Buzz
A woman walks by Matsushita's impressive 150-inch Advanced High-Definition Plasma Display. See more captivating HDTV images. Junko Kimura/Getty ImagesWhen HDTV first launched in 1998, it created a buzz among movie enthusiasts, sports lovers, and tech fans. Advertisements painted a picture of a television paradise with stunning resolution and immersive digital surround sound. HDTV also allowed for widescreen movie viewing without the distracting letterbox bars.
However, for many, HDTV hasn't quite lived up to the expectations of transcendent viewing experiences. Shoppers often find themselves overwhelmed by a sea of confusing terms and overwhelming options. Some even connect their new HDTVs only to find the picture quality disappointing. Thankfully, a few key facts can clear up these misunderstandings.
In this article, we will explore the distinctions between analog, digital, and high-definition formats, clarify acronyms and resolution levels, and provide insights into the United States' transition to all-digital television. We'll also guide you through everything you need to know if you're considering upgrading to HDTV.
Analog, Digital and HDTV
Analog TVs, such as this one, require a set-top converter to receive digital signals.
Image courtesy of Consumer Guide ProductsFor years, television viewing has relied on analog signals and cathode ray tube (CRT) sets. These signals consist of continuously varying radio waves that the TV decodes into picture and sound. Analog signals can be transmitted to your TV via airwaves, cable, or satellite. Digital signals, such as those from DVD players, must be converted to analog to be displayed on traditional TVs. (You can learn how the TV decodes these signals in 'How Television Works.')
While this system has served its purpose for many years, it does come with a few limitations:
- Traditional CRT sets show around 480 visible lines of pixels. For years, broadcasters have transmitted signals that work well with this resolution, but they don't have enough capacity to fill a large television screen with sufficient resolution using the analog signal.
- Analog images are interlaced – the electron gun in a CRT only draws half the lines in each pass. On some televisions, interlacing can cause the image to flicker.
- Converting video to analog reduces its overall quality.
The United States is in the process of transitioning to digital television (DTV). A digital signal transmits video and audio data as binary code (ones and zeros) instead of a continuous wave. For over-the-air broadcasting, DTV will typically use the UHF section of the radio spectrum with a 6 MHz bandwidth, much like analog TV signals have done.
DTV offers several benefits:
- Even on smaller TVs, the picture quality is noticeably better.
- A digital signal supports a higher resolution, so images remain sharp even on larger TV screens.
- Unlike interlaced video, digital video can be progressive, meaning the entire picture is displayed in each frame, rather than alternating lines of pixels.
- TV stations can broadcast multiple signals within the same bandwidth, a process known as multicasting.
- Broadcasters can add interactive content or extra information to the DTV signal, if desired.
- It also supports high-definition (HDTV) broadcasts.
However, DTV has one major drawback: Analog TVs cannot decode and display digital signals. Once analog broadcasts cease, you will only be able to watch television on your old set if you subscribe to cable or satellite services transmitting analog signals, or if you use a set-top digital converter.
This brings us to a common misconception about HDTV. Many people think that the United States is simply switching to HDTV, believing that all they need is a new TV and that HDTV will automatically be available once analog service ends. Unfortunately, this isn't the case.
HDTV is just one aspect of the DTV transition. In the following section, we'll explore HDTV in more detail, including how it differs from DTV.
Starting March 1, 2007, all new televisions in the U.S. were required to include DTV tuners or be DTV compatible. However, the shift to digital TV isn't complete yet. The proposed end date for over-the-air analog broadcasts is February 17, 2009.
DTV vs. HDTV
Standard vs. High-Definition Aspect Ratio
MytourThe Advanced Television Standards Committee (ATSC) has established voluntary guidelines for digital television. These include how sound and video signals are encoded and transmitted, as well as rules for various quality levels. All digital formats deliver superior quality when compared to analog signals, with HDTV standards representing the highest quality of all digital signals.
The ATSC has developed 18 widely used digital broadcast formats for video. The lowest quality digital format is comparable to the best that analog TVs can display. These 18 formats vary based on:
- Aspect ratio - Traditional TV sets feature a 4:3 aspect ratio, meaning they are four units wide by three units tall. In contrast, HDTV has a 16:9 aspect ratio, more closely resembling a movie screen.
- Resolution - The lowest resolution standard (SDTV) is similar to the picture quality of analog TV, reaching up to 704 x 480 pixels. On the other hand, HDTV’s highest resolution reaches 1920 x 1080 pixels, which is about ten times more pixel dense than analog TVs.
- Frame rate - A TV’s frame rate defines how frequently it can refresh with a full image every second. DTV frame rates often end in "i" or "p" to indicate whether they are interlaced or progressive. These frame rates range from 24p (24 frames per second, progressive) to 60p (60 frames per second, progressive).
Many of these formats share the same aspect ratio and resolution, with their frame rates acting as the distinguishing factor. When someone mentions a "1080i" HDTV, they are referring to a model with a resolution of 1920 x 1080 pixels capable of displaying 60 interlaced frames per second.
The 18 Primary DTV StandardsBroadcasters have the authority to choose which formats they wish to use and whether or not they will broadcast in high definition; many are already transmitting digital and high-definition signals. Electronics manufacturers determine which aspect ratios and resolutions their TVs will support. Consumers, in turn, decide which resolutions are most important to them and select new equipment accordingly.
