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best buy offers hdtv calibration: how does it rate (details inside) - Page 10

post #271 of 454
Quote:
Originally Posted by Bill Mitchell View Post

....I can imagine that out-of-spec slew between the differential signals or slew between the channels on a long low-quality/non-compliant cable could introduce quality problems on the video signal.

"a long low-quality/non-compliant" should read "potentially any"

I have had customers say they couldn't put an exact definition on the picture improvement, but the picture overall looked better, better color better image structure, sharpness, etc. This was the difference from a long passive cable that was considered to be functioning well, to an active HDMI cable.
post #272 of 454
Quote:
Originally Posted by LarryInRI View Post

I am not quite sure what you are trying to convey. Shannon's work, no matter how old, is the foundation for all digital transmission. His work is the basis for all modern digital communications and, in fact, was used for developing the communication systems on the first space probes over 40 years ago. Physics and math do not change. Technology does.

Shannon proved rigorously mathematically that if even a tiny amount of a digital signal can be recovered, the original signal can be reproduced. One can say that the argument against expensive digital cables goes back to Shannon and Nyquist.

tribestros said:

'I find it amusing everytime somebody tries to say, "hey hdmi cables are all the same" the only argument they have is "digital signal is 0s and 1s."'

I was only giving him a more detailed source to help him overcome his confusion.

Larry

Yes, you could correct for it if you had enough error correction....but perhaps you need to learn more about what is included in the HDMI Specs.

Secondly, error correction takes time, even milliseconds.....and with data traveling that fast (as in my example, .00001 millimeters apart on a highway), you would have a pile up to end all pileups while that error correction takes place (if it were actually there).
post #273 of 454
Quote:
Originally Posted by Bill Mitchell View Post

Looking at the HDMI 1.3 spec, it appears there is no error correct on the video data, just on the audio and control data. The quality of the information, then, depends on the cable meeting the specs. In particular, as the signals are transmitted using differential signalling on three separate channels, I can imagine that out-of-spec slew between the differential signals or slew between the channels on a long low-quality/non-compliant cable could introduce quality problems on the video signal.

As to how such data corruption might manifest itself visually, I cannot speculate. I have only very short cable lengths, so I've not observed any such problems.

Tests have shown even short cables do not pass all HDMI 1.3 specs.
post #274 of 454
http://www.audioquest.com/resource_t...t_rev_1_00.pdf

The video is perfect up until the data is too corrupt to reconstruct it.

No blur , no judder as a symptom of under-performing cables. You get a picture with hdmi or it falls apart.

See cliff effect.
post #275 of 454
You can get sparkles and more subtle pixelation when a cable is on the edge of acceptable performance. It will not make the image softer, but some might consider it to be "blurry" in a general sense. Judder is not related and I beleive that the term was misused when it was discussed earlier.

Bill, I believe if you read the HDMI spec more carefully, you will find that error correction is available at the packet level, which include both audio and video.
post #276 of 454
Quote:
Originally Posted by lcaillo View Post

You can get sparkles and more subtle pixelation when a cable is on the edge of acceptable performance. It will not make the image softer, but some might consider it to be "blurry" in a general sense. Judder is not related and I beleive that the term was misused when it was discussed earlier.

.

If people post on here and are unable to differentiate between softness and picture breakup. Describe sparklies as "blur" and misuse a term as simple to understand as judder.

May I humbly suggest that rather than come on here and cast aspersions on other's people's knowledge they should keep their heads down and continue to sell their over-priced special sharp and judder free hdmi cables , steal candy from babies , con old ladies out of their live savings or continue to work at best buy: or whichever scenario they find the least morally objectionable.
post #277 of 454
It really is not necessary to be derisive. May I suggest that you use complete sentences, proper grammar, and post in a more positive manner?
post #278 of 454
Quote:
Originally Posted by lcaillo View Post

It really is not necessary to be derisive. May I suggest that you use complete sentences, proper grammar, and post in a more positive manner?

I see every need to be derisive towards misinformed snake oil pedlars at every opportunity: especially when they go around referring to people demonstrably more learned than they are as "dumbasses".

