• • Colorado vNet Lighting System with remote internet access
• • Xantech HD Video Matrix over Cat5
• • dbx Zonepro Audio Matrix
• • Xantech 6.4″ Video Touchscreen control of all IR and serial devices
• • 7 – 54″ Panasonic Plasma TVs
• • 2 HD Pace Shawbox, 1 1TBExpander DVR, 1 DTC700 Shawbox and Shaw HD Direct
• • Computer audio and video input into matrix
• • 2 JBL LSR6332 Studio Monitors with JBL LSR6312 powered subwoofer in the bar area
• • Live band system consisting of JBL EON510 Speakers and a Soundcraft EPM8 Mixer
• • Wall Mount iPod Dock

As DVI and HDMI connections become more and more widely used, we are often asked: which is better, DVI (or HDMI) or component video? The answer, as it happens, is not cut-and-dried.

First, to clear away one element that can be confusing: DVI and HDMI are exactly the same as one another, image-quality-wise. The principal differences are that HDMI carries audio as well as video, and uses a different type of connector, but both use the same encoding scheme, and that’s why a DVI source can be connected to an HDMI monitor, or vice versa, with a DVI/HDMI cable, with no intervening converter box.

The upshot of this article–in case you’re not inclined to read all the details–is that it’s very hard to predict whether a digital DVI or HDMI connection will produce a better or worse image than an analog component video connection. There will often be significant differences between the digital and the analog signals, but those differences are not inherent in the connection type and instead depend upon the characteristics of the source device (e.g., your DVD player) and the display device (e.g., your TV set). Why that is, however, requires a bit more discussion.

What are DVI, HDMI and Component Video?

DVI/HDMI and Component Video are all video standards which support a variety of resolutions, but which deliver the signal from the source to the display in very different ways. The principal important difference is that DVI/HDMI deliver the signal in a digital format, much the same way that a file is delivered from one computer to another along a network, while Component Video is an analog format, delivering the signal not as a bitstream, but as a set of continuously varying voltages representing (albeit indirectly, as we’ll get to in a moment) the red, green and blue components of the signal.

Both DVI/HDMI and Component Video deliver signals as discrete red, green, and blue color components, together with sync information which allows the display to determine when a new line, or a new frame, begins. The DVI/HDMI standard delivers these along three data channels in a format called T.M.D.S., which stands for “Transmission Minimized Differential Signaling.” Big words aside, the T.M.D.S. format basically involves a blue channel to which horizontal and vertical sync are added, and separate green and red channels.

Component Video is delivered, similarly, with the color information split up three ways. However, component video uses a “color-difference” type signal, which consists of Luminance (the “Y”, or “green,” channel, representing the total brightness of the image), Red Minus Luminance (the “Pr,” or “Red,” channel), and Blue Minus Luminance (the “Pb,” or “Blue,” channel). The sync pulses for both horizontal and vertical are delivered on the Y channel. The display calculates the values of red, green and blue from the Y, Pb, and Pr signals.

Both signal types, then, are fundamentally quite similar; they break up the image in similar ways, and deliver the same type of information to the display, albeit in different forms. How they differ, as we’ll see, will depend to a great extent upon the particular characteristics of the source and display devices, and can depend upon cabling as well.

Isn’t Digital Just Better?

It is often supposed by writers on this subject that “digital is better.” Digital signal transfer, it is assumed, is error-free, while analog signals are always subject to some amount of degradation and information loss. There is an element of truth to this argument, but it tends to fly in the face of real-world considerations. First, there is no reason why any perceptible degradation of an analog component video signal should occur even over rather substantial distances; the maximum runs in home theater installations do not present a challenge for analog cabling built to professional standards. Second, it is a flawed assumption to suppose that digital signal handling is always error-free. DVI and HDMI signals aren’t subject to error correction; once information is lost, it’s lost for good. That is not a consideration with well-made cable over short distances, but can easily become a factor at distance.

