CEA J-STD-042-A Emergency Alert Message for Cable
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CEA J-STD-042-A Document Information:
Title
Emergency Alert Message for Cable
Consumer Electronics Association
Publication Date:
Nov 1, 2007
Scope:
This standard defines an Emergency Alert signaling method for
use by cable TV systems to signal emergencies to digital receiving
devices that are offered for retail sale. Such devices include
digital settop boxes that are sold to consumers at retail, digital
TV receivers, and digital video recorders. The Emergency Alert
signaling (EAS) scheme defined in this standard allows a cable
operator to disseminate emergency alert information related to
state and local-level emergencies and warnings in an efficient way,
while minimizing disruption to programming. While it is possible
for a cable operator to comply with EAS requirements by simply
replacing the source signal for all programs with an emergency
information channel, such switching is disruptive to viewing, is
overly intrusive for many kinds of local warnings and is
overly-complex for the cable operator to implement in a digital
cable environment where each transport stream may carry many
programs that would have to be individually interrupted. Based on
the priority level of the alert, the Emergency Alert message may
instruct the receiving device to force-tune to a designated
emergency broadcast channel.
Section 5 of this standard defines the syntax of the Emergency
Alert message and related descriptors. This message is in the form
of a standard MPEG-2 table and, when necessary, is delivered
in-band on cable transport streams that carry one or more programs
in-the-clear. Receiving devices without Point Of Deployment
(POD)1 modules in place process such messages in
accordance with requirements described in Section 7 of this
standard. For programs that are scrambled on a cable system, the
Emergency Alert message is delivered to the POD module using the
cable system's forward data channel. The POD module processes the
message as necessary and delivers it to the receiving device
out-of-band. As used in this standard, "out-of-band" refers to the
Extended Channel interface defined in ANSI/SCTE 28 2004 [5]. As
delivered to the receiving device by the POD module, the Emergency
Alert message is in the form of an MPEG-2 table as defined in
Section 5 of this standard. The receiving device then processes the
message in accordance with Section 7 of this standard.
The behavior of receiving devices in response to user actions,
such as channel changes or accessing onscreen displays, where such
user actions relate to acquisition and processing of Emergency
Alert messages, is out of scope of this standard.
1 The Point Of Deployment module is also known as a
CableCARD™ device.
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