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HDMI ARC and eARC: What they are, how they work


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#1 Tech 425

Tech 425

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Posted 03 December 2017 - 06:16 PM

HDMI ARC and eARC: 
What they are, how they work, and why you should care
 
 
 
 
HDMI ARC is one of the coolest TV features at your disposal. But if you're like most folks, you have no idea how it works, if you know what it is at all. Here's our explanation of what HDMI ARC is, and how it can make you life easier.
 
If you're the owner of a 4K TV or newer HDTV, A/V receiver, soundbar, or home theater in a box, you may have noticed (and then promptly forgotten) a little symbol on one of the device's HDMI inputs that says “ARC” or “HDMI ARC.” What does this mean? Hint: It has nothing to do with the reactor that powers Ironman's suits.
 
ARC stands for Audio Return Channel, which is a little-understood protocol that started showing up on HDMI-equipped devices a few years back, standing today as a ubiquitous standard. The technology is especially useful and has the potential to significantly simplify your home entertainment system. Unfortunately, few know it even exists, much less what it can do. Here, we'll go over the basics of ARC (as well as the forthcoming update to the protocol, called eARC) so you can put its powers to work for you.
 
First, a quick refresher on HDMI itself (feel free to skip ahead if you just need to know about ARC).
 
 
HDMI: The basics
 
HDMI has been around for over 13 years. You probably use it now, but you may not know how versatile it actually is. The system was created as a faster, more efficient way to deliver high quality digital video and audio to and from consumer electronic devices. A constantly evolving format, HDMI 2.0b was a baby step up from HDMI 2.0a, allowing for transmission of 4K Ultra HD video with HDR) at up to 60 frames per second, as well as the ability to transmit information for up to 32 channels of audio.
 
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The latest iteration, HDMI 2.1, which was just announced at the end of 2017, pushes the format even further. With HDMI 2.1, a single HDMI cable can carry 4K video at up to 120 frames per second, 8K video at up to 60 frames per second, and even 10K (now that is looking into the future!). That equates to faster and more efficient transmission to keep up with the monsterous amount of bandwidth video and audio of the future will require — right up to a whopping 48 Gbps! Want even more details? Here's everything we know about HDMI 2.1 so far.
 
Don't freak out, though! HDMI 2.1 format is fully backward compatible with all older hardware. This does not spell certain obsolescence for your existing entertainment system. While it is true that you will eventually need a new Ultra High Speed HDMI cable to take full advantage of the spec's new features, that need is at least a year away for even the most enthusiastic early adopters, and even further out that that for most of us.
 
Back to modern day: Many people currently use HDMI strictly as a means for connecting their cable boxes, Blu-ray players, and game consoles to their TV, but that little cable connection can do so much more.
 
Besides transferring both video and audio in a single feed, HDMI was also designed to carry what the industry refers to as “handshake” information from one device to another. These shared transmissions were originally intended to communicate copy protection data to prevent piracy, and transfer messages about what type of components were connected to each other, and what their capabilities were (and weren't).
 
But the system was also designed to share more complex messages as a part of what's called Consumer Electronics Control (CEC). CEC lets a single remote control operate features on up to 15 connected devices. There are as many names for CEC as there are electronics brands: Samsung calls it “Anynet +,” for instance. Unfortunately, the system has never really lived up to its potential, and is often mistranslated or simply lost between components from different manufacturers. ARC can help.
 
 
The power of HDMI ARC
 
ARC, along with help from CEC, can simplify your home theater system in two important ways. The first, and perhaps most useful feature HDMI ARC brings to casual users is the ability to use one remote for all of your audio device's most common functions. For this example, you may need to go into your TV's settings and activate CEC (Consumer electronics Control), usually found in the general settings. Once everything is set up, your TV remote control could power on your A/V receiver or soundbar at the same time as your TV, and control the volume of either of those devices. Simplicity is the name of the game here.
 
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In some cases, HDMI ARC sends your TV's audio to your sound system without you having to deactivate your TV's on-board speakers. In other cases, though, you'll need to go into the settings in your TV's menu to activate “external speakers” or “receiver” to send sound out from the ARC port to your audio device. (More on that below.)
 
The ARC HDMI port can also be handy for connecting outboard components like streaming devices, and make controlling them easier. Plugging a Google Chromecast into your TV's ARC port, for instance, may allow you to automatically switch sources or even turn on your TV when you click the cast icon on your phone or tablet. You may find similar results with other components as well, including Blu-ray players.
 
