Standard definition digital allows more channels.

Standard Definition Digital Television (SDTV)

Broadcasters have had reservations about HDTV because it costs a lot of money to convert to it and they have seen no apparent way to increase their revenues to recover that additional cost. With the development of high-quality digital compression, it is now possible to digitize the standard NTSC video signal and compress it so that four or more signals can fit into one standard NTSC 6-MHz bandwidth channel. This is what happens if you have one of those small mini-dish home satellite systems or digital cable. They send you multiple channels of digital video that have been compressed into one 6-MHz bandwidth. Your set-top receiver converts it to NTSC to display on your home TV. This is standard definition digital television (SDTV). The ATSC digital broadcast standard that has been approved for the United States includes both HDTV and SDTV. The SDTV picture can be in either the standard 4:3 aspect ratio or the wide-screen 16:9 aspect ratio. The two formats are summarized on the facing page.

Using this sort of system, broadcasters could send out multiple programs on their standard TV channel. Instead of having only one program at a time to sell to advertisers, they would have multiple programs that they could sell and they would have the chance to increase their revenues to cover the cost of converting to digital broadcasting.

No one can predict exactly what is going to happen in the future, but the best guess is that stations will use a combination of SDTV and HDTV in their broadcast day. Perhaps during the daytime hours they will provide multiple programs, and during the evening prime time hours and for important sporting events their programming will be in HDTV. New compression algorithms have been developed that allow one HDTV and one SDTV program over the same 6-MHz television channel. Conventional wisdom had predicted that few stations would have their own HDTV production equipment because it costs so much more than SDTV production equipment. Recently, however, the cost of HDTV production equipment has dropped dramatically so that today you can equip a station with HDTV for what SDTV cost just a couple of years ago. With this change HDTV production equipment might be found in just about any TV station.

As a consumer, if you buy a new digital television receiver or set-top converter, you will be able to receive and watch all of the digital formats.

1.  Normal aspect formats for SDTV.

2.  Wide-screen formats for SDTV.