CA2177735A1 - System and method for providing compressed digital teletext services and teletext support services - Google Patents

Abstract

A teletext system provides teletext services and teletext support services in a multiservice communica-tion system. Multiplex data streams for a plurality of services, including teletex data, are transmitted in a se-quence of frames between a transmitter location and a receiver location. Teletext information is transmitted in the format of a header packet and a data packet. The header packet contains information identifying the tele-text information according to page number as well as other filter fields, such as language (filter 4), time zone (filter 2), etc. By appropriate selection of the values of the filter fields, the operator is afforded greater flex-ibility in providing a variety of classes of service and service support to subscribers. In addition, the system may easily be reconfigured to support the addition of services or the cancellation of services.

Description

WO 95/156 ~7 2 1 7 7 7 3 5 Pcrlus9~l38~6 -- 8Y8TE~ AND METROD FOR PROVIDING COMPRES~ED DIGITA~
~EL~TE8T 8ERVICE~ AND TE~ETE~T 8~PPORT ~ERV~CES
This application is related by subject matter t~
U.S. application serial no. 08/161,160 entitled "System and Method for Transmitting a Plurality of Digital Services Including Imaging Services~ (44639-A-542) serial no. 08/160,~28 entitled "System and Method for Transmitting a Plurality of Digital Services Including Compressed Imaqing Services and Associated Ancillary Data Services" (44640-A-545), serial no. 08/161,840 entitled "Memory Efficient Method and Apparatus for Synch Detection" (44641-A-546), serial no. 08/161,159 entitled "A Multi-Service Data Receiver Architecture" (44642-A-547), serial no. 08/160,848 entitled "System and Method for Simultaneously Authorizing Multiple Virtual Channels"
(44643-A-550), and serial no. 08/160,830 entitled "System and Method for Trans~itting and Receiving Variable Length Authorization Control for Digital Services" (44643-A-554), filed concurrently herewith, and is a continuation-in-part of serial no. 08/101,974, entitled "Method and Apparatus for Uniquely Encrypting a Plurality of Services at a Transmission Site", filed August 4, 1993.
I. BaC~G~ of th- Inv-ntion A. Fi-ld of the Inv-ntion The present invention relates generally to digital signal transmission, and more particularly, to a system and method for providing digital services, including compressed teletext services and teletext support services, for selective display at a plurality of remote locations.
B. D-scriDtion of the Relevant Art With the growing trend toward a merger of the previously separate technologies of telecommunications WO 9S/1564~ 2 1 7 7 7 3 5 PCT~TSg~l38~6 including voice and data telecommunications and television including satellite, broadcast and cabie television, there has emerged an increased interest in developing adaptabie transmission systems capable of handling any one or more of a collection or plurality of such services The primary media investigated for providing such services to date comprise, for example, co~xi~l cabl-, land-based microwave, so-called cellular radio, broadcast FM, bro~cAst satellite and optical fiber, to name a few Each media has its own characteristics For exampl-, comparing cable and satellite for digital data transmission, cabl- tends to have a medium error rate, but, when errors appear, the errors come in long bursts Satellite as a media has a pretty poor error rate, primarily due to the requisite weak signal power, and hence, low signal to nois- ratio In satellite, then, the poor error rate i~ specially corrected utilizing such t~r~nique~ a~ convolutional error corrector~, not required in a cable environment In cop~n~ing U S application serial no 07/968,846 filed October 30, 1992 and entitl-d "System and Method for Trantmitting a Plurality of Digital Service ," there is de~crib d an enc~Asr for generating a multiplexed data stre~o c~rrying servic-s to remote locations via, for ex~cple, a satellite or a cable distribution network The gen-rated data stream comprises a continuous sequence of fra~ s, each frame comprising two field~, and each field comprising a plurality of lin-s A first group of lines of a field defines a transport layer and a second group of linc defines a service data region A feature of th- disclo~ed scheme is the ability to dynamically vary the multiplexcd data stream from field to field A

