What’s the Problem with HDMI Audio Return Channel?

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A What’s the problem with HDMI Audio Return Channel (ARC)? I’ve heard that most people simply give up on ARC and use an optical digital audio connection from their TV to their receiver instead because they can rarely get it to work between devices, especially ones from different manufacturers. What can the HDMI Forum do to improve the situation? —Phis Tomaskovic / via e-mail

Q The HDMI Forum already has taken steps to improve the situation by drafting the HDMI 2.1 specification. The new HDMI spec incorporates a long list of advancements to ensure compatibility with future technologies such as 8K/60fps and 4K/120fps video, but also addresses several limitations in the existing HDMI 2.0a spec, including ones surrounding ARC.

A key feature that HDMI 2.1 will bring is Enhanced Audio Return Channel (eARC). With eARC, audio signals benefit from higher bandwidth to support everything from Dolby Digital Plus and lossless Dolby True HD/DTS-HD Master Audio bitstreams to object-based formats like Dolby Atmos and DTS:X. This development is particularly important as more of us start to stream movies with multichannel and object-based audio soundtracks through our TVs, as opposed to playing them on physical discs.

Another aspect of eARC is advanced device control. ARC, which was first introduced in the HDMI 1.4 spec, relies on the HDMI CEC (Consumer Electronics Control) protocol. A problem with CEC is that different manufacturers use their own unique implementations (Bravia Link, Viera Link, etc.). CEC is also an optional feature that’s not required for certification of products by the HDMI Forum. HDMI 2.1, in contrast, will include a robust auto-detect mechanism plus more advanced audio signal control capabilities than what the current CEC specification provides.

HDMI 2.1 will require a new cable to support its full range of features. However, according to an HDMI Forum FAQ, some 2.1 features such as eARC can be made available on products with HDMI 2.0a connections via a firmware update (depends on manufacturer implementation). Also, new HDMI cables are not required for eARC — regular high-speed cables with Ethernet will do the trick.

uavAVTheaterGuy's picture

So I used to work for one of the biggest SONY dealers in Southern California. This last year when we got in the new soundbars, SONY account managers and reps came in to go over everything and their display setups.

When we got to the new soundbars, our account managers asked me why I used Optical to setup their soundbar instead of HDMI. I looked at them and asked them if they had ever tried initializing ARC from one of their TV's to their Soundbar.

After a few minutes of settings adjustments and everything, it still would not work. I recommended to them that they get with their engineering team to FIX this, because it is ridiculous to think that these products are supposed to be able to be purchased by the cusomter, setup at home by the customer, and work properly without a phone call back to the dealer, based on all the "recommended" setup methods via the manufacturer.

Needless to say but they shoved their little tails behind their legs and went home embarassed.

boulderskies's picture

Well done sir. I have been one of the lucky ones to get ARC working on a couple of different AVRs but there are many many others that have not and have resorted to optical. As you say, it is ridiculous to have one of the key tenents of a specification not actually be reliably implementable in the field.
Again, well done!

WildGuy's picture

nice to know that hdmi 2.1 spec will probably fix the ARC compatibility problems with eARC. nice to know eARC also supports up to latest Dolby Atmos and DTS-X. also nice to know HDMI 2.0a connections may supports eARC with a firmware update and older hdmi cables could support eARC too. cool. :D