When the first high definition TV (HDTV) sets hit the market in 1998, movie fans, sportsfans and tech enthusiasts have much excited, and for good reason. Ads for the setshinted at a television paradise with superior resolution and digital surround sound. WithHDTV, you can also play movies in original widescreen format without the "black bars"that some people find annoying letterbox.
But for a lot of people, HDTV has not delivered a ready-made source for transcendentexperiences in front of the tube. Instead, people went shopping for a TV and found themselves surrounded by confusing abbreviations and too many choices. Some haveeven hooked up their new HDTV set, only to find that the image is not good.Fortunately, a few basic facts easily dispel all of this confusion.
In this article we will see the differences between analog, digital and high definition,explain the acronyms and resolution levels and give you the facts on the transition ofthe United States to all-digital television. In addition, will tell you exactly what you needto know if you're thinking about changing to HDTV.
Analog, Digital and HDTV
For years, watching TV has involved analog signals and cathode ray tube (CRT) in September The signal is made of continually varying radio waves that results in a television image and sound. An analog signal can reach one person over the air TV through a cable or satellite. Digital signals, such as DVD players, are converted to analog when played on traditional TVs.
This system has worked well for a long time, but has some limitations:
- Set of conventional CRT monitors about 480 visible lines of pixels. Broadcasters have sent signals that work well with this resolution for years, and can not fit enough resolution to fill a huge television with the analog signal.
- Analog pictures are interlaced - a CRT's electron gun paints only half the lines for each step down the screen. On some TVs, interlacing makes the picture flicker.
- video conversion to analog format lowers its quality.
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| Analog TV |
DTV has several advantages:
- The image, even when displayed on a small television, is best quality.
- A digital signal can support a higher resolution, then the image will still look good when projected onto a TV screen larger.
- The video can be progressive and not interlaced - the screen displays the whole image of each frame instead of every other line of pixels.
- TV stations can broadcast several signals using the same bandwidth. This is called multicasting.
- If broadcasters choose to, they can include interactive content or additional information with the DTV signal.
- It can support high-definition (HDTV) broadcasts.
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| HDTV |
This brings us to the first big misconception about HDTV. Some people believe that the U.S. is switching to HDTV - that all that you need for HDTV is a new TV and we automatically have HDTV when analog service ends. Unfortunately, none of this is true.
HDTV is only part of the DTV transition. We will see HDTV in more detail, including what makes it different from DTV, in the next section.
The Advanced Television Standards Committee (ATSC) has set voluntary standards for digital television. These standards include how sound and video are encoded and transmitted. They also provide guidelines for different levels of quality. All digital standards are better in quality than analog signals. HDTV standards are the highest part of all digital signals.
The ATSC has created 18 commonly used digital broadcast formats for video. The digital format of lower quality is about the same as the highest quality of an analog TV can display. The 18 formats cover differences in:
Many of these rules are exactly the same aspect ratio and resolution - their frame rates differentiate them from each other. When you hear someone refer to a set of "1080i" HDTV, they're talking about one that has a native resolution of 1920 x 1080 pixels and can display 60 frames per second, interlaced.
Broadcasters get to decide which of these formats they will use and whether they will broadcast in high definition - many are already using digital and high definition. electronics manufacturers to decide what proportion of their resolutions and TV use. Consumers decide which resolutions are most important to them and buy their new equipment based on this.
Until the analogue switch-off date, broadcasters will have two available channels to send their signal - a channel for analog channel and a "virtual" for digital. Right now, people can look at a signal over-the-air digital only if they are in tune with the digital virtual channel of the issuer. After the analog transmission ends, the only signals people will receive over the air will be digital.
However, even if a digital signal is a better quality of an analog signal, not necessarily high definition. HDTV is simply the highest of all the DTV standards. But if you see a high definition picture and hear the accompanying Dolby Digital ® sound depends on two things. First, the station must be transmitting a high definition signal. Second, you must have the right equipment to receive and display. We will see how to get an HDTV set and the next signal.
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| Standard vs. high-definition aspect ratio |
- Aspect ratio - Standard television has a 4:3 aspect ratio - it is four units wide by three units high. HDTV has a 16:9 aspect ratio, more like a movie screen.
- Resolution - The lowest standard resolution (SDTV) will be about the same as analog TV and go up to 704 x 480 pixels. The highest HDTV resolution is 1920 x 1080 pixels. HDTV can display about ten times as many pixels as an analog TV.