This is an internet forum and my grammar and punctuation are quite sufficient for that purpose. Feel free to correct it yourself if the construction of my previous post offends you so.

If that was the main purpose of your post I'd suggest you are veering off topic and heading swiftly toward pettiness; which I have precisely zero interest in .
post #279 of 454
Quote:
Originally Posted by GlenC View Post

"a long low-quality/non-compliant" should read "potentially any"

I have had customers say they couldn't put an exact definition on the picture improvement, but the picture overall looked better, better color better image structure, sharpness, etc. This was the difference from a long passive cable that was considered to be functioning well, to an active HDMI cable.

Sorry, but BS.
post #280 of 454
Quote:
Originally Posted by ChrisWiggles View Post

Sorry, but BS.

Seconded ...sorry Glen.

And to be fair Glen is just relating an anecdote rather than his opinion of it.
post #281 of 454
Seems to me there was a reason the designed/developed passive, balanced passive and balanced active cables. Seems to me, unless you are getting all the packets delivered intact, as sent, you are not getting the whole picture. Whether the display or the individual sees the difference is another issue. An expensive cable does not guarantee accurate packet delivery, the construction and design do. People will always be taken by the numerous snake oil peddlers. The best defense against being taken is to do your homework and gain the knowledge necessary to make an informed purchase decision. I was a big believer in the performance results/improvements achieved by the, NLA, VizionWare active HDMI cables for long runs and their balanced passive HDMI cables for short runs. Point is, they "always" worked and furthermore they always seemed to resolve problematic HDMI issues.

The one thing we must do is realize that we are all individuals. AV Sales personnel and video calibrators do not come with a "BS in video calibration" from USC, MIT, Cal Tec, etc... Any BB, mom & pop store, or high-end store can be the starting point for the unique individual that makes his/her way to great success in the field. I like to think of myself as a fairly knowledgeable, professional calibrator, but my BS-Business from USC didn't start me in video calibration or make me any better at it than another, I feel that was all attributable to my abilities. We are not saying that all BB calibrators are bad, we are stating that the work environment and umbrella of corporate policy can have a profound effect on the acceptable calibration results of a BB calibrator. Additionally, the truly "professional" skilled calibrator may put more emphasis on getting the perfect picture (for that particular system) than doing it in a specified amount of time. IMO, when a BB calibrator is destined to become a "professional calibrator", they will leave the BB employment and become an independent professional calibrator who's personal reputation is on the line with each and every calibration. The effort to achieve desired final results is the same whether it is a $600 TV or a $200K home theater...... If one chooses to go with a BB calibrator or an independent calibrator, they learn a bit about the goal of calibration and should talk with/interview their prospective calibrator. If a calibration is a calibration and price is the only variable one can understand or see, there is not much that can be done.
post #282 of 454
Quote:
Originally Posted by ChrisWiggles View Post

Sorry, but BS.

Quote:
Originally Posted by Mr.D View Post

Seconded ...sorry Glen.

And to be fair Glen is just relating an anecdote rather than his opinion of it.

What can I say, I have seen/experienced the performance differences. We all need to realize that we are only talking high bandwidth, 1080/60p and 1080/24p.
post #283 of 454
Quote:
Originally Posted by lcaillo View Post

You can get sparkles and more subtle pixelation when a cable is on the edge of acceptable performance. It will not make the image softer, but some might consider it to be "blurry" in a general sense. Judder is not related and I beleive that the term was misused when it was discussed earlier.

Bill, I believe if you read the HDMI spec more carefully, you will find that error correction is available at the packet level, which include both audio and video.

With your prompting, I looked again at the spec. It appears to me, still, that the packet level includes only audio and control info, not video pixel data. In particular,

From pages 8-9:
Quote:
In order to attain the higher reliability required of audio and control data, this data is protected with a BCH error correction code and is encoded using a special error reduction coding to produce the 10-bit word that is transmitted.

From page 54:
Quote:
The input stream to the Source's encoding logic will contain video pixel, packet and control data. The packet data consists of audio and auxiliary data and associated error correction codes.

