This article needs additional citations for verification .(April 2024) |
The Analog Protection System (APS), also known as Analog Copy Protection (ACP), Copyguard or Macrovision, [1] is a VHS [2] and DVD copy protection system originally developed by the Macrovision Corporation. Video tapes copied from DVDs encoded with APS become garbled and unwatchable. The process works by adding pulses to analog video signals to negatively impact the AGC circuit of a recording device. In digital devices, changes to the analog video signal are created by a chip that converts the digital video to analog within the device. In DVD players, trigger bits are created during DVD authoring to inform the APS that it should be applied to DVD players' analog outputs or analog video outputs on a PC while playing back a protected DVD-Video disc. In set top boxes trigger bits are incorporated into Conditional Access Entitlement Control Messages (ECM) in the stream delivered to the STB.
In VHS, alterations to the analog video signal are added in a Macrovision-provided "processor box" used by duplicators.
Analog video formats convey video signals as a series of raster scan lines. Most of these lines are used for constructing the visible image, and are shown on the screen. But several more lines exist which do not convey visual information. Known as the vertical blanking interval (VBI), these extra lines historically served no purpose other than to contain the vertical synchronizing pulses, but in more modern implementations they are used to carry or convey different things in different countries; for example closed captioning.
Macrovision's legacy analog copy protection (ACP) works by implanting a series of excessive voltage pulses within the off-screen VBI lines of video. These pulses were included physically within pre-existing recordings on VHS and Betamax and were generated upon playback by a chip in DVD players and digital cable or satellite boxes. A DVD recorder receiving an analog signal featuring these pulses would detect them and display a message saying that the source is "copy-protected" followed by aborting the recording. VCRs, in turn, react to these excessive voltage pulses by compensating with their automatic gain control circuitry. This causes the recorded picture to wildly change brightness, rendering it annoying to watch. The system was only effective on VCRs made in the mid-1980s. In addition, these voltage pulses caused some TVs to lose track of the vertical blanking interval, meaning they no longer knew when one frame ended and the next began. This caused the picture to roll wildly up and down the screen on affected sets. [3]
A later form of Macrovision's analog copy protection, called Level II ACP, introduced multiple 180-degree phase inversions to the analog signal's color burst. Also known as color striping, this technology caused numerous off-color bands to appear within the picture.
APS can be also signaled digitally, in the CGMS-A bit field sent in the vertical blanking interval.
Historically, the original Macrovision technology was considered a nuisance to some specialist users because it could interfere with other electronic equipment. For example, if one were to run a video signal through a VCR before the television, some VCRs would output a ruined signal regardless of whether it is recording. This also occurs in some TV-VCR combo sets. Apart from this, many DVD recorders mistake the mechanical instability of worn videotapes for Macrovision signals, and so refuse to make what would be perfectly legal DVD dubs of legitimate video tapes, such as home movies. This widespread problem was another factor contributing to the demand for devices that defeat Macrovision. 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. In addition, Macrovision confuses many upconverters (devices that convert a video signal to a higher resolution), causing them to shut down and refuse to play Macrovision content.
Another form of analog copy protection, known as CGMS-A, is added by DVD players and digital cable/satellite boxes. While not invented by Macrovision, the company's products implemented it. CGMS-A consists of a "flag" within the vertical blanking interval (essentially data, like closed captioning) which digital recording devices search for. If present, it refused to record the signal, just as with the earlier ACP technology. Unlike digital recording equipment, however, analog VCRs do not respond to CGMS-A encoded video and would record it successfully if ACP is not also present.
There are also devices called stabilizers, video stabilizers or enhancers [4] 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 VBI 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. Individuals less experienced with such things can purchase video stabilizers.
Discs made with DVD copying programs such as DVD Shrink automatically disable any Macrovision copy protection. The ease with which Macrovision and other copy protection measures can be defeated has prompted a steadily growing number of DVD releases that do not have copy protection of any kind, Content Scramble System (CSS) or Macrovision. Digital recording devices (DVD recorders), on the other hand, often disallow the recording if they detect a protection signal on the input. The unit may display an error message about the program being copy protected.
