Shopping for a new television can be a little complicated today. This article will attempt to clear up at least part of the picture by explaining the difference between enhanced definition TV (EDTV) and high-definition TV (HDTV). In the process we'll also define standard definition TV (SDTV).

A certain amount of technical information is necessary. To start, a television displays a moving picture by running a set of still pictures in quick succession to create the illusion of movement. These still frames flash by at 30 frames per second. But to display a single frame, the TV must "paint" the screen or picture, line by line.

A standard television screen is comprised of about 480 scan lines. The TV receives data for the even numbered lines first, then must make a second pass to fill in the odd numbered lines to complete each frame. Both passes together take place in the span of 1/30th of a second. Because each pass paints every other line, this type of display is referred to as interlaced, or 480i. It is also called 525i because there are 45 additional "blank lines" built into every frame transmission to give the display time to reset itself. Nevertheless, the proper designation is 480i, or standard definition TV (SDTV).

This technology was fine for smaller screens, but as displays became larger the 480 scan lines became visible, as did artifacts created by the interlacing technique. Objects in motion that created offset or jagged lines between the first and second passes became visible on large screens, resulting in poor picture quality. Simply put, large screen TVs only magnified SDTV's shortcomings. Enter progressive scanning.

A progressive scan TV paints the entire frame in one sequential pass, eliminating much of the distortion that two-pass interlacing creates. Although the TV still receives the video frame in two parts, it combines the data before painting it by using an internal processor called a deinterlacer, also known as a line doubler. Progressive scan displays are specified as 480p or 525p, more commonly called enhanced definition TV (EDTV).

EDTV represents a significant step forward in display technology, creating a much finer picture than interlaced TV. The deinterlacer not only assembles the frame but also cleans up any artifacts in the process. Additionally, EDTV can paint a complete frame in 1/60th of a second, which allows it to paint the same frame twice. This creates a cleaner, more stable picture. EDTV also features a 16:9 aspect ratio, which means the display is rectangular or theater-shaped. Finally, EDTV can render high-definition broadcasting, or HDTV, while SDTV cannot.

You might be asking, "If EDTV can render high-definition broadcasting, why get a HDTV?" The short answer is that HDTV can display HD broadcasts in better resolution than EDTV. Though a quality EDTV looks closer to a HDTV than it does to standard television, all else being equal, the HDTV will outshine the EDTV when it comes to high-definition broadcasts by a margin that some experts put at about 20 percent. How does HDTV do this? By adding more scan lines for finer resolution and more clarity.

While EDTV has 480 scan lines, HDTV supports two high-definition broadcasting formats: 720p and 1080i. 720p is a progressive scan with 720 scan lines, while 1080i is interlaced with 1080 scan lines. Generally speaking, the more scan lines, the better the resolution, particularly when considering large screens.

It might sound counter-intuitive that HD broadcasting would employ an interlaced signal, but with so many scan lines any artifacts created are too small to be noticeable and the higher resolution is breathtaking. Even so, 720p is preferred for fast motion, as the progressive scan technique is able to repaint the picture faster, making motion smoother. Hence, football games and other sports are broadcast in 720p, while "normal" HD b

Answered by Nishu's , an ibibo Master, at 4:20 PM on October 19, 2008

Standard TV has 525 lines of interlaced video. Interlacing means that the video (which is split into 2 fields) gets shown alternately. Of the 525 lines only 480 have a video signal. That’s the 480i you see floating around in all the EDTV vs HDTV specifications.

HDTV stands for High Definition TV. EDTV is the 2nd best PQ that we have. EDTV stands for Enhanced Definition TV.

EDTV has the same 480 lines as SD, but they are progressive scan. SD uses 480i (interlaced) and EDTV uses 480p (progressive scan). DVD players uses progressive scan to display PQ and EDTVs do a great job of displaying them.

Answered by Shishir , an ibibo Master, at 8:44 AM on October 18, 2008

The consumer electronics industry has done a spectacular job spreading mass confusion about video. Time was when there was just TV. Now we've got SDTV, EDTV, HDTV, 480i, 480p, 525p, 720p, 1080i, progressive scan, component video, composite video, blah blah blah. Enough to make you feel like you need an engineering degree to buy a projector or TV.

And if you think you are confused now, just go talk to any sales rep on the floor of your local Buster's Big Screen Megastore and you will get some insight into what true confusion is all about. Many of those reps have little training and can't tell you anything meaningful about good video. Invariably however they are pushing the deal of the week and selling equipment that may be exactly wrong for your needs.

Let's talk basics. You want the best picture you can get for your money, right? OK. Getting there is actually easier than you think. Reading the rest of this article will give you most of what you need to sort out the good stuff from the junk.

