dvbserviceinformation-1211253359067242-8

DVB-SI introduction

Presentation on DVB-SI

Srikanth Eswaran

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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

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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

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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

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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)

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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

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Table Structure – PSI & SI (MPEG-2 & DVB)

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Example table associations - DVB

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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.

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Structure of PAT and PMT tables

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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.

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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.

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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.

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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.

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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

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PMT with CAT information

This has the control word that is sent to CA module

on receiver side to descramble the channel

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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)

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PID values for SI table sections

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Values for table_ids

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NIT section syntax example

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EIT section syntax example

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Descriptors in tables

Boquet name example in BAT

CA identifer descriptor

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Descriptor tags

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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

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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

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Thank you !

Questions?