CGMS-A

from Wikipedia, the free encyclopedia

CGMS-A ( C opy G eneration M anagement S ystem -A nalogue ) is a process, CGMS data along with analog (picture) signal information about DRM transfer permission levels.

CGMS is a copy protection mechanism that allows only one generation of copies of a distribution item, such as DVDs , to be made. This is done in that additional information is stored on the data carrier, from which it can be seen which parts of the contents of the data carrier may be copied and how often. With CGMS-A, the DVD player adds these CGMS data to its analog video output signal, which the DVD recorder recognizes and answers the CGMS bit by saying that it is preventing a recording.

The blanking interval of the picture signal is used analogously - as with macrovision or teletext - to transmit the information with signal levels as to whether and to what extent the picture signal can be recorded. The position, intensity and polarity of the pulses for CGMS-A is defined in such a way that it works with both SDTV and HDTV image transmission and is largely compatible with the signal forms mentioned above.