Editing Interlaced video (section)

==Benefits of interlacing==
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[[Image:Deinterlaced vs interlaced image.gif|thumb|250px|right|A GIF from [[HandBrake]], demonstrating the difference between deinterlaced and interlaced images<ref>{{cite web|title=Deinterlacing Guide|url=https://trac.handbrake.fr/wiki/DeinterlacingGuide|work=HandBrake|access-date=2012-07-12|archive-url=https://web.archive.org/web/20120511122509/https://trac.handbrake.fr/wiki/DeinterlacingGuide|archive-date=2012-05-11|url-status=dead}}</ref> ]] 
One of the most important factors in analog television is signal bandwidth, measured in megahertz. The greater the bandwidth, the more expensive and complex the entire production and broadcasting chain. This includes cameras, storage systems, broadcast systems—and reception systems: terrestrial, cable, satellite, Internet, and end-user displays ([[television set|TVs]] and [[computer monitor]]s).

For a fixed bandwidth, interlace provides a video signal with twice the display refresh rate for a given line count (versus [[progressive scan]] video at a similar frame rate—for instance [[1080i]] at 60 half-frames per second, vs. 1080p at 30 full frames per second). The higher refresh rate improves the appearance of an object in motion, because it updates its position on the display more often, and when an object is stationary, human vision combines information from multiple similar half-frames to produce the same perceived resolution as that provided by a progressive full frame. This technique is only useful, though, if source material is available in higher refresh rates. Cinema movies are typically recorded at 24fps, and therefore do not benefit from interlacing, a solution which reduces the maximum video bandwidth to 5&nbsp;MHz without reducing the effective picture scan rate of 60&nbsp;Hz.

Given a fixed bandwidth and high refresh rate, interlaced video can also provide a higher spatial resolution than progressive scan. For instance, 1920×1080 pixel resolution interlaced [[HDTV]] with a 60&nbsp;Hz field rate (known as [[1080i60]] or 1080i/30) has a similar bandwidth to 1280×720 pixel progressive scan HDTV with a 60&nbsp;Hz frame rate (720p60 or 720p/60), but achieves approximately twice the spatial resolution for low-motion scenes.

However, bandwidth benefits only apply to an analog or ''uncompressed'' digital video signal. With digital video compression, as used in all current digital TV standards, interlacing introduces additional inefficiencies.<ref>{{cite web|url=http://www.atd.net/HDTV_faq.html|title=HDTV and the DoD|archive-url=https://web.archive.org/web/19991018182937/http://www.atd.net/HDTV_faq.html|archive-date=October 18, 1999|access-date=March 14, 2019|url-status=dead}}</ref> EBU has performed tests that show that the bandwidth savings of interlaced video over progressive video is minimal, even with twice the frame rate. I.e., 1080p50 signal produces roughly the same bit rate as 1080i50 (aka 1080i/25) signal,<ref name="EBU_No1_1080p50"/> and 1080p50 actually requires less bandwidth to be perceived as subjectively better than its 1080i/25 (1080i50) equivalent when encoding a "sports-type" scene.<ref name="EBU_Detailed_1080p50">{{cite web|url=http://bura.brunel.ac.uk/bitstream/2438/1181/1/Fullext.pdf|title=Studies on the Bit Rate Requirements for a HDTV Format With 1920x1080 pixel Resolution, Progressive Scanning at 50 Hz Frame Rate Targeting Large Flat Panel Displays|date=2006-12-04|first1=Hans|last1=Hoffmann|first2=Takebumi|last2=Itagaki|first3=David|last3=Wood|last4=Alois|first4=Bock|work=IEEE Transactions on Broadcasting, Vol. 52, No. 4|access-date=2011-09-08|quote=It has been shown that the coding efficiency of 1080p/50 is very similar (simulations) or even better (subjective tests) than 1080i/25 despite the fact that twice the number of pixels have to be coded. This is due to the higher compression efficiency and better motion tracking of progressively scanned video signals compared to interlaced scanning.}}</ref>

Interlacing can be exploited to produce 3D TV programming, especially with a CRT display and especially for [[Anaglyph 3D|color filtered]] glasses by transmitting the color keyed picture for each eye in the alternating fields. This does not require significant alterations to existing equipment. [[Active shutter 3D system|Shutter glasses]] can be adopted as well, obviously with the requirement of achieving synchronisation. If a progressive scan display is used to view such programming, any attempt to deinterlace the picture will render the effect useless. For color filtered glasses the picture has to be either buffered and shown as if it was progressive with alternating color keyed lines, or each field has to be line-doubled and displayed as discrete frames. The latter procedure is the only way to suit shutter glasses on a progressive display.