(HDTV Primer Part 2) HDTV's Demystified

Frank's 2000 Inch TV

Ahhhh... Non one can write songs like that wordsmith, Weird Al!

As the advent of HD television, I am finding greater and greater semi-information coming from the cable companies, the TV companies, and the big box electronic stores.

This post's theme is going to explain exactly what the heck all the TV terms mean. 720i? What the heck is that?

Have no fear friends, I am here to help. If you are a regular reader here, then you know that I am constantly waging an information war against those who would spread lies about new TV technology.

First off, what is High Definition (HD) TV? It is, quite literally, pictures and video that are highly defined. When describing pictures, one uses the term "pixel" a clumsy contraction of the words "picture element". A pixel is, in reality, simply a dot on your screen. This dot has three colour components, red, blue and green. Depending how these colours are brightened or dimmed, gives the pixel an overall colour. Combine a whole bunch of pixels, and you get a picture. Change the colour of the pixels in a controlled manner, and you brain interprets it as movement.

A screen's picture quality is defined by its "resolution" or quite literally, how many pixels it has on its surface. The more pixels, the better the picture.

This is where HD comes in. TV's sold in North America throughout the 70's, 80's, 90's, and early 2000's were what was known as Standard Definiton (SD), 640x480 and multiples there of, also called NTSC (National Television System Committee). This meant that they had pictures that were 640 pixels wide by 480 pixels high.

Larger SD TV's used larger dimensions, but always in the ratio of 3 pixels wide, to two pixels high.

HD content uses a much higher number of pixels to define pictures, so it does indeed look better when displaying high definition content.

HD resolutions use a ratio of 16 pixels wide by 9 pixels high. Official HD resolutions are: HD 720 (1280x720), and HD 1080 (1920x1080). Technically, EDTV 480 (854x480), is not high enough to actually call it High Definition (and is not part of the HD Standard), so it is referred to as Enhanced Definition.

Here is a comparison of various resolutions in scale:


While many TV's rightly claim that they are HD displays, they are not all HD 1080. Make sure you read ALL the numbers, not just the price. There is a reason that giant *HDTV* is so cheap!

Another thing you have to know about is the "scan".

Dear God, more TV lingo? Yes, the "scan" was a term from the days when all TV's were Cathode Ray Tubes (CRT) in which a beam of electrons "painted" the picture on the screen, one line at a time from the top, 60 times per second.

Progressive Scan (PS) means that every line is painted on every scan. This gives the best picture as every line is utilized on the screen in every pass. However the delivery method of the media requires a high bandwidth since more information needs to be delivered. This is indicated as a p such as 720p or 1080p.

Interlaced Scan (IS) means that on the first scan, lines 1, 3, 5... etc. of a frame are painted, then on the next scan lines 2, 4, 6... etc. of the next frame are painted. The benefit is that half the bandwidth is needed at the sacrifice of picture quality, known as "combing". Additionally, IS has a "flickering" effect. Even though you may not be able to see the flicker with your eyes, it is known to cause eye strain and headaches after continuous use. This is indicated as an i such as 720i or 1080i.

If a TV can display progressive scan, it can display interlaced, but not the other way around.

Here is an example comparison between PS and IS. The fourth picture is how non-scanning TV's such as DLP, LCD, and Plasma display interlaced video.

Please note that the flicker shown for IS is exaggerated for demonstration purposes. It really is not that obvious.




This is an example of "combing". This is caused because the odd and even lines are displaying two different frames, so the picture does not line up properly. You can see that the source video was being transmitted by satellite, where bandwidth is a premium, hence the use of interlaced broadcast.



Current TV's use "comb filters" to try clean up the picture, but no filter can replace progressive scanning.

Now finally there is the display technology. While CRT is really the king of picture quality, they are very heavy, very thick, use alot of lead in the construction, and are limited to a one meter (diagonal) screen sizes. Newer TV's are thinner and lighter, saving money on shipping, and saving your back.

The first is Digital Light Processing (DLP) this uses a grid of tiny mirrors to project coloured light onto the screen. Each mirror represents one pixel. Cheaper models use a single DLP chip and a rapidly spinning colour wheel (red/blue/green) to project the picture. Higher quality images are obtained using three DLP chips, each with its own dedicated light beam (again red/blue/green).

While not as thin as LCD or plasma, DLP's are cheaper and more easily repaired when the light source burns out. They are also lighter and immune to "burn in".

DLP may also create eyestrain, are susceptible to the silk screen (ie. the screen surface is noticeable) effect and the screen door effect (ie. the pixels are spaced too far apart, showing a black, grid-like pattern). They may also be vulnerable to vibration, so if you have kids jumping around by the TV alot, the mirrors may be affected.

A Liquid Crystal Display (LCD) creates a picture by using liquid-crystal gels that react to electricity. The back of the display is evenly lit by the backlight and brightens the coloured liquid crystal cells. The cells can then be darkened by applying various voltages to the individual cells. Each gel cell only produces one colour (blue/green/red) so three cells, one of each colour, are grouped together in a pixel.

LCD displays are very thin, but don't produce true black, since they can never be truly opaque. LCD's are also vulnerable to dead pixels, where cells no longer respond to the voltages applied, thus becoming "stuck" on one colour. While negligible around the edge, it is very noticeable in the center area. Cheap models are also susceptible to screen door effect, blurring, and ghosting.