W09S/lS647 2 1 7 PCT~s9~/~38~

further feature of the disclosed scheme is that the data transmission rate of the multiplexed data stream is related to the fre~uency of known ~nalos video formats, i e frame, field and horizontal line rate~
In copending U S application serial no 07/970,918 filed Novemb-r 2, 1992, entitled "System and Method for Multipl-xing a Plurality of Digital Program Services for Tran~mission to Remote ~ocations, n there is described another system, this for` multiplexing a plurality of digital ~G~.am ~ervice~ compri~ing a collection of, for exampl-, video, audio, telet-xt, closed-captioning and "other data~ services According to the disclosed sch-m , a plurality of subframe data streams are gen-rat-d, each having a transport layer region and a y~ am data region These subframe data streams are then multiplexed together into superframes having a transport layer region and a subfram- data region While these disclosed transmi~ion systems permit a variety of ~ervices to be transmitted over various media to remote locations, there remains a need to provide yet other alternative arrangements more particularly adapted to th- wide variety of s-rvices that may be offered over various media and per~it th- end user at the remote location greater flexibility ov-r th- data content the u~er i~ ulti~ately enabled to receive I~cover, such a gyst-m ~h~~ b- able to be easily adapted to transmit an increasing number of different services in an increasingly efficient manner, for example, utilizing the same or less bandwidth In such multiservice communication systems, it is desirable to provide a teletext (sometimes referred to herein a~ "TTX") system TTX system~ included in the broader communication system may accomplish several WO95/156~7 2 1 7 7 1 3 5 Sg~/138~6 functions The TTX system may provide support to facilitate operation of the decoder by the subscriber Such support may take the form of menu pages, help pages, and/or program guides In addition, the TTX system should supply TTX services per se, such as stock reports, weather reports, and news Furthermore, the TTX system should provid- support for individual services included in th- multipl-xed signal For example, TTX support can facilitat- impulse pay-per-view (IPPV) purchases of television ~-rvice~ or provide the current program name for t-levision or radio services U S Patent No 4,866,770 provides an example of a teletext system i~o~orated into a multiservice system Teletext information is transmitted in a B-type multiplexed analog components (B-MAC) signal using two typ-~ of data format a teletext header and a text line The teletext h^a~Pr contains control information and the pag- nu~ber of the subsequent text page The text line contains a lin- of ASCII characters The display of TTX
information ~ay be initiated by either the ~ubscriber or by the system op~rator In ~ G~e, th- ~eco~r grabs the a~LG~iat- TTX page from the receiv-d signal and generate a t-xt mes~age therefrom The text message is th-n diQplay d Accordingly, the only way to distinguish betw-en TTX pag~s i~ according to page number In an analog environm-nt (- g , B-MAC), the number of s-rvtc-a (a g , radio, television, TTX or data) is limit-d typically to les~ than l0 services per multiplexed signal The TTX syst-m is implemented by allocating a pag- range from a maximum, g of 0-65535 (or 0000-FFFF in hexadecimal), for each specific TTX use In one such allocation, the page range 0-l000 may be restrict-d to TTX support of television services Once wogs/15~7 ~ 2 1 7,773 P~T~TS9~138~6 the definition of page ranges are allocated, they are fixed for the life of the system Thereafter, the configured system must support all possible services at all future times Furthermore, there is no other way to distinguish between teletext page~ except according to page number As a consequence! every different teletext page must have a different pag~ number, and the maximum page rang- ~erves as an ab~olute limit on the number of page~ that may be transmitted in the system Thus, rurrent t~let-xt ~ystem~ are inflexible ~T 8U~a~ 0~ t~ ~tio~
It is an ob~ect of the pres-nt invention to provide a teletext system in a multi-servics co~unication ystem having a high degr-- of flexibility of implementation It i~ a further object of the present invention to provide a telet-xt system in a multi-service communication system having a plurality of filters so that telet-xt pages may be may distinguished between on the ba~is of ~everal criteria It is a further ob~ect of the present invention to provide a teletext ~yst-m in a multi-service communication sy-t-m that permits each ~ervice to have the maximuc pag- range It i~ a further object of the invention to provide a t-l-t-xt y-t-m in a multiservice communication system th~t may b~ dynamically configured by a sy~tem operator The above object~ of the pr-sent invention and oth-r~ ar- achiev-d by a tel-t-xt system in a multi~ervice co~munication system in which teletext service and service support are implemented through a plurality of filter fields, including a page number field, in t-l-t-xt header packet~ By controlling the filter values of the filter fields, the operator may WO 9S/15617 2 1 7 7 7 3 5 Pcr/usg 1/138~6 selectively provide particular teletext services and/or service support to a particular class of subscribers without being limited by page number The present inv-ntion is highly flexible because the operator can configure the system in any way utilizing the filter fields when s~rvices are added or dropp-d Furthermore, the operator may define additional filter fields or redefine existing fields as the need arises The provision of filters ~Yra~S the range of choices that th- operator may mak- availabl- to th- subscriber B~S~r D~SC~YT~0~ or T~F D~A~S~8 A more complete appreciation of the present invention and many of the att~n~nt advantages thereof will b- readily obtained as the invention b comes better understood by reference to the following detailed description wh~n considered in connection with the accompanying drawing~
Figuro 1 is a system block diagram showing a transmitter sito 100 including an encoA~r and a receiv-r site 150 including a decoder according to the present invention for tran mitting control, low data rate, medium data rate (audio) and high data rate (video) data implement-d in a ~atellite communication~ ~ystem Figure 2A i~ a diagram ~howing a scalable multiplex frao-, including ~ynchronization words B~OCX SYNCH (also r-~ rred to h-rein as HSYNCH) and FRAME SYNCH, for tran~itting a digital data stre~m of low data rate (included within PACXETS), medium data rate (audio) and high data rate (video) data protected by Reed-Solomon ~nco~ing according to the present invention Figuro 2B is a ~-:on~ diagram of the frame of Figure 2A wherein the PACXETS area is further broken down into first and second regions, the first region including WO 95/156.~7 2 1 7 7 7 3 5 PCT~TS9~/138~6 packets with extra error protection and the second region including data protected only by Reed-Solomon encoding Figure 2C is a diagram showing that a sequence o f fra_-s in the form of Figure~ 2A or 2B are tran~mitted to a receiver according to the present invention Figure 3 is an encoder bloc~ diagram for one preferred embodiment of a portion of transmitter 100 of Figure 1 showing the connection of audio and video compres ors and low speed data formatters to a multiplexer under cG ~ol of a control computer for modulation by a modulator on to a carrier for transmission, for exampl-, by satellite as shown in Figur- 1 Figure 4 is a detail-d schematic block diagram of a multipl-x-r 110 of Figur-- 1 or 3 according to the present inv-ntion for ou~u~ing multiplexed data according to th- ~ultiplex fram- format of Figures 2A, 2B
and 2C
Figur- 5 depicts one pr-ferred embodiment of a teletext he~ row packet Figur- 6 d~picts on- preferr-d embodiment of a teletext data row p-~ki~
Figur- 7 illustrat-s a first embodiment of multiple pag~ grab logie in th- teletext Qy-t~
Figur- 8 illustrates a cond embodiment of multiple pag~ grab logic in th- telet-xt ~ysts~
Figur- 9 illustrates one pr-ferr-d embodiment of a filter co~parator Figurs 10 depicts on- pr-ferrod emh~iment of an aggregatQ filter co~parator depicted in Figures 7 and 8 Figur- 11 d-pict~ an example of a television service configuration according to the pre~ent invention W095/15647 2 1 7 7 735 PCT/liS9~/13846 _ Figure 12 depicts an example of a television and radio service configuration according to the present invention Figur-s 13A and 13B illustrate examples of text pages associated with the television and radio service configuration of Figure 12 Figure 14 illustrat-s the teletext header row and text row p~ckets uscd in implementing the text pages of Figures 13A and 13B
Figur- 15 d-picts an exa~ple of a television and multiple radio ~ervice configuration according to the ~L ~ ~~nt inv-ntion Figur-s 16A, 16B, and 16C illustrate examples of text pag-~ associat~d with the television and multiple radio service configuration of Figure 15 Figure 17 illu~trates the teletext header row and tsxt row p~c~ used in implementing the text pages of Figur-~ 16A, 16~, and 16C
Figur~ 18 depicts an example of a television with time zone and multipl- radio ser~ice configuration according to th- ~L ~s-nt invention Figur-~ l9A-19D illu~trat- xampl-s of text pages a~sociated with the tslevision with time zone and multiple radio ~er~ic- configuration of Figure 18 Figur- 20 illustrates the t-l-text h^a~^r row and text row pack-t~ used in implementing th- t-xt pages of Figur-~ l9A-19D
Figur- 21 depicts an example of a television with time zone and captions and multiple radio service configuration according to the pre~ent invention Figur- 22 depicts an example of the scope and rights of a teletext administrator Wo 9S/156~7 2 1 7 7 7 3 5 PCI/I'S9`~/13816 _ Figure 23 depicts an example of the scope and rights of a teletext administrator, ~ television manager, and a radio manager Figures 24A-24C illustrate text pages that may be created according to the example of Figure 23 Figur- 25 depicts an example of the scope and rights of a teletext administrator, a television manager, a radio manager, and two radio ~ervice users Figur-~ 26A-26B illustrate text pages that may be created according to the example of Figure 25 Figur- 27 depicts a first exampl- of the scope and rights of a teletext admini~trator, a t-levision manager, a radio manager, two radio service users, and a television time zone user Figure 28 illu~trate~ a text page that may be cr-ated according to th- example of Figure 27 Figur- 29 depicts a first exampl- of the ~cope and rights of a teletext administrator, a television manager, a radio manager, two radio service users, and a television tim- zon- user Figure~ 30A-30B illustrate text pages that may be created according to th- example of Figure 29 Figur- 31A illustrat-s an exa~ple of a template page Figur- 31~ illustrates a completed page ba~ed on the t-mplat- page of Figure 3lA
Figur-~ 32A-32B illustrate a possible page allocation ~or the deco~er embodiment of Figure 8 Figur- 33 illustrates a pos~ible correlation between TES ~ and service Figure 34 illustrates a possible page allocation for the decoder embodiment of Figure 9 WO9S/15~7 2 1 7 7 7 3 5 pcT~ss~ll38~6 D~Tr~ ~n DE8CRIPTlON OF T~ DRA~INa~
Figure 1 shows a transmitter site 100 including an enco~or and a receiver site 150 including a decoder according to the present invention applied in the environment of a satellite communications system Audio/vid-o compre~sor circuits 101(1) to 101(m) are shown for individually receiving audio ~-rvice data and/or video service data, for example, from a plurality of ~. G~L a~m-rs providing such services One such MPEG
video compr-ssor known in the art is a National Transcommunications, ~td (England) NTL 2000 V
compressor Similarly, a pluraiity of low data rate ervic-~, for xampl-, RS232 digital data, are received at low sp-ed data formatters 105(1) 105(n) Tha audio vid-o compre~sors compress the receiv-d medium and high data rate data in accordance with known algorithms (for example, in accordance with currently known or proposQd s~anAards such as MPEG I or II, audio or video, in particular, for example, ISO 11171 or ISO 13818) Control comput-r 120 ~upplies control information, preferably a- d_ta packet~, to the multiplexer 110 For example, th- dat_ pack~ts may be con~tructed by the control comput-r according to specified formats .e~ron~iv- to th- ntry of appropriate inQtructions into CO~LO1 co~put-r 120 Accordingly, the operator can ol the various modes of authorization made available by th- pr~sent invention Furthermore, control computer 120 may gonerat- tQletext data The t-letext data may or may not be compressed In addition, control computer 120 controls multipl-xer llO to time division multiplex the compressed medium and high data rate streams output from compressors 101(1) to 101(m) and the low data rate streams output from formatters 105(1) to 105(n) into a serial data WO 95/lS6.17 2 1 7 7 7 3 5 P~f~S9~/138~6 stream for output to modulator 130 The high speed data link connecting multiplexer 110 and modulator 130 may be coaxial cable, optical fiber or twisted pair, so long as the tran~mis~ion is relatively noise free and at sufficient data rate In a preferred, but nonetheless nonlimiting, embodiment the control informa_ion and the data streams are encr~pt-d Modulator 130 then modulates the multiple~ed digital data stream on to a carrier and up convert~ the carrier as necess~ry for transmission via, for exampl-, C or Xu band frequencies through a satellite antenna 140 Modulator 130 may preferably compri-~e a quadrature phase shift key modulator known in the art for ~atellite transmis~ion Satellite antenna 140 beams a signal including the modulated data to satellite 160 which may be functionally referred to as a transponder Tran~ponder 160 simply r-peats the received signal toward earth and ~atellite receiver antenna 151 Receiv-r site 150 typically includes a tuner/demodulator 154 for selecting onc of a plurality of channels to which ~atellite tuner/demodulator 154 may be tuned Tuner/d-~odulator 154 down conv-rts and outputs a demodul_ted data stre_m to clock and data recovery circuit 155 Clock and data recovery circuit 155 in turn outputs an rror corrected data stream and synchronization data to demultiplexer 158 Additional in~ormation cG :~rning a suitable clock and recovery circuit may be obtained from U S Pat-nt Application SeriAl No (Attorney Docket No 44852-A-549), entitled "Method and Apparatus for Locating and Tracking a QPSR
Carrier", filed concurrently herewith and incorporated herein by reference A user may input a selected channel via a selQctor, g remote control or using push buttons on a panel thereof, etc The selector will be referred WO 95/15647 PCTIUS9~/138'16 _ to herein as KBD 156 The channel selection information i sent to display control processor (DCP) 153 Under the control of DCP 153, the demultiplexer 158 outputs control information corresponding to the ~elected channel to DCP 153 The control information may be encrypted as di~cus~ed above Accordingly, th- DCP 153 supplies the encrypt-d control information to digital compression in-board ~-curity element (DI~E) 157 DISE 157 decrypts the CG~.~ ol information and det-rmines whether the decoder is authoriz-d to receiv- th- ~elected ch~nn~l If ~o, the DISE 157 ~upplies location information and d-cryption information to th- demultiplexer 158 via DCP 153 The demultiplexer 158 locates, demultiplexes (i e extracts), and decrypts th~ data stream and then provides the demultiplexed data streams to variou~ output ports to sub~cribQr equipm-nt 159 via peripheral data processors 152 In one pr-ferr-d ~mbodiment, th- demultiplexer is an application specific integrated circuit (ASIC) Furth-r details concerning the operation of the demultiplexer 158 and th- peripheral data yL._e~sors 152 may be obtain d from U S Pat-nt Application Serial No.
(Attorney ~o~k~L No 44642-A-547), entitled "A Multi-Servic- Data R c-iv-r Architecture~, filed concurrently h ewith and which i~ i ~oL~oLat-d herein by reference D-tall~ of a TTX proce~or will be discussed in greater d-tail b low Th- u~er or subscriber equipment may comprise, for exa~ple, st~n~d or high definition tel-vision reception equipm-nt, digital audio ~_eyLion equipment, digital data yrc_ -~ors or computers, vid~o game equipment, fac~imile receiver/printer~, energy management equipment and the like WO 9S/lS647 PCTI~ S9`~/138.16 21 77~35 The receiver site 150 may not only be a subscriber to services but may be a provider of services such ~s a cable television system operator In such a scenario, the receiver site 150 may not ~nclude typical subscriher equipment 159 but may include cable television system headend equipment known in the art including television modulator~ and digital audio service providin~ equipment and the like Referring now to Figure 2A, ther- is shown a generic frame having highly flexible characteri~tics However, it will b- L-C~J iz-d that th- pre~-nt inventiGn may be practiced in connection with other data frame structures, whether they are more flexible or le~ flexible than that de cribed below, without significantly diminishing the advantages of the pre~-nt invention The ~tatic or fixed elements of the depicted ~calable multiplex according to the pre~ent invention are BLOCK SYNCH (or HSYNCH) and FRAME SYNC All oth-r depicted elements of the frame are flexible and may change from medium to medium and from frame to frame For example, Reed-Solomon error correction parity data may be provided for satellite tran~mi~ion and omitted for le ~ error prone forms of media PAC~rS data compri~e~ co,~.ol information as well a~ low ~p-~d data services, such a~, for example, TTX
data ~loL.over, the delineation bctween what is shown as PACRETS data and areas fQr medium speed (audio) and high speed (video) data portions are flexible, and the figure is not intenA-~ to show that the h~n~rie~ between such form~ of data i~ fix-d at any one point in the frame A
predetermined structure is provided to the frame in that FRAME SYNCH follows the first byte of HSYNCH in a frame according to the prescnt invention PACKE~S data follows WO 9S/15647 2 1 7 7 7 3 5 PCI/US91/138~6 _, FRAME SYNCH, followed in turn by medium speed (audio) and high speed (video) data in that order There will always be so2e PACKETS data for control purpo~es but depending on the prioritie~ of data services to be tran~mitted there may not exist low speed data portions thereof, mediu~ speed data ~ection~ or high speed data sections of a particular frame A more detailed discussion of the data fram- structure is found in U S Pat-nt Application Serial No (Attorn~y Docket No 44639-A-542), entitled "Syst-m and Method for Tran~itting a Plurality of Digital Service~ Including Imaging Servic-s, n filed concurr-ntly h-r-with and which is incorporat-d herein by referenc- ~urther details concerning HSYNCH and FRAME SYNCH determination and L.cov~ry at a r-ceiver may be found in U S Application Serial No (Attorn-y nO~ No 44641-A-546), entitled "Memory Efficient M thod and Apparatu~ for Synch Detection, n filed concurrently herewith and incorporated herein by ref-r-nce The t-rm PACXETS is intended to refer to a collection of, for example, C6~ 01 or system data block~
which ar- intended to siqnal or CO~LO1 a rec-iver to, for xa~pl-, id-ntify th- data typ-~ or data sQrvices and th- r-~p-ctiv data beginning and ~n~n~ boundaries to follow Th- co ~ol data blocks may serve to limit the variety of ~ervices available to an end user as well as provide a ba~ia upon which the end u~er may control his rec-iv-r to r-ceive and output data ~rvices as he choo~-~ In other word~, according to ~o~- applications, th~ u~-r's ~-lection of ser~ices may be limit-d by their on-hand equipment and their pr-fe~nc~ to particular ones of th-e authorized servic-~ in particular WO 95/156~l~ 2 1 7 ;7 7 35 PCI`~S911138-16 -arrangements of the various multiplexed data streams or block~ that follow in the data stream Low speed data refers to teletext, facsimile, conditional access, alarm, energy managem-nt, certain audio and other data streams which typically exhibit data rates of le~c than sixty-four kilobytes per second Medium speed data refers to more ~ophi~ticated forms of audio such as "su~ound ~o~nAn and medium speed data rates between, for example, 64 kilobyte~ per second and Tl carri~r or Dl (telecommunications) rates of approximately one megabit pcr ~con~ High speed data refers to som- compress-d forms of vid-o transmi ~ion up to data rate~ required for high def inition color television, b- it in a MUSE, Europ-an, ~o-called Grand Alliance ~C, -~A U.S. format or other HDTV format Such a ~tructure i~ not intended to b- fix-d; for example, the present suggested data rates may be brokcn into only two regions of low and high spe~d data Nevertheless, for example, low spe-d data will always be included within PACKETS data and prec-de higher speed data ~ections of the frame, and high ~pecd data will always follow slower sp--d data and ~ c~d- th- fir~t HSYNCH and FRAME SYNCH
words for th- n-xt fram-Th- siz- of a particular frame is dictated by the tran~mi~$on medium and th- data to be carried One of th- f-atur-s of th- data fram- format disc~Q? d herein is a minimization of the numb4r of byt-s utilized for authorization of services and a maximization of the payload or information data portions of th~ fram- Thus, transmittcr power and signal to noi~e objectives are achieved along with information payload maximization Then, large frame~ are inherently more efficient, and there is an improv-d tolerance of long burst errors, for 2 1 7 7 7 3 5 PCI/US9'1/13846 example, in a cable or satellite environment Other factors weigh against the choice of too large a frame Th-se include the speed of achieving synchronization at a receiver and the cost of error correction circuitry such as memory costs at a receiver site In an error-pron- environment, error protection is provid-d by a R--d-Solomon block cod- denoted REED-SO~OMON and app~aring in Figure 2A as a narrow but long rectangular column at thQ right of th- figure As is shown in either Figure 2A or 28, the R--d-Solomon block code is app~n~ to the information data byt-s as forward error cGL~ction (FEC) parity byt~s The proportion of FEC bytes to information byt-~ is on the order of from one to ten p-r c-nt depen~in~ on th- particular medium or mixture of ~-dia or application Interleaving, wherein bytes of a number of blocks grouped in the depicted frame are shuffl-d b~L~n block~ according to a predetermined algorithm known to transmitter and rec-iver alike, may be employed to provide additional protection against ext-n~ burst~ of errors Further information concerning interl-aving may be found in U S Patent Applic~tion S-rial No (Attorn-y nocki~t No 44639-A-542), entitled "Sy~t-m and Method for Transmitting a Plurality of Digital S-r~ic-s Including Imaqinq Services," filed ' ~J~ L~ntly hor-with and which is incorporated herein by r~ r--~
A n-~rly square, but not p-rfectly ~quare, frame i~
pre~err~d and thus the practical maximum limit on the vertical dim-nsion i~ about 512 lines or blocks In keeping with such considerations and practical limitations on typical media bandwidths, a practical maximum number of video services is on the order of thirty-two and on concurrent audio services, sixty-four, Wo 9S/IS6~17 PCl/US9~/138`~6 assuming video and audio data compression is utilized without greatly sacrificing received signal resolution PACKETS data follows the FRAME SYNC word in the fr~e Certain PACKETS data is utilized to identify the numb-r of bytea provided in a frame for a particular service when byte ~tuffing is required Referring to Figure 2B, the PACKETS data portion of the multiplex frame may b- ~aid to further consist of two regions one r-gion including a MUX Structur- Control packet requiring additional forward rror coL-~-tion and a second region requiring now additional forward error corr~ction than the R-~d-Solomon co~ing provid-d for ach row or line (excluding HSYNCH) Other categori-s of PACXE~S data do not require additional forward error co~L~ction Th--- include video and audio co Llol, s-ed packets for decryption, cyclic sy~tem data, compo~it- virtual c~nnel and definition packets for providing what may be perceived as additional data ~-rvic~-, addre~s~d data pack~t~ for transmitting me~-ag-s to addr-ss-d ~cs~r~, tel-t~xt and utility data packets and other servic- packet~ Additional details of the variou- PACXETS data may b~ obtained fro~ U S Patent Application No (Attorn-y Dock-t No 44639-A-542), entitled ~Sy-t-n and M-thod for Tran-mitting a Plurality of Digital S-rvic~ Including Imaging Servic~s, n filed cc~ ntly her-with and which is incoL~o.at-d herein by r-~ renc-, and U S Patent Application Serial No, (Attorn-y Doc~ No 44643-A-554), entitled "System and Method for Tran~mitting and Rec-iving Variable Length Authorization Control for Digital S~rvices", filed concurrently her~with and which is incorporated herein by referencs.

