Serial Copy Management System

Last updated

The Serial Copy Management System (SCMS) is a copy protection scheme that was created in response to the digital audio tape (DAT) invention, in order to prevent DAT recorders from making second-generation or serial copies. SCMS sets a "copy" bit in all copies, which prevents anyone from making further copies of those first copies. It does not, however, limit the number of first-generation copies made from a master.

Contents

SCMS was also included in consumer CD-R, MiniDisc and Digital Compact Cassette (DCC) players and recorders. With the demise of these formats, SCMS is not in widespread use. However, the concept of SCMS was resurrected in the broadcast flag, a measure formerly mandated by the Federal Communications Commission (FCC) to limit the copying of digital TV signals. [1] SCMS flags are also included in the MP3 specifications, [2] though no known decoder or player honors them. Personal Computers were not required to include SCMS in the US. [3]

History

SCMS was created as a compromise between electronics manufacturers, mainly Sony and Philips, who wanted to make DAT machines available in the United States, and the RIAA, which had previously hampered the availability of DAT machines in the US with the threat of lawsuits. The RIAA did not want low-cost digital recorders readily available, since it felt that such technology would result in widespread piracy. These lawsuit threats resulted in a chilling effect, which prevented DAT decks from becoming readily affordable.

In 1987, a member of the RIAA proposed a system where DAT recorders would have copy protection in them. The copy protection would look for the presence of frequencies in a particular high-frequency band; if there was no audio present in this band, the recorder would assume that the music in question was copy protected, and would not allow recording of the music. The record companies would then release all music with this particular frequency band filtered out. It would be illegal to manufacture a DAT machine with the presence of audio in this frequency band; the RIAA was lobbying Congress to make this the law of the land.

The reaction to this proposed scheme was very negative. The Home Recording Rights Coalition orchestrated a letter writing campaign opposing this scheme. Editorials in musician's and home stereo magazines attacked this scheme. The proposed law never made it out of committee.

Even after this law was shot down, the RIAA still threatened to sue anyone who released an affordable consumer DAT recorder in the US. No one made such a recorder available.

In 1992, Congress passed the Audio Home Recording Act. In this law, blank digital media (including DAT tapes and music CD-Rs) would be taxed, with the money going to the RIAA, and a new copy protection scheme, SCMS, would be enforced. Blank analog media, such as cassette tapes, were not subject to the tax. SCMS was compulsory in digital media because there is zero deterioration of quality from copy to copy. SCMS was universally disliked by home musicians who used DAT decks to record their own music; the acronym was pronounced as a derogatory term, "scums". [4]

Technical details

SCMS copy protection looks for bits written in the subcode data in a digital link. [5] There are two bits which are relevant:

Copying is only allowed if the source signal for the recording is not copyrighted, or is copyrighted and is an original. If the source signal is a copyrighted recording, the recorder must set the "L" bit to "not determined" when it plays the copy, so that the copy cannot be copied digitally again.

Source CpSource LCopying allowedCopy LCopyable Copy
"Copyrighted""Original"Yes"Not Determined"No
"Copyrighted""Undetermined"NoN/AN/A
"Not Copyrighted"(any)Yes(same as source)Yes

Circumvention

Software and design defects in certain models of consumer Minidisc player allow SCMS to be defeated. Professional-grade Minidisc systems costing several thousand US dollars may have SCMS disabled as standard. Professional CD recorders, including all computer drives, have SCMS disabled and can also record audio onto data CD-R discs.

European electronic hobby magazine Elektor published a construction project in the 1990s. The device, once completed, was designed to be inserted in the digital link between SCMS enabled devices (the article was designed around the optical TOSLINK interface, but it would have been easy to adapt it to the S/PDIF coaxial link). The circuit intercepted the SCMS control bits, and changed the "Cp" bit to the "not copyrighted" state.

Similar functionality is often also included in commercially available bitrate-converters, like the Behringer Ultramatch.

There is another way that SCMS can be defeated, but it requires copying the Table of Contents from a blank disc that already allows copying, to a recorded 'copy disallowed' disc. The method is laborious, and suffers the disadvantage that the track marks and titles are lost in the process.

