In Broadcast - NABSHOW 2016 - 90


90

www.inbroadcast.com | NAB SHOW 16-21 April 2016 | InShow Guide

Cont'd from page 89...

Comprehensive
Monitoring for
Distribution Networks
Continuous Monitoring Benefits
Network monitoring systems can
be divided into two broad categories:
intermittent
and
continuous.
Intermittent or "sampled" monitoring
works on a periodic or round-robin
basis, where different points in the
network are monitored for discrete
time intervals. This type of system
might be used, for instance, in a
location where multiple streams are
present and the test system samples
each stream for a time interval
before moving on to the next stream.
In contrast, continuous systems are
able to measure and capture streams
around-the-clock, permitting a diverse
range of data to be captured for
real-time and after-the-fact analysis.
Constant monitoring of the target
signals and systems delivers a number
of important benefits to media
companies, such as those explained
below.
Rapid alerting/alarming, since
there are none of the gaps that occur
when intermittent monitoring is used.
This makes it much easier to quickly
spot anomalies and deliver alarms,
thereby helping to jumpstart problem
analysis and resolution.
Simplified troubleshooting, by
capturing signals immediately before,
during, and after anomalies so that

root causes can be more readily
discerned, and comparisons against
previous "known good" scenarios can
be made.
Upstream
source
validation/
verification, to check the quality
of incoming signals to ensure
that problems that are detected
downstream are not caused by preexisting flaws.
Downstream
performance
assurance, to allow tracking of signal
quality levels after they have been
handed off to distribution partners
or other entities that are involved
in delivering signals to the ultimate
viewer.
Full motion video logging, which
provides a recording of video
sequences that can be used to
perform detailed fault analysis of
error conditions that cause visible
artifacts to appear in the video
image, or cause signal measurement
limits to be exceeded. With accurate
recordings, long-term trends can be
tracked to discern gradual changes
and potentially correlate them to
underlying causes. Also, recordings
support the ability to diagnose the
causes of intermittent faults that may
only become apparent in signal flows
that are significantly downstream of
the original cause of the fault.
Key Monitoring Points
To get the full benefit of
continuous monitoring, the
best practice is to gather
data from as many places
as possible along the entire
broadcast chain from source
to viewer. By minimising
the length of the spans
between monitoring points,
the scope of problems that
can occur is constrained to a
smaller number of devices in
series, which simplifies error
diagnosis and remediation.
Also,
more
closely-spaced

monitoring points creates more
data for overall system performance
assessment and trend detection.
For linear networks such as CATV,
satellite, IPTV, and over-the-air
broadcast programmers and delivery
providers, there are several points
where monitoring and video capture
should be performed along the
broadcast chain. In general, any
places where signals are substantially
transformed are logical locations,
some of which are outlined below.
Master playout, where original
program materials are assembled and
placed into a coherent timeline for
delivery to viewers.
Handoff to/from playout service
provider, who may be providing
playout
services,
branding,
localisation, and delivery to multiple
distribution partners.
Encoder output, where the main
compression system generates a low
bitrate signal that can be transmitted
over various network technologies.
Verifying the proper insertion of
advertising triggers (SCTE codes) is
also important at this stage.
Multiplexer output, to verify that
each element of a multiprogram
stream has been properly combined
into an aggregate output signal.
Modulator/encapsulator
output,
in order to verify that the process
of packaging a multi-stream output
signal for transmission over a satellite,
IP, or private transport network
has been done correctly and no
degradations have been incurred by
the constituent signals.
Handoff between programmer
and MCVD, is an area of particular
concern,
since
ownership/
responsibility for the underlying
network changes at this point
to
permit
problems
detected
downstream to be clearly divided into
those that occurred upstream of the
handoff, and those that were caused
downstream, so that the appropriate

responsibility can be assigned for
resolution.
Transport streams (TS), are used
at multiple points along a broadcast
chain, and can be successfully
captured and analysed at many
different
locations.
Modulator
and transport network inputs and
outputs should be observed, as well
as multiplexer and demultiplexer
interfaces. A key factor in successful
monitoring is the ability to properly
handle encrypted signals, so that the
actual video and audio content can be
analysed and recorded along with the
generation of a full suite of transport
stream performance metrics.
Monitoring and capturing the actual
output of set-top boxes and other
viewer devices is incredibly important,
because this is the one place where
the results of all the upstream signal
processing become available. Given
the variety of interfaces that are
present on devices from various
service providers, having the flexibility
to capture signals from analog and
digital, as well as standard and highdefinition (with a future capability
for ultra-high definition), sources in
a variety of formats is essential for
accurately evaluating the full gamut of
consumer experiences.
For OTT networks, similar principles
apply to deciding where to perform
signal monitoring. Since a different
assemblage of service providers are
normally used for OTT offerings, it is
important to monitor OTT networks
just as carefully as traditional linear
systems.
A typical OTT workflow begins with
either a multi-bitrate encoder or
transcoder that generates multiple
versions of the source content, at
different resolutions, frame rates, and
quality levels. All of these different
profiles should be captured and
measured to determine if a valid set
of content streams is being created at
the first link in the process.
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