We frequently get questions from readers with LG 4K OLED or NanoCell/Super UHD TVs asking why they can’t get Dolby Atmos or Dolby TrueHD surround sound from their supporting television.

So, in the interest of updating and clarifying the issue here we offer a few insights readers have found helpful getting Dolby Atmos, Digital Digital+ and Dolby TrueHD surround sound from premium 4K OLED and LED-LCD TVs in LG’s 2017, 2018 and 2019 product lines. — Or in, certain cases, understanding why they cannot.

First the the good news: LG’s 2019 premium 4K (and 8K) televisions either already or soon will support HDMI 2.1 inputs, including the much-anticipated Enhanced Audio Return Channel (eARC) feature. That means, Dolby Atmos and even Dolby TrueHD lossless surround sound signals can be decoded by the TV and sent out (or passed through) over the eARC connector. This will clear up most of the issues that we’ve heard about from some readers over the past two years.

Part of the confusion surrounding some of these high-quality surround sound implementations concerns compatibility with external soundbars, AV receivers, stand-alone decoders and other devices that need to receive the signal from the TV over the previous-generation HDMI Audio Return Channel (ARC) connection.

Since the release of HDMI v.1.4, ARC was made available over one channel, and a number of advancements have occurred that have caught up to and surpassed the initial capabilities of the specification. First, the bandwidth requirements/benefits for streaming audio has gone up, enabling many over-the-top streaming services to move to a more robust Dolby Digital+ codec for online streaming. This has stretched the bandwidth limits of the original ARC specification.

The current ARC was designed to pass a maximum of approximately 1 Mbps (it was originally intended to be 384 Kbps), which is just big enough for DD+ but is insufficient to handle newer and more robust lossless surround sound formats that arrived later, including Dolby TrueHD, DTS Master Audio and others.

On top of these object-based audio formats including Dolby Atmos and DTS:X were introduced, bringing over-head height channels and other 3D sound effects to home theaters.

Dolby Atmos can be encoded as part of either a Dolby TrueHD stream or a Dolby Digital+ stream, depending on capacity/bandwidth requirements. When encoded in either version, the stream containing Atmos carries essentially metadata instructions for extracting and placing the location(s) of the sound of objects in relevant positions around the audience. Dolby TrueHD/DTS-HD Master Audio, which are both lossless variable bit-rate codecs, can take the same object-based information instructions (for Atmos or DTS:X respectively) but each requires significantly more bandwidth to do so.

In the same way, an Atmos encoded Dolby Digital+ stream contains metadata to extract and place object sounds around the room, except that format is lossy. (So the Atmos or similarly DTS:X information is compressed to fit in the limited HDMI-ARC space, but it lacks some of the clarity, depth and dimensionality of the lossless surround sound codecs transporting it).

Dolby Digital+ uses a more efficient compression technique than Dolby Digital at data rates from 96Kbps to 6 Mbps. It can also support up to 7.1 discrete channels, instead of just 5.1 for Dolby Digital.

Popular 4K UHD and HDTVs

Amazon’s Camera, Photo & Video Deals

Amazon Fire TV 4K Ultra HD Set-Top Media Adapter with Alexa

Amazon Fire TV Stick with Alexa Voice Remote

Amazon Echo Plus Voice Controlled Wireless Speaker and Home System Interface

Amazon Echo Dot Voice Controlled Home System Interface

Amazon Echo Spot with Alexa and Screen

4K Ultra HDTV Specials From Abt

Best Selling Soundbars and 5.1 Surround Systems

Spears & Munsil 4K/HDR Benchmark Test Disc, $39.95

Best Selling Blu-ray Players

On previous years’ LG 7 and 2018 8 Series OLED TVs and some Super UHD LED-LCD TV models with Dolby Atmos you can send the decoded Atmos surround information in the TV out over the HDMI ARC connector, but only when the signal is carried in a lossy Dolby Digital+ surround sound stream.

LG TVs also now support the lossless Dolby TrueHD decoding format internally, but in some older models this must be delivered into the television over a non-ARC HDMI input for decoding internally by the television.

One of the things that has made this whole issue so complicated is that when LG first introduced its Dolby Atmos OLED TVs, none of those sets had Dolby TrueHD support built in. That came later through a firmware update. And while a number of the brand’s premium TV models now support TrueHD, that format could only be when a TrueHD signal is input to the TV over a non-ARC HDMI input from a supporting device like a Blu-ray player. There was (until this year) no way to get the decoded Atmos/True HD signal back out of the TV over the old ARC version. The sound was only enjoyed through LG’s built-in sound system or integrated soundbar (like the one in the LG “wallpaper” 4K OLED models).

Further, the best way to enjoy Dolby Atmos or DTS:X presentations for that matter is when they are carried as part of lossless Dolby TrueHD or DTS-HD Master Audio soundtracks. Ideally, these should be played through a true multi-channel home theater speaker system, complete with overhead front and rear-channel channel speakers.

Again, this is because a television, even a good one like LG’s flagship W7 or W8 4K OLEDs from 2017 and 2018, respectively, with the supplied external soundbar (connected to the screen by a flat ribbon cable), will miss some of the dimensionality of the full Dolby Atmos/TrueHD experience with the smaller, more constricted speaker layouts.

