What is HDTV? EDTV? SDTV?
HDTV, EDTV, SDTV, Analog: What is the Difference?
Analog TV - First of all, your old classic CRT TV has 525 scan lines, although only 480 lines are displayed. It displays an interlaced image which means the TV has to scan the screen two times to build one complete image. Unless your TV is a monitor, it has a built in channel tuner that tunes NTSC broadcasts. The aspect ratio of the screen is 4:3 (pronounced four by three), which means for every 4 units the screen is wide, it is 3 units tall. This is your classic NTSC analog, soon to be obsolete, television.
Because analog televisions have an NTSC tuner, they cannot tune Digital TV (DTV) broadcasts. By adding an ATSC converter/tuner you can receive HD broadcasts over-the-air, but they will be down-converted to display on an analog TV set. It will look better than analog broadcasts but it will not look nearly as good as on an HDTV. Near the end of 2006 all television stations will be required to broadcast high-definition signals. The old analog broadcasts will be phased out. NTSC tuners will become useless and an ATSC tuner, set-top box or a CableCard will be required to tune the new HD broadcasts. If you subscribe to cable or satellite TV and use a set top box (STB), odds are your service provider will offer you a new ATSC STB to receive the new ATSC broadcasts. Otherwise you will have to purchase a converter for your analog TV. In regard to DVDs, an analog TV can display interlaced images from a DVD but most cannot display the higher quality progressive scan image.
DTV - Digital television encompasses all of the underlying standards for SDTV, EDTV and HDTV developed by the ATSC. A TV described as being DTV-ready, will be able to display the new digital broadcasts and will use one of the three standards listed below.
Standard-Definition TV - SDTV is frequently used, incorrectly, to describe old analog NTSC broadcast television. SDTV is the digital broadcast television standard defined under the DTV standards developed by the ATSC. An SDTV is defined as being able to receive an ATSC signal and in most cases will have 480 lines of resolution. If you buy a new TV today, it will not be compatible with the new standards unless it is DTV-ready. An SDTV will be the basic television compatible with the new standards.