Cisco CDE 220 Series Hardware Installation Manual page 26

Cisco CDA Visual Quality Experience Application Overview
The two error-repair options, Unicast Retransmission and Forward Error Correction (FEC), can be used
separately or together for Hybrid Error Repair. Each repair function has its own advantages and
limitations. Whether Unicast Retransmission or FEC or both are used, the subscriber does not detect the
error repair and no video artifact results.
Figure 1-3
network and in the customer premises equipment (CPE) of the subscriber.
Figure 1-3
SHE VHO
IPTV (RTP)
multicast streams
Encoders N-PE router
If FEC is used for error repair, an SMPTE 2022-compatible FEC stream generator, such as the Cisco
Digital Content Manager (DCM), is required. The FEC stream generator, shown in
located in the headend and sends application-layer FEC packets. RTP encapsulation is a prerequisite for
FEC.
The FEC stream generator, which is connected to the real-time encoders, subscribes to video channels
from the headend and encodes FEC for each channel. It is responsible for originating FEC packets
associated with individual channels and with primary multicast streams. For each FEC-enabled channel,
a primary media stream and two encoded FEC streams are sent over multicast addresses (see
Figure 1-4
FEC
stream
generator
Cisco Content Delivery Engine 205/220/250/280/285/420/460/475 Hardware Installation Guide
1-6
shows the location of the major network and VQE components in the service-provider
VQE Major Components
Metro network
FEC Stream Generator
Primary media stream
FEC 1 stream
FEC 2 stream
Chapter 1
VSO/CO CO
VQE Server
on CDE250
Unicast transmissions
to VQE Clients
DSLAM
PE-AGG router
Overview of the Content Delivery Engines
Customer premises
VQE Client
on Cisco STB
VQE Client
on third-party STB
VQE operates on errors
in this part of network
Figure 1-4, is often
Figure 1-4).