Finally Plasma displays work like millions of neon lights to produce colours in a grid pattern to produce a picture. Each cell contains a gas that is excited by electricity. The cell is coated by a special coating called a phosphor. The excited gas causes the phosphor to display its colour. Each phosphor can only display one colour, (blue/green/red), so three different phosphors are grouped together in each pixel. Plasma displays also have a backlight, to help brighten the image.

While giving a better picture than LCD, Plasma displays are way more expensive than either LCD or DLP and consume much more power. They do produce black better than LCD, but they are vulnerable to screen burn. Screen burn occurs when a single picture is displayed on the screen for a long period of time (such as pausing a movie while the TV is on and forgetting about it for a few hours. This damages the screen, causing that image to lightly be displayed permanently.

Also, LCD and Plasma TV's are not easily repairable. Hence, when it dies, you need to buy a new one. DLP's can be repaired depending on which component dies.

Do here is the big question, which would I choose?

My preference is the DLP, 1080p display. Failing that, I would go with an LCD, 1080p. I just can't justify spending tonnes of money on a plasma screen. I mean, its only television.

Now if they ever come out with SED screens... well, that's another story altogether.

I hope this little article has helped you sort out the quagmire that the big box stores have hoped to drown you in. Now you can go out and make an informed choice as an educated consumer.

Until next time, this is Soundwave saying, keep on having fun!

"bah weep graaagnah wheep ni ni bong"

(HDTV Primer Part 1) HDTV's - The true picture

I keep reading/hearing/seeing stories regarding hi-def TV's and how great they are, and by and large they are quite worthy pieces of technology, however, I am here to break down the hype surrounding them.

Now just to get this out of the way, I do not own a high def TV, nor is this article supposed to discourage you from buying one. I am a huge TV junkie and I do love watching television. I just don't want you to be suckered into paying too much for something you may not need or finding out later that a great picture needs more than just and expensive screen.

My first issue: DIGITAL. This seems to be the new buzzword of media presentation, digital. What does it mean? As far as I can tell, it means that the data is broken down into 1's and 0's in an electronic format. This is not synonymous with high quality. Digital signals CAN be high quality, but that is because the content is of high quality not because digital is inherently good quality. Old movies are not going to become super crisp and sharp just because they are digital.

The next detail, picture quality, is my most divisive issue. Is it worth the extra money? As RadioFreeG stated in his latest podcast, if you think you can just plug in your existing cable feeds and get hi-def picture, you are sorely mistaken.

Yes, existing feeds will look better since the screen is a higher quality, but its not hi-def. No, my friend, hi-def needs a hi-def signal to take advantage of your new screen. The only way to get that signal is with a digital receiver box, which you have to rent from your television provider. On top of that the free content is minuscule. To get HD content, you have to pay extra for that too.

Additionally, movies on disk will suffer from much the same problem. DVD's will look better, but they are not HD content, so you won't get super sharp whatever. To get HD content, first you need a Blue-Ray disk or HD-DVD disks. Then you need a Blue-Ray disk or HD-DVD disk player. Then you need the digital cables to transfer the protected content to the TV, lest you syphon the signal and make illegal copies of it.

In fact every path to get HD content requires an unbroken chain of content, HD compliant equipment, and finally the TV set. The TV is the last step in the chain, so why is that the first thing they try to sell you?

In a word, money.

You see, my objection isn't the selling of the TV's, its the ridiculous investment that they don't tell you about when you're buying the TV's. If you know that there's strings attached to your purchase ahead of time, you can do one of three things, 1) put off the purchase and live with what you have until it dies, 2) Mortgage the house and buy everything in one fell swoop and enjoy a super picture with surround sound in your own home theatre, or 3) realize you just want a huge screen TV or that you want to watch widescreen movies without letter-boxing and make a purchase without disappointment.

I prefer Option 3, but really any of these solutions is acceptable, provided they are made by an informed mind.

I know several people who went with option 2, maybe not the extreme as I described it, but they have their HD signal and TV and the picture is so amazing that they swear they will never go back. Again, never having experienced full HD quality, I cannot fault their logic.

However I will offer this. Standard definition to Hi-Def is not comparable to the shift from black and white to colour, or from silent films to "talkies". Those were major paradigm shifts. HD-TV is not. Wider screen and an improvement in picture quality? Not a major "revolution" in my books.

Personally, I'll hold off on an HDTV for as long as humanly possible. Why? Because in the not too distant future all stations will be broadcasting in HD for free, not just the premium channels. When that happens, the HD tuners will be built into the TV's much like cable TV tuners are now, so I won't have to rent one.

I work hard for my money, like most of your out there, I'm sure. While I do want to get some entertainment and enjoyment from my hard work, there comes a line that we have to draw to tell the media and content providers that "enough is enough, I don't want to give you any more of my money". Again, this message is reiterated in RadioFreeG's latest podcast. How much content are you willing to pay for? It is one thing if it was free, then give me all you've got. But, if I have to pay and pay and pay for entertainment, then I have to sit down and decide how much do I need, how much do I want to spend, and how much do I want to save for a rainy day?

Just a small thing to think about.

Until next time, keep on having fun.

"bah weep graaagnah wheep ni ni bong"