Our Television/Video System. There are over 250 million televisions in the United States. Almost all of them work exactly the same way. A video signal pumps information into a TV at the rate of 30 frames per second. Each frame is a still picture. But they are displayed so rapidly that they give the appearance of continuous motion, just like an animated cartoon.

Each frame of video contains about 480 active lines of information (482.5 actually, but we will talk round numbers here to communicate the concept). Now a single frame of video is actually painted on the screen line-by-line in two passes. On the first pass, the beam paints all of the odd numbered lines from 1 to 479, top to bottom. That takes 1/60 second. On the second pass it paints all of the even numbered lines from 2 to 480. That also takes 1/60 second. So it takes a total of 1/30 second to display all 480 lines of the frame. This display technique is known as "interlacing."

When they broadcast video information, they need to give CRT-type TVs time to reset the electronic beam to the top of the screen so it can get ready to paint the next sequence of lines. So they build in an interframe gap that equals about 45 lines. There is no picture information in this 45 line gap—it is there just to allow the TV time to get ready to receive the next frame. So the total number of lines in each frame is 480 + 45 = 525. You've probably heard that a TV set has 525 lines. Not so. The signal has 525 lines, but only 480 of them contain active video information that ends up on your screen.

Sometimes you will see this standard analog TV format designated as 525i, which means 525-interlaced. In common usage, a lot of people also use the term "480i" to refer to analog interlaced 480-line active video. However, the industry has recently defined a digital interlaced 480-line format under the array of DTV formats which is known as Standard Definition Television, or SDTV, and 480i is the correct designation for this format.

The Problem with Interlacing: Screen Size

For most of the 50 years that the plain ole "525i" television has been in existence, it has worked just fine. That's because TVs were small. On a 19" TV set the picture looks terrific because the scan lines and the errors introduced by interlacing are too small to see. But as TVs have gotten larger, the scan lines have become more visible.

Not only that, but the interlacing system creates weird "artifacts" when blown up to big-screen proportions. When there is motion in the picture, an object will have moved between the time the first half and the second half of the frame are painted. That makes straight lines break up and look like they've got jagged edges. And on a 60" TV or a genuine really big-screen image from a front projector, the visible scan lines and jaggies are enough to drive you nuts.

If you w

Answered by Gyan Singh , an ibibo Master, at 7:45 AM on October 18, 2008

Shopping for a new television can be a little complicated today. This article will attempt to clear up at least part of the picture by explaining the difference between enhanced definition TV (EDTV) and high-definition TV (HDTV). In the process we'll also define standard definition TV (SDTV).

A certain amount of technical information is necessary. To start, a television displays a moving picture by running a set of still pictures in quick succession to create the illusion of movement. These still frames flash by at 30 frames per second. But to display a single frame, the TV must "paint" the screen or picture, line by line.

A standard television screen is comprised of about 480 scan lines. The TV receives data for the even numbered lines first, then must make a second pass to fill in the odd numbered lines to complete each frame. Both passes together take place in the span of 1/30th of a second. Because each pass paints every other line, this type of display is referred to as interlaced, or 480i. It is also called 525i because there are 45 additional "blank lines" built into every frame transmission to give the display time to reset itself. Nevertheless, the proper designation is 480i, or standard definition TV (SDTV).

This technology was fine for smaller screens, but as displays became larger the 480 scan lines became visible, as did artifacts created by the interlacing technique. Objects in motion that created offset or jagged lines between the first and second passes became visible on large screens, resulting in poor picture quality. Simply put, large screen TVs only magnified SDTV's shortcomings. Enter progressive scanning.

A progressive scan TV paints the entire frame in one sequential pass, eliminating much of the distortion that two-pass interlacing creates. Although the TV still receives the video frame in two parts, it combines the data before painting it by using an internal processor called a deinterlacer, also known as a line doubler. Progressive scan displays are specified as 480p or 525p, more commonly called enhanced definition TV (EDTV).

EDTV represents a significant step forward in display technology, creating a much finer picture than interlaced TV. The deinterlacer not only assembles the frame but also cleans up any artifacts in the process. Additionally, EDTV can paint a complete frame in 1/60th of a second, which allows it to paint the same frame twice. This creates a cleaner, more stable picture. EDTV also features a 16:9 aspect ratio, which means the display is rectangular or theater-shaped. Finally, EDTV can render high-definition broadcasting, or HDTV, while SDTV cannot.

You might be asking, "If EDTV can render high-definition broadcasting, why get a HDTV?" The short answer is that HDTV can display HD broadcasts in better resolution than EDTV. Though a quality EDTV looks closer to a HDTV than it does to standard television, all else being equal, the HDTV will outshine the EDTV when it comes to high-definition broadcasts by a margin that some experts put at about 20 percent. How does HDTV do this? By adding more scan lines for finer resolution and more clarity.

