Well, the question of HDMI and distance is, on the whole, a complicated one. Certainly for extreme long runs, fiber-optic solutions are the ideal, but they tend to get pricey.
As long as the spec remains what it currently is, it's going to be very hard for anybody to greatly exceed the lengths which are now doable on conventional copper cable. The problem basically is that there's only so much permissible attenuation. The spec allows you to either pass a set of attenuation benchmarks or pass an eye-pattern test; a pass of either, even with the other failing, will pass the overall test and be compliant. At 23.5 AWG, the Series-1 fails the attenuation benchmark tests well before it fails the eye-pattern, but the eye-pattern itself, indirectly, imposes limits on attenuation, too, because if the amplitude of the signal drops too low, it'll start to impinge on the eye mask.
We have been back and forth with Belden on some development ideas to try to further extend the reach. The problem is that, with the bonded-pair design already having the return loss well under control, the only way to improve distance performance on the eye-pattern is to either reduce attenuation (which would require bigger wire, and correspondingly bigger dielectrics--and the cable is big enough already!) or to reduce capacitance. Capacitance is tightly tied to impedance, which is required to be 100 ohms on these data lines, and the only way to improve capacitance while holding impedance steady is to go to a different dielectric material--but, without going into too much detail there, it's fair to say that when you change dielectrics from good old solid PE to something with a lower dielectric constant, you start to face a new set of problems with dimension control and manufacturing consistency.
So, while I wouldn't be surprised if we're able to put out a 30-foot Category 2 cable sometime (we're about to start ATC testing on our new Ethernet designs), I'll be very surprised if, barring a complete change in the spec, we're ever able to put out a 40-foot Category 2 cable. Likewise, we might stretch the Series-F2, our 28 AWG cable, from 15/25 in Cat 1/2 to 20/30. We'll see.
The existing design unfortunately bears the stamp of HDMI's lowly origins. It was made backward-compatible with DVI, which was designed to be a computer-monitor interface, and which therefore was not usually needed to run over distance. Computer engineers seem to have a thing for twisted-pair data cables, and I think that the spec was written without a strong appreciation for just what kinds of problems a balanced-line configuration would create. The cable's got to have very high manufacturing consistency to avoid skew (intrapair and interpair) and return loss, and if HDMI had been run unbalanced (i.e., on coax) things would be easier.
Kurt
Blue Jeans Cable