Editing Digital video recorder (section)

====Analog broadcast copy protection====
Many consumer DVRs implement a copy-protection system called ''Copy Generation Management System—Analog'' ([[CGMS-A]]), which specifies one of four possible copy permissions by means of two bits encoded in the [[vertical blanking interval]]:
* Copying is freely allowed
* Copying is prohibited
* Only one copy of this material may be made
* This is a copy of material for which only one copy was allowed to be made, so no further copies are allowed.

CGMS-A information may be present in analog broadcast TV signals, and is preserved when the signal is recorded and played back by analog [[VCR]]s. VCRs do not understand the meanings of the bits but preserve them in case there is a subsequent attempt to copy the tape to a DVR.

DVRs such as TiVo also detect and act upon<ref>{{cite web|url=http://support.tivo.com/app/answers/detail/a_id/243 |archive-url=https://archive.today/20120718033009/http://support.tivo.com/app/answers/detail/a_id/243 |url-status=dead |archive-date=2012-07-18 |title=Questions about copy protection – TiVo |publisher=Support.tivo.com |date=2009-06-23 |access-date=2011-11-21 }}</ref> analog protection systems such as [[Macrovision]] and [[DCS Copy Protection]] which were originally designed to block copying on analog VCRs.