Triple-Play Service Deployment

160
Chapter 6: Troubleshooting Video in the Headend
Figure 6.6: The PAT and PMT tables are how the set top box identifies the programs and the
individual program elements. An analyzer that can decode the tables allows the user to verify
that the program elements have properly been identified by the encoder or any device that has
created a new multiplex of the MPEG programs.
Figure 6.6 illustrates an analyzer decode of the PAT and PMT tables.
With this protocol decode, a technician can confirm the
navigational information the set top box will use for this transport
stream. Descriptors (small tags of additional detail information) for
each program are also displayed here. Descriptors communicate
important program details to the receiver, such as audio type,
language, closed captioning information, copy control presence,
ratings, and more.
Figure 6.7 illustrates analysis of the PIDs present in a transport
stream. Here the technician can verify the components in the
stream and get details such as PID type and PID rate. Used in
conjunction with the PAT and PMT decodes, a technician can crosscheck
the MPEG PSI to the PIDs in the stream, confirming if the
PIDs a set top box will be expecting to see in the stream, are
actually present.