Until the analog shutoff occurs, broadcasters will have access to two channels: one for analog signals and another "virtual" channel for digital signals. Currently, viewers can only watch over-the-air digital signals if they are tuned to the broadcaster's virtual digital channel. Once analog broadcasting ceases, all over-the-air signals will be digital.
Although digital signals provide better quality than analog, this doesn't automatically mean the picture is high definition. HDTV represents the pinnacle of all DTV standards, but whether you get high-definition visuals and Dolby Digital® sound depends on two factors: the station must be broadcasting an HD signal, and you must have the proper equipment to receive and display it. In the next section, we'll explore how to obtain an HDTV set and signal.
DTV typically uses MPEG-2 encoding, the industry standard for DVDs, to compress the signal into a manageable size. MPEG-2 compression reduces the data's size by a ratio of approximately 55:1, discarding visual information that the human eye generally wouldn't notice as missing.
Purchasing an HDTV
The DTV transition marks another shift in television technology, but it's not the first. Back in 1946, the National Television System Committee (NTSC) started setting broadcast standards in the United States. In 1953, these standards were modified to accommodate color television, and in 1984, they were updated again to allow for stereo sound.
Unlike those earlier changes, which were backwards compatible (meaning you could watch the new signal on your old TV), DTV requires new equipment. The type of gear you choose will determine whether you can access and view high-definition video. If you're interested in purchasing a DTV set, refer to How Digital Television Works. In this section, our focus will be on HDTV.
When you begin shopping for an HDTV, remember that you'll need three essential components:
- A source, such as a local, cable, or satellite HDTV station
- A method of receiving the signal, like an antenna, cable, or satellite service
- An HDTV set
Most people begin by selecting the television set. You have a few options:
- An integrated HDTV, which comes with a built-in digital tuner, also called an ATSC tuner. If there's an HDTV broadcast available nearby, you can connect an antenna to the integrated set and watch the station in high definition.
- An HDTV-ready set, sometimes known as an HDTV monitor, which lacks a built-in HDTV tuner. These sets often include an NTSC tuner, allowing you to still watch analog TV. This option is great if you're not yet ready to make the full leap into HDTV but want the option for the future. Your picture quality will be improved over your old TV, but it won't reach full high definition until you add an HDTV receiver.
Building an HDTV that can display every possible ATSC format is essentially impossible. Consequently, HDTVs typically have one or two native resolutions. When receiving a signal, the TV will adjust the signal to fit its native resolution and, if needed, de-interlace it. A good guideline is to choose a set with a native resolution that aligns with the most common signals you plan to use. For film enthusiasts, displays with the highest resolution are ideal, while sports fans generally prefer the highest progressive frame rate available.
If you receive a signal with much lower resolution than your TV's capacity, the extra pixels won't improve the image. This explains why some people who've purchased HDTVs were disappointed with the picture quality – an analog signal just doesn't have enough detail to look crisp on a high-definition screen. However, as broadcasters switch to digital signals, this issue will improve significantly.
In the next section, we'll explore the different ways you can receive a signal for your TV and discuss how your current home entertainment equipment will work with the new technology.
While shopping, you may come across enhanced definition TV (EDTV) sets. EDTV is not one of the digital broadcast formats, but rather it describes the level of picture quality the TV can provide. EDTV offers better picture quality than SDTV, but it doesn't match the clarity of an HDTV. Most EDTV models are flat-panel LCD or plasma TVs.
Equipment and Signal
Photo courtesy of Consumer Guide Products. Using an antenna, you can access digital television free of charge. This Zenith model is particularly effective for receiving both UHF analog and DTV signals.After selecting an HDTV that meets your preferences for screen size, aspect ratio, and native resolution, it's crucial to ensure your existing devices are compatible with the new TV. If you already own equipment like a DVD player, DVR, or gaming consoles, make sure they can be connected directly to the TV or through an audio/visual receiver. Many HDTVs feature High-Definition Multimedia Interface (HDMI) ports that transmit audio and visual signals without compression. In some cases, adapters can be used to make your existing equipment work with your new TV.
Once you've set up your HDTV in your home, you'll need to acquire a signal. You can do this using:
- An antenna - Depending on how far you are from the broadcasting stations, a simple pair of rabbit ears might suffice, though a rooftop or attic antenna may be necessary for better reception. You can purchase an antenna designed specifically for digital signals, but any good quality VHF/UHF antenna should work just fine.
- Cable - Keep in mind that digital cable doesn't necessarily mean HDTV. You’ll need to check with your provider to find out which cable packages offer HDTV channels. Additionally, you will require either a set-top cable box or a CableCARD™ to decode and display the cable signal on your TV.
- Satellite service - Similar to cable, check with your satellite provider to confirm which packages and channels support HDTV broadcasts. Depending on your service, you may need an upgraded satellite dish and tuner to receive HDTV signals via satellite.
Televisions that are labeled "digital cable ready" or "plug-and-play" come with the ability to use a CableCARD. A CableCARD is a PCMCIA type II card, or PC card, which replaces the need for a set-top cable box. It encrypts and decrypts cable signals and can also help reduce cable theft.
Your cable company will install the card for you, and you'll pay a small monthly rental fee, which is typically cheaper than renting a cable box. Plus, you’ll eliminate the need for one extra remote control. However, current CableCARDs are limited to one-way communication only. This means that if you want to use interactive services like video-on-demand or Pay-per-View, you should wait for the next generation of CableCARDs to be released. For more information about CableCARD technology, check out Ars Technica.
