Talk:CGMS-A

Broadcast Flag is defining a permission to copy the source over Internet by 1 bit on/off control while CGMS is defining if this source can be recorded or not.

CGMS is originally defined to apply on analog source, however, it expanded to the digital source to manage a copy protection applying to composite and components video out. A digital source can carry VBI data (such as closed caption and CGMS) in analog source by MPEG video user data.

This extension raised a need to distinguish the original source type, analog or digital source in CGMS, as CGMS has only 2 bits, which cable developes CCI(Copy Control Information) rather than relying copy control on CGMS.

Once a source goes over Internet, it means it allows a recording on general device, however, how this Broadcast flag will work conjuntion with CGMS was never clarified in a specification. Esepcially, Broadcast flag is designed to be carried in PMT or EIT (by ATSC PSIP), but CGMS is carried by MPEG video user data. The data synchronization policy is required if there is conflict on CGMS and Broadcast flag, such as CGMS says copy never, but Broadcast flag says "On".

There is a CGMS-D

CGMS-D is functionally identical to CGMS-A, and maintained by the same organization. Conformance to them is required by DTCP ("5C") (which was recently accepted by cablelabs as a recognized interchange standard. So even if broadcast flags aren't recognized, no one will be able to buy a CE box that doesn't obey CGMS-D flags, because otherwise they would loose their DTCP status and DTCP devices would stop talking to them.

Anyway, CGMS is not on the way out due to the digital transition- it is like the monster in the B-Movie that jumps up again with a new life as CGMS-D.

Anyway- maybe the article needs to be generalized to CGMS and sections be put in for analog versus digital. -Mak 18:39, 8 July 2007 (UTC)