To explain further, Dolby TrueHD is a lossless codec that uses less space than a Pulse Code Modulation (PCM) track – an analog signal converted to an uncompressed digital form — but identical in sound to the original master. Dolby TrueHD supports up to eight full-range channels (with room for expansion) of 24-bit/96 kHz audio (at the discretion of the studio) up to a maximum of 18 Mbps bitrate.

So in 2017 and 2018 models, while you can get an LG TV’s decoded Atmos signal to work carried in a DD+ soundtrack over ARC, you would have to decide if the clarity of sound from that compressed format was good enough for you. If not, you were better off listening to the Ultra HD Blu-ray version with the Dolby Atmos or DTS:X content connected directly into a supporting AV receiver which was in turn connected to the television via an HDMI output carrying the video information.

Good news for those who buy a higher-end LG TV in 2019: things get much more flexible using the new Enhanced Audio Return Channel eARC feature specified for voluntary support in the new HDMI 2.1 specification. With that implementation carrying eARC’s ample bandwidth the full signal carrying the Dolby Atmos/Dolby TrueHD (or externally decoded DTS:X/DTS-HD Master Audio) experience can be enjoyed by the TVs internal sound system or by external devices using eARC as the output.

Enhanced ARC was also designed to get rid of the many device recognition and handshake issues that plagued the original ARC implementation. The eARC component is being fully tested and certified by the HDMI Group for use in many products that were designed and marketed as supporting it after firmware updates.

Calibrate and test the limits of your 4K/HDR television with the new Spears & Munsil 4K/HDR Benchmark Ultra HD Blu-ray Disc, $39.95.

Meanwhile, we’ve previously reported on the many new features and capabilities the HDMI 2.1 specification will bring to home theaters, topped off by up to 48 Gbps ultra high-speed bandwidth suitable for advanced high-frame rate (HFR) video in the latest high-resolution levels.

HDMI 2.1 will also allow the ability to support more robust high resolution video game play with dynamic high dynamic range (HDR), low input lag to the television, instant and automatic game mode optimization between the game console and television and clearer images with minimal tearing (via support for variable refresh rates).

But the most interesting of the new HDMI 2.1 features is the aforementioned eARC, which is voluntary for use by device manufacturers. LG was one of the first manufacturers to announce plans to support the feature in many of its 2019 premium televisions.

Unfortunately, this still doesn’t mean that viewers will be able to stream Dolby Atmos or DTS:X enhancements carried in either one of the lossless surround sound channel formats, because thus far none of the major over-the-top (OTT) streaming service providers is offering them. Most OTT streaming services carrying Atmos surround sound today–including Netflix, Amazon, Vudu etc. — continue to use the lossy Dolby Digital+ implementation to ship Dolby Atmos, leaving digital downloads, Ultra HD Blu-ray or HD Blu-ray players as the primary ways to listen to Atmos-supporting soundtracks (as well as DTS:X/DTS-HD Master Audio soundtracks) in a lossless Dolby TrueHD environment.

So if you don’t have a TrueHD supporting NAS device, Blu-ray or Ultra HD Blu-ray player and plan not to get one, the chances are streaming Atmos/Dolby Digital+ is pretty munch the only available alternative.

Furthermore, eARC for the first time allows connecting one of the above mentioned source devices directly into an HDMI 2.1 jack on the LG television and then sending the surround sound signal out to an external decoder over the HDMI 2 eARC port to an AVR or supporting soundbar. Alternatively, some 2019 premium LG televisions will be able to decode internally the Dolby TrueHD and Atmos soundtracks and play them through the set’s built-in speakers, the included soundbar, or even a set of connected WiSA wireless speakers (more on this below).

In a nutshell, the eARC feature in this year’s supporting LG 4K and forthcoming 8K TVs will carry lossless audio output as well as lossless audio pass-through. This ends the frustrating need today of looping source devices first through a receiver and shipping out signals carrying 4K and HDR profiles like HDR10, HLG and Dolby Vision to the television, as the television effectively becomes the switching control hub.

This avoids previous problems with unsupported video standards in an older AVR being blocked as new formats and add-ons emerge; remember the arrival of HDR metadata and new HDCP 2.2 content protection? The latter was notorious for having crippled legacy audio/video HDMI components in the early days of 4K Ultra HDTV. We are now up to HDCP version 2.3 now!

Most 2019 LG 4K OLED (W9, E9, C9) and 2019 4K NanoCell TVs (9500 and 9000) will support eARC on HDMI input 2, with the exception of the 8600 2019 LG NanoCell TV Series, which will omit eARC support, the company told us.

Get the new Spears & Munsil 4K/HDR Hand Forged Video Test Disc Here,$39.95.

As stated above, LG has said its 2019 OLED and flagship LED LCD TVs will also support WiSA wireless speaker connectivity that will be compatible with decoding Dolby Atmos and Dolby TrueHD audio. This means users can purchase a set of WiSA-certified wireless speakers from brands including Bang & Olufsen, Harman Kardon, and Klipsch, and have them work with the television to support up to eight channels of surround sound. No receiver necessary.

WiSA signals operate over the 5.2-5.8 GHz frequency band. The standard has less than 5 ms latency for 24-bit uncompressed audio sources.

On the video side, LG has said it will offer (when certified and available) full bandwidth 48 Gbps HDMI 2.1 ports in many of its 2019 4K TVs, enabling up to 4K at 120Hz.

By Greg Tarr

Have a question for the HD Guru? HD GURU|Email

Copyright ©2018 HD Guru Inc. All rights reserved. HD GURU is a registered trademark.