How exactly do Active HDMI cables work? The only info I can find is that it somehow analyzes the edge of the waveform, but no information beyond that. RedMere used to have explanations on their website, apparently, but as their website is defunct, all technical documentation is gone.
The RM1689 is an ultra low power semiconductor device that performs adaptive equalization and advanced cable de-skew to achieve unprecedented HDMI performance levels over low cost, narrow-gauge HDMI cabling. The RM1689 is embedded within the HDMI connector and enables the 3.4Gbps operation required to pass the rigorous v1.3 testing for CAT2 cables compliance. The use of our patented “Zero Power Active” technique together with the ultra low power RM1689 architecture enables these performance levels to be achieved without requiring external power.
Basically it uses Ethernet gigabit type signalling with cable equalization compensation with controlled differential transceivers without using the Ethernet interface using low capacitance cables able to reach 20m when passive cables have interchangeability issues and often fail at 10m.
So what happened in Redmere?
In 2012 RedMere (Cork, Ireland) & Toronto-based Fresco Microchip merged to become Spectra7 , a virtual reality company that relies on gigibit video interfacing.