I was recently asked a VERY good question about HDMI - why didn't the Ethernet Channel in HDMI ever seem to be made available for use?
HDMI Ethernet Channel (HEC) was introduced over a decade ago (yeah, already!) with v1.3 in 2006. It supports half-duplex 100Base-T, which would be fine even now for most Internet applications — general surfing, streaming, comms, etc. The HDMI spec only makes options available but it’s up to manufacturers to adopt such features and deliver them to us. For some reason HEC simply never took off.
The other frustrating component of this is that HEC also provides the platform for the better of two Audio Return Channel (ARC) modes. The basic is ‘Single Mode’, where only a single unshielded wire is used, with limited bandwidth and relatively high attenuation. If you’ve ever found that ARC won’t go the distance (more than 7-8m), that’s why. There is a far better approach in the spec called ‘Common Mode’ which uses the differential pair of HEC (by which it's then called HEAC, the inserted 'A' being for Audio return). So chances are if Ethernet Channel was broadly implemented, then that might have been the catalyst for enabling Common Mode, so ARC might have worked a lot better too (CEC being required to activate it notwithstanding!).
The wait is nearly over for HDMI 2.1, with its release now imminent. We'll have to wait and see if they're doing anything more with the Ethernet channel, but what we do already know if that Audio Return is stepping up to eARC, being enhanced. This supports full hi-res and immersive audio through ARC, enabling a huge boost to audio from OTA and OTT services in particular. I predict this will need the bandwidth and stability of Common mode ARC to operate, but again we'll have to wait and see...
Image source: hdmi.org