A lot of information about eARC is sprinkled throughout the LG C9 owner's thread and many owners or potential owners either don't care about the status of this feature or will have difficulty following the conversation and understanding what the current status is.
What is eARC and why do I care about it?
eARC stands for enhanced Audio Return Channel and is a new feature that was introduced as part of the HDMI 2.1 specification. Importantly, eARC does not require HDMI 2.1 hardware for implementation, only ethernet channel that is present in HDMI 2.0b hardware and certified cables.
"Traditional" ARC allows for the pass-through of ~1mbps audio channel from a TV to a connected sound device such as a home theater receiver (AVR) or soundbar. This can be used for delivery of audio data from the television's internal apps as well as the audio from HDMI sources that are connected directly to the display.
Due to the bandwidth limit only low bit-rate compressed audio can be passed over the ARC channel. This means that HD audio tracks from high quality sources such as game consoles and media/disc players can only be passed back to the sound device as 'core' audio (Dolby+, Atmos encoded into DD+, etc.).
ARC, as designed, requires that the Television and all connected devices are HDMI CEC integrated, so that the TV and sound devices can negotiate codecs, volume levels and source switching. This has caused many integration issues with ARC due to well known problems of poor HDMI control implementation between different vendors.
eARC is not supposed to require the use of an HDMI CEC handshake to operate. Instead, eARC utilizes only the Ethernet HDMI channel
over which codec negotiation and media delivery are supposed to happen.
eARC also allows for audio data rates of up to 37mbps which allows for transport of full uncompressed HD audio soundtracks in up to 7.1 channels as well as HD tracks in Dolby Atmos.
So, why do I care again?
Traditionally video devices were connected to displays and audio devices were connected to pre-amps and amplifiers. This insured that the signal path was as short as possible between video sources and displays as well as audio sources and pre-amplifiers. The advent of digital signal delivery of audio and video and HDCP copy protection meant that consumers increasingly needed to connect their sources to an Audio Video Receiver (AVR) in order to switch the audio and video out to their display device.
This causes a few problems;
eARC was specifically introduced to eliminate these limitations and produce the following benefits;
- AVRs are traditionally good at audio, not video. Video might be converted to a different resolution, frame-rate, color depth, etc., and sometimes it is not clear to the operator that this is being done.
- Audio/video processing inside of the AVR can result in significant audio/video sync problems to occur (lip sync) and in many cases it is not possible to correct these at each source. You might have sync correct from your cable box but not your BD player, for example.
- The use of a single input on the television means that the calibration settings or picture mode will not be correct for different sources. Your cable box might look better with a different picture preset than your BD player, and it's not always convenient (or even possible) to switch picture modes for different AVR input sources, some TVs have limited number of picture modes or calibration limitations with some modes, and so on.
- There are no HDMI 2.1 AVRs on the market. So any advanced video features such as VRR (variable refresh rate) or video frame-rates, resolutions and color depths that exceed specs of HDMI 2.0b (18Gbps) will not pass through any current AVR that is switching audio/video sources.
- Audio return channel does not depend on HDMI CEC removing integration limitations for audio return to work effectively.
- eARC means that as sources and audio formats are updated, it is not immediately necessary to update the AVR as long as the AVR is eARC capable. As long as a sound format can be converted to PCM at the source device for example it could be transmitted to an AVR over eARC even if the AVR otherwise doesn't support that sound format (*note that currently C9 does not support 5.1 and 7.1 PCM audio).
- eARC allows for the future use of higher quality audio streams in the apps built into displays.
- eARC REQUIRES lip sync correction for most sound formats as part of the specification so that audio and video will always be in proper sync.
- With the TV as the video switch for higher quality video sources all advanced video features should work properly, individual inputs can be configured for optimal picture quality, etc.
Another great summary of eARC and why you care about it is found in this article from Digital Trends;
eARC sounds great, what's the status of eARC with LG televisions in 2019?
LG C9 series are currently the only televisions in LG product lineup that support the eARC format as part of C9s larger HDMI 2.1 feature support.
It is assumed that other products in the 2019 LG lineup will also have support for this feature such as higher level OLED displays (E9, etc.) this will be updated as other products are confirmed to have support.
However, early adopters of C9 have discovered the following issues with LGs implementation of the eARC feature;
Is LG doing anything about these issues?
LG Community Forum has requests to address the two primary eARC issues identified;
eARC not available on some Denon AVRs;
- The LG implementation ignores the media handles for PCM 5.1 and PCM 7.1 audio, which means it is not possible to pass uncompressed HD audio from devices like game titles on consoles like Xbox/PS4 that send HD audio uncompressed. There is no technical reason this shouldn't work (and does work on competitor televisions from Sony) this is just an omission on LGs part in supporting the formats. This issue was first reported in rtings.com review of LG C9.
- Owners of 2017 Denon products have reported that their AVRs are not recognized by LG C9 as being eARC capable devices. It is reported that 2017 Denons also have this issue with other brand televisions so possibly this issue can only be fixed by Denon or that Denon and display makers will have to collaborate on a fix.
- It has been confirmed that LG C9 operates properly with eARC delivery when HDMI CEC is turned off on the source (TV) and destination (AVR). This is accomplished by removing HDMI configuration for target AVR in the LG C9 Connections Manager (reset configuration) and disabling ARC and TV control in the Denon/Marantz unit.... then enabling ARC and eARC w/passthrough in the C9 HDMI audio settings. It is unknown if this is functional across all AVR brands but strongly indicates that LG has properly implemented the feature so that it can be turned on independent of use of HDMI control (HDMI CEC).
LG PCM multi-channel support over eARC;
eARC test files;
JamalofLG LG Moderator
Posted on 2019-06-11 15:30:26 Flag
I will not have a timeline as to when a resolution will be issued, however, something is in the works to provide a resolution.
The following files can be loaded onto a USB drive, plugged into the LG C9 and played back to an AVR to determine if eARC is operational or not as the LG television (and many AVRs) give no indication that the feature is in use (important, the LG player and/or USB ports don't support HD audio so only non HD audio formats like DD 5.1, core DTS, etc., would be able to be tested this way).
Samples for testing the ARC/eARC link:
- lots of HD audio samples are available to download in the Kodi wiki - bitstreaming or uncompressed LPCM files are included;