Standard-definition television (or SDTV) is a television system that has a resolution that meets standards but not considered either enhanced-definition television (EDTV) or high-definition television (HDTV). The term is usually used in reference to digital television, in particular when broadcasting at the same (or similar) resolution as analog systems. In the USA, SDTV refers to digital television broadcast in 4:3 aspect ratio, the same aspect ratio as NTSC signals. When a television set is labeled "SDTV", this means that the set includes an ATSC tuner, but scans its picture in the same 480i pattern used in NTSC.
In the UK and most of Europe standard-definition television is mostly shown with a 16:9 aspect ratio as most people have a television with a 16:9 aspect ratio. Older programs with a 4:3 aspect ratio are shown in 4:3. The 16:9 aspect ratio is also known as 576i.
All content recorded for television broadcast in the UK and the Republic of Ireland have a 16:9 aspect ratio.
Standards that support digital SDTV broadcast include DVB, ATSC Standards and ISDB. The last two were originally developed for HDTV, but they have proved to be more often used for their ability to deliver multiple SD video and audio streams via multiplexing, than to use the entire bitstream for one HD channel.
In ATSC Standards, SDTV can be broadcast in 704 pixels × 480 lines with 16:9 aspect ratio (40:33 rectangular pixel), 704 pixels × 480 lines with 4:3 aspect ratio (10:11 rectangular pixel) or 640 pixels × 480 lines with 4:3 ratio. The refresh rate can be any of 24, 30 or 60 frames per second.
Digital SDTV in 4:3 aspect ratio has the same appearance as the regular analog TV (NTSC, PAL, SECAM) minus the ghosting, snowy images and white noise. However, if the reception is poor, one may encounter various other artifacts such as blockiness and stuttering.
When resolution is considered, both the resolution of the transmitted signal and the (native) display resolution of a TV set are taken into account. Digital NTSC, and PAL/SECAM-like signals (480i60 and 576i50 respectively), are transmitted at a horizontal resolution of 720 or 704 format.
|Video Format (WxH)||Name||Pixel aspect ratio (W:H)
|Pixel aspect ratio (W:H)
|720×576||576i||16:15||64:45||Used on D1/DV PAL (ITU-R 601)|
|704×576||576p||12:11||16:11||Used on EDTV PAL|
|720×480||480i||8:9||32:27||Used on DV NTSC|
|720×486||480i||8:9||32:27||Used on D1 NTSC (ITU-R 601)|
|704×480||480p||10:11||40:33||Used on EDTV NTSC|
Standard-Definition Television is a kind of television system that provides lower resolution than HDTV and higher resolution than analog TV does. The word 'SDTV' is generally used at the digital television broadcasting system that has a similar or litle 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.
According to a ATSC standard, SDTV broadcasts in three ways. First, at ratio of length and width 16:9 and resolution 704x480. 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 I mentioned at the 'Definition' tab, it has a better resolution than analog TV system, and has lower resolution than HDTV. Because it is kind of digital boadcasting system, it can broadcast not only analog TV program but also HDTV program(Of course there exists a difference in resolution). It is compared to anlog TV that can't broadcast HDTV program.
SDTV 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 imposible at analog TV. Compared to HDTV, it has lower resolution. But in fact, HDTV programs are not spread widely yet, and the cheaper price of SDTV makes consumers to use SDTV.
Generally, there are three types of TV. They are analog TV, SDTV and HDTV.
Price : AnalogTV < SDTV < HDTV
Quality : AnalogTV ≒ SDTV < HDTV
AnalogTV only can be compatible with analog signals, but both SDTV and HDTV can be compatible with not only analog but also digital signals.
|vidio format||name||pixel rate|