Page 56:
Quote:
Video Data Periods use transition minimized coding to encode 8 bits per channel, or 24 bits total per pixel.

Data Island Periods are encoded using a similar transition minimized coding, TMDS Error Reduction Coding (TERC4), which transmits 4 bits per channel, or 12 bits total per TMDS clock period.

Beginning at page 58, it describes the data island period, including the ECC generation.

I have not yet read the document cover-to-cover. But this time I did a search for every instance of the word "error" to see what was discussed. And I don't yet see where video pixel data is covered by any error correct. Honestly, I really am looking for it, I hope my citations above are not taken as trying to provoke an argument, I just don't see it.

Regards,
Bill
post #284 of 454
Quote:
Originally Posted by GlenC View Post

Seems to me there was a reason the designed/developed passive, balanced passive and balanced active cables. Seems to me, unless you are getting all the packets delivered intact, as sent, you are not getting the whole picture. .

You need to get "enough" packets in enough time through the cable to construct the picture.

If a cable is getting you enough packets you get the reconstructed picture.
If the cable was getting you all the packets you get the same reconstructed picture.

I know from experience an active cable will run longer than a passive one but the issue isn't one of picture quality improvement its of successful picture delivery over distance.

If two cables successfully deliver the picture the picture will be identical in each case.

If one of the cables fails to deliver the picture successfully the result is an obviously corrupt or non-existent picture not the comparatively more subtle assessments of sharpness , judder and color.

There is no middle ground its either corrupt or reconstructed successfully.

Advertising a genuinely premium quality hdmi cable as being desirable for long runs is perfectly sound. If you need a long run by all means spend a bit more money on the cable.

Recommending a genuine premium quality cable over a cheap albeit functional one as a means to enhancing subjective picture quality is snake oil.
post #285 of 454
Quote:
Originally Posted by GlenC View Post

What can I say, I have seen/experienced the performance differences. We all need to realize that we are only talking high bandwidth, 1080/60p and 1080/24p.

I use these formats all the time on various displays (often originally from 2k 10bitlog film scans) and the cable only has to be functional. If its not functioning properly the 'sparklies" are the initial symptom not subjective picture quality issues.
post #286 of 454
did anyone bother reading the audioquest pdf I posted?

If you did I cannot understand how anyone can insist that malfunctioning hdmi cables produce picture quality artifacts such as softness and judder. The audioquest article actually makes a case for high quality hdmi cables but from the perspective of length and high data rate functionality not subtle picture quality enhancent.

It even makes the point that succesfully functional cables will produce the exact same picture regardless of their maximum bandwidth capabilities.
post #287 of 454
Quote:
Originally Posted by Mr.D View Post

did anyone bother reading the audioquest pdf I posted?

If you did I cannot understand how anyone can insist that malfunctioning hdmi cables produce picture quality artifacts such as softness and judder. The audioquest article actually makes a case for high quality hdmi cables but from the perspective of length and high data rate functionality not subtle picture quality enhancent.

It even makes the point that succesfully functional cables will produce the exact same picture regardless of their maximum bandwidth capabilities.

I read the article. It provides a nice description of the eye-test for cable quality, i.e., how the QA process matches up with the spec.

I did see his claim that the picture will always be exactly the same. "Exactly" is a pretty strong claim. This is one of those cases where one can choose to believe the marketing literature or the spec itself. I don't see the support for what he says in the spec itself, for video pixel data. I do see it in the case of audio data, and the author is coming from an audio company. The thesis of the article is that cable quality does matter, especially for high bandwidth and long cable lengths, and that the purchaser should want to purchase from a company that does 100% testing to assure the quality standards are met, and I understand that argument.
post #288 of 454
Quote:
Originally Posted by GlenC View Post

What can I say, I have seen/experienced the performance differences. We all need to realize that we are only talking high bandwidth, 1080/60p and 1080/24p.

Except of course 1080p24 uses less bandwith than 1080i60.
post #289 of 454
Quote:
Originally Posted by sotti View Post

Except of course 1080p24 uses less bandwith than 1080i60.