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 controversial Digital Millennium Copyright Act. After April 26, 2002, no VCR may be manufactured or imported without Automatic Gain Control circuitry (which renders VCRs vulnerable to Macrovision). This is contained in title 17, section 1201(k) of the Digital Millennium Copyright Act. However, after 2002 there were still some mostly older VCR models on the market that were 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 protection was made illegal under section 1201(a) of the same controversial act.
In June 2005, Macrovision sent a cease and desist letter to "Lightning UK!", the maker of DVD Decrypter, a program that allows users to back up their DVDs by bypassing CSS and Macrovision. Macrovision later acquired the rights to this software. [5]
In June 2005, Macrovision sued Sima Products under section 1201 of the DMCA, claiming that Sima's video processors provided a way to circumvent Macrovision's analog copy protection. Sima received an injunction barring the sale of this device, [6] but the parties ultimately settled without a judgment on the legal issues. [7]
Analog television is the original television technology that uses analog signals to transmit video and audio. In an analog television broadcast, the brightness, colors and sound are represented by amplitude, phase and frequency of an analog signal.
TiVo Corporation, formerly known as the Rovi Corporation and Macrovision Solutions Corporation, was an American technology company headquartered in San Jose, California. Now operating as Xperi, the company is primarily involved in licensing its intellectual property within the consumer electronics industry, including digital rights management, electronic program guide software, and metadata. The company holds over 6,000 pending and registered patents. The company also provides analytics and recommendation platforms for the video industry.
NTSC is the first American standard for analog television, published and adopted in 1941. In 1961, it was assigned the designation System M. It is also known as EIA standard 170.
Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) systems, which, in turn, were replaced by flat-panel displays of several types.
VHS is a standard for consumer-level analog video recording on tape cassettes, introduced in 1976 by the Victor Company of Japan (JVC). It was the dominant home video format throughout the tape media period in the late 1970s through the early 2000s.
Composite video is an baseband analog video format that typically carries a 405, 525 or 625 line interlaced black and white or color signal, on a single channel, unlike the higher-quality S-Video and the even higher-quality YPbPr.
S-VHS (スーパー・ヴィエイチエス), the common initialism for Super VHS, is an improved version of the VHS standard for consumer-level video recording. Victor Company of Japan introduced S-VHS in Japan in April 1987, with their JVC-branded HR-S7000 VCR, and in certain overseas markets soon afterward. By the end of 1987, the first S-VHS VCR models from other competitors included the Hitachi VT-2700A, Mitsubishi HS-423UR, Panasonic PV-S4764, RCA VPT-695HF, and Toshiba SV-950. It has been standardized as IEC 60774-3 and IEC 60774-4.
In a raster scan display, the vertical blanking interval (VBI), also known as the vertical interval or VBLANK, is the time between the end of the final visible line of a frame or field and the beginning of the first visible line of the next frame or field. It is present in analog television, VGA, DVI and other signals. Here the term field is used in interlaced video, and the term frame is used in progressive video and there can be a VBI after each frame or field. In interlaced video a frame is made up of 2 fields. Sometimes in interlaced video a field is called a frame which can lead to confusion.
A digital video recorder (DVR), also referred to as a personal video recorder (PVR) particularly in Canadian and British English, is an electronic device that records video in a digital format to a disk drive, USB flash drive, SD memory card, SSD or other local or networked mass storage device. The term includes set-top boxes (STB) with direct to disk recording, portable media players and TV gateways with recording capability, and digital camcorders. Personal computers are often connected to video capture devices and used as DVRs; in such cases the application software used to record video is an integral part of the DVR. Many DVRs are classified as consumer electronic devices. Similar small devices with built-in displays and SSD support may be used for professional film or video production, as these recorders often do not have the limitations that built-in recorders in cameras have, offering wider codec support, the removal of recording time limitations and higher bitrates.
