Explaining HDMI while Solving the Cause of Blue-Screen Nightmares

May 2009

The nightmares

I relate this journey in hopes it will help you avoid your own.

Longtime readers know that I am a fan of HDMI. Any time a single cable can replace as many as 19 cables and all their functions, I’m a happy videophile. Add the fact that HDMI licensees must certify that their products are compliant with HDMI specifications before they can use the HDMI logo, I’m even happier. And the HDMI trade group certifies not just wires but the entire signal chain: receivers, processors, switchers, splitters, and amplifiers (all of which they collectively refer to as “repeaters”). What’s not to love?

Well, a few weeks ago, my wife and I rose from bed for our morning political fix from MSNBC, recorded on our DISH DVR. Not a single TV in the house had a DISH signal -- just the dreaded blue screens signifying that none was receiving a usable signal.

No problem, right? Obviously, the predicament wasn’t caused by a TV, because all six sets were showing the same blue screen. Must be a source or repeater that needed a hard reset. Our Integra DHC-9.9 A/V processor wasn’t getting a signal either, so I checked the Accell 2x8 HDMI switcher/splitter. It was frozen in the off position, which made it the likely source of our woes. But Accell’s tech support was language-challenged, and the only solution they offered was for me to return the unit. I replaced it with an Octava 4x4 HDMI switcher. The screens were still blue.

This made me think the villain was probably High-bandwidth Digital Content Protection (HDCP), the entertainment industry’s system for preventing digital copying of content. The lack of consistently dependable HDCP “handshakes” between A/V components is well known, and the fact that nothing was working made me believe that something like that was shutting down my whole system. I even tried recommendations from anonymous advisors on the Internet, who suggested specific and tedious solutions involving detailed ways of verifying and forcing handshakes in certain magical sequences that were often contradictory. I felt I was descending through the Nine Circles of Hell.

I called Octava. After a few minutes of personable, knowledgeable, polite tech support, their man Jeff asked me to try a straight DVD player. Bingo -- picture and sound everywhere. He postulated that the problem was with the circuit (DISH->Octava->Displays) and its inability to shake hands with a Dolby Digital system. I switched the DISH to PCM (mental note: switch back to DISH for films) and, magically, everything worked. But why should I have to go through all this over Dolby Digital? Besides, for several months now, everything had been working fine with the Accell in Dolby Digital. I called Integra.

A terrible idea. I still unhesitatingly recommend Integra’s processors for their ratio of cost to performance, but be sure you buy one from a good dealer. Integra’s support was worthless -- actually, worse than worthless. Their tech-support folks at first pointed fingers at all the other companies represented in my home-theater system: “Their fault.” I kept calling back, hoping for a better response, but the fourth guy was the worst of the bunch. He implied that I was dumb, and sounded as if he was terminally bored and that I was interrupting his beauty nap. And worse, that if I hadn’t been a cheapskate and bought “good” HDMI cables, none of this would be happening to him . . . or to me.

“Did you get Monster Cables?”

“No,” I said.

“You have to get good cables or it doesn’t work. What kind of TV do you have?”

“Well, I have several.”

“That’s the problem. Are they cheap brands?”

“No.”

“Well, go get some better cables. That’s the problem.”

“But I have really good cables.”

He got angry. Then I asked, “Why would it have worked before and not now?”

“Look, these things are complicated. Your problem is you need to get better cables.”

The conversation was going nowhere; I could tell that he was exasperated and just wanted to hang up: “Just take it to a repair station.”

“There isn’t one within 200 miles of me.”

“Then mail it.”

Thanks.

Years ago, one of the rites of passage of owning a car was learning how to take care of it. You learned to do tune-ups, set the points, change the plugs, install new filters, replace the fluids. The learning curve wasn’t steep, and you’d end up knowing how to not only service your own car but make minor repairs. Then car computers came along, and those of us who liked to work on our cars no longer could. If you couldn’t read and interpret the code and update the programming, you were out of luck.

Ditto for the older stereo and home-theater systems. You could at least get your system going, and it took only a little bit of logic to isolate most problems. You seldom had to call a manufacturer for technical support, and since they didn’t get many calls, they would treat you with some respect. Only phono cartridges and tubes presented difficult challenges of setup and maintenance.

