Guys, has anyone here read the HDMI cable test results on the Audioholics web site? Link here

Their conclusions correspond with what both sides of the debate here have been saying.

There's also an interesting article here buy one of the boffins at Tektronix to do with how construction methods affect signal performance. Link here

The part of their research which will be most relevant to the majority of consumers is:

I would have to disagree with your conclusion. You will notice a complete lack of the "this cable gives deeper blacks than that one" type of comment in that article.

Basically the cables either worked or they didn't. All the effects of a non working cable were exactly what you would expect, ie random noise and sparklies.

I agree. Perhaps some confusion arises from the fact that when we (the cable sceptics) say that a digital cable either works or does not, we do not mean that there must either be a picture as good as the original source or else a blank screen.

For us, "not working" means having an unacceptable level of errors, which manifest as random (and highly visible) degradation of the picture.

I never said anything about deeper blacks

There was a thread similar to this where I said we'd seen less noise, which is pretty much what you've said in the quote above; so we seem to agree

Perhaps we have different definitions of "both sides" then

By that I mean you have the side that says cable A produces more vibrant colours and deeper blacks than cable B and the other side that says this cannot happen.

Basically the Monster cable and Russ Andrews multi millionaire cables all claim enhanced picture quaility for their products. No no-one disputes that a cable can produce unwelcome artifacts into the picture but I rather think this is not what they mean.

It is certainly not what you read in the review pages of certain HiFi magazines. There they do talk of effects like deeper blacks or more picture detail or more vibrant colour.

The opposite view to that is that the signal is digital therefore it is a logical nonesense to sugest that the exact same sequence of ones and zeros can produce two different effects.

If you say that you have seen two cables produce different amounts of noise then that is perfectly explainable. The two cables are transferring the digital data differently. In other words one cable is introducing random bit errors that translate to noise or other artifacts on the screen. This is not really the opposite to saying a cable cannot produce different results if the data transferred is identical.

So in that respect yes, we are on the same side

http://www.homecinemachoice.com/node/2514

as promised here is the article

LEARN TO LOVE THE GRAIN

Hallelujah!!! Fanfares, trumpets, dancing girls and fireworks!!!!!

AT LONG LAST YOU'VE GOT THE MESSAGE - Hurrah!!!
:

That's all I've ever been saying, but no one was listening properly

That's not what it sounded like in your earlier posts:




Are you now claiming to have seen random and highly visible picture degradation with the cheaper cables used in your tests?

I haven't modified my position at all, and I think my message has stayed consistent all along.

I've always said we'd seen less noise and a much cleaner picture from the most expensive (and longest) HDMI cable. The cheapest and mid-priced cables (both of the same length, incidentally) seem to perform identically. That's it. Nothing more. Pretty much everything else I posted has been a clarification of my position and responses to other posts.

The only bit of missing info from this thread was that all the cables were 5mtr+ long. However, that info was posted in another recent thread on a similar topic in which many of the same contributors as here said exactly the same thing...


Except now it seems that noise can be present, and that the cables can make a difference, and as one DS'er wrote "It can be easily explained".

Perhaps other contributors here have been in such a rush to prove something that they never bothered to understand the questions I posed.

I think you may have misinterpreted the arguement.

No one claims that cables have NO effect, or if they do they don't know what they are talking about. A poor cable can corrupt the signal flowing through it producing random bit errors that the receiving equipment cannot recover from.

That is an entirely different arguement from the one that says cable A produces deeper blacks and more vibrant colours than cable B. If cable A and B in this instance produce identical digital signals at the TV then to all intents and purposes the results will be identical.

If they present different digital data at the TV then the results will not be the "deeper black" etc nonesense that one sees in the review pages of the HiFi press. Random bit errors simply don't work that way.

Noise and random picture break up are entirely an expected by products of poor signal transfer. So of course you will se a difference swaping from a poor cable to one that transfers the signal perfectly. However to claim that swapping between two cables that transfer the signal perfectly can have a difference is an entirely different matter and that is where the logic can start flying out the window

Well, I did not read or participate in any similar thread here, so you'll forgive me for not knowing what you or anyone else said before.

As far as I can recall (and it's been a while since I read the specs), HDMI does not have any forward error correction on the raw video data, although it does on the command protocols and (I think) on the audio. There's not enough time for backward error correction. So, yes, errors are possible.

What is quite clearly not possible are subtle improvements in the overall picture quality, and that is very much what your posts seemed to me to be claiming (and is absolutely what credulous magazine "reviewers" claim).

But here the argument really grinds to a halt, because you have no way of telling us exactly what it is that you believe you are seeing. Vague appeals to "noise" don't really help.

