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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.

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  • \$\begingroup\$ Then the answer is "probably not well enough". \$\endgroup\$ – Brian Drummond Oct 13 '16 at 17:28
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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.

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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.

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  • \$\begingroup\$ Thanks for the info. The HDMI port does have 5V power line, so why there is such an excitement about the almost standard re-driver/equalizer/de-empasizer technique? Maybe because it was in 2008? Nowadays SATA has them, USB3 has them, PCIe has them. \$\endgroup\$ – Ale..chenski Oct 13 '16 at 23:20
  • \$\begingroup\$ I'm not certain they all have the same attributes for spectral equalization and sub-nanosecond cable de-skew \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Oct 13 '16 at 23:32
  • \$\begingroup\$ I'm not sure about HDMI, but he other three have the same signal shape, and the same idea of signal "sharpening" and loss compensation. \$\endgroup\$ – Ale..chenski Oct 13 '16 at 23:51

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