So What Does Determine Image Quality?

Video doesn’t just translate directly from source material to displays, for a variety of reasons. Very few displays operate at the native resolutions of common source material, so when you’re viewing material in 480p, 720p, or 1080i, there is, of necessity, some scaling going on. Meanwhile, the signals representing colors have to be accurately rendered, which is dependent on black level and “delta,” the relationship between signal level and actual as-rendered color level. Original signal formats don’t correspond well to display hardware; for example, DVD recordings have 480 lines, but non-square pixels. What all of this means is that there is signal processing to go on along the signal chain.

The argument often made for the DVI or HDMI signal formats is the “pure digital” argument–that by taking a digital recording, such as a DVD or a digital satellite signal, and rendering it straight into digital form as a DVI or HDMI signal, and then delivering that digital signal straight to the display, there is a sort of a perfect no-loss-and-no-alteration-of-information signal chain. If the display itself is a native digital display (e.g. an LCD or Plasma display), the argument goes, the signal never has to undergo digital-to-analog conversion and therefore is less altered along the way.

That might be true, were it not for the fact that digital signals are encoded in different ways and have to be converted, and that these signals have to be scaled and processed to be displayed. Consequently, there are always conversions going on, and these conversions aren’t always easy going. “Digital to digital” conversion is no more a guarantee of signal quality than “digital to analog,” and in practice may be substantially worse. Whether it’s better or worse will depend upon the circuitry involved–and that is something which isn’t usually practical to figure out. As a general rule, with consumer equipment, one simply doesn’t know how signals are processed, and one doesn’t know how that processing varies by input. Analog and digital inputs must either be scaled through separate circuits, or one must be converted to the other to use the same scaler. How is that done? In general, you won’t find an answer to that anywhere in your instruction manual, and even if you did, it’d be hard to judge which is the better scaler without viewing the actual video output. It’s fair to say, in general, that even in very high-end consumer gear, the quality of circuits for signal processing and scaling is quite variable.

Additionally, it’s not uncommon to find that the display characteristics of different inputs have been set up differently. Black level, for example, may vary considerably from the digital to the analog inputs, and depending on how sophisticated your setup options on your display are, that may not be an easy thing to recalibrate.

The Role of Cable and Connection Quality

Cable quality, in general, should not be a significant factor in the DVI/HDMI versus Component Video comparison, as long as the cables in question are of high quality. There are, however, ways in which cable quality issues can come into play.

Analog component video is an extremely robust signal type; we have had our customers run analog component, without any need for boosters, relays or other special equipment, up to 200 feet without any signal quality issues at all. However, at long lengths, cable quality can be a consideration–in particular, impedance needs to be strictly controlled to a tight tolerance (ideally, 75 +/- 1.5 ohms) to prevent problems with signal reflection which can cause ghosting or ringing.

DVI and HDMI, unfortunately, are not so robust. The problem here is the same as the virtue of analog component: tight control over impedance. When the professional video industry went to digital signals, it settled upon a standard–SDI, serial digital video–which was designed to be run in coaxial cables, where impedance can be controlled very tightly, and consequently, uncompressed, full-blown HD signals can be run hundreds of feet with no loss of information in SDI. For reasons known only to the designers of the DVI and HDMI standards, this very sound design principle was ignored; instead of coaxial cable, the DVI and HDMI signals are run balanced, through twisted-pair cable. The best twisted pair cables control impedance to about +/- 10%. When a digital signal is run through a cable, the edges of the bits (represented by sudden transitions in voltage) round off, and the rounding increases dramatically with distance. Meanwhile, poor control over impedance results in signal reflections–portions of the signal bounce off of the display end of the line, propagate back down the cable, and return, interfering with later information in the same bitstream. At some point, the data become unrecoverable, and with no error correction available, there’s no way to restore the lost information.

