Editing VHS (section)

=== Copy protection ===

As VHS was designed to facilitate recording from various sources, including television broadcasts or other VCR units, content producers quickly found that home users were able to use the devices to copy videos from one tape to another. Despite [[generation loss]] in quality when a tape was copied,<ref>{{cite book|url=https://books.google.com/books?id=dqP8FCEiMGgC&pg=PA267|title=Bioimaging: Current Concepts in Light and Electron Microscopy|last1=Chandler|first1=Douglas E.|last2=Roberson|first2=Robert W.|publisher=[[Jones and Bartlett Publishers]]|date=2009|access-date=2022-04-09|pages=267–268|isbn=978-0-7637-3874-7}}</ref> this practice was regarded as a widespread problem, which members of the [[Motion Picture Association of America]] (MPAA) claimed caused them great financial losses.<ref>{{cite book|url=https://books.google.com/books?id=dTHxh9SAF-AC&pg=PA314|title=Time Strategies, Innovation and Environmental Policy|series=Advances in Ecological Economics|last1=Sartorius|first1=Christian|last2=Zundel|first2=Stefan|publisher=[[Edward Elgar Publishing]]|date=2005|access-date=2022-04-09|pages=314–318|isbn=1-84542-090-X}}</ref><ref>{{cite book|url=https://books.google.com/books?id=RQHFDwAAQBAJ&pg=PA209|title=Copyrighting Culture: The Political Economy of Intellectual Property|series=Critical Studies in Communication and in the Cultural Industries|last=Bettig|first=Ronald V.|publisher=[[Routledge]]|date=2018|access-date=2022-04-09|pages=209–210|isbn=978-0-8133-3304-5}}</ref> In response, several companies developed technologies to protect copyrighted VHS tapes from casual duplication by home users. The most popular method was [[Analog Protection System]], better known simply as [[Macrovision]], produced by a company of the same name.<ref>{{Cite web|url=https://hackaday.com/2018/05/27/rolling-old-school-with-copy-protection-from-the-1980s/|title=Rolling Old School With Copy Protection From The 1980s|date=May 28, 2018}}</ref> According to Macrovision: <blockquote>The technology is applied to over 550 million videocassettes annually and is used by every MPAA movie studio on some or all of their videocassette releases. Over 220 commercial duplication facilities around the world are equipped to supply Macrovision videocassette copy protection to rights owners...The study found that over 30% of VCR households admit to having unauthorized copies, and that the total annual revenue loss due to copying is estimated at $370,000,000 annually.<ref>{{Cite web|url=https://electronics.howstuffworks.com/question313.htm|title=How does copy protection on a video tape work?|date=April 1, 2000|website=HowStuffWorks}}</ref></blockquote>

The system was first used in copyrighted movies beginning with the 1984 film ''[[The Cotton Club (film)|The Cotton Club]]''.<ref name="deatley19850907">{{cite news | url=https://news.google.com/newspapers?id=lc8vAAAAIBAJ&pg=5630%2C870934 | title=VCRs put entertainment industry into fast-forward frenzy | work=The Free Lance-Star | date=September 7, 1985 | agency=Associated Press | access-date=2015-01-25 | author=De Atley, Richard | pages=12–TV}}</ref>

Macrovision copy protection saw refinement throughout its years, but has always worked by essentially introducing deliberate errors into a protected VHS tape's output video stream. These errors in the output video stream are ignored by most televisions, but will interfere with re-recording of programming by a second VCR. The first version of Macrovision introduces high signal levels during the [[vertical blanking interval]], which occurs between the video fields. These high levels confuse the [[automatic gain control]] circuit in most VHS VCRs, leading to varying brightness levels in an output video, but are ignored by the TV as they are out of the frame-display period. "Level II" Macrovision uses a process called "colorstriping", which inverts the analog signal's colorburst period and causes off-color bands to appear in the picture. Level III protection added additional colorstriping techniques to further degrade the image.<ref name="anarchivism-rip-vhs">{{cite web |url=http://anarchivism.org/w/How_to_Rip_VHS |title=How to Rip VHS |work=Anarchivism |date=December 14, 2012 }}</ref>

These protection methods worked well to defeat analog-to-analog copying by VCRs of the time. Consumer products capable of digital video recording are mandated by law to include features which detect Macrovision encoding of input analog streams, and disrupt copying of the video.{{citation needed|date=June 2018}} Both intentional and false-positive detection of Macrovision protection has [[Criticism of copyright|frustrated archivists]] who wish to copy now-fragile VHS tapes to a digital format for preservation. As of the 2020s, modern software decoding<ref>{{Citation |last=oyvindln |title=oyvindln/vhs-decode |date=2024-01-08 |url=https://github.com/oyvindln/vhs-decode |access-date=2024-01-08}}</ref> ignores Macrovision as software is not limited to the fixed standards that Macrovision was intended to disrupt in hardware based systems.