Street Address*:
Apt./Suite:
Zip Code*:
Home Telephone:

CableTV: How It Works

In order to show you how digital cable is different from analog television, it’s probably best to briefly describe how the once-standard television transmitted and projected network broadcasts.

  1. A series of images is captured by a video camera at a rate of 30 frames per second.
  2. The images are rasterized, which is a fancy word to describe when an image is translated into pixels. Pixels are very tiny dots which illuminate in an assigned color and intensity. Many, many pixels form an image.
  3. These pixels are then synchronized into horizontal and vertical sync signals aimed at the electronics inside a television, which will decode and transmit the image by telling each pixel on the television screen exactly what color and what intensity it must be to illuminate the image.

Such signals are called composite video signals. Their general make-up allows them to be transmitted through cables or broadcasted as radio waves.

Some could say computers are what is causing the death of analog television. While it works just fine, most of us have become spoiled by the high-quality resolution of our computer monitors--and an analog signal (typically 512x400 pixels, for a good analog television) can’t compete with even a low-resolution computer monitor (640x480 pixels). If you’ve ever watched an analog television next to a digital television, or even a high-definition television, you know what a drastic difference even a little increase in resolution can do. And you most certainly wouldn’t go back to analog.

Digital signals are completely different from analog on three different levels: format, aspect ratio, and compression. I won’t bore you with a detailed science lesson, but I will break down these three differences as briefly as I can.

  1. Formats: Digital television allows for a variety of formats. If you’ve recently looked for a new television, you’re familiar with the numbers: 840i, 720p, 1080i, etc. The “i” stands for “interlaced (30 complete frames per second) and the “p” stands for “progressive” (60 complete frames per second). The type of format will depend on the type and number of programming the television station is broadcasting.
  2. Aspect Ratio: Analog television sets have a nearly square 4:3 ratio, while high-definition ratio is set to 16:9. Why? it allows for a more complete capture of the image, and prevents the “full screen” shift that occurs when translating digital formatting to analog settings.
  3. Digital Compression: The reason digital cable can offer so many more channel options lies in its ability to compress its images with a bit rate that is compatible with the content. For example, content with a lot of motion (i.e. a football game) may require a higher bit rate. The ability to create additional channels comes when several images can be compressed to fit within the standard 19.39-Mbps digital stream.

This is a brief comparison, but it should give you enough of the basics to win a trivia question or two--or be able to tell your grandkids how crazy television used to be!