All about ARC and eARC, the two-way audio transmission protocol over HDMI

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Today, smart TVs, flat-screen TVs are no longer strange to users. However, it is possible that many brothers have not taken full advantage of the technologies equipped on audio-visual devices in their homes. This article will introduce the ARC – Audio Return Channel protocol and its advantages compared to the familiar Optical port so that you have more knowledge for living room decoration.

What are TOSLINK, ARC, and eARC audio transmission protocols?

TOSLINK is a protocol for transmitting traditional audio signals by an optical cable, researched and developed by the Toshiba company and launched in 1986. Familiar to most users with an Optical port or S/PDIF, the protocol TOSLINK is integrated on most devices with audio output/input, from CD/DVD players, recorders, desktop computers, and game consoles. The name Optical is also the method of TOSLINK protocol that transmits audio signals from the source to the peripheral device, using red light with a wavelength of about 650 nanometers (or varies depending on the signal being loaded) shining through the system. Reflector system inside the fiber optic cable. The TOSLINK protocol supports lossless two-channel PCM signal transmission, later optimized for compatibility with modern Dolby Digital and DTS Surround System audio technologies. Still, the quality is quite low due to inherent limitations in bandwidth.

Compared to TOSLINK, the ARC protocol or Audio Return Channel was introduced by the HDMI Forum in 2009, integrated with the HDMI 1.4 communication standard. The ARC protocol inside HDMI utilizes a huge bandwidth compared to TOSLINK to transmit high-quality audio data and complex signals such as Consumer Electronics Control (CEC). In addition, ARC supports bidirectional signal flow, allowing connected devices to communicate with each other.

After nearly ten years of launch, the ARC protocol has just been upgraded by the HDMI Forum to eARC or Enhanced Audio Return Channel, integrated with the new HDMI 2.1 standard. The eARC protocol improves the intelligent features of ARC. It supports high-end audio standards such as 5.1/7.1 Dolby TrueHD, uncompressed DTS-HD Master Audio, and 3D audio standards such as Dolby Atmos, DTS :X (up to 32 channels).

Where are the ARC and eARC protocols superior?

In addition to sound quality, the biggest advantage that ARC and eARC protocols offer is transmitting a bidirectional signal between the display screen and the audio device. Assuming your home entertainment system has a Smart TV, a Blu-ray player, and a soundbar that all support ARC, you only need one HDMI cord plugged into two HDMI ports that support ARC and another HDMI cord Plug it in from the Blu-ray player through the soundbar and you’re done. The soundbar will act as a central hub, retaining the audio signal and transmitting the image signal from the Blu-ray player to the TV. Better yet, thanks to the ARC protocol, when you use apps like Netflix, Zing Mp3, … or watch cable TV on Smart TVs, the sound will be transmitted via the HDMI cable to the soundbar instead of having to use it. Use an extra Optical cable to connect back to the soundbar.

Another strong point of the ARC protocol, eARC, is its ability to transmit complex CEC signals. In other words, on TVs and audio devices with ARC that will support remote control synchronization, use a single remote to increase or decrease the volume, turn the device on and off, etc. ARC, eARC can also be equipped with LipSync to help synchronize images/audio delays during signal transmission.

Some notes on compatibility issues of ARC and eARC

Of course, you must first own a TV and audio device with an HDMI jack that supports ARC. On the TV side, fortunately, the ARC protocol is in the specifications of the HDMI 1.4 standard, so your flat-screen TVs and smart TVs manufactured since 2009 will almost always support it. For audio devices, the HDMI-ARC input depends on the brand; you will need to check the specifications of the product you are interested in (such as Anker’s Soundcore Infini soundbar line without HDMI).

The eARC protocol that integrates with the new HDMI 2.1 standard was introduced earlier this year; LG, Samsung, and Sony brought a few compatible TV models to the CES 2019 event, so shortly, they will still price be quite expensive. Moreover, the HDMI 2.1 standard and eARC protocol are completely backward compatible with old technology, so you will not need to worry too much.

With signal cables, in general, if the HDMI cable is not too old (manufactured since 2009) and supports Ethernet, it is fine for you to use for HDMI-ARC connection. If you want to support eARC, you need an HDMI High Speed ​​or HDMI Ultra High-Speed ​​cable.

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