Then came the home-theater version of the car computer, sanctioned by the Motion Picture Association of America (MPAA) and its goon squad, headed by its president, the late Jack Valenti. His attacks began with home theater’s very first appliance: “I say to you that the VCR is to the American film producer and the American public as the Boston strangler is to the woman home alone.” (If you’d like to spend a half hour reading the most insane drivel about how the transfer of digital content was going to destroy the entertainment business, here is Valenti’s complete testimony before the House Judiciary Committee’s Subcommittee on Courts, Civil Liberties, and the Administration of Justice in 1982.)

The lasting result of Valenti’s paranoid rampages is copy protection, in the form of HDCP. That means we’re often stuck in limbo, vying to reach the goal of a home-theater system that works without having to deal with the nastiest recalcitrant miscreants from the worst technical support systems. Valenti, rest his soul, is probably laughing his tail off.

HDMI offers a few facts

The High-Definition Multimedia Interface (HDMI) is jointly owned by seven companies -- Hitachi, Panasonic, Philips, Silicon Image, Sony, Technicolor, and Toshiba -- who are in charge of creating the technology and its specifications. HDMI Licensing, LLC is in charge of collecting fees and ensuring compliance with HDMI specifications. At the time of writing, 930 companies held HDMI licenses. A fair number of other companies selling cheap cables use the HDMI logo but have never submitted their products for evaluation, nor do they pay HDMI licensing fees.

201005_venutiBecause HDMI is the highway for the HDCP handshake, I decided to call HDMI themselves. As a trade group, they aren’t set up to provide consumer support of any kind, but I’d had a good experience interviewing their prior president back in 2006. If nothing else, I thought he might be able to reveal to me the magical sequence of powering on and hooking up HDMI sources, displays, and repeaters that would allow the HDMI handshake to be made all around.

I sent the HDMI marketing people an e-mail requesting an interview with someone who could answer a few technical questions about the workings of the HDMI circuit from source to display, how to isolate problems, and HDMI’s future. I was surprised to hear that I’d be getting a phone call from Steve Venuti, the current president of HDMI Licensing, LLC; sure enough, he called me on his way to the airport to catch a flight to Korea.

“The [HDMI] logo implies that the product is from a real adopter, that it meets the minimal compliance, and it works,” Venuti said. “Unfortunately, there are pirates out there, especially in the world of cables. We see a lot of cables coming from China claiming to be HDMI-approved when they really aren’t. It’s harder to pirate a TV or a Blu-ray player.”

“How can you tell if an HDMI cable isn’t legitimate?” I asked him.

“If you find a really cheap cable -- just a couple of dollars -- with an HDMI logo, there is a good chance that that cable isn’t a truly certified product,” Venuti replied.

I asked if there was a list of genuine licensees on HDMI’s website that could be checked.

“The problem -- and this is true more with cables than with sources, displays, or repeaters -- is that many of our licensees are companies that are making the cables but they are not being sold under their name. Most all of the famous American cable companies are buying from places in China or Korea and repackaging the cables for their own use. You should always buy from a company that you trust or know.”

But wouldn’t it behoove HDMI to figure out a way to list the legitimate resellers?

“We’re contemplating a program that we hope to launch this year,” he said. “Most US cable companies are not licensees, because they buy the cables from a manufacturer. But that manufacturer may have applied to us to certify the cables. We’re going to try to set up a program for American cable companies where, if they can prove to us that they buy from a legitimate certified manufacturer, then we’ll list their product on our website.”

Which raised two big questions for me, about which I’ve received many letters from readers: What tests does an HDMI-certified device have to pass? And, if it passes those tests, what does the buyer gain by spending more money, instead of buying the cheapest device that passes the same tests?

“Pretty much, in terms of the HDMI function, the test is that it has to send, transport, or receive the signal in a way that it can be repackaged properly,” Venuti explained. “Repeaters (example: the video source switching in a processor or receiver) are really complex to measure. We test them very carefully, so that when we give our blessings to a receiver or a processor, it should work. One HDMI component should offer the same performance as the other, whether it is a long CAT line with individual receivers or a straight bundle of copper wires, and we don’t care what technology they use to get the signal from one place to the other as long as the signal is within spec. For both repeaters and cables, the signal from the source has to be strong enough to be read by the receiver chip and recompiled to a pristine signal. If so, and if they pay the licensing fee, they can display our logo.”

