Editing Progressive scan

{{Short description|Format of image storage or transmission in which each line is read sequentially}}
{{Distinguish|Progressive download}}
{{pp-vandalism|small=yes}}
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'''Progressive scanning''' (alternatively referred to as '''noninterlaced scanning''') is a format of displaying, storing, or transmitting [[moving image]]s in which all the lines of each [[Film frame|frame]] are drawn in sequence. This is in contrast to [[interlaced video]] used in traditional [[analog television]] systems where only the odd lines, then the even lines of each frame (each image called a [[video field]]) are drawn alternately, so that only half the number of actual image frames are used to produce video.<ref>{{cite web |url=http://neuron2.net/LVG/interlacing.html |archive-url=https://web.archive.org/web/20140222010640/http://neuron2.net/LVG/interlacing.html |archive-date=2014-02-22 |title=Interlacing |publisher=Luke's Video Guide |access-date= February 12, 2014}}</ref> The system was originally known as "sequential scanning" when it was used in the [[John Logie Baird|Baird]] 240 line television transmissions from [[Alexandra Palace]], United Kingdom in 1936. It was also used in Baird's experimental transmissions using 30 lines in the 1920s.<ref>Burns, R.W. ''John Logie Baird, Television Pioneer'', Herts: The Institution of Electrical Engineers, 2000. 316.</ref> Progressive scanning became universally used in computer screens beginning in the early 21st century.<ref name="fchdtv">{{cite book |title=Digital Video and Hdtv: Algorithms and Interfaces |last=Poynton |first=Charles A. |year=2003 |publisher=Morgan Kaufmann |isbn=1558607927 |page=56 |url=https://books.google.com/books?id=ra1lcAwgvq4C |access-date=27 January 2013 }}</ref>

== Interline twitter ==
{{Main|Interlaced video#Interline twitter}}
[[Image:Indian Head interlace.gif|thumb|right|200px|''Interline twitter'' when the refresh rate is slowed by a factor of three, demonstrated using the [[Indian-head test pattern]]]]
This rough animation compares progressive scan with [[Interlaced video|interlace]] scan, also demonstrating the [[interline twitter]] effect associated with interlacing. On the left there are two progressive scan images. In the middle there are two interlaced images and on the right there are two images with [[line doubler]]s. The original resolutions are above and the ones with [[spatial anti-aliasing]] are below. The interlaced images use half the bandwidth of the progressive ones. The images in the center column precisely duplicate the pixels of the ones on the left, but interlacing causes details to twitter. Real interlaced video blurs such details to prevent twittering, but as seen in the pictures of the lower row, such softening (or anti-aliasing) comes at the cost of image clarity. A line doubler shown in the bottom right picture cannot restore the previously interlaced image in the center to the full quality of the progressive image shown in the top left.

Note: Because the refresh rate has been slowed by a factor of three, and the resolution is less than half a resolution of a typical interlaced video, the flicker in the simulated interlaced portions and also the visibility of the black lines in these examples are exaggerated. Also, the images above are based on what it would look like on a monitor that does not support interlaced scan, such as a PC monitor or an LCD or plasma-based television set, with the interlaced images displayed using the same mode as the progressive images.

==Usage in storing or transmitting==
Progressive scan is used for scanning and storing film-based material on [[DVD]]s, for example, as [[480p]]24 or [[576p]]25 formats.  Progressive scan was included in the [[Grand Alliance (HDTV)|Grand Alliance]]'s technical standard for [[HDTV]] in the early 1990s.  It was agreed that all film transmission by HDTV would be broadcast with progressive scan in the United States.<ref name="histv">{{cite book |title=The History of Television, 1942 To 2000 |last=Abramson |first=Albert |author2=Christopher H. Sterling  |year=2007 |publisher=McFarland |isbn=978-0786432431 |page=245 |url=https://books.google.com/books?id=TOMOmmrvwCcC |access-date=27 January 2013 }}</ref>  Even if a signal is sent interlaced, an HDTV will convert it to progressive scan.<ref name="htfd">{{cite book |title=Home Theater For Dummies |last=Hurley |first=Danny Briere |year=2008 |publisher=John Wiley & Sons |isbn=978-0470444375 |page=200 |url=https://books.google.com/books?id=TKYEPusm3nsC |access-date=27 January 2013 }}</ref>

