Are all HDMI leads compatible with different versions of HDMI?

2007/05/23 16:07:02

Can you please tell me if HDMI leads are compatible with the different versions of HDMI? Do I need a newer lead to access HDMI 1.3 or are the leads all the same and only the inputs outputs different?

-- Submitted by: Gregory Klumpp

Answer by:
Ty Pendlebury

There is a short answer and a long answer to this -- we're going to attempt both.

In "theory" all HDMI cables are identical and the version only changes on the electronics side. The HDMI cable should feed whatever signal it receives from one end to the other unchanged, that is if it's of sufficient quality.

The problem is that HDMI signals require a huge amount of bandwidth, especially when you're talking about version 1.3 and Blu-ray/HD DVD streams. The issue is that of impedance -- the signal at one end needs to match the signal at the other because there is no error-checking in the HDMI standard. This usually means that all four of the twisted-pairs within the cable need to be of equal length (and diameter, etc.) and have an impedance of 100ohm. If the impedance varies from this number, then you can get jittering images, or usually, just a black screen.

So which cables are the best to use? We've heard anectdotal evidence of cheaper cables simply refusing to pass Blu-ray streams, but it's hard to recommend a brand -- it's a matter of trial-and-error unfortunately. Simply go for the amount you can afford, but we'd recommend spending over AU$70. In the office, we use Monster cables and they appear to work quite well, but they are twice as expensive as most other manufacturers. It may also be cheaper to buy cables from US or UK websites rather than paying local retail prices.

The other issue is HDCP. This is another matter entirely, and possibly the one that will trip up most equipment regardless of which HDMI cable you use. HDCP is the content protection standard tied into HDMI and is part of the handshake process used when you connect two (or more) pieces of equipment together. The HDCP "broadcast flag" is supposedly not being turned on till 2010, but we've seen plenty of equipment simply fail to talk to each other

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