Triple-Play Service Deployment

Chapter 7: Troubleshooting Video Service in the Field
PSI Data Error
Video programming using MPEG-2 compression technology create
an elementary stream for the audio and video portions of a
program. And, there may be more than one audio flow included if
different audio formats are included such as surround sound,
2-channel stereo, or different audio language selections. Each of
these packet flows is assigned a PID number. Each program also
contains additional data inserted into the flow called program
specific information (PSI) which is organized into tables of data. Two
critical items are the PMT and PAT table data items which tell the
decoder how to identify and organize all of these individual flows.
The table data must be present in the streams at minimum
intervals as required in a given network design. In addition, the
table data can be scrambled by an encoder. Scrambling must be
off. Analyzing streams for these items is critical to determining the
video stream quality.
Transport Stream Quality
Transport quality refers to the operations of a video distribution
network regarding delivery of the video material or programming
as it relates to IP packets. Depending upon the network
architecture, this may include analyzing packet flows within
various protocols such as RTP or TCP over IP. The most critical
metrics are packet loss and packet jitter.These two metrics provide
a direct measure of network performance, but are difficult to map
to subjective QoE quality.
183