HDMI ARC: How the Audio Return Channel works

In HDMI lingo, the function "ARC" has nothing to do with French triumphal arches, but is an abbreviation for Audio Return Channel. A TV equipped with Audio Return Channel (ARC) HDMI can receive as well as send audio signals via it in connection with an appropriate HDMI cable.

HDMI Arc Article image

The advantage: You save a cable. Namely, the previously necessary audio cable (eg S / PDIF) from the audio out of the TV to the audio in of the A / V receiver.

With HDMI ARC you can for example...
... connect a game console such as Playstation 4 or X-Box One directly to the TV via HDMI and return the sound to an A/V receiver if required.
... send Dolby Digital audio signals of a digital cable TV program from the TV to the surround system.
... Receive DVB-T via the TV and output the sound via an external amplifier.
... Connect a USB stick with video content to the TV and listen to the sound via a 5.1 system.
Two sketches follow for clarification:

The old configuration: without Audio Return Channel (ARC)
Configuration without HDMI ARC
Typical configuration without HDMI ARC

Setup in the sketch: A BluRay player is connected via HDMI to an A/V HDMI receiver. The A/V receiver receives data e.g. from a DVD/Blu-Ray player and forwards the signal via HDMI to the TV. The sound is output via the speakers on the A/V receiver.

Now the TV receives additional signals via, for example, an HD TV program with HD sound via an integrated receiver or via antenna cable. If you now want to output the sound of the TV program via the external speakers, the sound of the TV program must somehow come back to the AV receiver. Until now, you had to connect an additional cable to the audio-out output of the TV for this purpose (red connection above). Typically, this is done via S/PDIF or an optical Toslink cable. In this scenario, the TV and receiver are connected with two cables (one HDMI and one S/PDIF audio cable). How cumbersome, right?

And now HDMI ARC comes into play...

The new configuration: with Audio Return Channel (ARC)
HiFi configuration with HDMI ARC
HDMI configuration with Audio Return Channel - makes one cable less

The setup is the same as described above. So a BluRay player via HDMI to an A/V receiver, which in turn is connected via HDMI to a TV. The TV receives an HD TV program via an integrated tuner or an antenna cable, the sound of which is to be output via the audio receiver. Thanks to HDMI Audio Return Channel (ARC), the TV is now able to send the sound of the TV program directly to the A/V receiver via the HDMI cable, eliminating the need for second cabling via S/PDIF.

So HDMI ARC is a practical thing and transferable to many other circumstances. Whenever it comes to sending audio signals from the TV back to another HDMI capable device (e.g. A/V receiver), ARC can be used. It replaces the audio out of your TV in some cases, so to speak.

Of course, always provided that all connected devices support HDMI ARC:

How do I make sure HDMI ARC works for me?
Pay attention to the following points:

Both devices - TV and audio receiver - must support HDMI ARC (marking "ARC" directly on the HDMI port. If in doubt, refer to the operating instructions).
The intermediate HDMI cable must also support ARC. Most HDMI cables do, but this is usually not visible from the outside. If in doubt, get a new HDMI cable with explicit ARC support for testing.

As mentioned before: Not every HDMI input or output supports ARC. Connect your devices via the (partly specially marked) HDMI ARC port. Sometimes the HDMI port for ARC is not immediately recognizable. If in doubt, check the user manual or test different combinations until ARC works.
Enable HDMI ARC - common setting options
HDMI ARC often has to be enabled or selected separately in the menu of the TV (and the receiver!). How exactly that works, depends heavily on the manufacturer. Here are a few common options that you should try or activate in the menu of your TV:

Enable external audio output: Configure your TV via the general audio out settings. Often this also affects the Audio Return Channel via HDMI (example Sony: First Menu/Settings/Digital Settings/Basic Audio Settings/Audio Description: off and then Settings/Sound/Optical Output: Automatic).
Enable HDMI CEC: Some manufacturers enable/disable ARC functionality along with HDMI CEC features. HDMI CEC has different names depending on the manufacturer, e.g. EasyLink (Philips), Anynet+ (Samsung), Aquos Link (Sharp) or BRAVIA Sync (Sony).
Set receiver to HDMI ARC: Some AV receivers automatically recognize audio signals via HDMI ARC, others have to be set manually. How exactly this is done, can be found in the respective operating instructions.
Which audio formats does the Audio Return Channel support?
According to the HDMI Licensing Org., HDMI ARC supports all audio formats that could also be transmitted via an S/PDIF cable. Specifically, these are the following audio formats:

HDMI ARC: Supported audio formats

Dolby Digital Yes
Dolby Digital Plus No
Dolby TrueHD No
6 channel PCM audio Yes
8 channel PCM audio yes
(many thanks to Jonny for the listing!)

Here you can see the biggest disadvantage of ARC: HD audio formats like Dolby TrueHD or DTS HD are currently not supported! This is due to the fact that ARC was primarily designed for internal TV tuners, which output the sound (at that time and usually still today) in 5.1 or 7.1 PCM audio format at most. If you wanted to output an HD audio format via ARC today, this would - depending on the tuner - either be converted to another format (e.g. Dolby Digital) or the audio output would fail.

Those who currently want to play HD audio via their AV receiver will have to connect these signal sources directly to the AV receiver via HDMI.

However, despite all the theory, audio playback via ARC still depends significantly on your individual component mix (signal source, TVs, receivers) and their specifications. For example, if the AV receiver can receive 7.1 sound via ARC, but the TV only outputs stereo sound for some reason, there's unfortunately not much you can do.

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