The Differences Between Digital and Analog TV

Comparing Analog and Digital TV

The transition from analog to digital TV (DTV) broadcasting in the U.S. on June 12, 2009 changed the way consumers receive and watch TV, as well as what TVs were available to purchase.

Although TV transmission switched from analog to digital, some consumers may still be watching remaining low-power analog TV stations, subscribe to analog cable TV, and/or continue to watch analog video sources, such as VHS, on an analog, digital, or HDTV. As a result, understanding analog TV is still important.

People watching television
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Analog TV Basics

Before the DTV Transition, analog TV signals were transmitted in a manner similar to radio. Analog TV video signals were transmitted in AM, while audio was transmitted in FM.

As a result, analog TV transmission 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 U.S. analog TV transmission standard was referred to as NTSC.

NTSC was adopted in 1941 and came into popular use after World War II. NTSC is based on a 525-line, 60 field/30 frames-per-second at 60 Hz 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.

NTSC works, but one drawback is that color was not included when the system was initially approved and implemented – It wasn't added until 1953. As a result, the addition of color into NTSC has always been a weakness of the system.

NTSC became known by many professionals as "Never Twice The Same Color". This was due to the observation that color consistency often varied between programs and stations.

Digital TV Basics

Digital TV, or DTV, is transmitted as data bits of information, just as computer data is written or the way music or video is written on a CD, DVD, or Blu-ray Disc.

The DTV transmission system is referred to as ATSC (Advanced Television Standards Committee). Most DTV and HDTVs made after 2007 have ATSC tuners built-in.

A digital signal is composed of 1's and 0's. This means it is either "on" or "off". The quality of the signal does not vary within a specific distance related to the power output of the transmitter. The viewer sees a full quality image or nothing at all.

Unlike analog TV transmission, there is no gradual signal loss as the distance from the transmitter increases. If the viewer is too far from the transmitter or is in an undesirable location, the station is not accessible.

Also, unlike analog TV, digital TV transmission has been designed from the ground up to take all the main factors of the signal into consideration: B/W, color, audio (including surround sound), and text. Video can be transmitted as an interlaced (lines scanned in alternate fields) or progressive (lines scanned in sequence) signal.

Digital TV signals can be transmitted in up to 18 different resolution formats. However, the most commonly used are 480p (SD), 720p and 1080i (HD). 1080p (FHD) is not used for over-the-air TV transmission.

Although all HDTVs are Digital TVs, not all Digital TV broadcasts are HD, and not all Digital TVs are HDTVs.

Analog and Digital TV Differences

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 high definition (HDTV) images in digital form, but there is extra space can be used for transmitting:

Another difference between Digital and Analog TV is that DTV transmission supports the widescreen (16x9) aspect ratio format. This matches the aspect ratio of most Digital and HDTVs which more closely resembles the shape of a movie screen. This enables viewers to watch a 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 aspect ratio 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 take advantage of a 16x9 aspect ratio TV.

From DTV To HDTV and Beyond...

The transition from Analog to Digital and HDTV TV is only one step. There is another transition slowly being implemented.

This transition (referred to as ATSC 3.0 or NextGen TV Broadcasting) adds 4K resolution, enhanced picture and sound quality, over-the-air broadband and other capabilities to the TV transmission mix. Just as with the transition from analog to digital TV, ATSC 3.0 requires new tuners (add-on or built-in to TVs) to receive the signals, but support for the current DTV/HDTV system will remain in place for some time.