Triple-Play Service Deployment

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Interoperability and segmentation Test Case
Chapter 6: Troubleshooting Video in the Headend
Testing interoperability of equipment and isolating the source of MPEG problems
are common practices in digital video test.Two useful procedures are comparative
analysis of the MPEG stream at multiple test points, and simultaneous analysis of
multiple test points.
Digital video programs are created in an encoder and delivered via satellite to an
IPTV Headend by the content provider.The video is MPEG-2, and the IPTV operator
must convert this to H.264 for delivery over their DSL system. The provider
demodulates the RF satellite distribution and sends the MPEG-2 over DVB-ASI into
a transcoder.The output of the transcoder consists of MPEG transport streams, but
the video has been converted from MPEG2 to H.264 (MPEG-4). In this example, the
operator has observed occasional audio loss and tiling of the video on the
presentation of these programs.When TR 101-290 performance of these programs
at the egress of the IPTV headend is checked, consistent alarming for continuity
counter errors is observed. It may be assumed that the presentation issues are due
to data loss at the MPEG transport layer. The question to then be answered is from
where are the continuity counter errors originating?
To isolate the source, the technician must analyze the MPEG transport layer at
multiple test points back upstream (see Figure 6.10). With an MPEG analyzer that
supports a satellite RF interface, the technician can test the MPEG streams from the
dish before entering the IPTV headend. If the MPEG transport is suffering the same
errors from the dish, the technician can assume the problems are due to the
content provider’s network (encoder, multiplexer and RF distribution). If not, this
may indicate that problem originates in the IPTV headend. Working back towards
the egress, the technician can test at the input to the transcoder if the MPEG
analyzer has a DVB-ASI interface.Then, the technician may test again at the output
if the analyzer supports on Ethernet interface.