dvbserviceinformation-1211253359067242-8
Post on 23-Oct-2014
12 Views
Preview:
TRANSCRIPT
DVB-SI introduction
Presentation on DVB-SI
Srikanth Eswaran
2
PSI & SI – what are they
Program Specific Information (PSI) Defined in the MPEG-2 systems specifications
Provide information required to decrypt and display chosen event
PAT, PMT and CAT are three main tables in PSI
Service Information (SI) Information on available services
Frequencies which carry these services
Common interest categories/groups for these services
Events in a service
Network details of service help manage revenue flow to service providers
3
Impacts of errors
Errors in Audio – Video Cause annoyance to people watching the TV
Some glitches that users might put up with
No major revenue loss
Errors in Service Information Improper data display (EPG, etc) could make it difficult for users to make
purchasing decisions
Immediate loss of revenue for service provider
4
DVB Service delivery model
Refers to radio frequencies within the
RF spectrum 3Hz to 300 Ghz
Refers to radio frequencies within the
RF spectrum 3Hz to 300 Ghz
An automatic device that receives, amplifies, and retransmits a signal on a different frequency
An automatic device that receives, amplifies, and retransmits a signal on a different frequency
A sequence of programmes under the control of a
broadcaster which can be broadcast as part of a chedule
A sequence of programmes under the control of a
broadcaster which can be broadcast as part of a chedule
5
Why is PSI/SI required?
Automatic Tuning of receiver upon selection TSID and channel number are required to tune
Program location Program in BROADCASTING: set of elements having common start and
stop times
Program in MPEG: collection of elementary streams with same PCR_PID and program number
EPG (Electronic Program Guide) API (Application Programming Interface) CA (Conditional Access)
6
Table Structure – PSI & SI (MPEG-2 & DVB)
CAT
PAT
PCR
TSDT
SDTOTHER
TS
NITOTHER
Delivery Sys.
TOT
TIMEOFFSET.
RST ST
STUFFINGTABLE.
BAT
RUNNINGSTATUS.
SERVICEDESCRIPTION.
NETWORKINFORMATION.
EVENTINFORMATION.
BOUQUETINFORMATION.
NITACTUAL
Delivery Sys.
EITACTUAL
TS
SDTACTUAL
TS
TDT
PROGRAMMECLOCK REF.
PID=Ox0011
PID=0x0010
PID=Ox0011
PID=0x0010
PID=0X0012
PID=0X0012
PID=Ox0011
TIME ANDDATE.
PMT
EITOTHER
TS
EITACTUAL
TS
7
Table Structure – PSI & SI (MPEG-2 & DVB)
8
Example table associations - DVB
9
PAT & PMT
PAT Program Association Table
This table lists all the services found in this Transport Stream. Each service is identified by a PMT. The PAT is always on PID 0.
Program Map Table
This table identifies all the Elementary Streams within a service. There is one PMT per service, but there may be more that one PMT on the same PID.
10
Structure of PAT and PMT tables
11
SI Tables
NIT Network Information Table groups a number of Transport Streams together
provides tuning information for an IRD (Integrated Receiver Decoder).
For each different delivery mechanism (e.g. terrestrial and satellite) there is a different Network ID for same service
BAT Bouquet Association Table Provides group of services which are presented to the user as though they
were on the same Transport Stream.
The user may select different services within the bouquet, but be unaware that the IRD is in fact retuning its input to pick up a new transport stream within the network.
12
SI Tables
SDT Service Description Table provides a name, language codes, running status and country availability.
EIT Event Information Table
Present/Following information allows events on a service such as classifications like “running”, “not running”, “paused”, “starts in a few seconds”.
Schedule information is arranged by table, sub-table, segment and section into 3 hours blocks within which the program guide information can be transmitted.
In general, the EIT information may be scrambled, although different countries may provide regulations which restrict this practise.
13
SI Tables
TDT Time and Date Table Provides UTC (Universal Time) coded as MJD (Modified Julian Date)
TOT Time Offset Table Is used to provide time offsets to give local time.
RST Running Status Table These are sent out only once to update the status of an event. The RST
updates this information and allows timely automatic switching to events
ST Stuffing Table Used to replace or invalidate tables.
14
SI Tables for partial bitstreams
Partial bitstreams Are those that have only partial SI information corresponding to that
bitstream (for eg., recorded bitstreams)
DIT Discontinuity Information Table Used to inform a downstream device that transport stream information has
been removed and the stream may be a partial stream missing some SI tables.
SIT Selection Informative Table Used to inform a downstream device that Transport Stream
information has been removed and the streammay be a partial stream missing some SI tables.
15
Conditional Access Table
This table controls the scrambling of a service. It associates one or more CA systems with their EMM (Entitlement Management Message) stream and any other extra data that may be required.
CAT contents
This gives info that customer is authorized to decramble channels using ECMs that appear
later
16
PMT with CAT information
This has the control word that is sent to CA module
on receiver side to descramble the channel
17
How are the tables packed into transport streams?
Concept of Sections Syntatic structure used to map MPEG-2 & SI tables into TS packets Sections within each table limited to 1024 bytes, except EIT (4096b) Elements of a section
Table ID – which table is being referred to
Table ID extension – which subtable is being referred to
Section number – applies only to sub tables
Version number – indicates newer versions of table sent earlier
Current next indicator – ‘now’ or ‘next’ – either table to be used for current event transmissions or for future!
Mapping of these tables into TS packets (ordering, stuffing, etc)
18
PID values for SI table sections
19
Values for table_ids
20
NIT section syntax example
21
EIT section syntax example
22
Descriptors in tables
Boquet name example in BAT
CA identifer descriptor
23
Descriptor tags
24
Service information acquisition and storage
Mode of transmissions and receptions Data and object carousel way of transmitting schedules
SI parser on receiver end, which extracts PAT, PMT, SDT, EIT table information to retrieve mainly the list of services and events
Storage considerations Embedded database to store information from these tables particularly the
EIT and SDT to reproduce on EPG screen when requested by user
Customized databases, or choice of DBs like SQ-Lite (self-contained, serverless, zero-configuration, transactional SQL database engine)
Compression – any technique or using libraries such as zlib
Persistency of the DB cache into flash in file format
25
References
Digital Video Broadcasting (DVB); Specification for Service Information (SI) in DVB systems
ETSI EN 300 468 V1.3.1 (1998-02) - http://tinyurl.com/5ylbvb Interactive TV Web - http://www.interactivetvweb.org/ Neil Pickford - Communications Lab - http://happy.emu.id.au/lab/ DVB SI Basics - Snell and Wilcox - http://www.snellwilcox.com Digital Video Broadcasting - Instituto de Telecomunicações - Pólo de
Aveiro - http://www.av.it.pt/ ATSC - http://www.atsc.org SQLite - http://www.sqlite.org
26
Thank you !
Questions?
top related