See also

Related Research Articles

<span class="mw-page-title-main">Compact disc</span> Digital optical disc data storage format

The compact disc (CD) is a digital optical disc data storage format that was co-developed by Philips and Sony to store and play digital audio recordings. In August 1982, the first compact disc was manufactured. It was then released in October 1982 in Japan and branded as Digital Audio Compact Disc.

<span class="mw-page-title-main">Compact Disc Digital Audio</span> Data format used for audio compact discs

Compact Disc Digital Audio, also known as Digital Audio Compact Disc or simply as Audio CD, is the standard format for audio compact discs. The standard is defined in the Red Book, one of a series of Rainbow Books that contain the technical specifications for all CD formats.

<span class="mw-page-title-main">MiniDisc</span> Magneto-optical storage medium, mainly for audio (1992–2013)

MiniDisc (MD) is an erasable magneto-optical disc-based data storage format offering a capacity of 60, 74, and later, 80 minutes of digitized audio.

<span class="mw-page-title-main">VHS</span> Consumer-level analog videotape recording and cassette form standard

VHS is a standard for consumer-level analog video recording on tape cassettes invented in 1976 by the Victor Company of Japan and was the competitor to the ill-fated Sony Betamax system.

<span class="mw-page-title-main">Digital audio</span> Technology that records, stores, and reproduces sound

Digital audio is a representation of sound recorded in, or converted into, digital form. In digital audio, the sound wave of the audio signal is typically encoded as numerical samples in a continuous sequence. For example, in CD audio, samples are taken 44,100 times per second, each with 16-bit sample depth. Digital audio is also the name for the entire technology of sound recording and reproduction using audio signals that have been encoded in digital form. Following significant advances in digital audio technology during the 1970s and 1980s, it gradually replaced analog audio technology in many areas of audio engineering, record production and telecommunications in the 1990s and 2000s.

<span class="mw-page-title-main">Cassette tape</span> Magnetic audio tape recording format

The Compact Cassette, also commonly called a cassette tape, audio cassette, or simply tape or cassette, is an analog magnetic tape recording format for audio recording and playback. Invented by Lou Ottens and his team at the Dutch company Philips and released in August 1963, Compact Cassettes come in two forms, either containing content as a prerecorded cassette (Musicassette), or as a fully recordable "blank" cassette. Both forms have two sides and are reversible by the user. Although other tape cassette formats have also existed—for example the Microcassette—the generic term cassette tape is normally used to refer to the Compact Cassette because of its ubiquity.

<span class="mw-page-title-main">Digital Audio Tape</span> Digital audio cassette format developed by Sony

Digital Audio Tape is a signal recording and playback medium developed by Sony and introduced in 1987. In appearance it is similar to a Compact Cassette, using 3.81 mm / 0.15" magnetic tape enclosed in a protective shell, but is roughly half the size at 73 mm × 54 mm × 10.5 mm. The recording is digital rather than analog. DAT can record at sampling rates equal to, as well as higher and lower than a CD at 16 bits quantization. If a comparable digital source is copied without returning to the analogue domain, then the DAT will produce an exact clone, unlike other digital media such as Digital Compact Cassette or non-Hi-MD MiniDisc, both of which use a lossy data-reduction system.

A cassette deck is a type of tape machine for playing and recording audio cassettes that does not have a built-in power amplifier or speakers, and serves primarily as a transport. It can be a part of an automotive entertainment system, a part of a portable mini system or a part of a home component system. In the latter case it is also called a component cassette deck or just a component deck.

Sound can be recorded and stored and played using either digital or analog techniques. Both techniques introduce errors and distortions in the sound, and these methods can be systematically compared. Musicians and listeners have argued over the superiority of digital versus analog sound recordings. Arguments for analog systems include the absence of fundamental error mechanisms which are present in digital audio systems, including aliasing and associated anti-aliasing filter implementation, jitter and quantization noise. Advocates of digital point to the high levels of performance possible with digital audio, including excellent linearity in the audible band and low levels of noise and distortion.

A private copying levy is a government-mandated scheme in which a special tax or levy is charged on purchases of recordable media. Such taxes are in place in various countries and the income is typically allocated to the developers of "content".

