Standard-definition television (or SDTV) is a television system that uses a resolution that is not considered to be 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. The two common SDTV signal types are 576i, derived from the European-developed PAL and SECAM systems with 576 interlaced lines of resolution; and 480i, based on the American NTSC system.
In the USA, digital SDTV is broadcast in the same 4:3 aspect ratio as NTSC signals. However, in areas that used the PAL or SECAM analog standards, standard-definition television is now usually shown with a 16:9 aspect ratio, with the transition occurring between the mid-1990s and mid-2000s. Older programs with a 4:3 aspect ratio are shown in 4:3.
Standards that support digital SDTV broadcast include DVB, ATSC Standards and ISDB. The last two were originally developed for HDTV, but are more often used for their ability to deliver multiple SD video and audio streams via multiplexing, than for using the entire bitstream for one HD channel.
In ATSC Standards, SDTV can be broadcast in 720 pixels × 480 lines with 16:9 aspect ratio (40:33 rectangular (unsquare) pixel), 720 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 24, 30 or 60 frames per second.
Digital SDTV in 4:3 aspect ratio has the same appearance as regular analog TV (NTSC, PAL, SECAM) without the ghosting, snowy images and white noise. However, if the reception is poor, one may encounter various other artifacts such as blockiness and stuttering.
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 |
The pixel aspect ratio is always the same for corresponding 720 and 704 pixel resolutions because the center part of a 720 pixels wide image is equal to the corresponding 704 pixels wide image.
Category:ATSC Category:Digital television Category:Broadcast engineering Category:Broadband Category:History of television
ca:SDTV ceb:SDTV de:Standard Definition Television es:Definición estándar eo:Normdifina televido fr:SDTV gl:Televisión de definición estándar ko:디지털 표준 텔레비전 id:Televisi Resolusi Standar it:SDTV hu:SDTV ms:Televisyen definisi biasa nl:Standard-definition television ja:標準画質映像 no:Standard Definition TV pl:SDTV pt:Televisão de definição padrão ro:Televiziune cu rezoluție standard ru:Телевидение стандартной чёткости simple:Standard-definition television fi:SDTV sv:Standard-definition television uk:SDTV zh:標準畫質電視This text is licensed under the Creative Commons CC-BY-SA License. This text was originally published on Wikipedia and was developed by the Wikipedia community.
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