- Service Description Channel 1 -
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Service Description Channel (SDC)

 

The SDC contains information about the multiplex: description, label, conditional access, frequency information, frequency schedule information, application information, announcement support and switching, coverage region identification, time and date information, audio information, FAC copy information, and linkage data.

 

SDC describes the audio coder used, and the parameters associated with that coder. It also provides information about the sampling rate and bit rate used. The SDC gives information on how to decode the MSC, how to find alternative sources of the same data, and gives attributes to the services within the multiplex.

 

multiplex description data entity - type 0

 

Each SDC block contains a multiplex description entity. This data entity uses the reconfiguration mechanism for the version flag. The current configuration can always be signalled. During a reconfiguration (when the FAC reconfiguration index is non-zero) the next configuration shall be signalled. This data entity describes the multiplex of streams within the MSC multiplex. 

 

protection level for part A

2 bits

this field gives the overall coding rate for data in part A

protection level for part B

2 bits

this field gives the overall coding rate for data in part B

description for stream 0

24 bits

data length for part A 12 bits

data length for part B 12 bits

Total bits

28 bits

FAC indicates hierarchical frame not present

 

 

 

  

 

 

 

 

 

 multiplex description type 0 (hierarchical frame not present)

  

protection level for part A

2 bits

this field gives the overall coding rate for data in part A

protection level for part B

2 bits

this field gives the overall coding rate for data in part B

description for stream 0

24 bits

protection level for hierarchical 2 bits

reserved future use 10 bits

data length for hierarchical 12 bits

Total bits

28 bits

FAC indicates hierarchical frame present

 

 

 

 

 

 

 

 

 

multiplex description type 0 (hierarchical frame present)

 

The stream description for stream 0 depends on whether the MSC mode field of the FAC indicates that the hierarchical frame is present or not. Other streams are optional.

 

When equal error protection is allocated to the multiplex frame (i.e. only one protection level is used) then the data length for the part A fields shall be set to 0 and the protection level for part A fields shall be set to 0.

 

When unequal error protection is allocated to the multiplex frame then the part A shall be the higher protected part and part B shall be the lower protected part.

 

label data entity - type 1

 

Services may be labelled. The label is sent in every SDC block to enable fast display, although for data services the repetition rate can be lowered.

 

short id

2 bits

id that relates the information to the service id provided by the FAC

rfu

2 bits

reserved for future use and set to zero until defined.

label

n bytes

variable length field of up to 16 bytes defining the label using UTF-8 coding. The length of the label is given by the length field of the header

 

 

 

 

 

 

  

conditional access parameters data entity - type 2

 

This data entity allows the conditional access parameters to be sent.

 

short ID

2 bits

field contains the Id that relates the information to the service ID provided by the FAC

audio CA flag

1 bit

0: parameters do not refer to an audio stream

1: parameters refer to an audio stream

data CA flag

1 bit

field indicates the CA system used by this service

CA system specific information

n bytes

variable length field containing CA system specific data.

 

 

 

 

 

 

 

 

 

 

 

 

alternative frequency signalling: Multiple frequency network information data entity - type 3

 

This data entity is used to provide receivers with information about the DRM frequencies on which the whole multiplex of services can be found.

 

It is also used to provide receivers with information as to whether the frequencies can be used for seamless alternate frequency checking and switching,

 

synchronous multiplex flag

1 bit

0: multiplex is not synchronous (different content and/or channel parameters and/or multiplex parameters and/or

signal timing)

1: multiplex is synchronous (identical content, channel parameters,  multiplex parameters and signal timing)

layer flag

1 bit

0: base layer.

1: enhancement layer.

service restriction flag

1 bit

0: all services in the tuned multiplex are available on the frequencies given.

1: a restricted set of services are available on the frequencies given.

region/schedule flag

1 bit

0: no restriction.

1: region and/or schedule applies to this list of frequencies

service restriction field

0 or 8 bits

4 bits short Id flags

4 bits rfa

region/schedule field

0 or 8 bits

4 bits region Id

4 bits schedule Id

 n frequencies

n 16 bits

1 bit multiplier

15 bits frequency value

 

The coverage area of the DRM multiplex shall be divided into one or more geographic areas. The areas may overlap at their edges or they may be distinct. Transmissions that are receivable within each area are signalled as members of the same group.

 

alternative frequency schedule data entity - type 4

 

This entity allows a frequency schedule to be transmitted. 

 

schedule ID

4 bit

0: not used

1..15 schedules

day code

7 bits

1000000    Monday

0100000    Tuesday

0010000    Wednesday

0001000    Thursday

0000100    Friday

0000010    Saturday

0000001    Sunday

start time

11 bits

indicates the time from when the frequency is valid. Time is expressed in minutes since midnight UTC

duration

14 bits

indicates the time when the frequency is valid. Time is expressed in number of minutes

 

 

 

 

  

 

 

 

 

 

 

 

 

 

application information data entity - type 5

 

All data services (or data applications for audio services) are described by this data entity. Many applications may require additional data to describe them that is specific to that application.

 

short id

2 bits

short id for the service concerned

stream id

2 bits

id of the stream which carries the data service concerned

packet mode indicator

1 bit

0: synchronous stream mode

1: packet mode

descriptor

7 or 15 bits

the format of this field depends upon the value of the Packet mode indicator field:

when Packet mode indicator = 0:

3 bits rfa

1 bit enhancement flag

3 bits application domain

when Packet mode indicator = 1:

data unit indicator 1 bit

data stream is:

0: single packets

1: data units

packet id 2 bits

application data

packet length

indicates the Packet Id carried in the header of packets intended for this service

1 bit enhance-ment flag

0 : no enhancement

1 : enhancement

3 bits

application domain

source of the data application specification:

0:     DRM application

1:     DAB application

2-7: reserved

8 bits packet length in bytes

data field of each packet (plus three bytes for header and CRC fields)

application data

n bytes

When the application domain carries the value 1, the application data field shall be made up as follows:

 

reserved future use 5 bits

 

user application identifier 11 bits specified in TS 101 756

 

data fields as required by  specification

 

 


 

announcement support and switching entity - type 6

 

This feature indicates which types of announcements are supported by the tuned multiplex or by another multiplex.

 

short id flags

4 bits

relates the information to the Service id provided by the FAC

rfu

1 bit

reserved for future use and set to zero until defined

same/other multiplex

1 bit

announcements are provided by:

0:  multiplex being received

1:  another multiplex

announcement support flags

10 bits

b10000000  travel

b01000000  news flash

b00100000  weather flash

b00010000  warning/alarm

b00001000  reserved

b00000100  reserved

b00000010  reserved

b00000001  reserved

announcement switching flags

10 bits

b (0...7)

0: announcement type not valid

1: announcement type valid

 

each bit defined as above

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

DRM background
COFDM
FAC
SFN
MSC
SDC data 1
Multimedia
Bandplan
DRM future
DRM links
DRM audio
FAC sync
DRM multiplex
DRM modes
SDC data 2