Videotek VTM-2000 Specifications download pdf (Page 191)

Alarm Descriptions

VTM Series Installation and Operation Handbook

5-13

PID Error

A Packet Identifier (PID) error occurs when a data stream for each PID is not identified

for a period in excess of the range setting. The error might occur where transport

streams are multiplexed, or demultiplexed and remultiplexed.

ETR 290 2

Priority

The ETR 290 2

Priority menu contains the Transport Error, CRC Error, PCR Error,

PCR Accuracy Error, PTS Error, and CAT Error alarm settings.

Transport Error

The Transport Error alarm activates when the indicator that is a resettable binary

counter counts erroneous transport stream packets. The counter is intended for

statistical evaluation of the errors. If an error occurs, no further error indication should

be derived from the erroneous packet. There can be value in providing a more detailed

breakdown of the erroneous packets. Two examples showing the value of providing a

more detailed breakdown of the erroneous packets are:

• It provides a separate Transport Error counter for each program stream.

• It includes the PID of each erroneous packet in a log of Transport Error events.

CRC Error

The Cyclic Redundancy Check (CRC) checks for the Program Access Table (PAT),

Conditional Access Table (CAT), Program Map Table (PMT), Service Description

Table (SDT), Network Information Table (NIT), Bouquet Association Table (BAT),

Time Offset Table (TOT), Event Information Table (EIT), System Time Table (STT),

Master Guide Table (MGT), Virtual Channel Table (VCT), Region Rating Table

(RRT), and the Extended Text Table (ETT). A CRC Error alarm indicates if the

content of any selected table is corrupted.

PCR Error

A Program Clock Reference (PCR) is used to re-generate the local 27 MHz system

clock. If the PCR does not have sufficient regularity, the clock can jitter or drift and

the receiver/decoder can become unlocked. When irregularities occur outside the PCR

Error ranges, the PCR Error alarm activates. In Digital Video Broadcasting (DVB), a

repetition period of not more than 40 ms is recommended.

PCR Accuracy

A PCR Accuracy Error occurs when the synthesized color falls outside the set range.

A PCR accuracy of ± 500 ns is intended to be sufficient for the color subcarrier to be

synthesized from the system clock.

PTS Error

Presentation time stamps (PTS) determine the time when a picture is shown on the

screen. A PTS Error occurs when PTS is not detected in a signal. The PTS should

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Videotek VTM-2000 Specifications Page 191