Macrovision is notable for its video copy protection scheme of the same name. A VHS videotape or DVD (no laserdisc or video CD players implement it) encoded with Macrovision will cause a VCR set to record it to fail. This is usually visible as a scrambled picture as if the tracking was incorrect or the picture will fade between overly light and dark.
This is achieved through a signal implanted within the offscreen range (vertical blanking interval) of the video signal either encoded directly on the tape (as with VHS) or implanted by a chip in the player (as with DVDs.) NTSC and other video formats store the video signal basically as "lines". A portion of these lines are used for constructing the visible image by transposing them on the screen, but there are approximately 20 lines outside the visible range that are used for things like closed captioning and SAP alternate audio.
Macrovision inserts pulses into this non-displayed area. These signals cause the automatic tracking and gain control on VCRs to compensate for the varying strength. This makes the recorded picture wildly change brightness, rendering it unwatchable. On most televisions, the viewer on the screen sees nothing in ordinary use of the video because the signal is outside the visible area, but some TVs do not properly blank the vertical retrace and leave dotted white lines near the top of the picture. Some newer TVs also mistake the Macrovision pulses for synchronization pulses.
Macrovision is a nuisance to some because it can interfere with other electronic equipment. If one were to run their video signal through a VCR before the television, some VCRs will output a ruined signal regardless of whether or not it is recording. This also occurs in some TV-VCR combo sets. The signal also confuses home theater line doublers (devices for improving the quality of video for large projection TV's) and some high-end television comb filters.
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Some DVD players give the user the option of disabling the Macrovision protection.
There are also cheap devices called stabilizers for sale that filter out the Macrovision spikes and thereby defeat the system.
These products tend not to last long as the Macrovision company owns patents on both the Macrovision system and the most common ways of defeating the system, and the company can and does sue manufacturers of these devices.
The MPAA maintains it has every right to limit copying of movies, comparing DVDs to pay-per-view where the consumer is allowed to view the movie in question but nothing more. Many are concerned that the organization is attempting to quash fair use by disallowing consumers to make personal copies.
United States fair use law as interpreted in the decision over Betamax (Sony Corp. v. Universal City Studios) dictates that one is fully within their legal rights to copy videos they own, however the legality has changed somewhat with the Digital Millennium Copyright Act. In the US starting on April 26, 2002, no VCR may be manufactured or imported which does not contain the Automatic Gain Control circuitry (which makes VCRs vulnerable to Macrovision); this is contained in title 17, section 1201(k) of the Digital Millennium Copyright Act.
Furthermore, starting on October 26, 2001, the sale, purchase, or manufacture of any device that disables Macrovision copy protection will be illegal under section 1201(a) of the same act. However, the constitutionality of many of the act's provisions is under debate.Legal Issues