<span class="mw-page-title-main">Digital Compact Cassette</span> Philips-developed system with digital audio on compact cassette

The Digital Compact Cassette (DCC) is a magnetic tape sound recording format introduced by Philips and Matsushita Electric in late 1992 and marketed as the successor to the standard analog Compact Cassette. It was also a direct competitor to Sony's MiniDisc (MD), but neither format toppled the then-ubiquitous analog cassette despite their technical superiority, and DCC was discontinued in October 1996.

<span class="mw-page-title-main">Reel-to-reel audio tape recording</span> Audio recording using magnetic tape spooled on open reels

Reel-to-reel audio tape recording, also called open-reel recording, is magnetic tape audio recording in which the recording tape is spooled between reels. To prepare for use, the supply reel containing the tape is placed on a spindle or hub. The end of the tape is manually pulled from the reel, threaded through mechanical guides and over a tape head assembly, and attached by friction to the hub of the second, initially empty takeup reel. Reel-to-reel systems use tape that is 1⁄4, 1⁄2, 1, or 2 inches wide, which normally moves at 3+3⁄4, 7+1⁄2, 15 or 30 inches per second. Domestic consumer machines almost always used 1⁄4 inch (6.35 mm) or narrower tape and many offered slower speeds such as 1+7⁄8 inches per second (4.762 cm/s). All standard tape speeds are derived as a binary submultiple of 30 inches per second.

Ripping is extracting all or parts of digital content from a container. Originally, it meant to rip music out of Commodore 64 games. Later, the term was used to mean to extract WAV or MP3 format files from digital audio CDs, but got applied as well to extract the contents of any media, including DVD and Blu-ray discs, and video game sprites.

<span class="mw-page-title-main">Digital recording</span> Audio or video represented as a stream of discrete numbers

In digital recording, an audio or video signal is converted into a stream of discrete numbers representing the changes over time in air pressure for audio, or chroma and luminance values for video. This number stream is saved to a storage device. To play back a digital recording, the numbers are retrieved and converted back into their original analog audio or video forms so that they can be heard or seen.

<span class="mw-page-title-main">Audio Home Recording Act</span>

The Audio Home Recording Act of 1992 (AHRA) amended the United States copyright law by adding Chapter 10, "Digital Audio Recording Devices and Media". The act enabled the release of recordable digital formats such as Sony and Philips' Digital Audio Tape without fear of contributory infringement lawsuits.

<span class="mw-page-title-main">PCM adaptor</span> Encodes digital audio as video

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.

<span class="mw-page-title-main">Sound recording and reproduction</span> Recording of sound and playing it back

Sound recording and reproduction is the electrical, mechanical, electronic, or digital inscription and re-creation of sound waves, such as spoken voice, singing, instrumental music, or sound effects. The two main classes of sound recording technology are analog recording and digital recording.

The history of sound recording - which has progressed in waves, driven by the invention and commercial introduction of new technologies — can be roughly divided into four main periods:

<i>Recording Industry Assn of America v. Diamond Multimedia Systems, Inc.</i> 1999 United States legal case

Recording Indus. Ass’n of Am. v. Diamond Multimedia Sys., Inc., 180 F.3d 1072, 51 U.S.P.Q.2d (BNA) 1115 was a case decided by the United States Court of Appeals for the Ninth Circuit in 1999. The court applied the Audio Home Recording Act to the Rio digital audio player manufactured by Diamond Multimedia, concluding that the Rio was not a "digital audio recording device" under that statute.

References

  1. ↑ Techopedia (4 September 2011). "Serial Copy Management System" . Retrieved 18 April 2012.
  2. ↑ "Guide to Command Line Options". LAME. Retrieved September 29, 2018.
  3. ↑ Knopper, Steve (2009). Appetite for Self-Destruction . Simon and Schuster: Free Press. pp.  78–9. ISBN   9781416552154.
  4. ↑ Axford, Elizabeth C. (2004). Song sheets to software : a guide to print music, software, and web sites for musicians (2. ed.). Lanham, Md.: Scarecrow Press. ISBN   0810850273.
  5. ↑ "IS/IEC 60958-3". Archive.org. Bureau of Indian Standards. Retrieved 26 March 2019.
  6. ↑ "What is SCMS". Sweetwater. 1997. Retrieved 8 December 2021.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.