No point to make any other than eARC moving forward as the future devices & codex stay indeed better supported and the signal chain, heartbeats and so on are vastly improved.
Compared to existing home theater audio connectivity methods, HDMI 2.1 eARC provides a number of improvements:
1. eARC is the only forward-compatible solution, which ensures that the AVR will continue to work with newer televisions
2. Delivers uncompromised, full audio quality with nearly 30 times the bandwidth of optical
3. Engineered for far better inter-brand interoperability
4. Is easier to use
5. Simpler connectivity
Delivering Forward Compatibility
eARC delivers forward compatibility by removing the audio device from the video path. With a conventional AVR system, both the audio and video flow from source devices through the AVR and onto the TV.
Very often, a consumer’s TV and AVR are made by different manufacturers. eARC is designed to ensure exceptional compatibility and interoperability between these mixed-brand TV and AVR connections. The improved compatibility comes about firstly because video doesn’t flow through the AVR, and because the discovery mechanism of eARC is brand-new and dedicated specifically to audio devices and format discovery, as described below.
HDMI eARC is a must-have feature to look for when shopping for an HDMI AVR or sound bar because eARC is the only way to ensure future compatibility with HDMI 2.1 devices. In addition to future compatibility, eARC brings substantial improvements in simplicity, audio performance, and compatibility over any other audio interface, and is designed to last decades into the future.
Technical Details
How does eARC work?
eARC transmits a high bitrate audio signal from the television to the audio device using an HDMI with Ethernet cable. This cable was designed in HDMI 1.4. An HDMI with Ethernet cable has the same connector and pins as an ordinary HDMI cable. However, inside an HDMI with Ethernet cable, pins 14, 15 and 19 are constructed as a twisted, shielded pair – originally intended to serve as an Ethernet channel alongside HDMI. In HDMI cables without the Ethernet feature, these are simply straight-through pins, which cannot support transmission of the eARC signal.
The eARC signal transmitted by the television is similar to the format of a SPDIF audio signal, but it is transmitted at up to 98 megabits per second. Because of the protocol overhead, the maximum raw audio speed is about 37 megabits per second, which is the rate of eight channels of 192 kHz, 24-bit uncompressed PCM audio. (8 x 192,000 x 24 ≈ 36,864,000 bits per second
A one megabit per second, bi-directional data signal is modulated on top of the eARC audio signal. This bi-directional signal is used to allow the eARC TV to discover the eARC audio device. This data signal has several other functions: It allows the TV to read a list of audio formats supported by the audio device, allows the TV to send lip sync correction data, and it lets the audio device send regular “heartbeat” signals to the television, letting the television know that its built-in speaker should be muted. These data-related signals are mandatory in eARC devices. None of these signals are available in optical (TOSLINK) or SPDIF audio, and are optional in the older HDMI-ARC audio.
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