Glen did say "60p".
post #290 of 454
Quote:
Originally Posted by Bill Mitchell View Post

I read the article. It provides a nice description of the eye-test for cable quality, i.e., how the QA process matches up with the spec.

I did see his claim that the picture will always be exactly the same. "Exactly" is a pretty strong claim. .

If the data is sufficient to reconstruct the picture in both cases the picture will be exactly the same.

If the data loss through one cable was sufficient to impact picture quality you get sparklies (chunks of the picture are literally not there: white and green blocks instead) or no picture.
post #291 of 454
Quote:
Originally Posted by Mr.D View Post

I see every need to be derisive towards misinformed snake oil pedlars at every opportunity: especially when they go around referring to people demonstrably more learned than they are as "dumbasses".

This is an internet forum and my grammar and punctuation are quite sufficient for that purpose. Feel free to correct it yourself if the construction of my previous post offends you so.

If that was the main purpose of your post I'd suggest you are veering off topic and heading swiftly toward pettiness; which I have precisely zero interest in .

One can be constructive in correcting misconceptions and not fall to the level of others. Grammar is your choice, but better writing makes it more likely that you will be understood. The quality of what you write and how you write it may also suggest to others the level of credibility to attach to your postings. The very point of my posts is that your pettiness in deriding others detracts from the forum. You can correct people in a manner that elevates the thread. Please consider it.
post #292 of 454
Quote:
Originally Posted by Bill Mitchell View Post

With your prompting, I looked again at the spec. It appears to me, still, that the packet level includes only audio and control info, not video pixel data. In particular,

From pages 8-9:


From page 54:


Page 56:


Beginning at page 58, it describes the data island period, including the ECC generation.

I have not yet read the document cover-to-cover. But this time I did a search for every instance of the word "error" to see what was discussed. And I don't yet see where video pixel data is covered by any error correct. Honestly, I really am looking for it, I hope my citations above are not taken as trying to provoke an argument, I just don't see it.

Regards,
Bill

Perhaps you are correct. My understanding was based on discussions with an engineer from one of the vendors, and he may not have had a clear understanding of the spec.
post #293 of 454
Quote:
Originally Posted by Mr.D View Post

Glen did say "60p".

yeah I'm just saying he lumped 1080p24 in there like it is high bandwdith, when it's acutally lower than 720p60

1920x1080x24bx60hz= 2.8gbps
1920x540x24bx60hz = 1.4gbps
1280x720x24bx60hz = 1.26gbps
1920x1080x24bx24hz = 1.14gpbs

1080p24 is actually the lowest bandwidth HD signal and he named it specifically when talking about high bandwidth situations.
post #294 of 454
Quote:
Originally Posted by sotti View Post

yeah I'm just saying he lumped 1080p24 in there like it is high bandwdith, when it's acutally lower than 720p60

1920x1080x24bx60hz= 2.8gbps
1920x540x24bx60hz = 1.4gbps
1280x720x24bx60hz = 1.26gbps
1920x1080x24bx24hz = 1.14gpbs

1080p24 is actually the lowest bandwidth HD signal and he named it specifically when talking about high bandwidth situations.

I didn't want to get into every possible combination. Since I mostly deal with 1920x1080 displays and with a Lumagen in the path, 1080/60p is the most common signal. If you have a problem with 1080/24p, then you will have problems with 1080/60p, 720/60p, etc. ......... Most of this is moot, unless one is experiencing problems...... Solving for yourself is one thing, solving for a customer, they want it fixed!, no try this and try that........
post #295 of 454
Quote:
Originally Posted by sotti View Post

yeah I'm just saying he lumped 1080p24 in there like it is high bandwdith, when it's acutally lower than 720p60

1920x1080x24bx60hz= 2.8gbps
1920x540x24bx60hz = 1.4gbps
1280x720x24bx60hz = 1.26gbps
1920x1080x24bx24hz = 1.14gpbs

1080p24 is actually the lowest bandwidth HD signal and he named it specifically when talking about high bandwidth situations.

