Measurements on the MPEG-2 Transport Stream - Digital Video and Audio Broadcasting Technology - page 193

whose PID is not indicated by this mechanism, the so-called unreferenced
PIDs. According to DVB, an unreferenced PID may be contained there
only for half a second during a program change.
An unreferenced_PID (Fig. 11.10.) occurs when

• a packet having an unknown PID is contained in the transport

stream and is not referenced within a PMT after half a second at
the latest.

188 byte

4 byte
header

184 byte
payload

Optional
adaptation
field

Header

Transport
error
indicator

Payload
unit start
indicator

Transport
scrambling
control

Adaptation
field
control

Sync
byte

Transport
priority

Continuity
counter

PID

8 1 1 1 1 3 2 2 4 B i t

Fig. 11.10. Unreferenced PID

11.15 Errors in the Transmission of Additional Service
Information

Apart from the usual information, additional service information
(SI_other_error) can be transmitted for other channels, according to DVB.
These are the NIT_other, SDT_other and EIT_other tables.
The SI_other tables can be recognized from the PIDs and table_IDs in
Table 10.4. also lists the time limits.
An SI_other_error occurs when

• the time interval between SI_other tables is too great,
•

the time interval between SI_other tables is too small.