Macrovision

Macrovision notable for its video copy-prevention 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 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 a few lines outside the visible range that are used for things like closed-captioning and SAP alternate audio. This is the area that the Macrovision signal also resides. It is merely a garbled signal spike. 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 all over the picture. It does cause the automatic tracking and gain control of the recording VCR to constantly compensate, causing the video to become distorted.

Macrovision is a nuisance to some people because it can interfere with other electronic equipment. If one were to run their video signal through a VCR before the television, some VCRs (or TV sets with a built-in VCR) will garble the signal regardless of whether or not it is recording. 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. And of course, United States fair use law as interpreted in the Betamax decision[?] dictates that one is fully within their legal rights to copy videos they own.

Some DVD players give you the ability to shut the Macrovision spike off. 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 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 the manufacturer of defeat devices.

It is the position of film and television studios that Macrovision is necessary to prevent piracy and that they are fully within their rights to add a block to someone exercising their fair use rights. It is also the position of these studios that one does not have any right to copy their own videos, and they have attempted to lead the courts to rule the same.

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 the Macrovision spikes); 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.