WO 95/lS647 2 1 7 7 7 3 5 PCTIUS91/13816 Figure 2C illustrates that a sequence of frames in the form of Figures 2A or 2~ are transmitted to a receiver according to the present invention The sequence Or frames need not be composed of identical allocation of packets, low speed data, etc Rather, the content of individual frame~ may altered by the operator in accordanc- with th- services and authorization control desir-d ~
Now, an ~nco~er according to th- present invention will be furth-r d-scrib-d with ref~renc- to Figure 3 It has alr-ady b -n described that an -ncoAer according to the pre~ent inv-ntion typically involves A/V compressors 101(1) to lOl(m) Particular suggest-d capacities for on- such A/V com~ or, for exampl~, compressor 101(1) are to limit the nu~ber Or input video ~tream~ to 1 and to provide up to a maximum of four audio input streams (or two st-r-o ~tream-) each compri~ing left and right input str~a~s It has also been de~cribed that low speed data formatters 105(1) to 105(n) b provided Typically, how~v~r, ach low sp-ed data formatter may handle, for exampl-, sixt-~n or even thirty-two input data streams Consequ-ntly, it is cont-mplated that the number of such for~att-r~ r quir-d will nu~k~r only 1 or 2 However, any nu~ r Or low sp-Qd data formatters may be i~plemented consistent with the principle~ of the present invention Low speed data foroatters typically receive low ~peed data in a pred-termined format, such as RS232, and strip the data of any hie~r data, ~tart data, stop data, parity data and such d-F nAinq on the pr-determined and id-ntiri-d input data stream ~o that only true information carrying data remains in a serial data stream Wo 95/156~7 2 1 7 7 7 3 5 PCr/li59`11138 ~6 Now, the multiplexer llo of Figure 3 will be described in further detail with reference to Figure 4 Audio/video service streams A1 to An are received from audio/video compressors at audio/video data buffer ~10 Service multipl-xer 110 operates to multiplex a plurality of digital service streams for transmission to remote locations Also shown are inputs to a low speed data buffer 412 from low speed data formatters 105(1) to 105(n) Buffer 410 (audio/video) and buffer 412 for low speed data pr-ferably signal a buffer fullness condition to the next functional element, for example, encryption block 415, if encryption i~ de~ired, or on to multiplex fram- formatter 418 for low sp-ed data Encryption block 415 is int~n~ to rGyL~!nt the inclu~ion of, for example, single or double tier~ of ncryption in accordanc- with seed~ and key- and particular, predetermined algorithDIs a~ required for the digital servic- str-am~, for example, in a pay environment Other digital data is input from a text/graphics input computer, for example, t-letext data to text data p~c~ or 416 via computer interfac- 414 to the service multiplexer 418 Conditional acce~ data i~ input, for example, from a billing comput-r or subacrib~r service computer for ~torage in conditional acce~ data buffer 417 Cond~tional access data typically defines the ~-rvice~ p-cially pay services, to which a subscriber haa ~ub~crib d This data interfac-d al~o via interface 414 is ~L C :- s~ed and packeted into protect region PACXETS via conditional access data ~Lc_e~ing block 417 for input to multiplex formatter 418 Thus, at the output of multiplex (r~UX) block 418 is a multiplexed frame structure a~ describ-d by Figures 2A, 2B and 2C The output digital str-am is Reed Solomon WO 9S/lS6~7 2 1 7 7 7 3 5 PCT/US9`1/138-16 encoded according to an appropriate encoding sche~e depending on the noise characteristics of the tran~mission media by a well known Reed Solomon encoder 454 Then, preferably in a highly noisy environment, the frame is interleaved on a byte(s) (rows and columns switching) basis at interleave block 462 Interleave circuit 462 interlQaves the data frame by transposing row and column addr-~ses of data within th- rrame Lastly, HSYNCH and FRAME SYNC~ are inserted into the frame just prior to transmission at synch in~-rt block 458 This data then appears at a receiver at its original location in th- fram- while all oth-r data is int-rleaved The format of the TTX infor~ation will now be described Th- TTX syQtem supports two types of TTX
pacXet~ a h-ad-r row p~cke~ and a data row packet The header row pack-t defines the characteristic~ of the data row pack-t(s) th_t follow it In a preferred embodiment, the data row packet compri~-s 40 8-bit characters Of course, the ~ nt invention is not limited in this respect One of ~kill in the art will reCo~nize that an alternative number of characters as well as an alternativ- nu~k r of bit~ p-r character can be implement-d Figur- 5 illustrat-s a pr-ferred configuration of a hea~~r row pack~t The specific fields and bit allocation should not b- considered to limit the present invention The PACXET TYPE fi-ld identifies the packet as a teletext h~ -r packet Accordingly, a filter (not shown) in the demultiplexer 158 can extract a TTX header packet from other data DECCDER TYPE enables "filtering"
based upon decoder type in the event that different types of d~co~ers are used in the system The concept of filtering in conn-ction with the pre~ent invention will WO 95/lS6~7 2 1 7 7 7 3 5 PCT~Sg~ 138~J6 be discussed in greater detail below The ENCRYPT FLAGindicates whether the page is encrypted or not Accordingly, the decoder can determine whether or not to decrypt the teletext data by the ENCRYPT FLAG The FORWARD LINK F~AG and the BACKWARD ~INK F~AG indicate re~pectively wheth~r the pag- is forward and backward link-d A value of "1" for any of ENCRYPT F~AG, the FORWARD LINK F~AG, and BACKWARD LINK FLAG may represent enablem-nt of th- feature and a value of "0" may represent a di~able~-nt of the featur~ Of course, it will be ~o-J~i zed that any particular protocol is acc-ptabl- ~o long as the tranQmitted information is properly understood at the decoder The BOX MODE indicates whether or not a page is displayed on the ~ubscriber's viewing ~cre-n in a box If a pag- is boxed, the portion of the ~creen surrounding th- text may b specifi~d to b- black or vid-o In one pr-f-rr~d m~odiment, two bit~ ar- a~signed to BOX MODE
Of the two bit~, a BOX FN~R--~ bit indicates whether BOX
MODE i~ enabled and a BOX R~CXI-KGu~v bit indicates whether th- h~ck~round is black or video A~ pag-~ are placed onto transmi~sion an increasing portion of TTX bandwidth is occupied This ia particul~rly tru- where teletext ~ G~ ~ of multiple s~rvices i8 provided As a result, the grab time for sp-cific pag-- is increas-d The START ROW field reduce~
the number of rows that are required to be transmitted per page by specifying the first non-empty row Accordingly, tran~mission bandwidth need not be wasted transmitting the empty rows at the top portion of pages such as, for example, caption pages which usually only have a single row of text near the bottom of the screen WO 95/156~S7 2 1 7 7 7 3 5 Pcr~Tsg~/l3~6 START ROW further implements a pa~e annotation feature of the present invention, which reduces the transmission requirements for pàges that have empty rows embodded within text rows In addition to indicating the first non-empty row of text, START ROW indicate~ the row in which all s~ e~ent text rows are to be placed Ther-for-, empty rows between row~ of text on a page may b~ omitted by including a 9~9::nd ~a~r row packet with the n-w START ROW The annotation h~a~-r row packet is diff-rentiated from the page h~a~-r row packet by a single bit START FLAG Wh-n START FLAG is, for example, "1", the ~a~~r i~ a pag~ r indicating that a new page i~ about to be r-ceived and all page memory should be cleared Any subsequent h-aders with START F~AG
having a valu-, for exa~pl~, of "0~, are annotation headers and cause all sub--qu-nt text rows to be annotated onto th- pag- in the a~yLoyLiate row indicated by START ROW Thu-, START FLAG ~ignals whether the particular page is a n-w pag- or an annotation page Example~ of the use of the START ROW and START F~AG
fields in conn-ction with ~tart pages and annotation page~ are provided below one of a plurality of charact-r s-t~ (e g , 32 in one pr-ferr d mbodi~ent) may b- select-d using the rU'~'~TER SET fi-ld Th- PAGE NUMBER field enables the ~c~r to ~-lect pag-~ of text according to page number Thu~, th~ tran~mitted PAGE NUMBER can be used to filter a tran~ ion o that only th- r-qu-~ted page of text is grabb d Accordingly, PAGE NUMBER may b considQred a filter fi-ld for purposes of th- pre~-nt invention One preferred teletext h~a~r that includes eight a~.e~ate filter fields (al~o ref-rr-d to herein as filter fi-ld~) will be disc~ b-low However, the WO95/15647 21 77735 PCI/l~S9~11381~
number of aggregate filter fields may vary depending on the requirements, for example, of the operator, the system, or the subscriber The eight general p~~pose aggregate filter fields FILTERS 1-8 are available to allow the broadcaster and decoder to selectively screen the teletext pages These eight fields may be defined by the bro~Acaster as desired Each aggregate filter field has an a~soci_ted value By way o~ example, several preferred uses of the filter fields are discuQsed below FILTER 1 may be a ~ervice numb r filter having, for example, an 8-bit value for allowing pages to be d-sign_ted for specific services within a s-rvice category (e g , TV service ~1 may have a different teletext page than TV service ~2) FILTER 2 m_y b- a tim- zon- filt-r having, for ex~mple, a 3-bit valu- that _llows tim- zone spocific data to be retrieved by the A~coA^r Th~ brqaAca~ter may specify that any text page i9 time zon- specific at th- time of broadcast For example, the broa~cacter may wish to transmit text reporting a 3 00 PM Eastern StanAArd Time start time of a particular show for display only at televisions within the r-gion u~ing East-rn Sta~Aard Time If FILTER 2 is not enabled (i e , the text is not time zone specific), the t-xt pag- will bQ grabb~d by A-co~-rs regardless of th- ti~e zon- Wh-n enabl-d, the ncoder could use an addltional h-ad-r to annotate the tim- and date row onto a previoùs time zone independent page of t-xt The time zon- o~ th- A~CoA~r may be program~ed into the DISE, and may be chang-d by the broadcaster using an addre~sed data packet (ADP) specific to the ~:oAi~r A t-xt page may be further d-~ignated according to ~ervice category, for example, TV, radio, data, etc , using FI~TER 3 FILTER 3 has 5-bit~ in the instance WO 95/156~7 PClIUS9`~113846 illustrated in Figure 5 By way of example, a TV service may have a specific black out page ~hich is different from radio, data, or text blackout page By enabling FILTER 3 and a~signing each service category a specific code, a TV service specific black out page can be achieved FILTER 4 and FILTER 5 may b- us~d to designate information pccific to language or security element usinq, for exampls, 4 bits and 1 bit, respectively A
subscriber may enter a desired languag- for service in th- A~ A-r via a keyboard IIGLto~r, each decoder may hav- a Ae~ s ~er typ- definition ~ O~L amm-d as a fixed valu- in it~ d~c-A~r int-rnal s-curity el-ment (DISE) Accordingly, th- ~coA~r filter field would b- responsive to th~ ~Lo~Lu~-d A~coAer typ- d-finition By u~ing FILTER 4 and FILTER 5, th- text p~ge would only be displayed at A a~oA~rs having a matc~ing language and security element filter Additional FILTERS 5-8 may be used for oth-r purpos-~ s-lected by th- broadcaster Alternatively, on- or mor- FILTERS could be re erved for future purpo---A pow rful advantag- of th- pr-s-nt invention i~ the ability to co~bin- filters to nabl- th- broaA~ter to control which sub-crib rs receiv~ a particular page of t-xt For instance, a page of text may LC~ nt a video black out p~go for display by ~L~nch languag-, Eastern St~A-~d Tim ~ rs Alternativ-ly, menu pages that are com~on to all services and ti~e zon- may be trans~itt~d A FILTER FN~rF byte is preferably included to indicate which of FILTER 1-8 ar~ enabl-d For example, FI~TER ENABLE may have a bit that corresponds to each of the available filters A "1" may indicate that a WO 9S/IS6~7 2 1 7 7 7 3 5 PCT~Sg~/~38~6 particular filter is activated and a "o" may indicate that the filter is disabled, or vice versa When a FILTER ENA~LE bit indicates that the corresponding filter is activated, the teletext page will be grabbed~only if the value in the designated FILTERS 1-8 match a corresponding filter value stored in the decoder When a FILTER FN~RrF bit indicates that th- corresponding filter is disabled, the t-let-xt page is ~rabb~d if all other enabled filter values match Of course, the FI'TER
FN~t.F field may be implemented in numerous other ways A TEXT ~F~F~TAB STREAM NUMBER field is used by the encoder to indicate th- physical text s~rvic- number used for encryption The physical text ~ervice number, encryption, and decryption will b- discusfied further below Thi~ fi-ld is i~ o~d wh-n the ENCRYPT FLAG
indicates that there is no encryption Th- dccoder may use the TEXT ~FMFUTAL STREAM NUM~ER field to determine seed validity if required FIGURE 6 illustrates one preferred embodiment of a teletext data row packet The PACXET TYPE field identifi-- th- pack-t a~ a t-letext data row packet Accordingly, a filter (not shown) in the demultiplexer can extract a t-l-t-xt data row p-~k~ from other data DECODER TYPE nables filtering based upon the type of decod-r Th< r-~ainder of the teletext data row packet may b allocated for teletext data For example, 40 8-bit character~ (i e 320 bits total) may comprises a tel-t-xt row However, this i-~ in~n~-~ merely as an example The nu~ber of total bit~ (which would determine t~- numbQr of characters if th- number of bits per character wer- fixed) and the number of bits per character may vary in accordance with the present invention WO 9S/15647 2 1 7 7 7 3 5 PCI`/US9~/13846 The encoder may be configured to construct the TTX
header and data row packets as discussed above The reception of TTX information by the decoder will now be discus~ed The demultiplexer 158 determines whether a received packet is a teletext packet (TTP) as opposed to another packet according to its packet type information The entire TTP i~ extracted from other packets and is transmitt-d to a Micro-proces~or and Teletext (PMS) section of the demultiplexer 158 On- of the functions of the PMS may be to perform multiple page grabs of teletext pages The PMS mu~t be able to handle the maximum data rate without losing any data It is preferred that all TTPs have th- same length Difficultie~ handling the received TTP~ having different length~ may ari~- if the demultipl-xer 158 expect~ the header in a ~pecific location The demultiplex-r 158 compares the page nu~ber of the header row packet with a requested page number A
