the inherent lack of correlation.
Many of the issues that can
cause problems in IP networks
can be traced back to packet
jitter. Excessive packet jitter can
lead to buffer overflows and
underflows causing dropped
packets and stalled data flows.
Other problems stem from tim-
ing delay and asymmetry of
PTP packet flows. In hybrid
SDI and IP workflows, it is also
necessary to ensure that the
relationship between the SDI
and IP video is consistent to
enable seamless frame accurate
switching.
For a successful and seamless
deployment of an IP-based
broadcast
infrastructure,
interoperability
testing
of
equipment from various ven-
dors in the network is also of
utmost important. To achieve
that, the IP test and measure-
ment instruments need to sup-
port the latest IP standards as
they are adopted by the indus-
try. Since IP video technology
and standards are still evolving,
the IP monitoring equipment
needs to be easily upgradeable
to keep up with the changes as
well. Therefore, it’s important to
select hybrid IP test gear with a
software-based architecture so
it can keep pace with the rapid
pace of change.
Figure 1: Time-correlated video and IP errors are key to understanding if impairments
are being caused by IP errors.
Figure 2. Traditional video monitoring and audio bars are useful in confirming errors.
EFFICIENT TROUBLE-
SHOOTING
Successful deployments of
hybrid and all-IP infrastructure
for video will require the ability
to establish root causes quickly
and efficiently. The first step is
to understand whether visible
impairments are being caused
by IP errors or if some other
fault is causing the impairments.
Figure 3. Measuring the time relationship between black burst/tri-level sync and PTP.
Figure 1 shows how a network-
monitoring tool can be used to
track time-correlated video and
IP errors. This is made possible
by correlating the time stamps
of video errors and packet
82 • Broadcast Beat Magazine • www.broadcastbeat.com
errors.
A video CRC error, however,
does not in itself confirm that
the video is impaired making
it desirable to use traditional
monitoring methods such as
picture and waveform displays