This is not accurate math, it's actually more complicated than that since it all runs in 10-bit, even if the video is only 8-bit. You also have to include the extra line time and extra lines where all the rest of the data (audio, etc) rides, so the data rates are higher than that.

It's kind of a mess, but for instance AFAIK 1080i and 720p run at the same bitrate. Some rates like 480i/480p send pixels twice, it also varies whether you're sending 4:4:4 or 4:2:2, etc etc.

For instance your first number of 2.8 gbps is not accurate for 1080p60, it's 4.45gbps.
post #296 of 454
Quote:
Originally Posted by GlenC View Post

What can I say, I have seen/experienced the performance differences. We all need to realize that we are only talking high bandwidth, 1080/60p and 1080/24p.

What differences and how did you measure them, on what test patterns?

HDMI cabling absolutely can and does fail. And when that happens, you lose pixels, or large chunks of the image (lost lines entirely, really bad snow, etc), or total loss of image (complete snow). You don't get things like judder, softness, changes in color, or anything like that. If you're seeing that you are seeing other things, or you're "seeing" things that aren't real. It's really as simple as that.
post #297 of 454
Quote:
Originally Posted by ChrisWiggles View Post

This is not accurate math, it's actually more complicated than that since it all runs in 10-bit, even if the video is only 8-bit. You also have to include the extra line time and extra lines where all the rest of the data (audio, etc) rides, so the data rates are higher than that.

It's kind of a mess, but for instance AFAIK 1080i and 720p run at the same bitrate. Some rates like 480i/480p send pixels twice, it also varies whether you're sending 4:4:4 or 4:2:2, etc etc.

For instance your first number of 2.8 gbps is not accurate for 1080p60, it's 4.45gbps.

Or if you're sending RGB.

My only point was 1080p24 has lower bandwidth requirements that 720p60. If 720p60 works on an HDMI run 1080p24 should work, 1080i60 will likely work, but 1080p60 may not work at all (since it's twice the bandwidth of anything else).
post #298 of 454
Quote:
Originally Posted by sotti View Post

Or if you're sending RGB.

My only point was 1080p24 has lower bandwidth requirements that 720p60. If 720p60 works on an HDMI run 1080p24 should work, 1080i60 will likely work, but 1080p60 may not work at all (since it's twice the bandwidth of anything else).

Yes, I've run into several situations where 1080i60 or 1080p24 works just great, but 1080p60 has various problems, or is totally failed.
post #299 of 454
Quote:
Originally Posted by ChrisWiggles View Post

What differences and how did you measure them, on what test patterns?

I didn't/haven't measured it with test patterns. It was more an overall improved picture while watching. This was my experience, I can't prove it and I don't intend to try. Everyone is free to believe what they want. However when someone that didn't see what I did, says I am wrong and couldn't have seen a difference, well..........
post #300 of 454
Quote:
Originally Posted by GlenC View Post

What can I say, I have seen/experienced the performance differences. We all need to realize that we are only talking high bandwidth, 1080/60p and 1080/24p.

I agree with you 100% and those that say BS are in denial.

One can look at a woman and know which looks more attractive, but you cannot point out every detail why. There is a ratio between the eyes, the width vs the height of the face, the Ratio of the Bust, Hips and Waist etc etc etc.

However, when you make a call as to who is a 10 and who is a 5, just saying one is more attractive than the other is just as subjective as the consumers noted in your story. They cannot tell why, that doesnt mean it doesnt exist.

All the naysayers remind me of those that said transistors were perfect even though those that trusted their ears knew there was harmonic distortion that was not present in tubes, which later became a standard measurement for any equipment with transistors involved known as thd. Ditto for the "perfect" digital of the CD, compared to those who actually listened and compared. If the ignorant want to present opinions of what should happen in a perfect world - great. We don't live or view TV in a perfect world.

Hell, Contrast Ratio has no Industry standard and is easy to manipulate by the size of the white square(s) on the screen - and Best Buy is running TV Spots telling how much they know about Contrast Ratio vs Walmart. I can't wait to have fun in a Best Buy with that one.
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