DVI and HDMI connections, for this reason, are subject to the “digital cliff” phenomenon. Up to some length, a DVI or HDMI cable will perform just fine; the rounding and reflections will not compromise the ability of the display device to reconstruct the original bitstream, and no information will be lost. As we make the cable longer and longer, the difficulty of reconstructing the bitstream increases. At some point, unrecoverable bit errors start to occur; these are colloquially described in the home theater community as “sparklies,” because the bit errors manifest themselves as pixel dropouts which make the image sparkle. If we make the cable just a bit longer, so much information is lost that the display becomes unable to reconstitute enough information to even render an image; the bitstream has fallen off the digital cliff, so called because of the abruptness of the failure. A cable design that works perfectly at 20 feet may get “sparkly” at 25, and stop working entirely at 30.

In practice, it’s very hard to say when a DVI or HDMI signal will fail. We have found well-made DVI cables to be quite reliable up to 50 feet, but HDMI cable, with its smaller profile, is a bit more of a puzzle. Because the ability to reconstitute the bitstream varies depending on the quality of the circuitry in the source and display devices, it’s not uncommon for a cable to work fine at 30, 40, or 50 feet on one source/display combination, and not work at all on another.

The Upshot: It Depends

So, which is better, DVI or component? HDMI or component? The answer–unsatisfying, perhaps, but true–is that it depends. It depends upon your source and display devices, and there’s no good way, in principle, to say in advance whether the digital or the analog connection will render a better picture. You may even find, say, that your DVD player looks better through its DVI or HDMI output, while your satellite or cable box looks better through its component output, on the same display. In this case, there’s no real substitute for simply plugging it in and giving it a try both ways.

This article was found on the Ecoustics forum.

Telco, cable and LAN distribution distribution center

Media Room setup

1994 Pro Sound News Article

1994 Sound & Video Contractor Article

1998 Crown Audio Installations Around The World Brochure

Western Canada Wilderness Committee

• • Xantech multi-zone audio system
• • Tru-Audio Speakers
• • Radio Ra Lighting
• • Theatre Room with Fixed High Contrast Wall Screen and Sanyo HiDef Projector

This property was recently the highest listed property in Canada.  The extensive systems integration included numerous Touch Panels, over twenty zones of HVAC, Theater room, roller blinds and exterior shutters, a full 5.1 system built into the master bedroom, integration with the lighting system, gas fireplaces, internet cameras and of course sound throughout.  When you ring the front doorbell, the Superman Theme Plays through the house speakers.  Every device can be controlled from the Touch Panels.  When this project was designed in 2002, AMX control systems used a now obsolete product line named Panja.   As with all computer based products, there has been incredible progress in how things are designed and controlled.  This was state of the art then.

• • Architect – Chow Low Hammond Architects Inc.
• • Builder – Canpro Construction Ltd.

You’ve read the arguments.

You’ve heard about the differences between liquid crystal display and plasma televisions. And you’ve decided an LCD screen is the one for you.

Join the crowd. A report released in March by the Consumer Electronics Marketers of Canada indicates that LCD panels are this country’s No. 1 choice – and by an impressive margin.

Last year, nearly 3 million flat-panel LCD and plasma sets shipped in Canada. Of those, LCD outsold plasma by a ratio of nearly 5-to-1. In this household, LCD came close to winning the battle for our bucks.

Until, that is, we were able to compare the competing technologies in real-world conditions: in our cramped TV room.

Rewind to late December. After a couple of years of fence-sitting, we decided to pull the pin and purchase an LCD set.

Why LCD? Part of the reason was because several friends owned them and the pictures looked great. Nice and bright, with colours that popped. Also, prices of sets with the features we wanted had dropped substantially.

Why not plasma?

Good question. As a former electronics salesman and three-time attendee of the Consumer Electronics Show in Vegas, I take my widgets seriously. I pore over specs and reviews.

