special report quality control
reference, then you can compare it to
validate the stream. However, this is
not practical in a production or content
delivery environment. Your content is
constantly changing and real-time
reference signals are scarce. The task of
So what else can you tell about the
ensuring
data? If you know that the data
quality of
conforms to a specific standard, you
service is not
can check the data against the rules
set forth in the standard to ensure that
trivial.
none of the rules are violated. This is
Complex
defined as compliance testing and it is compression
the only practical strategy for catching
systems and
data corruptions. Passing a bit-stream
IP delivery
compliance test is the best indicator
that your data is coded correctly.
systems
With an off-line conformance
challenge
testing tool, errors can be detected in even the
your media files and fixed before they
best of
get to the viewers. As an additional
levels, such as the RTP and transport being transmitted, which is why it is
today’s
bonus, errors introduced by hardware
layer, can provide a certain level of important to have a multi-viewer that
engineering
devices or software bugs can be
confidence in the data integrity. can handle compressed streams as
isolated in the production workflow.
resources.
However, without compliance and the final quality assurance check for
Analysing the performance of these
Without the decode testing at the ES layer there is
any production system. The ideal
devices can also help in purchasing
no guarantee all services (including multi-viewer would give some type
proper tools,
and upgrade decisions. Also, over time
audio, video, text and other metadata) of status for all the data-streams
it is
problems may appear in your
are correct and without corruptions. present in the programme including
impossible
hardware or through software
Compliance violations at the RTP video, audio, text, and other service
upgrades. These trouble spots can be
to monitor
and transport level will generate data. True quality assurance of your
indentified early and dealt with before
the different
violations in the audio/video layer but real-time media means you would
they cause significant media quality
audio/video corruptions will not causeabstraction also do bit-stream conformance
problems.
compliance violations in other testing for all monitored programmes.
layers and
Verification of media parameters
abstraction layers. Testing on all the Having built-in conformance testing
compression
such as extra audio channels,
levels is the best strategy to ensure allows your engineers to test for
standards,
captioning, teletext, copyguard and
your media content is delivered ‘out errors on all of your delivery content,
ratings information becomes an easy
especially
the door’ as expected. This can be with alarms and logs for reporting
task if it is built into a bit-stream
when there achieved with a combination of RTP
purposes.
conformance tester since parameter
testing, ETR-290 testing, video
is such a
data must be extracted for detailed
conformance, audio level testing, and What happens when errors
massive
conformance testing. These media
corresponding metadata service are detected?
volume of
parameters can change every time
decoders.
your media content is edited,
data
After identifying problem media files
transformed or manipulated. The
involved.
Complete workflow testing before transmission, an off-line file
entire stream must be checked from based stream analyser is essential to
start to end and is most time efficient
Testing for conformance, media quickly trouble shoot the problem and
if it is combined with the conformance
parameters, and missing data should to validate a fix. There are many off-
testing process.
be done every time the content is line stream analysers on the market
The existence of a media stream
changed, such as after encoding, but few are capable of performing in
within your content is also easy for a
transcoding, or multiplexing. To be this environment because of the slow
conformance tool to check. For
practical, testing must be done by an analysis speeds coupled with the fact
example, if the media stream is
automated system, performed at that content media files tend to be
absent, then there is no data to run
speeds much faster than real-time so large. A fully optimised analyser that
conformance on. The conformance
that production throughput of your has faster than real-time analysis and
engine can also check other media
workflow is not adversely affected. fast playback is an absolute
stream detection rules while the bulk
Using tools that provide greater requirement for the production
of the work would already be done by
throughput allows operators the environment. When problems occur at
the conformance engine. Testing for
flexibility to test at more points in the the transmission stage, a real-time,
missing media streams can also help
workflow, catching problems earlier compression analyser with the ability
ensure completeness for regulatory
before they waste resources, and time to view the live content can help
requirements.
propagating to later stages. quickly identify and assess the
Real-time compliance testing can severity of the problems so that a
also be done on many of the different
Final line of defence solution can be found before viewers
layers that exist in your IPTV get upset. All of this is necessary to
environment, but the most important
Seeing is believing. Nothing can keep your operating costs low and
layer to look at is the elementary
convey the viewer experience better ensure the quality of service your
stream (ES). Compliance testing at
than seeing the actual programme customers demand.
42 l ibe l march/april 2009 l
www.ibeweb.com
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