particular pag- number may be requested as a consequence o~ a sub~criber's channel selection, for example, or automatically by th~ o~ upon the G~ ence of an event If th- requ-Qted page number i~ found in the received data, the text data packetQ that follow the h~a~r row ~ark~ are written into a memory, e g a r~ndo~ acc-~ m-mory (RAM), until a new header packet is received Th- demultiplexer 158 can store 16 text pages including ~ r row data and have four page number comparator~ in one exemplary embodiment When a paqe has been received and written to RAM, a page grabbed status flag will b- -t for the DCP 153 The DCP 153 command structure may comprise a page grab command, paqe number, compare reqister number (e g , 0-3), and RAM paq- to write to (e g , 0-15) Status read WO 9S/156~ 2 1 7 7 7 3 5 PCT/US9~/138~6 commands return the current status for the outstanding page grabs and thereby permit the DCP to monitor the status of page grabs The DCP 153 and the demultiplexer 158 have access to the text header flags using a Read RAM
command The text header may also include filter values for category, service, time zone, language, security element, etc Each of these fields can be enabled or disabled via the filter enable flags The demultiplexer 158 sets a row counter to the starting row number in the header row packet The d-multiplexer will not modify current data in the pr-viou~ text rows to ensure prop-r page construction If the text page reguire~ space characters in the previous rows, either the encoder may transmit a full pag- or the DCP may issue a clear page command The demultiplexer then checks for page overflow to ensure that i8 does not write into the next text p~ge in RAM
Row annotation and filtering may cause pages to be reconstruct-d row by row in no particular order A
single row may be erased, creat-d, and overwritten before a page is reconstructed If a page is also being displayed at th- same tim- it is reconstructed, the display may behave erratically While reconstruction is in ~L V~ rows m~y appear, disappear, and then re-app-ar with different data Th- rate at which this o~ d-pends on the number of annotation rows required to construct the pag-To avoid this difficulty, the DCP 153 may implementpage swapping thereby ensuring that reconstruction and display of a page do not interfere with each other The DCP 153 may request page grabs only to a RAM that is not on display Once the page has been grabbed, the demultiplexer 158 must discontinue grabbing the page and WO 95115647 2 1 7 7 7 3 5 PCT~S9~"38~6 inform the DCP 153 that a grab is completed The DCP 153 can then cau~e the completely reconstructed page to be displayed and initiate another grab into a non-displayed RAM By rei~suing the grab, the DCP 153 implements a continuous grab The demultiplexer 158 must be capable of automatically stopping a page grab as soon as a page has been reconstructed If it were to continue to grab the page, the DCP 153 could cau~e the page to be displayed while it i8 being reconstructed The indication to the DCP 153 that th- page grab has been completed should only be set when a complete page ha~ been recon~tructed This is indicated in the d-~ultipl-xer 158 by a matching header row (i e , a header row having the correct page numb r and filter valu--) with the START FLAG set followed by another header row with a START FLAG ~et The ENCRYPT F~AG indicates that th- current annotation page i~ e,~ ed Without limiting the invention, the encryption may be conducted on an annotation page by annotation page basis Encryption may be performed only on data row~ following the header row, and a co~pl-t- page may con~i~t of encrypted and non-encrypted rows The DCP 153 will load the text d~ ion ~-~d very ~e~sion When the demultiplexer 158 finds th- page ~a~r, it load~ the current text seed for th- ses~ion and decrypt~ the entire page Accordingly, t~e text data may be ~tored in the clear in the RAM
The di~play su~o~L, logic u~ed to di~play a page onto a televi~ion screen, for example, control~ the text data to b- s-nt to the character generator It also controls the display attributes regue~ted by the DCP 153 or from the TTX header row packet The character set WO 9S~15647 2 1 7 7 7 3 5 PCT/I.~S9~/138~6 number allows selection from several font ROMs For example a 5-bit number may be used as upper a~dress bits in addition to an 8-bit text data Thus, the CHARACTER
SET field of the header row packet may form part of an address for retrieving a particular character in a particular font from ROM
Figure 7 illustrates an exemplary embodiment of multiple page grab logic 70C of a d-multiplexer 158 The multiple page grab logi~ 700 comprises page grabbers 710-1 to 710-n, pag- display logic 750, and page display random acces~ me~ory (RAM) 760 After extraction from th- multiplexed signal in another portion of th- demultiplex-r 158, a received TTX
hea~er row pac~et 705 is sent to each o~ the page grabbers 710-1 to 710-n How_vc~, different page grabb-rs may grab difr-rent page~ according to the requested page and~or r-qu- t-d filter values supplied thereto by the DCP Different requestQd page and/or requested filter values may be applied to each page grabber in ord-r to control the page grabber~ to grab different p~g-~ Each of the pag- grabbers 710-1 to 710-n m~y b- identical in structure and operation Accordingly, th- description of t~e operation of page grabb r 710-1 b low is equally pertinent for any of the other p~g- gr~bb rs and a specific discussion of paye gr~bb rs 710-2 to 710-n will not be pro~ided herein Page grabber 710-1 comprises a page comparator 715-1, AND logic circuit 720-1, a~e~ate ~ilter comparator 725-1, pag- grab logic 730-1, d~ or 735-1, and page construction random access memory (RAM) 740-1 The A~D
logic circuit 720-1 and the page grab logic 730-1 may together be considered a page grab logic circuit Assuming that the received TTX header row packet is WO9~/15647 2 1 77735 PCT/US9`~/13846 -supplied to page grabber 710-i, the PAGE NUMBER field is supplied to the page comparators 715-1 where it is compared to a requested page number The page comparator output-~ a matching signal to an AND logic circuit 720-1 on the basis of the comparison to indicate whether or not a match occurred In addition, the FILTER field and the FI~TER ENA~LE field of the receiYed TTX header row packet are supplied to an a~yL~ate filter comparator 725-1 The a~Lc~te filter comparator 725-1 compares the FILTER
field valu-s with requested filter values and compares whether the particular filter i~ enabled at all The aggregate filter comparator 725-1 outputs a matching ~ignal to AND logic circuit 720-1 on the basis of the comparison to indicate whether or not a match occurred Details concerning th- d-termination of an output value for an a~L_~te filter comparator are provided below in connection with Figure 9 and 10 If, for example, both the page comparator 715-1 and the aggregat- filter comparator 725-1 indicate a match, the AND logic circuit 720-1 ou~ s a first signal, e g , a "ln, to the page grab logic 730-1 lf, however, either the pag- co~parator 715-1 or th- a~ ate filter comparator 725-1 do not indicate a match, the AND logic circuit 720-1 o~ a s~c:n~ signal, e g , a "0", to the pag- grab logic 730-1 In addition to receiving the output from the AND
logic circuit 720-1, the page grab logic receives various other field~ of the received TTX h-a~r row packet, such as PACXET TYPE, START F~AG, and START ROW The TTX data stream, which may be comprised of the data row packets, is decrypted in d-cryptor 735-1 and then supplied to the page grab logic 730-1 The page grab logic ?30-1 determines on the basis o~ the signal from the AND logic WO 95/156~7 2 1 7 7 7 35 PCT/US91/13816 circuit 720-1 whether the received TTX header row packet describes a teletext information it should qrab If not, the next TTX header row packet is interpreted If TTX header row packet describes teletext information that should be grabbed, the page grab logic 730-1 implements a state machine that is used to maintain the page construction in page construction RAM 740-1 After extraction from the multiplexed signal by a portion of the demultiplexer, TTX data stream is applied to the multiple page grab logic 700 Page construction RAM 740-1 is constantly updated with data from the TTX data stream that is supplied via the page grab logic 730-1 As the TTX data stream is received, the h~ r row packet is interpret-d by page comparator 71S-l, a~ ate filter comparator 725-1, and pag- grab logic 730-1 The information from the header row packet 705 is used by page grab logic 730-1 to generate read/write commands, RAM enable commands, and address information that place subsequent data rows into the correct addrese in page construction RAM 740-1 to form the portion of the teletext pag- defined by the teletext header row packet Updat- of the page construction RAM 740-1 stops when the request-d page is completely grabbed At this time the page grab logic 730-1 send a "grab complete" signal to pag- display logic 750 The grab logic 730-1 then releases ~o,-lol of the page construction RAM 740-1 The pag~ display logic 750 controls the page construction RAM
740-1 using read/write commands and RAM enable commands to copy the page into page display RAM 760 The constructed page may then be displayed from page display RAM 760 For example, a character generator may read the data out of RAM 760 and access corresponding pixel data in a ROM (not shown) The character generator must WO 95/156-~7 2 1 7 7 7 3 5 PCT/US9~/138~16 generate the appropriate address information to access the RAM and ROM
This implementation of multiple page grab logic 700 offers maximum flexibility since each page is supplied with the complete set of logic reguired to grab that page As a re-ult, each page grab does not affect any other~
Figur- 8 depicts an alternat ve embodiment of multiple page grab logic The multiple page grab logic 800 include page grabbers 810-1 to 810-n, aggregate filter comparator 825, d~cryptor 835, page display logic 850, and pag- display RAM 860 Pag- display logic 850 and page display RAM 860 op-rate in the same manner as de~cribed in connection with Figur- 7 Each page grabber includes a page comparator 815-1, AND logic circuit 820-1, page grab logic 830-1, and pag- construction RAM 840-1 As abov-, AND logic circuit 820-1 and page grab logic 830-1 may together be consid~red to form a page grab logic circuit Each of the page grabbers 810-1 to 810-n shar- an aggregate filter comparator 825 and a decryptor 835 A~ a r-sult, multipl~ page grabs can only be achiovQd if each pag~ to b grabbed is encrypted in the sam- way and ha- the same filter settings The multiple page grab logic 800 otherwisQ functions in a similar manner to multiple page grab logic 700 In th- above description, any number of page grabb r~ may be implemented For example, four page grabbers may b used in one preferred embodiment Figur- 9 depicts an example of a single filter comparator 900 that may be used in aggregate filter comparator 725-1 to 725-n and 825 The single filter comparator 900 comprises an n-bit comparator 910 and an OR logic circuit 920 The n-bit comparator 910 receives W09S/156'~7 2 1 77735 PCI/I~S9~113816 an n-bit filter value from the received TTX header row packet and an n-bit filter requested value As discussed above, the filter requested value may be input by the sub-criber or read out of a memory in the decoder The filt-r requested values may have b-en read in~o the memory pursuant to an in~truction from the operator, the su~criber, or on the basis of th- hardware implemented by the d~-o~-r The n-bit comparator 910 outputs a first signal, g "ln, if the receiv-d filter value matches the request-d filtlsr value and outputs a second signal, e g , "on, if th-re is no match Th- OR logic circuit 920 rec-iv-s the ou~L of the n-bit comparator at a first input terminal and receives a filter enable bit from the received h~A~r row packet at an inverted -~conA input terminal The OR logic circuit 920 will output a matc~i~g signal indicating a "filter match" if ith-r the filt-r is disabled or if the n-bit filter value matches the n-bit filter rcqucsted value Otherwi~s, th- OR logic circuit will output a "filter not matched" signal Of course, it should be clear that OR logic circuit may be r-placed with other logic circuit~ to produce the similar results if the protocol u~ed by the n-bit comparator 910 and/or the filt~r enabl- bit wer- differ-nt Figure 10 illu~trates a specific embodiment of an aggr-gatQ filter comparator 1000 such as that depicted as 725-1 to 725-n in Figure 7 or 825 in Figure 8 The a~Lsq~te filter comparator 1000 i~ shown as comprising eight separate filter comparators 1010-1 to 1010-8 and an AND loqic circuit 1020 Each filter comparator 1010-1 to 1010-8 may be of the type depicted in Figure 9 Of course, the use of eight filter comparators is intended as an example, and any number of separate filter WO 95/15647 PCI`/US9'1/138.~6 comparators may be implemented consistent with the c3~nt invention Each filter comparator 1010-1 to 1010-8 receives corresponding filter values, a filter enable value, and filter request values Figure 10 provides an example of the number of bits received by each filter comparator However, the number of bits shown is intended to match the TTX h-ader row packet shown in Figure S and should not be consid-red limiting The v~y~ of each filter comparator 1010-1 to 1010-8 is supplied to an input terminal of AND logic circuit 1020 The AND logic circuit 1020 ouLy~s a matching signal indicating "a~ ate filter match" or a signal indicating ~aggr-gatQ filter not match-d n As discus--d in connection with Figurs 9, if an individual filt-r comparator 1010-1 to 1010-8 detects that either th- filt-r is disabled on the basis of the filter enable signal or that th- filter values match the requ-sted filter valu-s, it outputs a "filter match"
signal, e g "ln Otherwi~e, the filter comparators 1010-1 to 1010-8 output a "filter not matched" signal, e g "0~ Thu-, the AND logic circuit 1020 ou~u-s an "aggr-gate filt-r match~ signal if each individual filter comparator 1010-1 to 1010-8 ou~y~s a "filter match"
signal If, however, any one of filter comparators 1010-1 to 1010-8 outputs a "filt-r not matched" signal, the AND logic circuit 1020 will output a na~Lc~ate filter not match-d~ signal A~ above, AND logic circuit 1020 may b r-plac-d by other logic circuit~ dep~nAi~g on the signal protocol us-d Th- configuration of the digital multiplex allows for dyna~ic creation and deletion of virtual channels Th- filters of the TTX system allow the bro~Acaster to dynamically configure the TTX according variety of WO 9S/156.~7 2 1 7 7 Pcr~ sg~ ~ 38 1t~

