OASIS Emergency Management TC

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  • 1.  IF Broadcast Pointers

    Posted 08-10-2004 19:43 
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    Subject: IF Broadcast Pointers
    







    



    Following up from the IF discussion this morning, hope this helps move
things along. Note these are true IF level specs where referenced (i.e.
packet level encapsulation and transport delivery) -- not application
layer transport abstractions.

For broadcast we have a couple of breakdowns for the USA marketplace.

=== Digital Cable:

http://www.scte.org/documents/pdf/SCTE182002ANSIJSTD042DVS208.pdf

Defines the injection of EAS for cable networks using OOB broadcast.
This is a cable_emergency_alert message inside an MPEG2 ts (transport
stream). Digital cable set top boxes can be triggered with messages
using this. We've implemented this at RCN, Comcast and I believe a few
others with a product called DEAS.

=== Analog Cable and Analog terrestrial/OTA (over the air):

http://www.chyrongraphics.com/products/codi/index_b.html#codieas

Since there is no universal addressability for analog systems (VBI is
not ubiquitously supported), automated character generators are used.
Above is one. Basically a simple video re-encoder with an overlay text
crawl. Oxtel, Matrox, and others do the same thing. One can classify
these systems as legacy, since when analog NTSC is phased out they will
cease to be used in favor of table packet injection as described above
and below.

=== ATSC (digital terrestrial/OTA):

http://www.atsc.org/standards.html

For delivery to digital set top boxes in the realm of SI (service
information (mpeg ts metadata)) data the following are pertinent: a/65b.
For delivery of data to PC or TCP stack capable receivers, the following
are pertinent: a/90, a/92. A/92 and A/65b are the most widely 'used'.
We're currently using A/92 for CAP transport via a product called
AlertStorm. Triggering of alerts for digital set top boxes is still up
in the air, but the most likely candidate is a DCC (directed channel
change) trigger, to force receivers to tune to a channel, and then tune
back (the last part is not implemented or specced yet) to the original
channel after the emergency notification is completed. 

A/92 is the only viable injection method currently, as settop boxes do
not support DCC, and most stations use static PSIP table
servers/injectors. One must implement a metadata channel for description
of content details and addressability. All A/92 vendors do this in their
own way, but in a way so as not to be specific to any datatype. Please
note that although A/92 defines SDP for metadata, it is *not* sufficient
for anything but basic data descriptors. To be blunt, no-one uses it.

Also note that many A/92 systems can be deployed on any IP system, and
transparently carried over UDP-capable networks (i.e. satellite to
terrestrial to lan to WIFI to NexTel, etc.) and decoded by any OS
embedded or other with multicast-capable TCP stack.

=== Satellite (directv, echostar, etc.):

These providers use either DVB or proprietary transport streams. DVB
resembles ATSC in some ways. Commercial satellite providers roll out
receivers to their specifications, and each provider requires a
proprietary alert injection system (if supported at all). This is too
big a nebulous to cover and the best approach is probably to blanket
these services under proprietary/custom.

The IFSC one-way data delivery document adds some bulk to these
comments.

I think that covers it all. If we need to look at worldwide broadcast
standards then this list will need a lot of addition and refinement.

Cheers
Kon


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