Cisco Headend System Release 2.7 Betriebsanweisung
Troubleshooting Scenarios
4022446 Rev B
79
Macroblocking Issues
Description
The picture on an SDV channel freezes, shows blocking, or shows tiling
(macroblocking).
(macroblocking).
Possible Causes
Some type of interference with the external signal.
The signal-to-noise (S/N) ratio is out of range.
The signal level is not within the acceptable working range.
Too much compression has been applied to the signal. (See pages 87–89 for steps
to troubleshoot.)
to troubleshoot.)
Diagnosing the Issue
See the following table to diagnose why the SDV channel is freezing, showing
blocking, or showing tiling.
blocking, or showing tiling.
Important:
The page number for the diagnostic screens may vary, depending on the set-top
model.
model.
Please check all of the diagnostic screens and fields contained in the following
table before you call Cisco Services. Various combinations of failures will point to
the source of any potential problems as listed in the following examples.
Examples:
table before you call Cisco Services. Various combinations of failures will point to
the source of any potential problems as listed in the following examples.
Examples:
If the signal levels are good, the S/N value is poor, and there is a rapid
change in byte counts, then noise ingress is present.
change in byte counts, then noise ingress is present.
If the signal levels are poor, the S/N value is poor, and there is a rapid
change in byte counts, then there is a "drop" problem.
change in byte counts, then there is a "drop" problem.
If the signal levels, S/N value, and byte counts are good, and a problem
continues to exist, an issue exists prior to the QAM or transport network.
continues to exist, an issue exists prior to the QAM or transport network.
Access the following
diagnostic screen.
Evaluate the
following field.
What value do I want
to see?
Page 1
–Status Summary
Tuner (or Tuner 1 if a DVR
set-top
set-top
Frequency level of inband
tuner should display in the
"white"
tuner should display in the
"white"
—acceptable range
-8dBmV to +8dBmV
—
recommended range
Note: If the tuner value
appears in amber or red,
check the signal levels.
appears in amber or red,
check the signal levels.