 
In through the out door
 
As touched on above, the other important function ARC performs is sending audio signals both “upstream” and “downstream” over a single connection, meaning signals can travel in and out of a device over a single ARC HDMI port and cable. “Downstream” refers to signal that is being passed from the source, say a Blu-ray player, “down” to another device. “Upstream” would then mean sending signal the opposite way over the same cable. Why is that necessary? Convenience and sound quality.
 
For those who use an Audio/Video receiver (or a soundbar with multiple HDMI inputs) as a hub instead of their TV, ARC can simplify cable connections. While audio and video from various sources is going directly to an A/V receiver in this kind of setup, any audio coming from the TV still needs to get to the receiver or soundbar somehow.
 
For example: Let's say that you like your television's built-in streaming apps better than the apps built into your Blu-ray player, or even a Chromecast. Any audio from those streaming apps, like Netflix, Hulu, etc. — or an over-the-air antenna — need to get to your receiver somehow. In the past, this would have required that you connect an optical digital audio cable to link your TV with your receiver. But with HDMI ARC, audio can be sent back down to the receiver through the same cable that already connects the two devices. For those with wall-mounted TVs, that's at least one less cable to snake through the wall!
 
If you think that sounds great, just wait for eARC, likely coming to devices as early as 2018. As we explain in more detail below, with eARC, your TV's audio processing capabilities are no longer part of the equation. You will be able to get the very best surround sound to any of your audio devices with no compromise.
 
Today, TV's dumb down audio signal from glorious surround sound signals to basic 2-channel audio before passing them down an HDMI cable. With eARC, the original, full-resolution audio signal can be sent down the HDMI cable — again, the very best sound, no compromises.
 
Let's say you don't have an A/V receiver, though. As noted above, many soundbars (from Yamaha's affordable YAS-207 to Samsung's powerful HW-K950 Dolby Atmos) also include HDMI inputs to allow a direct connection from a Blu-ray player or other source, allowing you to better preserve the audio quality.
 
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Again, today you can connect the bar to your TV via the ARC HDMI connection to pass the video signal to the TV, and also to receive audio back from TV programming, or any other components connected to the TV. With eARC, that connection just gets better, with no degradation of the audio signal imposed by your TV.
 
 
eArc: The new kid in town
 
With HDMI 2.1 comes eARC, short for Enhanced Audio Return Channel, the new standard designed to allow for better audio resolution from your TV. The new configuration will require eARC support from both your TV and your audio device, which means your devices must support HDMI 2.1 — older HDMI versions will not support eARC. Once standard, eARC will allow easy access to high-bit-rate sound from your TV.
 
This essentially allows you to output the best surround sound signal, including top 3D surround sound like Dolby Atmos and DTS:X, from over-the-air broadcasts, internal streaming apps, and Blu-ray players or game consoles connected directly to your eARC-enabled TV.
 
Previously, decoding high-bit-rate audio like Dolby Atmos required plugging your source device into a compatible audio/video receiver or similar device, as most TVs are limited to outputting compressed surround sound or even stereo audio. With eArc, you'll be able to plug your HDMI devices directly into the TV, which will then send the uncompressed, high-quality audio to a soundbar, receiver, or amplifier directly from the eARC port.
 
What's more, since the HDMI 2.1 spec will offer faster data transfer with more bandwidth, both audio and video will essentially be transferred in real time, with no more worries about adjusting sync issues between the two. Ever had trouble with lip-sync problems? Those issues will be a thing of the past with eARC.
 
In theory, this new protocol also means manufacturers could create a new wave of audio-only receivers, soundbars, and amplifiers, as your TV would be able to handle the video signal, while still allowing for the highest quality audio to make its way to your sound system. This could significantly reduce the cost of all kinds of home theater components!
 
Obviously, it will take a while before eARC is everywhere, but when it is here, we'll enjoy a new level of simplicity and flexibility.
 
With that in mind, it's important that we point out new technology takes time to become widely available. Don't hold off on buying that new receiver or 4K HDR TV you've had your eye on. HDMI 2.1 is a very forward-looking, future-proofing technology still in its infant stage, and while very small corners of the world have begun enjoying 8K content, most of us are still waiting for the full incorporation of 4K content into our setups.
 
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n other words, this is a gradual evolution, and not one that should keep you from enjoying the still burgeoning world of 4K HDR TVs and Dolby Atmos/DTS:X-enabled audio devices. Like all technologies, the future of home theater is announced and planned long before it becomes the standard. Yes, it is impossible to stay on top of the very latest and greatest from home theater land — and that's OK.

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