Digital Signal Processing Reference
In-Depth Information
3.7.2 The Transport Scrambling Control Bits
The two Transport Scrambling Control Bits show whether the payload part
of a TS packet is scrambled or not. If both bits are set to zero, this means
that the payload section is transmitted unscrambled. If one of the two bits
is not zero, the payload is transmitted scrambled. A Conditional Access
Table is then needed to descramble the payload.
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
188 byte
4 byte
header
184 byte
payload
Optional
adaptation
field
Header
Optional
fields
depending
on flags
Adaption
field
length
Discontinuity
indicator
...
...
...
5 flags
PCR
8
1
5
4 2
b i t
Fig. 3.49.
Other details in the MPEG-2 transport stream
3.7.3 The Adaptation Field Control Bits
These two bits indicate whether there is an extended header, i.e. an adapta-
tion field, or not. If both bits are set to zero, there is no adaptation field. If
there is an adaptation field, the payload part is shortened and the header
becomes longer but the total packet length remains a constant 188 bytes.
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