What is DTV? Is there a difference between DTV and HDTV?
Before you upgrade your existing TV with a digital-to-analog converter box or purchase a new television set, you’ll want to be able to distinguish the difference between the two video signals.
This guide will hopefully give you a very basic run down about Digital Television (DTV), High Definition Television (HDTV), and the technology they are replacing…Standard Definition Television (SDTV).
If you're looking for more in-depth information about DTV and HDTV, I highly recommend the following resources:
High-definition television - Wikipedia, the free encyclopedia
The Difference between HDTV, EDTV, and SDTV
HDTV FAQs: What is the Difference Between Digital TV and HDTV?
Before DTV there was SDTV…
The digital transition on February 17th, 2009 will bring an end to analog broadcasted signals for over-the-air stations in the U.S.
Analog televisions signals are classified as Standard Definition Television (SDTV) signals, which are broadcasted to your television set at the rate of 480i lines of information per each frame. Since the average television will display 30 frames per second, you can immagine just how fast 480i lines have to be displayed across the entire screen.
Why is there an "i" after the 480? The "i" refers to interlacing, and it was created to reduce the amount of information (also known as bandwidth) sent by television broadcast towers to consumer television sets. How does it work? Each frame of video is actually displayed in two different phases. The first phase paints the odd number lines out of the 480 lines on a television set, and the second phase paints the even lines.
So, what's wrong with SDTV and 480i, why the upgrade to DTV?
On smaller television sets (21" and smaller), 480i has great picture quality because the lines of resolution and interlacing are small, and hardly noticable to a viewer.
On larger television sets, the lines of resolution grow in size, causing the interlaced lines to become more noticable. The overall picture quality suffers as well, due to any small imperfections being blown up on a larger screen that wouldn't normally be seen on a smaller screen.
As sales in large screen television sets have grown in the past two decades, so has demand for better picture quality. So what can be done to increase picture quality?
- Increase the lines of resolution from 480 to 720 or 1080
- Go from interlaced to progressive scan, which means your TV will display a complete scan for each of the 30 frames instead of the two phases that are used to complete one frame for interlaced.
DTV (also known as EDTV) and HDTV
DTV: The Digital Transition Will Make DTV the Standard in Television Viewing
DTV (also known as EDTV: Enhanced Digital Television) is the next step towards improving television technology, by broadcasting TV signals at a resolution of 480p per frame. The "p" is defined as progressive scan, and it paints a complete frame on a television, instead of painting the frame in two phases like Standard Definition Television broadcasts.
DTV will also provide surround sound audio, but will require extra equipment and cables, which is a little bit outside the aim of this article. Please post questions if you have any...
16:9 Aspect Ratio and the Black Bars at the Top and Bottom of a Television
With DTV at 480p, you're able to receive a much more fine or sharper picture, and you get another benefit: 16:9 aspect ratio (also known as wide screen). Broadcasts set at a 16:9 ratio will provide a viewer with a theater like experience by providing more picture information on the left and right sides of a television screen. A common complaint about this technology is that a viewer is forced to see black bars on the top and bottom of a television screen. To remedy this, most new television sets are now sold with a 16:9 aspect ratio screen, which can reduced but not always eliminate the black bars at the top and bottom of a screen.
If DTV provides a better picture, how does it differ from HDTV?
In short, HDTV is DTV, but DTV is not HDTV. Confused?
HDTV broadcasts provides more lines of resolution than the standard DTV broadcast. Since DTV has 480p lines of resolution, HDTV can be broadcasted at three different high-definition broadcasting formats: 720p, 1080i, and 1080P.
720p is a progressive scan with 720 lines of resolution.
1080i is interlaced with 1080 lines of resolution.
1080p is progressive scan with 1080 lines of resolution.
In terms of which is the better picture quality, generally you can assume that the higher the the lines of resolution, the better the picture quality.
How much of an improvement does HDTV provide over DTV/EDTV? The best answer to this question is to walk or drive to your local electronics store and get a demonstration from someone qualified to show you. You may want to have the demonstrator find channels that are broadcasting only in 480p, flip to a 720p or 1080i broadcast. On smaller televisions, you may not notice a huge difference, but it will be noticable. On larger television sets, have them demo the same 480p, to a 720p or 1080i format. It should become more evident that the 720p and 1080i broadcasts are much more sharper and clearer than the 480p format.
So long SDTV, Hello DTV and HDTV
Hopefully this article has helped you better understand the basic differences between SDTV, DTV/EDTV, and HDTV. There are many more technical advantages that DTV will bring to the table over SDTV such as using less broadcast bandwidth to provide the same channel programming; you can use the links provided at the beginning of the article for finding more in-depth information.
As always, please post questions and feedback to this article so that we can better the DTV community.
