Digital +. eARC, however, broadens the old limitation from 1 Mbit / s to 37 Mbit / s. EARC can therefore carry uncompromised surround sound, such as the Dolby Atmos variant used with an Ultra HD Blu-ray movie.
A real breakthrough? Yes, but at the same time it doesn’t really matter. The Netflix trend means that the added value of eARC is relative in terms of bandwidth. After all, an HDMI-ARC connection is sufficient to transmit surround sound from streaming services, even when it comes to Dolby Atmos. After all, Netflix and co use Dolby Atmos height channels embedded on Dolby Digital Plus, which takes up less bandwidth than the Atmos channels embedded on Dolby TrueHD (as you will find with Ultra HD Blu-ray movies). Is that going to change? Given that in a soundbar scenario you get relatively little in terms of quality from the step from DD + to TrueHD and that that step would consume much more internet bandwidth, we do not think that streaming services will do this quickly.
ARC is not eARC
With eARC, the audio is sent in a different way than ARC. That means that those two techniques are not compatible. Still, new eARC sound bars will probably work if you connect them to older TVs. After all, the HDMI Forum is asking audio manufacturers to offer ARC as a fallback option. However, it remains a question, it is not an obligation. For a soundbar manufacturer that is now releasing a device, it would be commercial suicide not to support ARC, but who knows what it will be like in a few years when eARC has become commonplace. Perhaps you will get sound bars that do not want to work with TVs that only have HDMI-ARC.
HDMI 2.1
There is a connection between the new HDMI 2.1 standard and eARC. But you don’t need one for the other. eARC is just like a number of other new functions (such as Auto-Low Latency Mode or ALLM) also available with HDMI 2.0. So you see, for example, AV receivers that support eARC, but not 4K / 120fps or 8K that makes HDMI 2.1 possible. From 2021 we expect that new audio devices will all support HDMI 2.1. Actually, that should probably already be the case in the autumn of 2020, but due to the corona crisis, many soundbars and receivers have been postponed.
The TV as a central hub
Even more fundamental than the other technology, there is a completely different philosophy behind eARC than with ARC. With eARC, the television becomes the central hub to which all sources are connected. So all audio from source devices goes to the television and is then sent through the TV to the audio device that is connected to the HDMI eARC port. Even if you own an AV receiver , the HDMI Forum thinks, you would still have all sources connected to the television. The main reason for doing this is that you no longer have to switch an AV receiver because a new HDMI standard is emerging. After all, most HDMI updates revolve around video enhancements.
With ARC you had to replace both the receiver and the screen if you wanted to take advantage of those innovations (or hang your source devices on your TV), with eARC you only have to change the display. A practical consequence of that eARC philosophy is. that more and more audio devices only have one HMDI port.
This trend is already visible in sound bars. Connecting a console or TV decoder directly to your soundbar is no longer recommended. As long as your TV has enough inputs, that’s not so bad. It is important to the eARC philosophy that all sound (including from those source devices) is brought to the soundbar in the highest quality. The eARC philosophy implicitly implies that there is some kind of passthrough option in your TV settings. How else would the audio stream from a video source reach your audio device unchanged? But this is where the problem is, because in practice this passthrough option sometimes turns out not to be there. For example, it appears that some new LG and Samsung TVs do not transmit DTS streams – possibly due to licensing discussions, although we do not receive confirmation.
Where can you find Atmos?
If you don’t have a headache yet, we would like to give you one last push towards migraines by pointing out that Netflix, Amazon and other streaming services do offer Dolby Atmos soundtracks. But not always and not on every device. For the average consumer it is a soup. Netflix on our LG C9 in the living room and the Sony KD-A9F in the test room offers roughly the ‘Space Force’ series with Atmos. But with the slightly older Samsung TV from 2016 that is normally also used for tests, you get Dolby Digital 5.1 with the same series. The differences sometimes have to do with technology, but also often with license agreements. A tangle that reviewers can hardly get over, let alone the ordinary consumer.
Dolby Atmos is a great experience with the right audio device or surround setup. But if you really want to experience it, then you have to find out that your source can deliver it. Admittedly, this is probably only a challenge if your television is a little older. A new eARC-compatible device may support Dolby Atmos via the apps of streaming services. And otherwise you have to invest in a suitable media player, such as an nVidia Shield (2019) or an Apple TV 4K. But beware: an older TV will not necessarily forward an audio stream arriving on an HDMI channel unchanged to the HDMI-ARC port. Maybe that Dolby stream will be converted to stereo.
Xbox Series X and PlayStation 5
There is another big unknown: what will the next-gen consoles offer? We suspect that the next Xbox will deploy on Dolby Atmos, just like the current Microsoft console, but it looks like Sony will opt for MPEG-H with the PlayStation 5 – a 3D codec that is used by TV channels in Asia. has made modest progress. At Sony, that codec is ‘disguised’ with the name 360 Reality Audio.
Conclusion
On paper, eARC appears to be the solution to many of the problems people encountered with HDMI-ARC. But was the standard the real problem? No, if something didn’t work properly, it was also how manufacturers implemented the technology, often with their own unofficial approach or adaptation. eARC seems better equipped against this, but we are already noticing that the new standard is not being used quite as expected. The universal pass-through from HDMI input on the TV to the eARC port appears to have limitations in practice, for example. And that obviously undermines the hoped-for universality of eARC. The fact that the discovery phase is now better organized is very positive.
