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 television, as well as what TV models are available to purchase. Although television transmission also switched from analog to digital, some consumers still watch remaining low-power analog TV stations and/or continue to watch analog video sources, such as VHS. As a result, understanding analog TV is still important. We break down the differences between the two formats.

Two people setting up an HDTV
Lifewire / Bailey Mariner

Analog TV Basics

Before the big digital transition, analog TV signals were transmitted similarly to radio. Video signals were transmitted in AM, while audio was transmitted in FM. The transmission was subject to interference such as ghosting and snow as a result, 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 is called NTSC. It was adopted in 1941 and became popular after World War II. It's 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 where each frame is scanned in two fields of 262 lines, then combined to display a frame of video with 525 scan lines.

One drawback is that color wasn't included when the system was initially approved and implemented. It wasn't added until 1953, a weakness of the system.

NTSC became known by many professionals as "Never Twice The Same Color." This is because 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's either "on" or "off." Unlike analog TV transmission, there's 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 is 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. 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, it can accommodate not only high definition (HDTV) images in digital form, but the extra space can be used for transmitting:

Another difference is 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. You can get more of the action in one camera shot during a sporting event, such as viewing the entire length of a football field without making look like it's a long distance away from the camera.

A 16x9 aspect ratio television set 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 like DVDs can take advantage of a 16x9 aspect ratio.

Beyond DTV

The transition from analog to digital and HDTV TV was only one step. Many televisions now come in 4K resolution (referred to as ATSC 3.0 or NextGen TV Broadcasting), bringing enhanced picture and sound quality, over-the-air broadband, and other capabilities. 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.

Beyond 4K, there's 8K resolution, but it's still beyond the reach of most consumers and few cameras have the ability to shoot in the format. Because of this, 8K likely won't become mainstream for at least a couple of years.