classifications, for example, language, service category, service number, time zone, and security element of course, the TTX system may be configured based on other distinctions that the broadcaster may find desirable It is important to understand that the filters are definable by anyone who operates the system Accordingly, the operator may use the filters to control which subscribers receive particular text and which subscribers do not Furthermore, by constructing appropriate TTX pages, the TTX system of th- present invention is capable of offering the following functions n-twork control including menu, help, and d~: ~A~r authorization status pag-s; teletext programs, which are primarily teletext program offering~, for example stock reports, weather ~eyo~L~, tc ; teletext for non-t-let-xt yLO~L ams such as teletext captioning or busine~s television (BTV) type teletext; broadcast or general message , for example broadca~t of a telet-xt pag- to all decoders;
transmission of personal messages such as teletext pages targeted to a ~pecific decoder or group of decoders; and an electronic program guide The Ai~cq~r is such that it always attempts to specify a requ-sted page using the fin-st "granularity "
In other worAJ, the d-multiplexer will attempt to grab a pag- using th- highest specificity of requested filter valu~ uch a~ specific language, specific service category, sp-cific service number, specific time zone, specific security elem-nt, etc A filter allows the broadcaster to dynamically overrid- the r-quested filter values by proper selection of filt-r valu-s in the transmitted signal At the encoder, each TTX page may tagged as specific (i e , filter enabled) or global (i e , filter disabled) WO 9S/15647 2 1 7 7 7 3 5 PCT~Ss~/138~6 for each of the filters A global page is grabbed by thedecoder no matter what the filter values are In other word~, the filters are disabled for a global page A
specific page is grabbed only by decoders t~at have matching filter values By selectively transmitting global or specific pagc~, the broadcaster may control what g-ts displayed by a decoder when it grabs a page Furthermore, the operator can r-configure the filter by creating pag-s that allow a subscriber to make a selection For example, a operator can allow subscribers to s-l-ct betw--n Spanish language and English language text by cr-ating a menu pag- inviting the sub~criber to mak- a s-lection The tran~itted Sp~ni sh page can be transmitt-d with a different filter value than the English page R-spon~ive to the subscriber's selection, the page grab logic will grab the page having the selected filter value The following exampl-~ are designed to illustrate the operation of a filt-r system for implementing a tiered tel-vision service ~L~OLk In a ~imple case, the network co~pris~s on- tel-vision s-rvic~ that is authoriz-d by tier~ No oth-r authorization features (such as blark~t, per-per-view (PPV), impul~e pay-per-view (IPPV), fr-e ti~e, etc ) are ~nrported The minimal TTX 8~G~ ~ay consist of the following thre- TTX pages "No XOM~ (XOM refers to the "key of the month" which is a ba-ic authori2ation control); "Service Tier Not Authorized~; and a main menu All filters would be di~abled for thes- pages thereby allowing every decoder to rec-ive them Figure ll illustrates the network consisting of one television service having the three TTX pages Each column Le~re~-nts a filter, in this case service WO 951156~17 2 1 7 7 7 3 5 PCI/I~S9`1/138~6 category, service number, and time zone Of course any number and type of filter may be added depending upon the type of classification the operator wishes to set up Th- global column represents the condition where the filters are disabled Figure 11 may be considered to represent th- situation where other available filters are disabled Figure 12 illustrates an example where a single radio servic- is added to the network of one television service depicted in Figure 11 The TTX configuration may be modified to allow for both television ~-rvice and radio service categori-s While the "No XOM" and "main menu" page~ remain global pages, a "Radio Authorized"
page is created and the "Servic- Tier Not Authorized"
page is mad- into two pages a "TV Service Not Authorized" page and a "Radio Service Not Authorized"
page The creation of the category specific "Service Not Authorized" pages is accomplished by creating the two pages and enabling th- cat-gory filter accordingly The "Servic- Not Authorized" pag-s may be created in several way- The simpl~st way is to create two independ-nt i~ages for the two page~ While more complicat-d, it is more effici-nt in terms of transmi~sion bandwidth to create a global "Service Not Authoriz-d~ t-mplat- page and two annotation pages that are particular to the services The global template page would hold th- portion of the pag- that is common to both servic- categori-t, for exampl-, "You Are Not Authorized For n The annotation pages hold the TTX rows that are specific to the service, such a~ "The Prime Movie Channel" for the television service category or "Easy-Listening ~adio" for the radio service category An example of such pages is depicted in Figures 13A and 13B

