SDTV is a DTV format that provides a picture quality similar to DVD. SDTV has a range resolutions below those of HDTV and no defined aspect ratio. Because a compressed SDTV digital signal is smaller than a compressed HDTV signal, broadcasters can multicast or transmit up to five SDTV programs simultaneously instead of just one HDTV program. With today's analog television system, only one program at a time can be transmitted.