Service Information(SI) • As defined by : ETSI Well we have adopted it ! What is it ? Compiled by Wayne Dickson SMIREE MIEAust. CPEng. Member SMPTE WTD
Is it needed ? Service Information(SI) • DVB Service information is an enhancement of MPEG PSI (Program Specific Information) • It provides extra information which the receiver can use. • Although MPEG PSI is all that basically essential, as the receiver will be designed to require DVB SI, DVB SI will also be essential. • Hence FACTS has to study and recommend the requirements for Australia.
Past Analysis of : DVB SI ATSC PSIP Current FACTS SI Project Group studying DVB SI for suitability for Australian conditions. Standards Australia Receiver and Transmission working groups developing requirements Future Australian study groups to change DVB/ETSI Standards to avoid a unique Australian standard. STATUS Service Information(SI) Found DVB SI best fit to DVB Modulation for Terrestrial, Cable and Satellite. ATSC PSIP is a restricted SI set to suit ATSC 8VSB Terrestrial and QAM on Cable plus NTSC. It may prove to have increased efficiency compared to DVB SI for the ATSC system.
PURPOSE Service Information(SI) • Required for : • Automatic Tuning of receiver upon selection • Programme location • EPG (Electronic Programme Guide) • API (Application Programming Interface) • CA (Conditional Access)
Structure Service Information(SI) • Before an explanation of how the basic requirements are provided by the DVB SI, an understanding of the structure of DVB SI is required. • The DVB SI structure has it’s derivation in MPEG ISO/IEC 13818-1 and is defined in a set of tables. • The primary link between DVB SI and MPEG is the“PSI” (Program Specific Information) in MPEG and is contained primarily in the “PAT”, “PMT” and “CAT” set of tables
NIT ACTUAL Delivery Sys. PID=0x0010 PID=0x0000 NETWORK INFORMATION. PID=P BOUQUET INFORMATION. BAT PMT SDT ACTUAL TS SERVICE DESCRIPTION. PID=Ox0011 EIT ACTUAL TS EIT OTHER TS PID=Ox0001 CAT EIT ACTUAL TS EVENT INFORMATION. PID=0X0012 PID=0X0002 PCR TSDT TOT PID=0X0012 TDT TIME OFFSET. PSI and DVB SI Tables DVB OPTIONAL MPEG DVB MANDATORY NIT OTHER Delivery Sys. PID=0x0010 PAT PID=Ox0011 SDT OTHER TS PID=Ox0011 ST RST STUFFING TABLE. PROGRAMME CLOCK REF. RUNNING STATUS. TIME AND DATE.
General • What is a program ? • MPEG has a definition which is different to that normally understood. • A “programme” in broadcasting is a collection of elements with a common time base and the same start and stop times. • A programme in MPEG is a collection of elements with a common time base only. That is a collection of elementary streams with same PCR_PID and referenced to the same program_number
General contd. • Hence a conventional Broadcaster of a TV channel or service having one program would be composed of a series of “broadcaster programmes” or events with the same program_number and a common PCR_PID. • In other words the PCR time base effectively creates a virtual channel which may be associated with a single or multiple program_numbers. • A TV channel having multiple programs would have multiple program_numbers with either single or multiple PCR_PID between program streams. • NOTE : Services with different program_numbers may draw upon the same video as with the case of multilingual srevices.
General contd. • Decoding the correct program (ie “channel”) ? • Where there are several Transport Streams available to a decoder, in order to successfully demultiplex a program, the decoder must be notified of both the transport_stream_id (to find the correct multiplex) and the program_number of the service (to find the correct program within the multiplex). • Note again the program here refers to the channel not the event or actual broadcast program. • Now to the various main table purposes :
Table Functions(MPEG) • PAT (Program Association Table) • provides the link between the transport_stream_id, the program_number and the program_map_id (PMT). • PMT (Program Map Table) • when pointed to from the PAT, the PMT provides the associated group of elements (video, audio etc) with the program_number. • CAT (Conditional Access Table) • provides the association between CA system(s) and their EMM (Entitlement Management Messages) streams and any special parameters associated with them.
Table Functions(DVB SI) • NIT (Network Information Table) • provides a grouping of Transport Streams and tuning information such as channel frequencies and modulation characteristics. • SDT (Service Description Table) • lists the names and other information of all the services contained within the Transport Streams. • EIT (Event Information Table) • contains information about present, following and future events.
Table Function linked toDVB SI Purpose • Automatic Tuning of receiver upon selection • from the information contained in the NIT and subsequently the PAT and the PMT the decoder tunes automatically upon selection within some version of an EPG. • Programme location • an event selected via an EPG would be indentified by a programme stream which would be located via the PAT and PMT associated with the selected Transport Stream.
Table Function linked toDVB SI Purpose • EPG (Electronic Programme Guide) • Combining primarily the EIT and the SDT, both the time and description is provided to the viewer via some form of EPG ranging from “vanilla EPG’s”, simple “eye plate style” displays to full blown EPG’s, either from Receiver manufacturers designs or downloaded EPG’s with GUI interfaces designed by the Networks. • This information so constructed and displayed can be used to provide a Parental Guidance lock function through PIN number access.
Table Function linked toDVB SI Purpose • API (Application Programming Interface) • some form of API must be used to allow the control by the viewer or installer of the decoder / receiver. The API software provides the connection between the applications (eg. EPG) and the hardware. • Some API’s may employ MHEG-5 multimedia support and Java programming language for EPG generation. • CA in practice is reliant upon EPG’s and the API’s.
Table Function linked toDVB SI Purpose • CA (Conditional Access) • connection to the EMM is provided by the CAT. • the EMM allows a single decoder to view the programme material which is scrambled via a DVB “common scrambling algorithm” by providing the key to the code word which is involved in the scrambling. The code word is sent via the ECM (Entitlement Control Message).
QuestionsSome of many ! • Does each Network have to carry each others EPG information ie carry each others EIT and SDT ? • Is there a need to define a minimum receiver requirement for : • API’s ? EPG ? CA ? Memory ? • How will the Australian Parental Guidance fit into DVB SI ? • What data overhead will be allowed for SI ? • How will SI be managed in the Network and in translators ? • How will time zone scenarios be managed ?
QuestionsSome of many ! • How will Software downloads to consumers be managed from the individual Networks ? - eg EPG enhancements • How will a particular receiver manufacturer manage software downloads for his sets alone ? • each manufacturer will have a unique recognition of the header of software • how is it reliably sent out ? It has been suggested that up to 20 minutes could be required where the receiver cannot receive ! • Will receivers be required, in the “standby” mode, to scan all multiplexers and download SI (EPG in particular) and any software (Networks and manufacturers ) ? • What will the refresh rate and overhead be required in the multiplex for SI including CA ? • Your QUESTIONS ?