- Frame rate - the rate of developing a set describes how many times you create a complete picture on the screen every second. DTV frame rates usually end in "i" or "p" to indicate whether they are interlaced or progressive. DTV frame rates range from 24p (24 frames per second, progressive) to 60p (60 frames per second, progressive).
Many of these rules are exactly the same aspect ratio and resolution - their frame rates differentiate them from each other. When you hear someone refer to a set of "1080i" HDTV, they're talking about one that has a native resolution of 1920 x 1080 pixels and can display 60 frames per second, interlaced.
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| The 18 Primary DTV Standards |
Until the analogue switch-off date, broadcasters will have two available channels to send their signal - a channel for analog channel and a "virtual" for digital. Right now, people can look at a signal over-the-air digital only if they are in tune with the digital virtual channel of the issuer. After the analog transmission ends, the only signals people will receive over the air will be digital.
However, even if a digital signal is a better quality of an analog signal, not necessarily high definition. HDTV is simply the highest of all the DTV standards. But if you see a high definition picture and hear the accompanying Dolby Digital ® sound depends on two things. First, the station must be transmitting a high definition signal. Second, you must have the right equipment to receive and display. We will see how to get an HDTV set and the next signal.
Buying HDTV
The DTV transition is not the first amendment of the television signal. In 1946, the National Television System Committee (NTSC) began setting standards for issuing American. In 1953, NTSC standards changed to allow color television, and in 1984, they changed to allow stereo sound.
These changes were different from DTV switch because they were compatible - you could see the new signal on the trusty old TV. With DTV, you'll need some new gear and the gear you choose will affect whether you can receive and display high-definition video. You can learn about purchasing a set in DTV Digital Television How it works - here, we will focus on HDTV.
When you start shopping, keep in mind that HDTV requires three parts:
- A source, like a local, cable or satellite HDTV station
- One way to receive the signal, like an antenna cable, or satellite service
- An HDTV set
Most people start with the set. You can choose:
An integrated HDTV, which has a digital tuner, also known as an ATSC tuner built in. If a station near you is broadcasting in HDTV, you can connect an antenna to an integrated set and watch the station in high definition.
HDTV-ready set, also called an HDTV monitor, which does not have an HDTV tuner. HDTV-ready televisions often have NTSC tuners, so you can still watch analog TV with them. This is the option for you if you want to have HDTV capabilities later on, but are not ready for the financial commitment now. The image quality will be even better than on your old TV, but will not be high definition until you get an HDTV receiver.
Designing and building an HDTV can display all ATSC formats would be virtually impossible. For this reason, HDTVs have one or two native resolutions. When the TV receives a signal, you scale the signal to match its native resolution and de-interlace the signal if necessary. A good rule is to choose a set that has a native resolution matching the signals you plan to use more often. Movie fans usually want to display the highest resolution possible. Sports fans generally want displays with the highest possible frame rate progressive.
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| An HDTV-ready plasma TV |
If you receive a signal that has a much lower resolution screen can display, all the more pixels will not help to look better. For this reason, some people who bought HDTVs are dismayed at the quality of the picture - the existing analog signal simply does not have enough detail to set up well in high definition. Broadcasters to change a digital signal, this problem will improve substantially.
In the next section, we'll look at options for getting a signal to the TV, and the compatibility of your home entertainment equipment.
Equipment and Signal
When you've found an HDTV with a screen size, aspect ratio and native resolution you want, you must ensure that the equipment you already own will work with it. If you already have a DVD player, DVR, gaming console or other equipment, make sure that they can connect directly to the TV through a receiver or audio / visual. Many HDTV High-Definition Multimedia Interface (HDMI) connections, which can transmit audio / visual for the TV without compression. In some cases, you can use adapters to make your equipment compatible with the set.
Once you've got your set and installed in your home, you need to get a signal. To get a signal, you can use:
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| With an antenna, you can get digital television for free. This Zenith model works best for UHF analog and DTV signals. |
- An antenna - Depending on the relative position of the stations you want to see a set of rabbit ears might do, but you might need a rooftop or attic antenna. You can buy an antenna that is specially made for digital signals, but any reliable VHF / UHF work.
- Cable - Keep in mind that digital cable is not the same as HDTV. You'll need to check with your provider to determine which packages include HDTV stations. You'll also need a decoder or set-top or a CableCARD ™ to allow your TV to receive and decode the cable signal.
- Satellite service - As with cable, check with your provider to determine which plans and stations use HDTV signals. You may need a different satellite dish and tuner to receive HDTV signals via satellite.