W095/15617 21 77735 PCI`,'~'S9`1~138~J6 A third way to create the "Service Not Authorized~ pages is to create a global page that is specific to one of the service categories, e g a "The Prime Movie Channel Is Not Authorized", and create annotation rows that overwrite the television specific portions of the global page with radio specific text Accordingly, the global page acts as a default page in the event that a specific selection is not made by the sys~em operator With r-fer-nce to Figur-s 13A and 13B, it can be seen that row 8 contains thc common row and therefore constitutes the global category pag- It is marked as prot-cted on th- global 1-VQ1 in the l-ft column, and thus cannot be chang-d by operators authorized only to cr-at- pag-s for television or radio All other rows may be filled with category specific text In the examples - of Figur-~ 13A and 13B, only row 9 hold~ category specific text Th- transmi~sion of th- pages for Figures 13A and 13B requir- only six (6) rows of TTX a h~a~er row and a data row for the qlobal cat-gory, a h~a~qr row and a data row for th- t-l-vision category, and a header row and a data row for the radio category A format for the TTX
rows is illu~trat-d in Figure 14 Figure lS illustrates the example where multiple radio s~rvice~ ar- provid-d The creation of two or more radio ser~ic-s may be su~o~Led by using a service number filter In th- example of Figure lS, the "Radio Authorized~ pag- has been left as a radio category global page Therefore, any authorized A~ r tuned to a radio channel will get the same pag- The "Radio Authorized"
page could easily be made radio service specific by applying the service number filter to the page WO 95/15647 2 1 7 7 7 3 5 PCr/~,'S9~/138-~6 _.
The "Radio Not Authorized" page is specific for each of the radio services, in this example, three as shown in Figures 16A-16C In each page, row 7 is protected as a global row Row 11 i~ a radio ~ategory specific row and is, thus, common to all radio category pages Row 9 contains the radio service specific text ~ransmission of the TTX support for the configuration depicted in Figure~ 15 and 16A-16C requir-s twelve (12) rows of TTX
The twelve (12) rows of teletext are depicted in Figure Figur- 18 depicts the example of Figure 15 with the addition of t-levision s~rvice tim- zone information The tslevision "S-rvice Not Authorized" page is received by all d^coA^rs not authorized for televiqion In this example, th- information pres-nted in the television "Service Not Authorized" page could contain the start time of the next tel-vi~ion ~G~ . Accordingly, the user would be pro~pted to try again at later time However, th- start tim- of the next tel~vision program may be different d~pending on the time zone in which the AecoA^r i- locat-d Th- local time for a particular ~coA~r is di~play-d in th- ideal case A time zone filter may b~ us-d to implement local time display acro~s a vari-ty of tim- zon-s Bcc~u~- th-re is only one tel-vi ion service in the pres-nt exa~ple, ther- is no ne-d for a service number filter for th- television service category Accordingly, th- servic- numb~r filter for the tel-vi-ion category may be disabled It should b- clear that if several different television service~ were implem-nt-d, a service filter for the television category may be easily implemented In the present example, however, the time WO 95/lS6~7 2 1 7 7 7 3 5 PCT/l S9 1/138~6 zone filter is set for each time zone that is supported as illustrated in Figure 18 Figures l9A-19D illustrate the individual TTX pages that may be created As in the above examples, row 7 in each of Figures l9A-19D remains global, rows 9 and 11 are category specific, and row 12 i5 time zone specific Figure 20 illustrates the various row~ of information used to transmit In all, twenty-two (22) rows are required to transmit the "Service Not Authorized" page for all categori-~, s-rvices, and time zone~
Figure 21 illustrates th- exampl- of Figure 18 with th- addition of a closed captioning to ~u~o~L, for example, for-ign language~ Lin~ 21 captions (i e , captions which appe~r on line 21 of the displayed tel-vision signal) allow ~ G~L of dual language closed caption~ The availability of such clo~-d captioning can be facilitated by enabling a languag- filter In the previous examples, th- global pag-~ were said to be available to all ~co~r~ without r-striction However, if a language filt-r is impl-mented, all pages would be available to all ~i~coA-r~ without re~triction only if the languago filter wa~ al~o di~abl-d for all page~ An operator may choo~ to provide full dual language support by cr-ating all of th- required TTX pag-~ for the second languag- and setting th- dual language filter a~op~iat-ly Alternatively, Engli~h may b- used as a dofault global language and the alternate language alone can b~ ed with closed captioning Thus, all pages would b- in Engli~h with only the caption page ~electable to the alt-rnative language The latter example is depicted in Figure 21 The syste~ of TTX SUp~G~ L for multiple virtual channels require~ operator maint~n~nce Accordingly, it WO95/1561? 2 1 77735 PCII~S9~1138.1~
is therefore convenient for operators bestow li~ited authority on maintenance persons, hereinafter referred to as users, to perform network maintenance functions It should be noted that "users" in this context differs from "subscribers" to whom the services are provided In an embodiment of the present invention, a user is defined with a user nam- and privilege~ The user name identifie~ the u~er to 'he ~y~tem Privileg-s de~ine the user's L e-~o,~ibilities Privileses may have two component~ scope and rights Scope i~ th- segment of the network available to the user Ihe rights define what actions the user is permitted to take in the availabl- n~twork For example, a user may have the right to VIEW, EDIT, or CREATE VIEW rights only permit the user to read data EDIT right~ allow th- user to read and modify any data within the user's scope The CREATE right allowe the u~-r to view and edit data, as well as set filters to any value within the user'~ scope The scop- ~ay b sp-cified ba~ed on the filters Each scop- f$1ter may be set to the following values GLOBAL, ALL, or a list of specific filter values The setting of a 8COp- for a us-r define~ which set of page filters ar- accessible, not whxt the pag- filters are thQmselve~ s-t to T~erefore, pag- filters and scope filters a~ us-d herein ~ust be distinguish-d As noted abo~-, ~cope filters define the list of accessible page filters The u~er's scope con~ists of all data that pass th- scope filt~rs When a filter is ~et to GLO~AL, only data that ha~ the filter disabled will pass A filter set to ALL will p-rmit all dat~ to pa~s A filter set to specific values will only allow data with the filter disabled or with the specific filter values to pass WO 9S/15647 PCT/~TS9 1/138 ~6 __ The following example illustrates how users can be creat~d It is assumed that a network has a single television service Each system will have a TTX
administrator will full privileges as illustrated by the definition shown in Figure 22 Because the only service offered is televi~ion service, only the TTX ad~inistrator is required Th- TTX administrator creates complete page~ Ther- is no reason to restrict access becau~e there are no other users Figure 23 illustrates the example of Figure 22 where a single radio ~ervic- is added Th- addition of the radio s-rvic- can be accommodat-d by creating a user to manage the tel-vision service and a u~er to manage the radio ~ervic- Th- tel-vision ~anager is a~igned all television related r-sponsibiliti-s Accordingly, the risk that the TTX admini~trator accidently modified radio service data wh-n acc-ssing televi~ion related data is reduced As can be se-n from Figure 23, the TTX administrator can disallow modification of languag- depcnd~nt data by th- t-l-vi~ion manager and the radio manager by defining their scop- and rights in co~rection with the language filter as GLOBAL and VIEW, respcctively All data has the language filt-r disabl-d for this xampl-, and the TTX ad~ini-trator ha~ res-rv-d thc right to create new languago~ and ha~ r-stricted th- rights of the radio and t~ vision managers thereto Both managers are given view rights to languag- data to thereby allow them to retri-ve page-The ~anag-rs have been given CREATE rights to their respective cat-gories This allow~ them to ~odify and cr-ate category specific data for th-ir categories WO 9S/15647 2 PCI`II S9`11138~6 -- The TTX administrator creates the global "Service Not Authorized" page shown in Figure 24A As can be seen, rows 1-7 and 13-19 have been designated as global row- Only users who have at least EDIT rights with their scope set to ALL or GLOBAL on every filter may modify these rows Rows 8-12 have be~n allocated for use by category manag-rs Because the television and radio service managers are invested with CREATE rights with respect to their categori-s, they may customize rows ~-12 For exa~pl-, the television manager may create the page shown in Figure 24B The radio manager may create th- pag- shown in Figure 24C Not- that rows 8-12 have been allocated for televi~ion cat-gory u~e by the television manager and for radio category use by the radio category manager - The addition of multiple radio services to the example of Figure 23 can be supported using thc same user configuration, in which ca~e th- radio category manager would also b responsible for each radio service Alternatively, n-w u~ers may b- creatQd a~ illustrated in Figure 25 In Figure 25, a n-w user for radio service 1 - and a n-w u~-r for radio servic-~ 2 and 3 have been created Th- radio manager has decided to grant the new radio J-rvic- u-er~ EDIT right~ only with respect to their radio ~-rvice~ Thus, the new radio service manag-r- will only b- able to modify data corre~ponding to th-ir radio ~-rvices They are not able to create new radio service number specific data With the exception of the TTX administrator, the radio manager has retained sole ro~pon~ibility for allocating radio service number specific data The radio manager creates the "Radio Service Not Authorized" page for radio service 1 as illustrated in WO 951156~7 2 1 7 7 7 3 5 PCr/US9 1/138~16 Figure 26A Rows 8-12 remain radio category pages The radio manager allocates row g for user by ra~io service 1 Only having EDIT rights with respect to radio service 1 data, the radio service 1 user cannot modify rows 8, 10, 11, and 12 Radio service 1 user may enter data on row 9 only as shown in Figure 26B All other rows may be viewed but not changed The radio manager must rep-at the page creation for radio service~ 2 and 3 This may be accomplished by replacing th- servic- filter value of 1 with 2 and 3, respectively ~ikewi~-, u~ing EDIT rights, radio service 2 and 3 u~-r also create~ the requir-d service pages by entering th- a~.G~-iat- data in row 9 Figur- 27 illustrates a sy tem similar to that of Figure 2S with the addition of a us-r definition ~upporting television time zone data As illu~trated in Figure 27, the n-w television tim- zon- user has EDIT
rights with resp-ct to television time zone data and VIEW
rights with re~pect to language, category, and service number data Accordingly, the time zone user is respon~ible sol-ly for television time zone specific pages The t-levision tim- zone user thus has the ability to modi~y t-l-vision tim- zone specific data, but not create n-w television time zone specific data The t-levision manager has as~umed the ~e~o ~ibility for allocating tel-vi~ion time zone specific data Th- television time zone user can create the page illustrated in Figure 28 for time zon- 1, for example The television manager may create the page of Figure 28 wit~ row 12 empty and allocated for time zone 1 The pag- mu~t b- recreated for each time zon- with row 12 allocated for each available time zone The television WO95/156'17 21 77735 PCI`II~S9`1/13816 ~ time zone user fills in row 12 with the appropriate time zone data Figure 29 illustrates an user definition scheme in which clcsed captioning television services are supported In this case, the responsibility for television captioning is delegated to the television manager The television manager has been given CREATE
rights to the global language and language 1 The television manager may thu~ create global and language 1 speci ic data Accordingly, th- televi~ion manager is provided with a wide range of pow~r to support language 1 for all tel-vision data, not only for captions As illustrat-d in Figures 30A and 30B, the television manag-r may create two empty page~, both as~igned to th- tel-vi~ion category, but one for global language and for language 1 data For example, Figure 30A may represent an English language caption page and Figure 30~ may .c~.c3ent a French language caption page With some networks, such as impulse pay-per-view (IPPV) networks, for example, it is desirable or even nec~ ry to provide TTX syste~ support to guide a subscrib-r th-ough ~ ur--, such as to purcha~e an event for IPPV Th-~e networks ~ay require, for example, program sp-cific information to b- nter-d on a TTX page In t~e ca~e of IPPV, for example, a ~ubscriber would liX-ly be reluctant to purchasQ a program unles~ he knew the titl- and cost of the program Such information may chAn~ relatively frequently and would require a considerable in~estment in manpower if the pages had to be manually updated and placed on transmission It i~ pos~ible to take advantage of circumstances in which broader clasQes of information remain relatively constant even though specific information changes WO9S/lS~7 21 77735 pCT~Sg~ll38~6 Erequently Again, using IPPV as an example, every IPPV
program ha~ a title and a cost, however the exact values of change program to program Accordingly, a generic TTX
page could be created with place holders where the changing data can be placed Such pages will be referred to herein as skeleton pages, and the place holders will be referr-d to a~ templates On a program change, new templates may be loaded and automatically modify all skeleton pages Of cour~e, as the above description suggests, sk-leton pages are not re tricted to IPPV
networks While th- following exampl- will be described in the cont-xt of IPPV, it should be und-rstood that any network that has r-latively frequently changing data over relatively static TTX pages may tak- advantage of skeleton pages to automatically update pages A skeleton page illustrat-d in Figure 31A The "S%" attribute in the title row identifie the page a~ a skeleton page with a template deli~it-r "%n Of course, skeleton pages and template delimit-rs can be identified in other ways All templates are n~m d and plac-d in the skeleton page surro~ d by ~ The placement of the "%n'~ determine~
the size of th~ te~plate For exa~ple, the above page has the following templates movie rating, PR; movie title, TIT~E; ~tars of the movie, STARS; and the cost of the ~ov1e, COST When the program is aired, the te~plates must be filled Figure 3lB depicts the skeleton page of Figure 3~A having PR - "G"; T~TLE ~
It's A Wond-rful Lifen; STARS ~ nJames Stewart"; and C~ST
= nS 2 50~
Logical filters allow for the dynamic allocation and ordering of the physical filters discussed above In the ~iscussion of Figures 11-3lB, it was assumed that the WO95/156~7 2 1 77;735 PCTIIJS9~/13816 initial allocation of bits to each physical filter and their definitions will be sufficient to support all T~X
features, present and future In addition, the above description included implied a hierarchy for the filters For example, filters were activated first by language, then by category, service numb-r, time zone, etc While somo filter typ-~ may have an implied priority, other may not For example, all things being equal, the language filter may hav- the highest priority or the lowest priority How-ver, in the context of specific system~, ther- may bo a valid reason to allocate a language filter as the highest priority, or as th- low-~t priority For example, the system operator may wish to create users re~ron~iblo for maintaining a sp-cific language In such a ca~-, th- language filt-r may be set to have the highest priority Alternatively, if pay-per-view (PPVJ
were important, an operator may set category to the highest priority and create u~ers to manage the PPV movie category A logical f ilter is a grouping of physical filters Each physical f ilter may b~ a member of only one logical filter Th- logic~l filter is created by combining all of the physical filter values The physical filter numk r det-r~in-~ how the physical filt-r values are concatenat-d For example, the higher the physical filter nu~k~r the higher the bit position Accordingly, a logical filter comprised of physical filters 1 (PFl), 5 (PF5), and 7 (PF7) will hav- a phy~ical filter value constructed by concatenating PF7, PF 5 and PFl, with the PF1 bit oc~u~ying the least significant bits and the PF7 bits oo~u~ying the most significant bits The physical filter value may be padded with, for example, Os of WO 95/156-~7 2 1 7 7 73 5 PCT/I;S9`1/138~S6 course, the specific ordering for concatenation and the padding bits should not be considered limiting An existing logical fil'er can be extended by adding another physical filter to the group, or a new filter of any size may be created from unused physical filters by grouping them together Furthermore, logical filters oan be assigned hierarchies A hierarchy may be created, for example, by assigning logical filter numbers to each logical filt-r with the lower the logical filter number, the higher th- ordering However, this should not be con~idered to limit the present invention Encryption and allocation will now be discussed Encryption i~ perform-d at th- en~o~^r and decryption is performed at the ~coA~r Additional details concerning encryption may be found in U S Patent Application Serial No 08/101,974, ntitled "Method and Apparatus for Uniquely Encrypting A plurality of Ser~ices at a Transmission Siten, filed August 4, 1993 and incorporated herein by refer-nce The term "allocation" refers to the assiqnment of page ranges within a maximum page range for particular classifications of service Allocation may become nece~-ary for more limited embodiment~ of the enco~r and/or ~co~~r In one preferred embodiment of the pre~ent inv-ntion, the multiplsxer may perform the ~nco~in~ or encrypting functions and thus may be con~idered an ncoder or encryptor The term "encryptor"
