Macrovision

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Image:Macrovision Logo 280x91.jpg Macrovision is a company that creates electronic copy prevention schemes, established in 1983. The name is also sometimes used to refer to certain video copy prevention schemes developed by that company.

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History

Macrovision Corporation was established in 1983. The 1984 film "The Cotton Club" was the first videocassette to be encoded with the Macrovision technology when it was released in 1985. By the end of the 1980s, most major Hollywood studios were utilizing the Macrovision technology. The technology was extended to DVD players when they were first launched in 1997.

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Macrovision for video

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 (excluding very old models, modified VCRs, or those approved for "professional usage"). This is usually visible as a scrambled picture as if the tracking were 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 physically recorded directly on the tape (as with VHS) or created on playback by a chip in the player (as with DVDs).

NTSC and other video formats store the video signal 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 to 40 lines outside the visible range that are used for different things in different countries, like closed captioning.

Macrovision inserts pulses into this non-displayed area. These signals cause the automatic gain control on the recording VCR 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 no effect in ordinary playback of the protected 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.

Another modification also used in Macrovision protection is the addition of colorstripes—rapidly modulated colorburst signals.

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Technical problems

Macrovision is considered a nuisance to specialist users because it may 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 it is recording. This also occurs in some TV-VCR combo sets.

The signal has also been known to confuse home theater line doublers (devices for improving the quality of video for large projection TVs) and some high-end television comb filters.

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Legal issues

Some DVD players give the user the option of disabling the Macrovision technology. This is possible since the signal is not stored on the DVD itself; instead commercial DVDs contain an instruction to the player to create such a signal during playback. Some DVD players can be configured to ignore such instructions.

There are also devices called stabilizers, video stabilizers or enhancers available that filter out the Macrovision spikes and thereby defeat the system. The principle of their function lies in detecting the vertical synchronization signal, and forcing the lines occurring during the vertical blanking interval to black level, removing the AGC-confusing pulses. They can be easily built by hobbyists, as nothing more than a cheap microcontroller together with an analog multiplexer and a little other circuitry is needed.

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 consumers are fully within their legal rights to copy videos they own, however the legality has changed somewhat with the Digital Millennium Copyright Act. After April 26 2002, the law changed in the United States of America to state that 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. There are a number of older VCR models that are not affected by Macrovision.

On October 26 2001, the sale, purchase, or manufacture of any device that has no commercial purpose other than disabling Macrovision copy prevention was made illegal under section 1201(a) of the same act.

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SafeCast

Main article: SafeCast

SafeCast a type of software copy protection for legacy computer applications marketed by Macrovision. It is or has been used by such popular software packages as Intuit's TurboTax and many recent Adobe software products, and has occasionally been the source of controversy.

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RipGuard

In February 2005, Macrovision introduced their new RipGuard technology. This is designed to prevent (or reduce) digital DVD copying by altering the format of the DVD content in such a way as to disrupt the ripping software. Macrovision claims that 97% of all current DVD rippers will not be able to copy a DVD protected by RipGuard technology, however, it can be bypassed with the use of AnyDVD.

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Legal Issues

In June 2005, Macrovision sent a cease and desist letter to "Lightning UK!", the maker of DVD Decrypter, a program that allows users to backup their DVDs by bypassing CSS and Macrovision protection, which can also be used for piracy. They later acquired the rights to this software and withdrew it from circulation on the internet.

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References

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See also

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External links

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