FAQ

What is the Difference Between Digital TV and Analog TV?

Although television transmission transitioned from analog to digital in the U.S. on June 12, 2009, there are still consumers that may be watching the few remaining low-power analog TV stations, subscribe to analog cable TV services, and/or continue to watch analog video sources, such as VHS, on either analog, digital, or HDTVs. As a result, the characteristics of analog TV are still an important factor to be aware of.

The difference between Analog TV and Digital TV has its roots in the way the TV signal is transmitted or transferred from the source to the TV, which, in turn, dictates the type of TV the consumer needs to use to receive the signal. This also applies to the way a DTV converter box has to transfer a signal to an analog TV, which is important for those consumers that use DTV converters to receive television programming on an analog TV set.

Before the DTV Transition was in place, standard analog TV signals were transmitted in a manner similar to radio.

In fact, the video signal of analog television was transmitted in AM, while the audio was transmitted in FM. Analog TV was subject to interference, such as ghosting and snow, depending on the distance and geographical location of the TV receiving the signal.

In addition, the amount of bandwidth assigned to an analog TV channel restricted the resolution and overall quality of the image. The analog TV transmission standard (in the U.S.) was referred to as NTSC.

NTSC is the U.S. standard that was adopted and came into popular use after World War II. NTSC is based on a 525-line, 60 fields/30 frames-per-second at 60Hz system for transmission and display of video images. This is an interlaced system in which each frame is scanned in two fields of 262 lines, which is then combined to display a frame of video with 525 scan lines.

This system works, but one drawback is that color TV broadcasting was not part of the equation when the system was approved. The implementation of color into the NTSC format has been a weakness of the system, thus the term for NTSC became known by many professionals as "Never Twice The Same Color". Ever notice that color quality and consistency varies quite a bit between stations?

Digital TV, or DTV, on the other hand, is transmitted as data bits of information, just as computer data is written or the way music is written on a CD. In this way, the signal is basically "on" or "off". In other words, the intent of DTV technology is that the viewer either sees an image or nothing at all. There is no gradual signal loss as distance from the transmitter increases. If the viewer is too far from the transmitter or is in an undesirable location, there is nothing to see.

On the other hand, unlike analog TV, digital TV has been designed from the ground up to take all the main factors of the television signal into consideration: B/W, color, and audio and can be transmitted as an interlaced (lines scanned in alternate fields) or progressive (lines scanned in linear sequence) signal. As a result, there is greater integrity and flexibility of signal content.

In addition, since the DTV signal is made up of "bits", the same bandwidth size that takes up a current analog TV signal, can accommodate not only a higher quality image in digital form, but the extra space not used for the TV signal can be used for additional video, audio, and text signals.

In other words, broadcasters can supply more features, such as surround sound, multiple language audio, text services, and more in the same space now occupied by a standard analog TV signal. However, there is one more advantage to the ability of a Digital TV channel's space; the ability to transmit a High Definition (HDTV) signal.

Lastly, another difference between Digital TV and Analog TV is the ability to broadcast programming in a true widescreen (16x9) format. The shape of the picture more closely resembles the shape of a movie screen, which enables the viewer to see the movie as the filmmaker intended. In Sports, you can get more of the action in one camera shot, such as viewing the entire length of a football field without making look like it is a long distance away from the camera.

A 16x9 TV can display widescreen images without a large amount of picture space taken up by black bars on the top and bottom of a widescreen image, which is what you see if such images are shown on a standard TV. Even non-HDTV sources, such as DVD can also take advantage of a 16x9 TV.



What is the Difference Between Digital TV and HDTV?

Here is where things may start to get confusing for the consumer. All HDTV is digital, but not all Digital TV is HDTV. As stated previously, in the answer to question #1, the same bandwidth for digital TV broadcasting can either used to supply a video signal (or several) and other services, or can be used to transmit a single HDTV signal.

Although there are technically 18 different standards for digital TV broadcasting (all Digital TV tuners are required to decode all 18 standards), the practical application of DTV has come down to 3 standards. These standards are: 480p, 720p, and 1080i.

480p

If you have a progressive scan DVD player and TV, you are familiar with 480p (480 lines of resolution, scanned progressively). 480p is similar to the same resolution of standard broadcast TV (and is referred to as SDTV or Standard Definition Television), but the image is scanned progressively, rather than in alternate fields. 480p does provide an excellent picture (especially on smaller 20-27" screens). It is much more film-like than standard cable or even standard DVD output, but it only provides half the potential video quality of an HDTV picture, therefore its effectiveness is lost on larger screen sets.

Although 480p is part of the approved DTV broadcasting scheme, it is not HDTV. This standard was included as one of the DTV broadcasting standards to provide broadcasters the option of providing multiple channels of programming in the same bandwidth as a single HDTV signal. In other words, 480p is just more of what we already have with only a slight increase in image quality.