may al~o b- used herein to refer to an item or seed used to e~ y~ particular text data Prior to di~cussing the specific of allocation, encryption will be discussed briefly In the encrypt block 415, the ~ncqAer may maintain a teletext seed table (TST) of n teletext seeds TS0, , TSn, wherein n can be any whole number For example, n may be 31 thereby W095/15617 2 1 77735 PCI`/IIS91/138~t6 ._ yielding 32 teletext seeds Each teletext seed ~so, , TSn in the teletext seed table represents a unique way of encryption and may be considered a physical teletext el-mentary stream (TES) Accordingly, the teletext seed table maps ach teletext seed TSO, , TSn to a corresponding TTX elementary stream TES 0, , TES n Alternativ-ly, a table of TS's need not be stored in a table if th- encryptor automatically generates TS's based on a TES Accordingly, TES in the teletext he_der would indicat- to the encryptor how to g~nerate the TS's for encryption Each teletext seed in the teletext se~d table may be generated e_ch cryptocycle by perrorming a seed expansion using a 32 bit random number and a seed procreation number Th- details of the seed expansion will not be di~cu~sed in herein However, the m_nner in which the teletext seed~ are generated is not material so long as each TS iJ unigue. In addition, it i~ required that some mec~A~ism b~ provided to for delivering all TS's to the d~coAor~ Seed generation provide~ one method for generating uniqu- TS's and for delivering them to the ~cl~A~r~ .
As di~cu~ed above, the TTX system of the pre~ent invention ~ay b configured to provid- such teletext services as n~t~o.h control, teletext ~ro~Lams, teletext for non-t-l-t-xt programs, broa~ca~t or general messages, per~onal me~age~, and an electronic program guide among other po~sibilities The particular filter ~ettings, encoder requirements, ~^ro~r requirements, and page range for each of these teletext f-atures according to two specific embodiments will be described below with reference to Figures 32A and 32B, re~pectively It should be ~-cr~J~ized that the specific embodiments woss/1s~7 2 1 7 7 7 3 5 PCT~S9~/138~6 discussed below are intended to be mere examples and that other embodiments are possible Three filters specify a teletext page with a particular ~ervice service category, service number, and control The control filter may correspond to FILTER 6, FILTER 7 or FILTER 8 of the TTX header row packet As discus~ed above, the service category filter can specify between one of a nu~ber of service cateaories such as TV, radio, text, data, etc The service number identifies a particular s-rvice offer-d from a service category Thu~, service category and service number together uniquely identify a particular service The control filtcr is u~-d to identify TTX pages which are part of a TTX service per se and pages which are used to support other services For network co,Llol pages, the filter setting for the control filter is, e g "l~ The category and service number filters may hav any setting, i e "don't care" as illu~trat-d in Figur-s 32A and 32B The network control pages may occupy on- of two page ranges depending on implementation for reason~ discussed further below The two pag- ranges are illustrated in Figures 32A and 32~ Of course, it should b- clear that the maximum range of 0000-FFFF is not int~ to limit the present invention for any of the TTX features One of the telet-xt s-Qds in the teletext ~eed table of the encoder is allocated for network control pages Any encrypted pages which hav- the control filter set must be encrypted with this telet-xt seed In the simplest case, the enco~r has a fixed allocation for network control pages In other words, one particular seed of the teletext seed table will always be allocated for the network control pages A more complicated implementation may require WO 9S/15647 2 1 7 7 7 3 5 PCT/I~S9~/138 16 dynamic allocation of TES #'s for encryption on-demand In either case, the DISE of the decoder generates the network control seed every cryptocycle Broadcast or general messaqes (also referred to as broadcast pag-s) have the same security concerns and can be handled in the same manner as the network control pages Th- nature of the broadcast requires that all broadcast page~ have all filters except the control filter disabl-d so that all decoders will receive the pag- The control filter will be enabled and set to, e g , "1~ to indicat- a network control page For t-let-xt programs, the category filter may be set to any one of the available teletext categories, e g , TTXl, TTX2, , TTX~, where m is the number of different t-letext categorie~ TTXi of Figures 32A and 32B i~ a category as a TTX type category The service number filt-r may be set to n, which may b- any available service number for a particular category The control filter is enabled and s-t to, e g "o", to indicate the abs-nce of a network ~G,LLol page The page range for teletext ~G~omS is illustrated in Figures 32A and 32B
The encoder muat allocat- (either fixed or dynamic) one tel-text ~e-d table entry for every TTX s-rvic- in order to ensur- that ach TTX service is e Ly~Led differently A mapping of this allocation, i e , TES ~ to filter valu-s us-d to identify a particular servic- (just for each rvic- category and service number) is maintained in th- ~n~o~-r The enro~or transmits information concerning how to generate th- seed to the DISE 157 by placing th- TES ~ into the PACXETS data, for example, in the virtual r~nn ~1 packet Once encryption is enabled, all TTX service pages will have their service category and service number WO 9S/156~1~ 2 1 7 7 7 3 5 PCI`I~JS9`~/138~6 - filters enabled Disabling a filter may cause rows to be shared between pages Encryption of these rows may cause conflicts with specific annotation rows which are encrypted with a different seed For example, a single page may include annotation rows that are specific to different services and that are encrypted differently as w~ll as on- or more common row~ If the service category and ~ervice number filters were di~abled, the decoder would erron-ou~ly usc both annotation row~ to construct the page ~-cau~- the decryptor is lo~ded with the teletext ~eed for the page to be grabbed, the common rows may be transmitt-d without encryption to prevent any problems decrypting the page at different decoders Alt-rnativ-ly, multiple d-cryptors may be provided for de_LyyLing multiple rows encrypted differ-ntly Telotsxt support for non-teletext services may be implemented xactly a~ a TTX service The category filter may be s~t to any non-TTX category, e g , television, radio, etc The service number filter may be set to n, which is any available service number for the selectQd cat-gory As above, th- control filter is set to, e g ~0~, to indicate the absence of a network control page Each of th- filter values and the page rang- is illu-trated in Figures 32A and 32B
Sinca encryption for non-TTX ~ervices is supported in the sam way as TTX services, the encoder has the same r-quir~nt~ a~ for TTX service~ The only difference betw-en th- two may be the method of allocating teletext seed table entri-s to the services ~or example, TTX
services may hav- a fixed allocation, thereby ensuring that a TES will always be available, and non-TTX services may be allocated dynamically on a first come first served basis Thus, once all of the TES's are allocated, a non-wo gS/156.~7 2 1 7 7 7 3 5 PCT/US9~"38~6 TTX service cannot be encrypted Of course, non-TTX
services may have a 'ixed allocation and non-TTX services may be allocated dynamically Both TTX and non-TTX
services having TTX support appear identical to the decoder Therefore, the decoder must handle the TTX
support of non-TTX services in th~ sam- manner as TTX
services Personal messages (PMs) may be considered a text service PMs are typically initiated at the encoder for transmission to a subset of decoders PMs may be encrypted addre~sed data packets (ADPs) which deliver the TES t, page nu~ber and a time stamp indicating when the releasQ of th- PM teletext sQed is to terminat- The ADP
is a particular kind of PACXETS data packet that may be r-c-ived only by individual ~-co~rs Group PMs may be implement-d by individually addr~sing each decoder in the group Depending on security concerns, all PMs may be encrypted the same way Thus, the PMs would be secure from all thos- who do not receive them However, it is conceivable that a PM may be received by a subscriber (who was ~-nt a different PM) other than to whom the it was addret~-d Alternatively, PMs may be classified in groups having different encryptors Each of the groups may be con~idered a different service because each has it~ own e,~L~Lor Handled as a TTX ~ervice, the PMs may have a category filter setting of TTX and a service number filter setting of n, where n is any PH TTX service number Th~ control filter may b~ ~et, e g , to "o~, to indicate the absence of network control data The filter values and page range for PMs is illustrated in Figures 32A and 32B The transmission of PM pages and ADPs must woss/ls~7 2 1 7 7 7 3 5 PCT~9~/138~6 be tightly coupled in time because the ADP trlggers the page grab If either the PM or the ADP is bsent, the page is not re~eived The PM ADP has a limited life span and th- encoder must ensure that the PM page is transmitted with sufficient frequency within this life span The DISE must release the PM teletext seed for a limited number of cryptocycles after it receives the PM
ADP .
The electronic program guide (EPG) may be offered as a ~t~n~rd feature or as a revenue generating TTX
service If offered as a standard feature, the EPG pages may bQ tr-ated as network control pag-s For example, the s~nAard electronic y-o~Lam ~ide could be acces~e~
as a s-lection from a main menu Accordingly, the ela_L~Gnic ~Lo~Lam guid- would oc~y a portion of the network CO~LO1 page range as illu-~trated in Figure 32A
since these pages would be indistinguishable from other network control pag-s Alternativ-ly, the EPG may be offered as a TTX
service, where the EPG pages may be treated as a unique TTX service TTX service ele_~LGIlic ~G~Lam guide requir-~ that the ~coA^r tune to th- TTX service A
virtual chann-l will be available to support the ele~ G~ic ~ am guide and a full range of EPG pages is possible as illu~trat-d in Figure 32B The filter s-tting~ for TTX service electronic program guide are identical to TTX service filter settings, namely the cat-gory filt-r is set to TTX, the servic- number filter is set to n, and the control filter is set, e g "o", to indicate the ab~ence of network control pages The encoAer maintains TTX encryption by mapping services to teletext seed table entries In one implementation, there is one fixed allocation for the WO 9S/1~6~7 2 1 7 7 ~ 3 5 PCI/l:S9~/138~i network control pages and the rest are dynamically allocated for use by the electronic program guide, personal messages, and service pages, both TTX and TTX
support for non-TTX services In a more flexible implementation, all pages may be dynamically allocated The allocation example depicted in Figure 33 allows for eay calculation of teletext seed table entries The network control pages will have a reserved TES ~ cf 31 The personal messages will have a reserved TES # of 30 Thi~ limit~ the personal message~ to one physical text stream, i e only one cla~s of encryption for all personal mes~ages However, th- TES ~ may still be tran~mitted in the ADP to allow for future reallocation In the simplest ca~e only one type of TTX category exists By reserving TTX service TES ~s starting at 0, the TES ~ can be made to co~e~ond with the TTX service number Only non-TTX s~rvice numb-rs would not have a simple correlation with TES ~g The encoder will dynamically allocate TES ~s to non-TTX servic-s The allocation sch-me de~cribed above is particularly u~eful wh-n the multiple pag- grabbing logic is ~imilar to that depicted in Figur- 7, where each page grabbcr h~J its own d-cryptor and aggregate filter comparator How-ver, multiple page grabbing logic similar to that depicted in Figure 8 limits the available allocation of page range~ for particular services As in Figure 8, each page grabber shares a decryptor (the seed limitation) and aggregate filter comparator (the filter limitation) As a result, each page grabb~r will use the same filter values and decryption seeds with only the page number unigue to each grab One consequence of the filter limitation is that the decoder i8 forced to perform only one TTX function at any WO 9S/lS647 PCI'/US9~/138~6 _ time, i e , grabbing network control pages, or viewing a TTX service, or receiving a personal message, etc However, it is desirable to receive personal messages in the background even if the decoder is viewing other TTX
pages Therefore, in order to implement a system that meets subscriber and operator expectations, the TTX
functions that may occur simultaneously must be identified Further, each of these TTX functions must generate matche~ for the same aggregate filter comparator Since only the page number may be used to identify these TTX functions uniquely, the simultaneous TTX functions must exist together in the page addre~s space If, for example, broadcast pages, network control pages, service related pages, and personal messages each must be capabl- of being received simultaneously, the dDcoAer must simultaneously grab broadca~t pages, network control or service related pages, and personal message page~ If bro~cast pag-s are lumped together with network control pages, the simultaneous grabs could be ~Yr~nA~ to n-twork control pages including broadcast pages, service related pages (i e , TTX service pages and TTX gu~ o~ for Non-TTX s-rvices), and personal message pages In th- exa~ple of Figure-~ 32A and 32B, network control pagos were identified by the control filter Und-r the filter limitation, setting the filters to grab a network co ~ol page prevents service related and personal message pages from being grabbed since they have their unique CG ~ol bits cleared Thus, the control filter may no longer be used since it is unique for network control pages Network control pages must be distinguished from service related and personal messaqes using the pag~ number filter The result is that the WO 9SIIS647 2 1 7 7 7 3 5 PCI`/US9`1/138J6 network control pages may no longer occupy the full page rang- of OOOO-FFEF Rather this page range must be divided among the various TTX features Service related and personal mes~age pages use the category and service n~mher filters to identify themselves The service related and network control pagss grabb d will depend on the particular service that the d-coder is tuned to The do~oA^r retrieves filter information from the virtual chA~l selected by the subscrib~r for viewing Howev-r s-tting the filters according to the virtual c~ann l prevent~ personal mQssag-s fro~ being rec-ived sinc~ th-y have th-ir own unique category (TTX) and ~ervice nu~ber which may be different fro~ the chann~l select~d by the subscriber A~ with the ~o~k control pag-s a portion of th- full pag- range mu~t b allocat-d for personal messages The personal message~ may no longer enable the category and servic- nu~ber filters Both must be disabled to allow any decoder to receive th-~ no matter which virtual channel i~ b ing viewed The new page ranges for the features are illu~trat- in Figur- 34 Despit- th- li~itation in page range other defined filters may still b- enabl-d Thus ~-veral pages having the sa~e paq~ nu~ber may be disting ~ ~h ~ using these filter- Th- operator ~ay en~ure that the subscriber rec-ives certain messages by disabling these filters The ncryption of the pages describ-d above does not c~a ~ Th~ d-t-rmination of which pag- belongs to which servic- al~o does not change In so~- implementations the encod-r can determine the usage of a page based on its ser~ice category and service number filters In other implementations the page number must also be used to identify the TES for encryption WO9SI15647 2 1 77735 PCI`IUS9~/138~6 The seed limitation prevents the decoder from ~rabbing multiple pages that are encrypted with a different teleteXt seed A11 services cannot be encrypted with the same teletext seed for security rea~ons The TTX decryptor may be modified to allow for multiple teletext seeds Ideally there should be exactly as many teletext se-ds as there are simultaneous T~X
functions, for exa~ple, three in the case discussed abov- It may be acc-ptable to ~pecify that a broadcast page may not b- e -~y~-ed, sinc- the broadcast is received by all en~ rs If this is the case, then only two seed- n-ed to be support-d While the pr-s-nt invention has been disclosed with re~pect to a preferred embodim-nt and modifications th-r-to, it i~ to be und-rstood that the invention is not limit-d to the preci~- embodimentJ and that various change~ and ~odification~ may b- effected therein by tho~e in the art without departing from the scope and spirit of the invention

