Digital Satellite TV vs Standard Television
Digital Satellite TV
Television broadcasting has developed quickly over the last twenty years. Previously the only option was broadcast television, which uses radio waves to transmit the data to the television set.
The sound and vision are transmitted separately - vision requires a bandwidth of around 4MHz and another 2Mhz for sound. This means that television stations are broadcast on frequencies in a similar way to the way radio stations operate.
Early satellite television still used radio waves in the form of C-Band Radio in the 3-7 GHz range. Today most satellite broadcasting is done digitally resulting in far superior quality of sound and vision. The providers, such as DirecTV, pay the stations to broadcast their material from their satellite and encode the signal before beaming it to the satellite into something that it can handle.
Most providers today use the MPEG-2 format and can compress signals by over 50 times and consequently are able to broadcast far more channels than if the signals were delivered in an uncompressed format. After broadcast, the receiver de-codes the encrypted signal. This stage of the process is used to prevent the signal being picked up by unauthorized users.
There are two main types of compression, and are used according to the type of program that is being compressed. Intraframes contain the complete data for one frame. As there is more data to handle the compression is smallest in this form. A Predicted frame contains the information that has changed since the last frame; therefore the picture is essentially based on the previous frame. Let's take a portion of a movie that is the same length of time as a weather report. As the action changes more quickly in a movie from one frame to the next, there will be more intraframes, meaning that maximum compression of the movie scene is far less than the maximum compression of the weather report.
As far as the viewer is concerned, digital satellite television has far more possibilities than conventional satellite broadcasts. These are particularly noticeable in sports events where, for instance, many companies today are able to let the user specify which camera angle they would like to see a match from, or even which match they would like to see. It has also allowed the possibility of viewing one channel and recording from others at the same time, or with the right equipment, recording from more than one channel at once. Viewers can interact with the television to a greater degree than previously possible, entering competitions or voting with the touch of a button. Gaming through the television has developed since the introduction of digital services, and perhaps most importantly, many satellite companies are now offering high-speed internet services that operate through television sets. This is a particularly useful service for users who live in rural areas where there are no ADSL or cable providers.