A DVD recorder is an optical disc recorder that uses optical disc recording technologies to digitally record analog or digital signals onto blank writable DVD media. Such devices are available as either installable drives for computers or as standalone components for use in television studios or home theater systems.
D-VHS is a digital video recording format developed by JVC, in collaboration with Hitachi, Matsushita, and Philips. The "D" in D-VHS originally stood for "Data", but JVC renamed the format as "Digital VHS". Released in December 1997, it uses the same physical cassette format and recording mechanism as S-VHS, but requires higher-quality and more expensive tapes and is capable of recording and displaying both standard-definition and high-definition content. The content data format is in MPEG transport stream, the same data format used for most digital television applications. It used MPEG-2 encoding and was standarized as IEC 60774-5.
A PCM adaptor is a device that encodes digital audio as video for recording on a videocassette recorder. The adapter also has the ability to decode a video signal back to digital audio for playback. This digital audio system was used for mastering early compact discs.
A video reference monitor, also called a broadcast reference monitor or just reference monitor, is a specialized display device similar to a television set, used to monitor the output of a video-generating device, such as playout from a video server, IRD, video camera, VCR, or DVD player. It may or may not have professional audio monitoring capability. Unlike a television set, a video monitor has no tuner and, as such, is unable independently to tune into an over-the-air broadcast like a television receiver. One common use of video monitors is in television stations, television studios, production trucks and in outside broadcast vehicles, where broadcast engineers use them for confidence checking of analog signal and digital signals throughout the system. They can also be used for color grading if calibrated, during post-production. Banks of reference monitors are also a common sight on the sets of newscasts, showing internal or external feeds.
Copy Generation Management System – Analog (CGMS-A) is a copy protection mechanism for analog television signals. It consists of a waveform inserted into the non-picture vertical blanking interval (VBI) of an analogue video signal. If a compatible recording device detects this waveform, it may block or restrict recording of the video content.
Guide Plus+, TV Guide On Screen, TV Guide Daily, TV Guide Plus+ and Guide Plus+ Gold or G-Guide are brand names for an interactive electronic program guide (EPG) system that is used in consumer electronics products, such as television sets, DVD recorders, personal video recorders, and other digital television devices. It offers interactive on-screen program listings that enable viewers to navigate, sort, select and schedule television programming for viewing and recording. The differing names are only used for marketing purposes – the entire system is owned by Rovi Corporation, the successor to Gemstar-TV Guide International. In 2016, Rovi acquired digital video recorder maker TiVo Inc., and renamed itself TiVo Corporation.
Video Encoded Invisible Light (VEIL) is a technology for encoding low-bandwidth digital data bitstream in video signal, developed by VEIL Interactive Technologies. VEIL is compatible with multiple formats of video signals, including PAL, SECAM, and NTSC. The technology is based on a steganographically encoded data stream in the luminance of the videosignal.
The analog hole is a perceived fundamental and inevitable vulnerability in copy protection schemes for noninteractive works in digital formats which can be exploited to duplicate copy-protected works using analog means. Once digital information is converted to a human-perceptible (analog) form, it is a relatively simple matter to digitally recapture that analog reproduction in an unrestricted form, thereby fundamentally circumventing any and all restrictions placed on copyrighted digitally distributed work. Media publishers who use digital rights management (DRM), to restrict how a work can be used, perceive the necessity to make it visible or audible as a "hole" in the control that DRM otherwise affords them.
Copy Control Information (CCI) is a two byte flag included in digital television streams that allows content owners and cable operators to specify how content can be duplicated. Originally defined as part of the 5C copy protection specification devised by DTCP working group back in 1998, it was later defined as part of the FCCs Plug and Play agreement in 2003.
A videocassette recorder (VCR) or video recorder is an electromechanical device that records analog audio and analog video from broadcast television or other AV sources and can play back the recording after rewinding. The use of a VCR to record a television program to play back at a more convenient time is commonly referred to as time shifting. VCRs can also play back prerecorded tapes, which were widely available for purchase and rental starting in the 80s and 90s, most popularly in the VHS videocassette format. Blank tapes were sold to make recordings.