720p

720p (720 lines of resolution scanned progressively) is also a digital TV format, but it is also considered as one of the HDTV standards. As such, ABC and FOX use 720p as their HDTV broadcasting standard. Not only does 720p provide a very smooth, film-like image due to its progressive scan formula, but image detail is at least 30% sharper than 480p. As a result, 720p provides an acceptable image upgrade that is visible on both medium (32"- 37") size screens as well as larger screen sets. Also, even though 720p is considered high-definition, it takes up less bandwidth than 1080i, which is covered next.

1080i

1080i (1,080 lines of resolution scanned in alternate fields consisting of 540 lines each) is the most commonly used HDTV format, and has been adopted by PBS, NBC, CBS, and CW (as well as satellite programmers HDNet, TNT, Showtime, HBO, and other pay services) as their HDTV broadcast standard. Although there is still a debate as to whether it is that much better than 720p in the actual perception of the viewer, technically, 1080i provides the most detailed image of all the 18 approved DTV broadcast standards. On the one hand the visual impact of 1080i is lost on smaller screen sets (below 32").

However, the two drawbacks to 1080i are:

1. It takes up the most bandwidth of all the DTV broadcast formats.

2. It is an interlaced signal, which means that the displayed image is made up of lines that are scanned alternately instead of progressively as in 480p and 720p.

3. 1080i cannot be displayed in its native form on an LCD, Plasma, or DLP television, so those types of sets need to convert the 1080i signal to either 720p or 1080p in order to display the image on the TV screen.

In other words if you have a 1080p HDTV, a Flat Panel or DLP TV will deinterlace the 1080i signal and display it as a 1080p image. This essentially removes any visible scan lines present in the interlaced 1080i image, resulting in very smooth edges. By the same token, if you have a 720p HDTV, your TV will deinterlace and downscale the 1080i image to 720p for screen display.




What Is There To Watch On HDTV?

There are a growing number of programs to watch in HDTV, especially now that DTV Transition has taken place. All of the major networks: ABC, NBC, CBS, FOX, CW, and PBS broadcast a growing portion of their schedules in HDTV. Here is a list of TV stations broadcasting in DTV or HDTV. If your favorite local station is not on the list, give them a call to find out their current status with regards to DTV or HDTV.

In addition, Discovery, Showtime, HBO, HDnet, TBS, TNT, ESPN, and FOX Sports, and even the CNN and FOX news channels have HDTV signal feeds. As a result, almost all cable systems around the country are now providing HDTV cable service, including systems owned by COX, Comcast, Cablevision, and Time Warner (Check with your local cable company for service in your area).

Also, with the changeover from analog to digital-only television broadcasting that occurred in 2009, local stations are getting onboard with an increasing number broadcasting their local news programs in high definition.

The two main satellite service providers, DirecTV and DishNetwork offer a growing number HDTV channels as well. Check with your satellite service for information on channels and any additional fees.

However, although there is quite of bit of programming available in HDTV, accessing the programming can be frustrating for some consumers.

For example, local HDTV broadcasts are available over-the-air via antenna, but your local cable outlet may not be passing all those signals through your cable system.

In addition, although Satellite offers the most HDTV programming (via sport channels and movie channels), they may not offer as much in the way of local or network HDTV programming. Although this is changing fast.

Then, there is the issue of pricing. Some cable systems offer some basic HDTV services for no extra charge, but most offer an HDTV tier of local channels and movie channels for an extra fee, and some often charge extra on top of that for services such as ESPN-HD and Discovery-HD, and, of course, any HD movie channels. HDTV is still going through growing pains, despite the DTV transition. There definitely needs to be continuous improvement in the consistency of channel and program offerings, as well as pricing.

Also, now that we have executed the DTV Transition that occurred on June 12, 2009, all analog television broadcasts are now turned off (with some specific exceptions), so all full-powered television stations are now broadcasting digitally.

A very useful resource to find out what HD channels are available in your area, whether over-the-air, cable, or satellite, check out Where is HD?. Also, check out a comprehensive daily listing of what is being shown in HDTV.

Upscaling DVD Players, Blu-ray, and HD-DVD

In addition to HDTV television shows, another way to get the most out of your HDTV is with an Upscaling DVD player, or a Blu-ray Disc or HD-DVD player (for those that still own an HD-DVD player). Upscaling DVD players have the ability to match the pixel resolution of a standard DVD to that of your HDTV. Although this is not the same as watching your DVD in true high definition, you will see a definite improvement in the image quality of your DVDs when played on an upscaling DVD player through an HDTV.

For more details on what DVD Upscaling is and how it works with HDTVs, check out my article: DVD Video Upscaling - Important Facts.

As mentioned in the above paragraph, as good as DVD upscaling is, what you really need to enjoy pre-recorded video in true high definition is a Blu-ray or HD-DVD player connected to your HDTV. For more details on this new way to enjoy to the most out of your HDTV - check out my articles: Blu-ray and HD-DVD - What You Need to Know, Blu-ray and HD-DVD FAQs. and Before You Buy a Blu-ray or HD-DVD Player.

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