Why Are There Different Forms of DTV?
Networks and other over-the-air broadcasters have a specific amount of broadcast capacity, or bandwidth, in which to carry DTV signals. If a broadcaster wants to transmit the best picture quality (HDTV) it will require most of its available broadcast channel capacity. A broadcaster might choose the option to broadcast as many as 6 programs in the same channel at a lower definition (SDTV), or a mix of HDTV and one or two SDTV programs.