My position remains that the improvements you think you are seeing would vanish under controlled test conditions, because I simply do not believe that errors could manifest in sufficient numbers to produce a noticeable difference without entirely destroying the viewing experience and resulting in the cable being condemned as faulty.

Once again words are being put in my mouth. I NEVER referenced any magazine reviews or made claims (as has been suggested elsewhere) that blacks were improved.

In very simple terms the OP asked if it was worth spending money on a Monster HDMI cable. The response was overwhelmingly "No"; the argument being "...if it works, it works." More posts were added along the lines of "I've got a really cheap cable and it works perfectly (I think £2.99 was even mentioned in one post) ...blah blah blah."

At no point did anyone else here say "Actually cheap cables might be prone to a bit more noise or interference." I was the first and only person to suggest that this might be the case, and I was roundly condemned for it.

I wrote at length in post #47 to question how it might be possible for errors to creep in to the signal via the HDMI cable that would manifest as picture noise.* Yet again those points were mostly ignored, and the usual round of bigoted responses followed...




The message was coming across loud and clear. "They all work the same, so the cheapest you can buy if fine as long as you have a picture." Well that's something I don't agree with.

The cheapest might give a picture but in my tests they might also included a chunk of picture noise too. It was only when I tried something substantially more expensive that this noise disappeared.

Perhaps you've all been too fixated on the idea that a higher priced cable "performs better" and so added your own agendas. Maybe it would have helped if I'd have said that the cheap cables didn't work as well; but then the inevitable response would have been "Must be a faulty cable."

I started this with a genuine interest in finding out why there was a difference between cables in respect of picture noise, and I hoped to find some enlightened thinking here. How wrong I was. I'm sorry to say this but it was like I'd just hit the "regurgitate" button. Talk about knee-jerk reactions, it was like a chorus line No one paying attention; all just just falling over themselves to quote impressive looking specifications instead of trying to understand the question at hand.

I'm now more convinced than ever that the "cheapest is best" route is wrong. The cable might work; as in "give a picture" but there's also a good chance it will add unwanted picture noise too. Some of those problems are going to be hidden by poor or default set up on TV's.

As much as I hate seeing people ripped off on expensive HDMI cables I am also against them wasting even more money on a TV upgrade when the real culprite strangling their system performance may be that "bargain" HDMI cable that they bought because someone on a forum said "It's digital mate, 0's & 1's, they're all the same"




* Noise: You might be happier with the terms "aberrations, chroma errors" or whatever; quite frankly I think I'm passed caring now.

well its all getting a bit personal here isnt it ?

not wishing to get pilloried for this but is there a chance that you simply need much more noise than manifests itself in a domestic environment for the benefits of a 'quality' HDMI to become apparent ?

I hadn't particularly intended following up on this thread but since you originally asked for "What I'm interested in doing is looking at 0's and 1's theory in closer detail.", and what I (and a lot of other people) politely did was just that, I'm a bit annoyed at this kind of attitude.

Anyway, putting that aside, I'm wonder if part of the misunderstanding here is that perhaps you aren't visualising what the sort of digital noise we are talking about looks like. To that end, I've put together a sample image which I've corrupted in 4 quadrants:

http://i422.photobucket.com/albums/p...noisetest2.jpg

Apologies that photobucket has jpg'd the file up, I'd hoped to keep it as an uncompressed file but I haven't ever had a need to upload a file to an image host before...

The top left corner has no new noise introduced. The top right has 1% noise, bottom left 5% noise, bottom right 10% noise. In each case, the "noise" is single bit errors, psuedo-randomly distributed.

I'm not trying to suggest that the actual pattern of the erroneous bits might match what you would see in the field for an HDMI cable in trouble, but the sort of visual errors introduced are very much the kind of thing (for an RGB encoded image at least).

The point is that even a "low level" of noise will still mean that some pixels are *really* obviously wrong. It isn't like an analogue noise, where a low level of noise is just a slight error distributed over the whole image.

That's why I (and many others) have been suggesting that if you saw an image like this, you might consider the cable to be broken rather than just not "the best".

Richard.

I rather fancy that remark is aimed in my direction. I have never said YOU made such claims. I merely pointed out that these are the kind of claims one gets from the likes of Russ Andrews etc. There may have been a period of confusion over exactly what you saw in your tests since you were a bit ambiguous as to what exactly you were describing.


No the original question was about a sign saying you had to buy a particular brand of cable for the best picture quality. Which is patently untrue as there are many other cables, some cheaper and some even more expensive that can give the same result.


