With the new batch of sound bars, AV receivers and televisions, you now see a new sticker on the packaging: HDMI eARC. This successor to HDMI-ARC promises better sound quality and ease of use. So progress – although the story turns out to be a bit more complex than hoped in practice.
What is HDMI eARC?
What is eARC correct? For that we must first talk about its predecessor, HDMI-ARC. This standard has been around for a while and as the name implies, this technology is part of the wider HDMI standard. Version 1.4 to be exact, introduced more than eleven years ago. HDMI-ARC was 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, as it were, against the current, because an HDMI cable, according to the original HDMI thinking, only served to bring video to the television. Not to transfer audio to another device. For that you only had to use a separate optical cable.
Perhaps that is why ARC was only added much later to the very first HDMI standard, 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 that there would be reason to take the audio from a television “outside”. Now that seems strange, but in the early 2000s the soundbar was still a relatively new invention. Who at that time wanted better sound with his image, only had to use an AV receiver to bundle video sources and drive speakers. In that view, the TV was just a ‘stupid’ screen.
Trend 1: AV receivers become 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. The one his death turned out to be the other the bread. There was no escaping: more and more people just wanted an audio device that they could quickly and easily connect to their TV set. Complicated receivers with their own video switching capabilities and extensive speaker setups, hardly anyone wanted to. As home cinema enthusiasts, we would say, “They are wrong.” But that’s a different story.
Trend 2: Streaming displaces 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 of streaming services (such as Netflix) on the TV itself became very popular. In short, television itself became the source of content – and therefore also of the accompanying sound. Nowadays, if there is still an external device 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 latest generation surround codec, both for physical carriers and streaming services. At first Atmos seemed like something for the avid home cinema builder and irrelevant for people who “only” bought a soundbar. However, the technology does not stand still, allowing an increasingly accurate reproduction of surround (including height channels) through a soundbar. In 2020, such a device still cannot match a good setup with discrete speakers. But it cannot be denied that placing and connecting eleven speakers in a room with an AV receiver takes much more effort than installing and connecting a soundbar. Not to mention the price difference: a top-level soundbar with Atmos costs around 1,000 to 1,500 euros, with the occasional highlight such as the 2,500 euros Sennheiser Ambeo Bar . For a setup with receiver and speakers that offers 5.1.4, you will soon lose 4,000 – 5,000 euros. Or much more. Spending 2.5 to four times more for better quality but less convenience, few sign for that.
The same, but different
HDMI-ARC has proven to be very useful, but for different reasons. the standard runs 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, but technically eARC is completely different. Where ARC uses the CEC channel for 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 turned out to perform fickle. This is not so bad for reporting a volume change (and that will therefore continue to be done at eARC 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 surround encoding in a streaming service app.
So a plus of eARC is that fewer problems may occur with the combination of audio device television. Additionally, this data channel is also used to control the lip sync. eARC audio devices should therefore play sound perfectly synchronized with the picture.
The biggest advantage that everyone points out is that the eARC connection has more bandwidth than HDMI-ARC. The latter was limited to maximum compressed 5.1 streams, such as Dolby Digital +. However, eARC extends the old limitation from 1 Mbit / s to 37 Mbit / s. As a result, uncompromised surround sound can be carried over eARC, such as the Dolby Atmos variant used with an Ultra HD Blu-ray film.
A real breakthrough? Yes, but at the same time it doesn’t really matter. The Netflix trend means that the added value of eARC in terms of bandwidth is relative. 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 handle Dolby Atmos height channels embedded on Dolby Digital Plus, which takes up less bandwidth than the Atmos channels embedded on Dolby TrueHD (as you 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 HDMI eARC
At eARC the audio is sent in a different way than ARC. That means that the 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 asks 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 how it will be in a few years if eARC has become commonplace. You might get sound bars that don’t want to work with TVs that only have HDMI-ARC.
There is a connection between the new HDMI 2.1 standard and eARC. But you don’t need one for the other. eARC, like some other new features (such as Auto-Low Latency Mode or ALLM), is 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 may already be the case in the fall of 2020, but many sound bars and receivers have been postponed due to the corona crisis.
The TV as central hub
Even more fundamental than the other technology is that behind eARC there is a different philosophy than with ARC. With eARC, the television becomes the central hub to which all sources are connected. Thus, all audio from source devices goes to the television and is then sent by the TV to the audio device that is connected to the HDMI eARC port. Even if you own a AV receiver the HDMI Forum thinks, you would still have all the sources on the television. The main reason for doing this is that you no longer have to switch an AV receiver because a new HDMI standard appears. After all, most HDMI updates revolve around video enhancements.
At 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), at eARC only the display can be changed. A practical consequence of that eARC philosophy is. that more and more audio devices only have one HMDI port.
This trend is already visible, especially for 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. An important part of the eARC philosophy is that all sound (including those source devices) is brought to the soundbar in the highest quality. So the eARC philosophy implicitly implies that there is some sort of passthrough option in your TV settings. How else would the audio stream from a video source get unchanged with your audio device? But here the shoe pinches, because in practice the passthrough option sometimes turns out not to be there. For example, it appears that some new LG and Samsung TVs are not transmitting DTS streams – possibly due to licensing discussions, although we do not get confirmation of that.
Where to find Atmos?
If you don’t have a headache yet , we’re happy to give you one last push toward migraines by pointing out that Netflix, Amazon and other streaming services do offer Dolby Atmos soundtracks. But not always and not on every device. It is a soup for the average consumer. Netflix on our LG C9 in the living room and the Sony KD-A9F in the test room offers the series “Space Force” with Atmos. But with the slightly older 2016 Samsung TV that is normally also used for tests, you also get Dolby Digital 5.1 with the same series. The differences sometimes have to do with technology, but often also with licensing agreements. A tangle that reviewers barely touch, 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, you have to find out that your source can supply it. Admittedly, this is probably only a challenge if your television is slightly older. A new eARC compatible device may support Dolby Atmos through the apps of streaming services. Otherwise, you have to invest in a suitable media player, such as an nVidia Shield (2019) or an Apple TV 4K. But note: an older TV will not necessarily forward an audio stream coming in to 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’s still a big unknown: what will the next-gen consoles offer? We suspect that the next Xbox will bet on Dolby Atmos, just like the current Microsoft console, but it looks like Sony will choose MPEG-H with the PlayStation 5 – a 3D codec that will be available on TV channels in Asia. modest advance. At Sony, that codec is also “disguised” with the name 360 Reality Audio.
On paper, eARC seems to be the solution to the many problems that people with HDMI-ARC experienced. But was the standard the real problem? No, if something did not work properly, it also depended on how manufacturers implemented the technology, often with their own unofficial approach or modification. eARC seems to be better equipped to do this, but we already notice that the new standard is not used 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 of course undermines the hoped universality of eARC. The fact that the discovery phase is now better organized is very positive.