ARccOS protection
{{about|Sony's copy-protection system|the inverse trigonometric function of the cosine|arccos (trigonometry)}}
{{update|date=November 2010}}
ARccOS (Advanced Regional Copy Control Operating Solution) is a copy-protection system made by Sony that is used on some DVDs. Designed as an additional layer to be used in conjunction with Content Scramble System (CSS), the system deliberately creates corrupted sectors on the DVD, which cause copying software to produce errors (see bad sector). The corrupted sectors are in areas of the disk that most DVD players do not access, but most copying software does.
Despite being promoted as "fully compatible with available DVD players and drives,"{{cite web |title=ARccOS |url=http://www.sonydadc.com/americas/prod.newtech.arccos1.go |accessdate=2007-04-18 |archiveurl=https://web.archive.org/web/20070510052739/http://www.sonydadc.com/americas/prod.newtech.arccos1.go |archivedate=2007-05-10 |url-status=dead }} some DVDs with ARccOS cannot be played on some DVD players: Sony DVPCX995, Toshiba SD4700, Harman Kardon DVD101, Microsoft Xbox and others.{{cite web | title = Sony copy protection taking heat again: now DVDs won't play | author = Erik Hanson | work = engadget | date = 2007-04-16 | url = https://www.engadget.com/2007/04/16/sony-copy-protection-taking-heat-again-now-dvds-wont-play/ | accessdate = 2007-04-17 | archiveurl= https://web.archive.org/web/20070420113300/http://www.engadget.com/2007/04/16/sony-copy-protection-taking-heat-again-now-dvds-wont-play/#comments| archivedate= 20 April 2007 | url-status= live}} Sony has announced a future firmware update for their players to fix this incompatibility issue.{{cite web | title = Sony Pictures DVDs have a new a copy protection that makes the movies unplayable on some Sony (and other makes) DVD players! | date = 2007-04-19 | url = http://sonystrikesagain.wordpress.com/2007/03/19/hello-world/ | accessdate = 2007-04-21 | archiveurl= https://web.archive.org/web/20070518084437/http://sonystrikesagain.wordpress.com/2007/03/19/hello-world/| archivedate= 18 May 2007 | url-status= live}}{{cite web | title = Sony admits, fixes problem with DVD DRM | author = Jacqui Cheng | date = 2007-04-18 | url = https://arstechnica.com/news.ars/post/20070418-sony-to-replace-incompatible-dvds.html | accessdate = 2007-04-19 | archiveurl= https://web.archive.org/web/20070427001721/http://arstechnica.com/news.ars/post/20070418-sony-to-replace-incompatible-dvds.html| archivedate= 27 April 2007 | url-status= live}} One revision of the ARccOS scheme used by Sony was incompatible with a higher number of players than average. Sony has offered to replace those discs for owners having problems; the replacement discs will have a newer version of ARccOS coding on them, which Sony claims is more compatible.{{cite web | title = Sony fixes problem with ARccOS-protected DVDs | author = Adrian Kingsley-Hughes | date = 2007-04-18 | url = http://blogs.zdnet.com/hardware/?p=360 | access-date = 2007-04-21 | archive-url= https://web.archive.org/web/20070427055945/http://blogs.zdnet.com/hardware/?p=360| archive-date= 27 April 2007 | url-status= dead}}{{cite web | title = Sony Replaces ARccOS-Protected DVDs | date = 2007-04-19 | url = http://www.cdrinfo.com/Sections/News/Details.aspx?NewsId=20244 | accessdate = 2007-04-21 }} Some DVD rental companies have warned users that the Sony DVDs in question may not play on their machines.{{cite web | title = Netflix ARccOS Warning | website=Netflix | url = http://www.netflix.com/FAQ?p_faqid=2462 | accessdate = 2008-09-09 }} Many DVD rippers have been designed to overcome ARccOS protection; it is also naturally overcome by using ddrescue, a Linux utility designed to copy images with errors.