CGMS-A


CGMS-A

Copy Generation Management System - Analog (CGMS-A) is a copy protection mechanism for analog television signals. It is not the same as the Broadcast flag, which is designed for use in digital television signals. The concept is the same as the Broadcast flag [ [http://techdirt.com/articles/20080529/0258571254.shtml Techdirt: Microsoft: It's Not The Broadcast Flag, It's A Different Flag] ] . There is a digital form of CGMS specified as CGMS-D which is required by the DTCP ("5C") protection standard.

History

CGMS-A has been in existence since 1995, and has been standardized by various organizations including the IEC and EIA/CEA. It is used in devices such as PVRs/DVRs, DVD players and recorders, D-VHS, and Blu-ray recorders, as well certain television broadcasts. More recent TiVo firmwares comply with CGMS-A signals.

Applications

Implementation of CGMS-A is required for certain applications by DVD CCA license. D-VHS and some DVD recorders comply with CGMS-A signal on analog inputs. The technology requires minimal signal processing.

Standardization

CGMS-A is standardized in IEC 61880 to appear in the 525i and 480i video signal as vertical blanking interval (VBI) data on line 20. According to ETSI EN 300 294 for 625 line SD output resolutions it is signaled via widescreen signaling (WSS) in line 23 (bits number 12 and 13, group 4). IEC 61880-2 and in EIA-J (without specifying the meanings of the bits) places it to line 41 of 520p signal. EIA/CEA-608-B puts it to line 21 for 525i and 480i. EIA/CEA-805 for component video interfaces standardizes it to line 41 for 480p signal, line 24 for 720p signal, and line 19 for 1080i signal.

Signalling

EIA-608-B specifies meaning of the 7-bit field placed on the data lines. The bits 4 and 3 contain the CGMS-A values, the bits 2 and 1 contain the Analog Protection System (APS) value, the bit 0 is the Analog Source Bit (ASB) specifying if the signal originates from a pre-recorded material, bits 5 and 6 are reserved.

CGMS-A is signalled by 2 bits in the vertical blanking interval (VBI) signal of analog television broadcasts according to the following matrix:

* - CopyNoMore was not a part of the original standard. The 0,1 value originally was "Reserved".

Removal

The signal itself can be easily stripped by normalizing the VBI, e.g. using a video stabilizer to counter the side effects from Macrovision's manipulation of the VBI. CGMS-A VBI data is commingled or generally near captioning signals, so removal of CGMS-A will likely remove captioning as well.

The scheme can be made more robust by adding the Rights Assertion Mark (RAM); when the RAM is present but CGMS-A is not, copying is denied, turning the scheme into a permission-based one. The RAM can be encoded by using the VEIL technology.

See also

* [http://www.cptwg.org/Assets/TEXT%20FILES/ARDG/CEA%20ARDG%20CGMS-A%203-6-03.ppt Copy Generation Management System - Analog] (PowerPoint)
* [http://msdn.microsoft.com/library/default.asp?url=/library/en-us/gdi/devcons_4h9u.asp Microsoft VIDEOPARAMETERS structure for Windows GDI video connections]
* [http://techdirt.com/articles/20080529/0258571254.shtml Techdirt: Microsoft: It's Not The Broadcast Flag, It's A Different Flag]

References


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • CGMS-A — (Copy Generation Management System Analog) ist ein Verfahren, CGMS Daten zusammen mit analogen (Bild )Signal Informationen über DRM Berechtigungsstufen zu übertragen. CGMS ist ein Kopierschutzmechanismus, der von einem Vertriebsstück, zum… …   Deutsch Wikipedia

  • CGMS — Das Copy Generation Management System (CGMS) ist ein Kopierschutzmechanismus u. a. für DVDs, der von einem Vertriebsstück nur eine Generation von Kopien zulässt. Für DAT Technologie eingeführt, heißt das Verfahren dort SCMS. Die analoge Variante… …   Deutsch Wikipedia

  • CGMS — L acronyme CGMS qui provient de l anglais Copy Generation Management System signifie littéralement, système de gestion de génération de copie. Il s apparente à une restriction anti copie. Ce dispositif électronique et logiciel a pour objet de… …   Wikipédia en Français

  • CGMS — Copy Generation Management System (Computing » General) * Coordination on Geostationary Meteorological Satellites (Academic & Science » Ocean Science) …   Abbreviations dictionary

  • CGMS — • Coast Guard Message System …   Maritime acronyms and abbreviations

  • CGMS — abbr. Copy Generation Management System (CD) …   United dictionary of abbreviations and acronyms

  • Broadcast flag — Ein Broadcast Flag [ˈbɹɔːdkɑːstˌflæg] („Ausstrahlungskennzeichnung“) ist eine Form der digitalen Rechteverwaltung (engl. Digital Rights Management, abgekürzt DRM) für den Einsatz bei Fernsehübertragungen. Auf Verlangen der Rechteinhaber senden… …   Deutsch Wikipedia

  • Broadcastflag — Ein Broadcast Flag [ˈbɹɔːdkɑːstˌflæg] („Ausstrahlungskennzeichnung“) ist eine Form der digitalen Rechteverwaltung (engl. Digital Rights Management, abgekürzt DRM) für den Einsatz bei Fernsehübertragungen. Auf Verlangen der Rechteinhaber senden… …   Deutsch Wikipedia

  • Ocean observations — The following are considered essential ocean climate variables by the OOPC[1][clarification needed] that are currently feasible with current observational systems. Contents 1 Ocean climate variables 1 …   Wikipedia

  • Convoys Wharf — St Albans being launched at Deptford Dockyard in 1747. Painting by John Cleveley the Elder Convoys Wharf, formerly called the King s Yard,[1] is the site of Deptford Dockyard, the first of the Royal Dockyards, built on a riverside site in… …   Wikipedia


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.