Deviser S7200 User Manual page 66

Part II: Settings and Measurements
Priority 2 Parameters
(1) Transport_error: Every MPEG-2 transport stream packet contains a bit called Transport Error Indicator
which is transmitted right after the sync byte. This bit flags any errors in the transport stream packets at
the receiver. During the transmission, bit errors may occur for various reasons. If error protection (at least
Reed Solomon in DVB and ATSC) is no longer able to repair all errors in a packet, this bit is set indicating
this packet can no longer be utilized by the MPEG-2 decoder and must be discarded.
A transport_error occurs when the transport error indicator bit in the TS header is set to 1.
(2) CRC_error: During transmission, all tables in the MPEG-2 transport stream, whether they are PSI tables or
other private tables according to DVB (SI tables) or according to ATSC (PSIP tables), are protected by a
CRC checksum. It is 32 bits long and transmitted at the end of each sector. Each sector, which can be
composed of many transport stream packets, is thus additionally protected. A CRC error has occurred if
these checksums don't match the content of the actual section of the respective table. The MPEG-2
decoder must then discard this table content and wait for this section to be repeated.
A CRC_error occurs when a table (PAT, PMT, CAT, NIT,...) in a section has a checksum that doesn't
match its content.
(3) PCR_repetition_error: The PCRs are used to re-generate the local 27 MHz system clock. If the PCRs are
not transmitted with sufficient regularity, then this clock may jitter or drift. The receiver/decoder may
even go out of lock. In DVB, a repetition period of not more than 100 ms is permitted.
A PCR_error occurs when
 The difference between two successive PCR values of a program is greater than 100 ms, and no
discontinuity is indicated in the adaptation field or Header Optional adaptation field, or
 The time interval between two packets with PCR values of a program is more than 40 ms.
(4) PCR_discontinity_indicator_error: Occurs when a discontinuity of the PCR values has not been signalled
appropriately by the discontinuity indicator.
(5) PCR_accuracy_error: Occurs when the PCR jitter exceeds ±500 ns.
(6) PTS_error: Occurs when the spacing between two PTS values is greater than 700 ms.
(7) CAT_error: An MPEG-2 transport stream packet can contain scrambled data, but only the payload must
be scrambled, never the header or the adaptation field. A scrambled payload is flagged by two special
bits in the TS header, called the Transport Scrambling Control bits. If both bits are set to zero, there is no
scrambling. If one of the two is not zero, the payload part is scrambled and a Conditional Access Table
(CAT) is needed to descramble it. If this is missing or only rarely there, a CAT_error occurs. The CAT has a 1
as PID and also a 1 as table ID. Apart from the EIT in the case of the transmission of a program guide, all
DVB tables must be unscrambled.
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