Claims (15)

WHAT IS CLAIMED IS:

1. In a receiver of a communication system for receiving digital data streams of a plurality of services multiplexed in a sequence of frames, wherein a frame of said sequence of frames includes a teletext header packet defining at least a portion of a teletext page and having a plurality of filter fields, each filter field having a filter value, an apparatus for generating a teletext page comprising:
extracting means for extracting the teletext header packet from the frame, wherein said teletext header packet includes a page number filter field having a page number value and a plurality of aggregate filter fields each having a filter value;
comparing means for comparing the filter value for each filter field of the extracted teletext header packet to a corresponding requested filter value and for generating a matching signal if each filter value matches the corresponding requested filter value, wherein said comparing means comprises:
a page comparator for comparing the page number value to the requested page number value; and an aggregate filter comparator for comparing the filter values of the aggregate filter fields to corresponding requested filter values, wherein the aggregate filter field comprises a language filter field having a language value, and wherein said aggregate filter comparator comprises a filter comparator for comparing the language value to a requested language value; and constructing means, responsive to the matching signal, for constructing the portion of the teletext page defined by the extracted teletext header packet.

2. The apparatus of claim 1, wherein the aggregate filter field comprises a category filter field having a category value, and wherein said aggregate filter comparator comprises a filter comparator for comparing the category value to a requested category value.

3. In a receiver of a communication system for receiving digital data streams of a plurality of services multiplexed in a sequence of frames, wherein a frame of said sequence of frames includes a teletext header packet defining at least a portion of a teletext page and having a plurality of filter fields, each filter field having a filter value, an apparatus for generating a teletext page comprising:
extracting means for extracting the teletext header packet from the frame, wherein said teletext header packet includes a page number filter field having a page number value and a plurality of aggregate filter fields each having a filter value;
comparing means for comparing the filter value for each filter field of the extracted teletext header packet to a corresponding requested filter value and for generating a matching signal if each filter value matches the corresponding requested filter value, wherein said comparing means comprises:
a page comparator for comparing the page number value to the requested page number value; and an aggregate filter comparator for comparing the filter values of the aggregate filter fields to corresponding requested filter values, wherein the aggregate filter field comprises a service number filter field having a service number value, and wherein said aggregate filter comparator comprises a filter comparator for comparing the service number value to a requested service number value; and constructing means, responsive to the matching signal, for constructing the portion of the teletext page defined by the extracted teletext header packet.

4. The apparatus of claim 1, wherein the aggregate filter field comprises a time zone filter field having a time zone value, and wherein said aggregate filter comparator comprises a filter comparator for comparing the time zone value to a requested time zone value.

5. In a receiver of a communication system for receiving digital data streams of a plurality of services multiplexed in a sequence of frames, wherein a frame of said sequence of frames includes a teletext header packet defining at least a portion of a teletext page and having a plurality of filter fields, each filter field having a filter value, an apparatus for generating a teletext page comprising:
extracting means for extracting the teletext header packet from the frame, wherein said teletext header packet includes a page number filter field having a page number value and a plurality of aggregate filter fields each having a filter value;
comparing means for comparing the filter value for each filter field of the extracted teletext header packet to a corresponding requested filter value and for generating a matching signal if each filter value matches the corresponding requested filter value, wherein said comparing means comprises:
a page comparator for comparing the page number value to the requested page number value; and an aggregate filter comparator for comparing the filter values of the aggregate filter fields to corresponding requested filter values, wherein the aggregate filter field comprises a security element filter field having a security element value, and wherein said aggregate filter comparator comprises a filter comparator for comparing the security element value to a requested security element value; and constructing means, responsive to the matching signal, for constructing the portion of the teletext page defined by the extracted teletext header packet.

6. In a receiver of a communication system for receiving digital data streams of a plurality of services multiplexed in a sequence of frames, wherein a frame of said sequence of frames includes a teletext header packet defining at least a portion of a teletext page and having a plurality of filter fields, each filter field having a filter value, an apparatus for generating a teletext page comprising:
extracting means for extracting the teletext header packet from the frame, wherein said teletext header packet includes a page number filter field having a page number value and a plurality of aggregate filter fields each having a filter value;
comparing means for comparing the filter value for each filter field of the extracted teletext header packet to a corresponding requested filter value and for generating a matching signal if each filter value matches the corresponding requested filter value, wherein said comparing means comprises:
a page comparator for comparing the page number value to the requested page number value; and an aggregate filter comparator for comparing the filter values of the aggregate filter fields to corresponding requested filter values; and constructing means, responsive to the matching signal, for constructing the portion of the teletext page defined by the extracted teletext header packet, wherein the teletext header packet further includes a filter enable value corresponding to each of the aggregate filter fields, each filter enable value having either a first or a second value, wherein said aggregate filter determines for each aggregate filter field a match if (1) its filter value matches the corresponding request filter value and the corresponding filter enable value has a first value or (2) the corresponding filter enable value has a second value, wherein said each filter value is independently compared to each of the corresponding requested filter value and each corresponding filter value must match the corresponding request filter value if the matching signal is to be generated."

7. In a receiver of a communication system for receiving digital data streams of a plurality of services multiplexed in a sequence of frames, wherein a frame of said sequence of frames includes a teletext header packet defining at - 63a -least a portion of a teletext page and at lest one teletext data packet associated with the teletext header packet having a page number filter field having a page number value and aggregate filter fields having aggregate filter values, an apparatus for generating a teletext page comprising:
extracting means for extracting the teletext header packet from the frame;
page comparator, each comparing the page number filter value of the extracted teletext header packet to a respective requested page number value and for outputting a matching signal of the page number filter value matches the respective requested page number value;
at least one aggregate filter comparator for comparing the aggregate filter values of the extracted teletext header packet to requested aggregate filter values and for outputting a matching signal if the aggregate filter value matches the requested aggregate filter value;
page grab logic circuits, each responsive to the matching signal from one of the said page comparators and the matching signal from the at lest one aggregate filter, for outputting page construction information according to the at least one teletext data packet and to the teletext header packet; and page construction memory associated with each page grab logic circuit for receiving the page construction information thereby forming the portion of the teletext page defined by the teletext header packet.

8. The apparatus of claim 7, wherein the at least one teletext data packet is encrypted, and further comprising:
at least one decryptor for decrypting the encrypted teletext data packet an for supplying the decrypted teletext data packet to said page grab logic circuits.

9. The apparatus of claim 7, further comprising:
a plurality of aggregate filter comparators, each comparing the aggregate filter values of the extracted header packets to the respective requested aggregate filter - 63b -values and for outputting a matching signal to one of said page grab logic circuits if the aggregate filter value match the respective requested aggregate filter values.

10. The apparatus of claim 9, wherein the at least one teletext data packet is encrypted, and further comprising:
a plurality of decryptors, each decryptor decrypting the encrypted teletext date packet and for supplying the decrypted teletext data packet to one of said grab logic circuits.

11. A method of constructing at least a portion of a teletext page defined by a teletext header packet in a data frame, the data frame comprising a multiplex of digital data streams corresponding to a plurality of services, the teletext packet includes a plurality of filter fields, each filter field have a filter value, said method comprising the steps of:
extracting the teletext header packet from the frame wherein said teletext header packet includes a page number filter field having a page number value and a plurality of aggregate filter fields each having a filter value;
comparing the filer values for each filter field of the extracted teletext header packet to corresponding requested filter values;
generating a matching signal if each filter value matches the corresponding requested filter value wherein said comparing comprises:
comparing the page number value to the requested page number value; and comparing the filter values of the aggregate filter fields to corresponding requested filter values; and constructing the portion of the teletext page defined by the extracted teletext header wherein the teletext header packet further includes a filter enable value corresponding to each of the aggregate filter fields, each filter enable value having either a first or a second value, wherein said aggregate filter determines for each aggregate filter field a match if (1) its filter value - 63c -matches the corresponding request filter value and the corresponding filter enable value has a first value or (2) the corresponding filter enable value has a second value, wherein said each filter value is independently compared to each of the corresponding requested filter value and each corresponding filter value must match the corresponding request filter value if the matching signal is to be generated.

12. The apparatus of claim 3, wherein the aggregate filter field comprises a category filter field having a category value, and wherein said aggregate filter comparator comprises a filter comparator for comparing the category value to a requested category value.

13. The apparatus of claim 5, wherein the aggregate filter field comprises a category filter field having a category value, and wherein said aggregate filter comparator comprises a filter comparator for comparing the category value to a requested category value.

14. The apparatus of claim 3, wherein the aggregate filter field comprises a time zone filter field having a time zone value, and wherein the aggregate filter comparator comprises a filter comparator for comparing the time zone value to a requested time zone value.

15. The apparatus of claim 5, wherein the aggregate filter field comprises a time zone filter field having a time zone value, and wherein the aggregate filter comparator comprises a filter comparator for comparing the time zone value to a requested time zone value.