HDMI 2.1 eARC Technology

Enhanced Audio Return Channel Solutions for HDMI 2.1

HDMI 2.1 includes a home theater feature called eARC, or Enhanced Audio Return Channel, which will ensure forward compatibility between audio devices such as a Sound Bar, A/V Receiver (AVR) and TV. eARC is designed to deliver forward compatibility because it removes the audio device from the video path.

With a conventional AVR, both the audio and video flow through the AVR and onto the TV. With eARC, the TV sends an audio-only eARC signal to the AVR. This keeps the AVR out of the video stream, which dramatically extends the lifetime of AVRs in today’s home theater systems.

HD and 4K/UHD TVs let consumers create a home theater with immersive video and surround sound, which can fully reproduce the movie theater experience. Until now, configuring and using these systems has been complicated and often inconvenient. Mixing and matching audio and video devices from different manufacturers doesn’t always work smoothly, often requiring the use of two remotes in order to switch inputs, control volume, and so forth. The HDMI 1.4 Audio Return Channel (ARC) feature improves this somewhat, but it does not offer the full audio performance of HDMI.

eARC technology provides a dedicated audio link within the HDMI cable, which substantially improves compatibility, simplicity of use, and audio performance. This audio link utilizes the two pins used for the HDMI Ethernet Channel and ARC feature: a dedicated differential pair providing a “system within a system,” specifically for high performance audio. The eARC pair has its own dedicated discovery and control functions, enabling it to operate independently of the HDMI version in use, and providing a “green field” for creating compatibility among products from different manufacturers.

The differential signal used in eARC can transmit the full bandwidth of HDMI audio, up to 8 channels of 24-bit, uncompressed 192 kHz audio. This can enable up to 32 channels of audio as well as all of the well-known compressed audio formats, including Dolby Atmos and DTS:X. The dedicated control signal also transmits lip sync information to ensure that audio and video work together seamlessly in a home theater. A heartbeat signal is continually transmitted by the audio device to the television. This heartbeat signals the television to mute its own speaker automatically, and un-mute in case of signal loss.

Function TOSLINK HDMI ARC HDMI eARC
Cable Used Optical SPDIF HDMI HDMI with Ethernet
Stereo Support Yes Yes Yes
Compressed 5.1 Very Limited Yes Yes
Uncompressed 5.1 No No Yes
Uncompressed 7.1 No No Yes
High Bitrate
- Dolby Atmos
- Dolby TrueHD
- DTS: X
- DTS-HD
 
No
No
No
No
 
No
No
No
No
 
Yes
Yes
Yes
Yes
Maximum Audio Bandwidth ~384 Kbit/sec ~1 Mbit/sec 37 Mbit/sec
Link Discovery No CEC eARC data channel
Capability Discovery
(Audio EDID, etc.)
None CEC eARC data channel
Lip Sync No (Optional) (Mandatory)
TV Mutes & Controls Volume No Yes (CEC) Yes (CEC)
Powering TV Powers Audio Device No Yes (CEC) Yes (CEC)
ARC Fallback No N/A Yes

Soundbar

AVR