==Usage in TVs, video projectors, and monitors==
Progressive scan is used for all LCD computer monitors and most [[High-definition television|HDTVs]]. Most [[cathode-ray tube]] (CRT) [[computer monitor]]s and CRT-type displays, such as [[Standard-definition television|SDTVs]], needed to use interlace to achieve full vertical resolution, but could display progressive video at the cost of halving the vertical resolution. Before HDTV became common, some [[television]]s and video projectors were produced with one or more full-resolution progressive-scan inputs, allowing these displays to take advantage of formats like [[PALPlus]], [[progressive scan DVD player]]s, and certain video game consoles. Early HDTVs supported the progressively-scanned resolutions of 480p and 720p with [[1080p]] displays available at higher cost. At the debut of [[Ultra-high-definition television|UHD]], TVs had emerged on the consumer market in the 2010s, also using progressive resolutions, but usually sold with prohibitive prices<ref name="pricing uhd tvs">[[4K resolution|4k resolution wikipedia page]], that includes a table of 4k display devices with their corresponding prices. Retrieved 29 May 2013.</ref> ([[4K resolution|4K HDTVs]]) or were still in prototype stage ([[8K resolution|8K HDTVs]]).<ref name="sharp first 8k tv">[http://www.techradar.com/news/television/hdtv/sharp-dazzles-with-8k-tv-prototype-vp-says-production-about-4-years-off-1124330 Sharp 8k TV launch], Displayed at CES 2013, the Sharp 8k UHD TV. Retrieved 29 May 2013.</ref> Prices for consumer-grade 4K HDTVs have since lowered and become more affordable, which has increased their prevalence amongst consumers. Computer monitors can use even greater [[display resolution]]s.

The disadvantage of progressive scan is that it requires higher bandwidth than interlaced video that has the same frame size and [[Refresh rate|vertical refresh rate]]. Because of this 1080p is not used for broadcast.<ref name="tph">{{cite book |title=Television Production Handbook |last=Zettl |first=Herbert |year=2011 |publisher=Cengage Learning |isbn=978-0495898849 |page=94 |url=https://books.google.com/books?id=rNhWA5g1LN4C |access-date=27 January 2013 }}</ref>{{Obsolete source|reason=Dated to 2011, but over the last 10 years the communications industry modernized a lot so that i don't think it really applies anymore|date=July 2021}} For explanations of why interlacing was originally used, see [[interlaced video]]. For an in-depth explanation of the fundamentals and advantages/disadvantages of converting interlaced video to a progressive format, see [[deinterlacing]].

===Advantages===
The main advantage with progressive scan is that motion appears smoother and more realistic.<ref name="diov">{{cite book |title=Digital Overdrive: Communications & Multimedia Technology 2011 |last=Andrews |first=Dale |year=2011 |publisher=Digital Overdrive |isbn=978-1897507018 |page=24 |url=https://books.google.com/books?id=Wj_UYxxaKqcC |access-date=27 January 2013 }}</ref> There is an absence of visual artifacts associated with interlaced video of the same line rate, such as interline twitter. Frames have no interlace artifacts and can be captured for use as still photos. With progressive scan there is no need to introduce intentional blurring (sometimes referred to as anti-aliasing) to reduce interline twitter and eye strain.

In the case of most media, such as DVD movies and video games, the video is blurred during the authoring process itself to subdue interline twitter when played back on interlaced displays. As a consequence, recovering the sharpness of the original video is impossible when the video is viewed progressively. A user-intuitive solution to this is when display hardware and video games come equipped with options to blur the video at will, or to keep it at its original sharpness. This allows the viewer to achieve the desired image sharpness with both interlaced and progressive displays.

Progressive scan also offers clearer and faster results for scaling to higher resolutions than its equivalent interlaced video, such as upconverting 480p to display on a 1080p HDTV. HDTVs not based on [[Cathode-ray tube|CRT]] technology cannot natively display interlaced video, therefore interlaced video must be [[deinterlacing|deinterlaced]] before it is scaled and displayed. Deinterlacing can result in noticeable [[Deinterlacing#Deinterlacing methods|visual artifacts]] and/or [[input lag]] between the video source and the display device.

==See also==
* [[1440p]]
* [[Deinterlacing]]
* [[High Efficiency Video Coding]]
* [[Progressive segmented frame]]: a scheme designed to acquire, store, modify, and distribute progressive-scan video using interlaced equipment and media

==References==
{{Reflist}}

{{Video formats}}

[[Category:Display technology]]
[[Category:Television technology]]
[[Category:Ultra-high-definition television]]