Triple-Play Service Deployment

Chapter 6: Troubleshooting Video in the Headend
This simultaneous cross-layer analysis has great value in
troubleshooting as well, especially if complete MPEG analysis is
available in addition to this MPEG/IP monitoring display. For
example, if video is suffering from tiling, the IPTV headend
technician can check this SimulTrack view to confirm whether
there have been any obvious IP or MPEG layer problems on that
program. If none have been reported, the technician may pursue a
deeper MPEG inspection of that program to confirm the status of
the PCR. If none is detected there, the technician can record a
section of the MPEG transport stream, extract the video
elementary stream, and use an elementary stream analyzer to
confirm whether the content has native problems. The method is
the same as described earlier for the MPEG transport streams. It
has simply been extended to the Ethernet layer by way of GigE test
access to the MPEG analyzer. Ultimately the goals are the same:
determine if the problem is due to transport (MPEG or IP) or
content, identify the source (equipment or provider) and enact
steps for resolution.
Managing Video Test in the IP Realm
It is important to note that MPEG test at the Gigabit Ethernet layer
is different from MPEG test in an MPEG environment.The moment
MPEG transport streams are put in a Gigabit Ethernet stream, they
are effectively “broken.” The tight spacing and network jitter
requirements of MPEG are violated instantly; the IP jitter alone is
order of magnitudes greater than PCR jitter. However, different
does not mean invalid. The MPEG protocol remains intact.
Therefore, tests of PSI and descriptors, PIDs, and continuity
counters all remain valid. Even PCR measurements have validity. In
fact, they continue to be very telling to the health of the MPEG
transport streams. PCR accuracy and spacing are non-temporal
measurements, meaning the rate of PCR arrival is irrelevant. PCR
jitter becomes noise to the IP jitter. But, if this is tracked per flow in
the Ethernet pipe, it is indicative of the level of buffering required
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