Is there any reason to spend a lot of money on transferring an HDMI signal?

“Yes and no,” Venuti said. “For instance, when we test a cable, we test it in a lab and make sure it does what it should. At home, you may do a lot of other things with it: wrap it around poles, run it through walls, or even hide it under a carpet and walk on it. If it’s just a signal from point A to point B, comparing between two compliant cables shouldn’t matter. But we don’t test durability, so the sturdiness of the cable itself might warrant extra expenditure. Pretty much, in terms of the HDMI function, if it’s going to receive the signal and repackage it properly, then one repeater should be the same as the other. In terms of the signal from a source to a repeater and through to the display, it shouldn’t make any difference between currently certified products.”

Another rumor, one I’d just heard from the tech-support folks, is that HDMI-certified cables can work only when they’re a certain short length. Was that true?

“That’s not entirely true,” Venuti said. “There is no definitive statement about length in the standard. What happens is, we hook it up to a source signal, and what comes out has to be a perfect reproduction of what went in, and with enough signal strength to be capable of being recompiled. The manufacturers can make the cables or transmission system as long as they want, as long as it still works at the other end. Now, physics is working against you, so getting over 10 to 15 meters is difficult. With [HDMI] 1.4 3D, we are now at really high bandwidths, so my guess is getting over 10 to 15 meters with a passive copper cable will be pretty difficult.”

What should readers do if their systems are screwed up and they think a lack of HDCP handshaking is to blame?

201005_hdmi_inside“Years ago, when we first launched, HDCP was a complex technology, and the testing wasn’t always picking everything up,” Venuti replied. “So for the first few years, we felt that it was a major issue. At this point, though, even Best Buy is telling us that the number of handshake problems that come up is very small. Still, installers are doing some pretty complex things, and these are challenging to troubleshoot. The technology is so complex, and we’re doing so many things on one cable. And the installers can’t stay up to date as quickly as the technology is changing. So I do admit, troubleshooting is really tough. The more you understand what’s going on inside the cables, the better you’ll understand how to troubleshoot, so we’re trying to train folks. A company called Quantum Data makes a test tool that allows the HDCP metadata to track the data with a PC. Most times the root cause is difficult to find, unless you can see what’s in that datastream.”

What about the home-theater enthusiast who can’t afford expensive test equipment?

“A reboot is the most common way in a digital world. Then try different input ports, and you might at least get your system to work. But you won’t understand why it’s failing. In order to get that, you need someone with training who has the right tools. We’re working with CEDIA [the Custom Electronic Design & Installation Association] right now to make sure there are people in the field who know how to do that.”

What have we learned?

You have to decide for yourself whose version of reality you trust. In the brave new all-digital world, odd components and drivers can fight with each other in ways we’ll never figure out with our five senses. We need test gear, and a working understanding of how our components operate. Here’s what I believe about HDMI, HDCP, and digital transmission.

1.   We’re stuck with HDCP and/or its progeny.

2.   Until wireless transmission is as good as wired, HDMI is a stellar way to transmit A/V signals.

3.   HDMI’s testing is at worst adequate; at best, it’s perfectly representative of the real world (I think it leans toward the latter).

4.   HDMI’s certification process means that a product has been designed correctly, not that the actual manufactured products are free of defects; such defects, unless they are endemic, should not be blamed on HDMI.

5.   You need a good dealer and/or a good setup person; otherwise, if a problem arises, it will be difficult to trace it to its source.

6.   An HDMI-certified product that costs many times as much as another HDMI-certified product had better have very good justifications for its higher price, in addition to the name of the manufacturer. Good companies with a history of high-quality customer support deserve to charge somewhat higher prices, but when one HDMI cable costs $50 and another of the same length costs $1000, I’m going to be at least skeptical, if not cynical.

Back home

What happened with my own system? Using a bypass method, I concluded that the problem was in my Integra DHC-9.9’s HDMI section. As I write, it’s at the repair shop.

. . . Wes Marshall
wesm@soundstagenetwork.com