Standard-definition television
Standard-Definition Television is a kind of television system that provides lower resolution than SDTV and higher resolution than analog TV does. The word 'SDTV' is generally used at the digital television broadcasting system that has a similar or little bit higher state of resolution to the 'analog television system'. Digital broadcasting system uses digital signals when they receive sound and movie. It is compared to analog TV that uses analog signals.
Broadcasting
changeAccording to an NTSC standard, SDTV broadcasts in three ways. First, at ratio of length and width 16:9 and resolution 720x480. Second, at ratio 4:3 and resolution 704x480 Lastly, at ratio 4:3 and resolution 640x480. The first one has best quality, second one is next, and the last one is the worst. The screen's frame can be 24, 30, 60 per second. These are similar level with DVD. As mentioned at the 'Definition' tab, it has a better resolution than analog TV system, and has lower resolution than SDTV. Because it is a kind of digital broadcasting system, it can broadcast not only analog TV programs but also HDTV program (Of course there exists a difference in resolution).
Merit
changeSDTV has a similar state of resolution compared to analog TV, but SDTV is more vivid than analog TV because it has less noise and it has better sound. The point that SDTV uses a digital broadcasting system makes SDTV have many accompaning functions. For example, multitasking, electronic program guide, and so on. This functions are impossible at analog TV. Compared to SDTV, it has lower resolution. But in fact, SDTV programs are not spread widely yet, and the cheaper price of SDTV makes consumers to use SDTV.
Comparison
changeGenerally, there are three types of TV. They are analog TV, SDTV and SDTV.
Price : AnalogTV < SDTV < SDTV
Quality : AnalogTV ≒ SDTV < SDTV
AnalogTV only can be compatible with analog signals, but both SDTV and SDTV can be compatible with not only analog but also digital signals.
Digital definition resolution
change| Video Format | Resolution | Pixel Aspect Ratio | Equivalent square-pixel resolution |
| PAL 4:3 | 704×576 | 12:11 | 768×576 |
| PAL 4:3 | 720×576 | 12:11 | 786×576 |
| PAL 16:9 | 704×576 | 16:11 | 1024×576 |
| PAL 16:9 | 720×576 | 16:11 | 1048×576 |
| NTSC 4:3 | 704×480 | 10:11 | 640×480 |
| NTSC 4:3 | 720×480 | 10:11 | 654×480 |
| NTSC 16:9 | 704×480 | 40:33 | 854×480 |
| NTSC 16:9 | 720×480 | 40:33 | 872×480 |