While EDTV has 480 scan lines, HDTV supports two high-definition broadcasting formats: 720p and 1080i. 720p is a progressive scan with 720 scan lines, while 1080i is interlaced with 1080 scan lines. Generally speaking, the more scan lines, the better the resolution, particularly when considering large screens.

It might sound counter-intuitive that HD broadcasting would employ an interlaced signal, but with so many scan lines any artifacts created are too small to be noticeable and the higher resolution is breathtaking. Even so, 720p is preferred for fast motion, as the progressive scan technique is able to repaint the picture faster, making motion smoother. Hence, football games and other sports are broadcast in 720p, while "normal" HD b

Answered by Deepak , an ibibo Master, at 7:16 AM on October 18, 2008

EDTV, or 480p, doesn't sound like much compared to HDTV. But it is in fact a major step forward in picture quality. On a big screen it looks closer in quality to HDTV than it does regular television. And it is here today in its full glory. Most DVD players on the market output both interlaced and progressive signals, and they are getting better and cheaper by the month. So every DVD on the market can be played in EDTV right now!

Now in order to take advantage of 480p, you need two things: (1) a video source such as a DVD player that outputs that signal, and (2) a television or projector that can take that signal as an input. Warning: Most televisions being sold cannot take 480p. Most home theater projectors, even the least expensive ones under $2,000, can.

So here is your first absolute rule for buying a new video display, whether it is a projector or a TV: if you want maximum video quality, make sure to buy a TV or projector that is 480p compatible.

But, you ask, what about regular interlaced video sources like cable television, VCR, laserdisc, and so on—how do I play those signals on a progressive scan video system?

Well, no problem. You simply to feed your new projector or TV the interlaced signal. All progressive scan display systems can take interlaced signals as well. That is because they have a device on board called a deinterlacer or line doubler.

Here is what a line doubler (deinterlacer) does: It takes a 480-line interlaced signal from your cable TV or VCR or laserdisc player or DVD player and recombines the odd and even lines into a sequential 480-line progressive signal. Furthermore, when good line doublers recombine the lines, they look for motion offsets (the jaggies), and make adjustments to smooth them out. So their job is to convert a 525i signal into a much cleaner 480p signal. Some of them do this better than others, but most of them produce a much better signal than they started with.

Furthermore, since the projector/TV scans from top to bottom in 1/60 second, all 480 lines are displayed in that time. So what does the line doubler do with the second 1/60 second, since new frames are arriving at the speed of only 30 frames per second? Simple. It feeds the same 480-line frame to the display a second time.

So, contrary to what you might assume, a line doubler does NOT double the number of lines. Rather it doubles the number of times the 480 lines are painted on the screen during the 1/30 second frame display time. This increases brightness and stability of the image. But most importantly, the elimination or reduction of the jaggies gives you a much cleaner picture.

It used to be that the internal line doublers in projectors and TVs were not very good. They could recombine the lines easily enough, but they weren't capable of smoothing out the motion artifacts. So many folks invested in separate external line doublers that were much more sophisticated. These days internal line doublers are MUCH more comprehensive than they used to be. So the need for an external doubler has diminished. Today, whether you could benefit from investing in an external line doubler or not depends on the quality of the doubler already built into the projector.

So let's forget about HDTV for a moment. The big leap forward that is accessible to everyone right now is EDTV, which is simply progressive scanning. I had friends over recently and I put on the Eagles "Hell Freezes Over" DVD, displaying it on a 120" diagonal screen. They were stunned at the picture quality—"I've never seen ANY big screen ever look that good," said one. "So that's HDTV huh?" Nope. That's just regular DVD my friends, played on a progressive scan DVD player.

The broadcast industry is struggling toward conversion of our system to High Definition Television (HDTV), a conversion which presumably will be complete in another five years. HDTV doe

Answered by Mohd Saqib , an ibibo Master, at 12:33 AM on October 18, 2008

Shopping for a new television can be a little complicated today. This article will attempt to clear up at least part of the picture by explaining the difference between enhanced definition TV (EDTV) and high-definition TV (HDTV). In the process we'll also define standard definition TV (SDTV).

A certain amount of technical information is necessary. To start, a television displays a moving picture by running a set of still pictures in quick succession to create the illusion of movement. These still frames flash by at 30 frames per second. But to display a single frame, the TV must "paint" the screen or picture, line by line.

A standard television screen is comprised of about 480 scan lines. The TV receives data for the even numbered lines first, then must make a second pass to fill in the odd numbered lines to complete each frame. Both passes together take place in the span of 1/30th of a second. Because each pass paints every other line, this type of display is referred to as interlaced, or 480i. It is also called 525i because there are 45 additional "blank lines" built into every frame transmission to give the display time to reset itself. Nevertheless, the proper designation is 480i, or standard definition TV (SDTV).

Answered by Comp Geek , an ibibo Citizen, at 11:46 PM on October 17, 2008