Triple-Play Service Deployment

Chapter 6: Troubleshooting Video in the Headend
MPEG over IP
Thus far, this chapter has addressed testing MPEG compression
and MPEG transport, but has not addressed testing as it relates to
IP transport. This is due to the fact that, ultimately, the video
processing in an ITPV headend is very much the same as a digital
cable headend or a satellite uplink.The encoding, content provider
distribution, ingress, re-encoding and multiplexing are generic
video functions, and exist independent of the distribution
technology. As we near the egress edge of any headend, the MPEG
transport is prepared for the distribution network. Digital cable
will modulate MPEG transport to a RF QAM carrier. Satellite will
modulate MPEG transport to an RF PSK carrier. Providers will
encapsulate MPEG transport to an IP “carrier.”
This is where everything finally begins to look more like IP. AVC
compression technology has reduced video bandwidths to the
point where single video programs can be delivered at bit rates
sustainable on a DSL network. By packaging each video program
as an MPEG single program transport stream (SPTS), and
leveraging the switching and routing capabilities of the IP
network, the video delivery system can be molded into a point-topoint
model that better fits the existing IP network model. Instead
of sending many programs down a fat pipe and switching
between channels locally at the set top box, a handful of specific
programs are sent down a smaller pipe, and programs are
switched remotely. Although outwardly this seems to be a
straightforward process, there is a twist: the true enabler of digital
television is the MPEG-2 transport stream. To successfully deliver
IPTV, the provider must be able to deliver these MPEG2 transport
streams intact over their IP network.
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