Editing Standard-definition television (section)

== PAL and NTSC ==
The two SDTV signal types are [[576i]] (with 576 [[interlaced]] lines of resolution,<ref name="auto">{{cite web |title=What means 576i? |url=http://www.afterdawn.com/glossary/terms/576i.cfm |website=Afterdawn.com}}</ref> derived from the European-developed [[PAL]] and [[SECAM]] systems), and [[480i]] (with 480 interlaced lines of resolution,<ref name=":02">{{cite web |title=What means 480i? |url=https://www.afterdawn.com/glossary/term.cfm/480i |website=afterdawn.com}}</ref> based on the American [[NTSC]] system). SDTV [[refresh rate]]s are 25, 29.97 and 30 [[frames per second]], again based on the analog systems mentioned.

In North America, digital SDTV is broadcast in the same [[Fullscreen (aspect ratio)|4:3 fullscreen aspect ratio]] as NTSC signals, with [[16:9 aspect ratio|widescreen]] content often being [[center cut]].<ref name=":1">{{cite web |title=All-Digital Television Is Coming (And Sooner Than You Think!) |url=http://www.fcc.gov/cgb/consumerfacts/digitaltv.html |url-status=dead |archive-url=https://web.archive.org/web/20080929041527/http://www.fcc.gov/cgb/consumerfacts/digitaltv.html |archive-date=Sep 29, 2008 |website=Federal Communications Commission}}</ref>

In other parts of the world that used the PAL or SECAM color systems, digital standard-definition television is now usually shown with a [[16:9 aspect ratio]], with the transition occurring between the mid-1990s and late-2000s depending on the region. Older programs with a 4:3 aspect ratio are broadcast with [[Active Format Description|a flag]] that switches the display to 4:3. Some broadcasters prefer to reduce the horizontal resolution by anamorphically scaling the video into a [[pillarbox]].{{Citation needed|date=April 2024}}