HDMI cables and why any old cheap cable will not do

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HDMI cables and why any old cheap cable will not do

Postby embleton » Sat Oct 24, 2015 2:32 am

The signals along an HDMI cable are digital but a square wave representing a perfect bit requires an infinite bandwidth and cannot be transmitted down any old cheap HDMI cable at high speed because of that fact; in fact a square wave cannot be represented purely for this is an infinite frequency and all transmission media will not carry an infinite frequency, period.

The transmission of signals down an HDMI cable is digital but it doesn't mean transmission theory doesn't apply, in fact, it is somewhat more important because of the rise and fall times of almost square waves representing digital bits for the signals for video and audio. The clock timing for sampling these bits is of ultimate importance and it won't sample the signal perfectly unless it arrives correctly time wise.

The higher the definition and frame rate of the video the more bandwidth requirements for the HDMI cable, and therefore the better the HDMI cable frequency response requirements, much the same as transmission of analogue high-frequency signals and that is a fact.

The signals along an HDMI cable are digital but a square wave representing a perfect bit requires an infinite bandwidth and cannot be transmitted down any old cheap HDMI cable at high speed because of that fact; in fact a square wave cannot be represented purely for this is an infinite frequency and all transmission media will not carry an infinite frequency, period.

The transmission of signals down an HDMI cable is digital but it doesn't mean transmission theory doesn't apply, in fact, it is somewhat more important because of the rise and fall times of almost square waves representing digital bits for the signals for video and audio. The clock timing for sampling these bits is of ultimate importance and it won't sample the signal perfectly unless it arrives correctly time wise.

The higher the definition and frame rate of the video the more bandwidth requirements for the HDMI cable, and therefore the better the HDMI cable frequency response requirements, much the same as transmission of analogue high-frequency signals and that is a fact.

As anyone will tell you when they've tried poorly constructed HDMI cables and when these distort the video and audio signal intermittently, proving the fact that HDMI cables don't just work in an on and off fashion as some reviewers would have you believe; and they try to convince us there are not lesser extents of digital video signal deterioration that are just not noticeable by the average viewer, for they don't know what to look for in picture quality much the same as these reviewers that state any cheap HDMI cable will do, eg: CNET that have offered poor advice on more than one occasion, the reviewers at CNET are idiots as are several other magazines that followed the advice of a single person, Geoffrey what, with only a Gmail email address, you may be a good writer but you talk absolute rubbish about technology or electronics! It's like somebody stating run a 1mm squared cable for a mains ring when the larger 2.5mm squared cable is a requirement by electrical law.

Even one magazine review stated HDMI cables carry digital signals and the signal will always be the same, then they measure a bit error in 50 frames that proves the fact that HDMI cables do indeed impact the signal per their measurements and checksum hashes, period, but they stated otherwise that it was okay to have a single error in 50 frames, bloody hell in may be hard to detect with the eye but the error was there; so don't state HDMI cables make no difference, they do when errors are detectable in only 50 frames and that was likely in ideal conditions, you bloody measured it! Whether it's a cheap cable or expensive one makes no difference, it proves errors occur that affect picture quality and that is a fact!

If any old cheap HDMI cable will do, as some reviewers suggest then why not attach a piece of string between the video media devices, why not because it won't work. I also point out that there are different HDMI standards for the frequency requirements for ever increasing high definition, ultra-high definition and 3D video signal content, if any old cheap cable will do then these standards would not need altering at all and that has not been the case.

Video and audio signals are transmitted down the cable represented in larger quantities than bits, but bytes, words and more complex patterns; and when these signals are disturbed it will result in video and audio distortion; jitter and timing jitter has an impact on digital signals and this is especially present on poorly constructed HDMI cables, it is undesirable and does result in poorer quality of frame and lines in the picture scan quality that occasionally are visible on the pictures. It is not the case that HDMI cables behave digitally signal transmission wise in either it works or not, quality does matter in ensuring perfect representation of digital video data, it is truly an occasional jitter bit error will not be noticeable by the viewer, so slight imperfections in cables are not easily noticeable but do understand that bit errors do impact picture without the complete loss of video and audio signals.

I'm not stating that individuals spend fortunes on their HDMI cables, but don't just walk into the likes of any electrical shop and buy a £5-£10 HDMI cable just spend a little more and buy quality, for intermittent signals will cause poor quality pictures and can ultimately cause electrical circuitry failure, say the plug falls out of the socket and a metal case shorts a pin, that will be more expensive to repair than the £20-£30 that you should have spent on a solidly well made HDMI cable in the first place. I use Cambridge HDMI cables myself.
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