But for some reason – likely something I’d read a few years back – it was stuck in my head that plasma was an inferior technology. I was concerned about the issue of burn-in, where fixed content that’s onscreen for long periods leaves an electronic ghost of itself.

This was an issue, and an undeniable one, with the first generations of plasma: Leave your set running for days on a channel with a stock ticker or channel logo and you ran a serious risk it would leave a permanent imprint. (“Have you been watching the Playboy Channel?” Me? No. “Then where did those faded bunny ears come from?”)

It also didn’t help plasmas that LCDs had such a commanding lead in sales. As a result, most of the ads I perused – and most of the models in stores – were LCD. Its sheer dominance of the market left me with a subliminal impression that plasma was on its way out.

In a nutshell, that’s why we were in the LCD camp. We’d also decided to go with 120 Hz technology, where the screen refreshes 120 times per second. This helps ensure fast-action content like sports remains smooth.

Armed with the ratings from Consumer Reports – along with recommendations from other websites and friends – we narrowed it down to a few 40- to 42-inch sets. After comparing features in a couple of stores – we found it near-impossible to compare picture quality in big-box surroundings – I felt confident in buying a Samsung LN-40A630, along with a Sony Blu-ray player.

After connecting the Samsung with a good HDMI cable and running audio from the Blu-ray to a home theatre system, we were good to go. I popped in a Blu-ray disc and – presto! – we had a tremendous picture.

Alas, the magic didn’t last. In the real world, not every DVD is yet available on Blu-ray. And not all of the programming we watch is piped to our TV room in HD.

The real test would be what the set looked like with compressed, standard-definition television on the screen. Plain old TV.

And there, the Samsung failed to impress. The high-resolution screen seemed to struggle with low-definition content. There were occasional digital artifacts – squarish hunks – that appeared for brief periods of time.

These hiccups were constant reminders that we were watching a piece of digital technology, not losing ourselves in entertainment.

I turned to the Internet and discovered (now that I was actually looking) that burn-in is no longer the issue it once was on plasmas. I read glowing customer reviews from plasma owners on websites such as Futureshop.ca. I learned that plasma TVs refresh at a much higher rate than LCDs, meaning motion should look more liquid.

And I was reminded, repeatedly, that many aficionados (and even impartial testers) still believe plasma produces a better overall picture than LCD.

“A good plasma TV’s deep black levels and high contrast can do justice to almost anything you watch, including movies and TV programs with dark scenes,” states a Consumer Reports wrap on the topic. “Most LCD sets have trouble displaying the same strong, dark blacks as plasma sets. On certain LCD sets, uneven brightness from the backlight can create cloudy areas that can be distracting in dark scenes.”

Late one night, I returned home, in a snowstorm, with a 42-inch Panasonic plasma (model TH42PZ85). I wedged the giant box into our TV room. My wife, who’d heard nothing from my mouth except talk of colour banding and refresh rates, gave me a withering glance.

“Wait, honey!” I said hopefully. “We can compare LCD with plasma!”

Her response: “I’m going to bed.”

It was close to midnight when I’d finished unpacking the plasma (it’s a little more awkward when you’re doing it by yourself). I plugged in the HDMI cable, flicked on the remote, and held my breath.

And then, slowly, exhaled.

Bingo!

This was what I’d been looking for. Regardless of the programming, the colours seemed more true, more natural. The experience of watching the Panasonic felt more, well, cinematic. Or at least it did to my bleary eyes that night.

The real test would come the following evening, with both of us wedged in that room full of cardboard.

We compared, in A/B fashion, the two sets with a variety of sources. We tried Blu-ray, regular DVD and standard definition programming.

And, for us, the plasma was more pleasing. By a long shot.

“I really wouldn’t have believed there could be so much difference,” said my wife – which I took as some sort of vindication.

We’ve now had the Panasonic for four months, and continue to feel we made the right choice. For us, it really was worth the second look.

Jun 11, 2009

Scott Simmie
TORONTO STAR