I might take offence at being quoted here but let that pass Read again. I agree cables can differ in their ability to transfer data accurately. But provided the cable does transfer data accurately then it is irrelevant how much it cost. An expensive cable is just as capable of screwing up the signal as a cheap one. The number of zeros in the price is NO guide to quality.

The whole point is about ACCURACY. That is the only parameter of interest. As I and others have been trying to explain if two cables transfer the digital data accurately then it seems to defy logic to suggest that the picture quality can differ just because one is made from some exotic material and the other is a bit of damp string.

Introduce errors in the transmission, which is entirely possible, and you are likely to see a difference if the receiving device is incapable of correcting those errors, either because the signal lacks error correction data or the errors are too great.

That will manifest itself as random "noise" in the picture. Which for want of a better description is unwanted variations from the correct pixel value.

Fairly obviously if you swap from a cable that corrupts the bitstream to one that does not you will see a difference. But if you swap between two cables that do not corrupt the bitstream then I fail to see how there can be any difference in picture quality.


Somewhere along the line I think there has been a bit of going off in slightly different directions.

A poor cable will more than likely make itself known in the form of picture disturbance, noise, sparklies call it what you will. Basically there will be bits of the picture that don't look right.

That is an entirely different matter to the "deeper blacks and more vibrant colour" (if I dare re-use that phrase ) issue. It is this claim made by some in the HiFi press and elsewhere that some of us take exception to.

The kind of effects that poor cable materials and/or construction have on the signal are unlikely to be subtle. At least not in the way you may think reading the back pages of What HiFi for instance.

To summarise.

A good cable is one that transfers the digital data from A to B with out any errors. A poor cable is one that doesn't

Cost is no indicator of the ability of the cable to transfer data.

A poor cable will be very noticeable by and large as the effects of signal corruption are unlikely to be very subtle.

I dont really see how you can get a bitstream output from that noise source. If you check the link surely thats an analogue source?

Speaking as a broadcast engineer used to dealing with analogue and digital signals, that posted picture is an analogue source suffering from noise. It is most definitely not the way noise or corruptions manifest themselves on a signal in the digital domain.

In the digital domain, you'll see things like sparklies (random pixes of peak white or black, or some other colour), line flashes, usually green or purple, or just no picture at all as the receiving end is unable to equalise the signal enough to recover the timing information even if the data is still corrupt. HDMI is carried as a clock signal, and digital red, green and blue signals - all balanced signals. So corruption could result in pixels going any colour, or wrong shade of colour - but never affecting the whole screen in the same way in every frame, due to the random nature of noise.

Question for anyone thinking of buying an expensive HDMI cable - how much did you spend on your DVI cable to connect your PC to your Monitor? Probably nothing as a cheap DVI cable came with the bundle, and yet you're probably perfectly happy with the picture on the monitor.

Now here's the rub - DVI and HDMI are one and the same signal, with the sole difference (excluding connectors) that HDMI can also carry audio where DVI can't. Both are also HDCP capable.

Sorry, I don't understand what you are meaning, so I'm confused too. I took a digitised image (24 bits per pixel, 8 bits each for RGB channels) and randomly flipped bits to show the effect of digital errors can have on pixel colour values.

I'm not sure what bit you mean is analogue?

Ahh, so you've manipulated a digital picture from a PC in a way that would be indicative of analogue noise on an analogue signal.

Digital corruption due to noise doesn't manifest itself in that way your picture shows.

Isn't that exactly what my image is showing? On pixels which have suffered a single bit error, the colour can entirely change - with the amount of the effect varying on the bit position of the affected bit. I was trying to demonstrate that this is an entirely different effect to noise on an analogue signal. If the data I had used had been in a colour space with a luminance channel (rather than RGB as I used) then the sparklies would have a fair chance of just being a variation in luminance rather than what we have seen here.

But all in all, that image is showing the effect of what happens if you randomly flip bits in an image in the digital domain...

I don't really see how I have manipulated it in a way that analogue noise would affect a analogue signal - I've created single bit errors in a digital data stream. Of exactly the sort that digital error detection and correction schemes are designed to detect and correct. What's wrong with that analogy?

I'm not suggesting that the distribution of such single bit errors is indicative of exactly what would happen, but I was wanting to illustrate how the colour of pixels can change if single bits are flipped.

the analogue noise source i refered to was the seagull sorry lol

Ah - I see

You should know not to joke when people are talking about something as serious as video leads

Went to a TV retail event in Norwich yesterday and boy were they plugging monster stuff and boy were people buying it to go with their new sets. A device which looked like a surge protection socketbank was claimed to purify the electrical current and improve sound and vision, the price £130, this was going well with a £90 HDMI lead, it seems a fool and his money.....