United States Patent (19) 11 Patent Number: 4,890,321 Seth-Smith et al. (45) Date of Patent: Dec. 26, 1989 (54) COMMUNICATIONS FORMAT FOR A 4,636,854 1/1987 Crowther et al. .................... 380/20 SUBSCRIPTION TELEVISION SYSTEM 4,694,491 9/1987 Horne et al. .......................... 380/20 PERMITTING TRANSMISSION OF 4,739,510 4/1988 Jeffers et al. .......................... 380/15 NDIVIDUAL TEXT MESSAGESTO 4,768,228 8/1988 Clupper et al. ....................... 380/20 SUBSCRIBERS OTHER PUBLICATIONS (75) Inventors: Nigel Seth-Smith; Cameron Bates; Lowry, "B-MAC: An Optimum Format for Satellite Samson Lim; William van Rassel; Television Transmission', SMPTE Journal, Nov., Robert Yoneda, all of Toronto; Keith 1984, pp. 1034–1043. Lucas, Richmond Hill, all of Canada The CCIR Study Group Report Document 10-11S/106-E of Sep. 23, 1983. (73) Assignee: Scientific Atlanta, Inc., Atlanta, Ga. Chouinard et al., "NTSC and MAC Television Signals 21 Appl. No.: 253,320 in Noise and Interference Environments', SMPTE 22 Filed: Sep. 30, 1988 Journal, Oct. 1984, pp. 930-949. Primary Examiner-Thomas H. Tarcza Related U.S. Application Data Assistant Examiner-Linda J. Wallace (63) Continuation of Ser. No. 883,310, Jul. 8, 1986, aban Attorney, Agent, or Firm-Banner, Birch, McKie & doned. Beckett (51) Int. Cl'....................... H04N 7/167; H04N 7/10; 57 ABSTRACT H04N 7/04 A subscription television system in which individual (52) U.S. C. ........................................ 380/20; 358/86; decoders are enabled to receive individually addressed 358/145; 358/147; 380/21; 455/4; 455/6 messages is disclosed. The composite signal, including (58 Field of Search .................... 380/APS 20, 21, 23, video and teletext, also comprises addressed packets 380/25; 455/4, 6; 358/86, 142, 145, 147; 370/60 which are detected by decoders and which indicate that References Cited a message addressed to a particular subscriber is forth (56) coming, and system control data. In a preferred embodi U.S. PATENT DOCUMENTS ment, both addressed packets and teletext are en 4,205,343 5/1980 Barrett .................................. 380/18 crypted. The addressed packet is decrypted using a 4,245,245 1/1981 Matsumoto et al. .................. 380/20 decoder-specific code and a transmitted code, while the 4,292,650 9/1981 Hendrickson ......................... 380/20 teletext message is decrypted using a decryption key 4,361,852 i 1/1982 Katzfey ............................... 358/145 4,388,645 6/1983 Cox et al. ............................ 358/147 contained in the system control data. The teletext mes 4,393,404 7/1983 Cox et al. ............................ 358/147 sage cannot be received until the addressed packet has 4,484,027 11/1984 Lee et al. .......................... 380/20 X been decrypted. Therefore, redundant levels of security 4,531,020 7/1985 Wechselberger et al. ............ 380/21 are provided to the system. Messages for display to the 4,531,021 7/1985 Bluestein ............... ... 380/21 user can be selected in response to user initiated com 4,536,791 8/1985 Campbell et al...................... 380/10 mands, in response to decoder initiation, or in response 4,577,332 3/1986 Brenig ............................... 371/69 X 4,600,921 7/1986 Thomas ............................ 380/18 X to the transmitter. 4,603,349 7/1986 Robbins ................................ 380/20 4,613,901 9/1986 Gilhousen et al. ................... 380/20 13 Claims, 19 Drawing Sheets r154 ADDRESSED PACKETS 8 SYSTEM DATA (VIA RAM 24) / 150 (l52 MATS 2 INPUT B-MAC WB MICROPROCESSOR AND TELETEXT SUPPORT DECODER HARDWARE AUDIO DISPLAY U.S. Patent Dec. 26, 1989 Sheet 1 of 19 4,890,321 U.S. Patent Dec. 26, 1989 Sheet 2 of 19 4,890,321 I6 FIELDS CONTAIN COMPLETE SYSTEM DATA TRANSMISSION 3O FRAMES PER SECOND 2"FIELDS"PER VIDEO FIG2 "FRAME" VBIOR SEED) 2OBITSBURST COLOR 40VIDEO l f 2Bifs ET 42 iii.FIG 3 1 i? 3655. (if SIGN MAGNITUDE WBIOR VIDEO ABCAE-51 ECIT TOTAL BITS IIIT Eisis DIGITALAUDIO-3 6Bisof 12 Bits of Ecc 44-BITS OF EACH OF STEPSIZE/ FORENCODED?) PARTY 6 CHANNELS 46-rBANDEDTHINFO 48-yAUDIO FIG4 HBIDATA UTILITY BITS 1 521 U.S. Patent 4,890,321 BINITNOLIWZINOMHONAS2 U.S. Patent Dec. 26, 1989 Sheet 6 of 19 4,890,321 I FULL FIELD MODE SELECT KEY SOURCE CODE ENCRYPTED PROGRAM 2 SEGMENT ID PROGRAM TER NUMBER SERVICE TER NUMBER FIG10 12 PROGRAM NUMBER P4CKETA OF SYSTEM DATA COST OFCURRENT PROGRAM 14 DECRYPTION KEY (1st SEGMENT FAST SCRAMBLING SELECT DECRYPTION KEY (2NSEGMENT) U.S. Patent Dec. 26, 1989 Sheet 7 of 19 4,890,321 32 DECRYPTION KEY (3SEGMENT) BLACKOUT CODE | | PROGRAM COST (MSB) FIG.ff 5 CHECK BITS PACKETB OF SYSTEM I FINGERPRINT TRIGGER DATA IMPULSE ENABLE 5 AUDIO/DATA CHANNEL USAGE PROGRAM RATING ACTIVE VIDEO USAGE GENERAL MESSAGE SOURCE SWITCH REQUEST SCRAMBLED PROGRAM TRACKED PROGRAM U.S. Patent Dec. 26, 1989 Sheet 8 of 19 4,890,321 PAY-PER-LISTEN RESERVED PORT CONTROL BITS COMMERCIAL CONTROL COMMAND COMMERCIAL CONTROL DATA FIG 2 PACKETC OF SYSTEM DATA 8 CHECK BITS 24 RESERVED 62 U.S. Patent Dec. 26, 1989 Sheet 10 of 19 4,890,321 |-—S118G9I————SII883|| 06 00] U.S. Patent Dec. 26, 1989 Sheet 1 of 19 4,890,321 USER INITIATED SYSTEM INITIATED puPINITIATED USER REQUESTS ADDRESSED PACKET, BILLING UPDATE HO INFORMATION: SENT 8 DETECTED DUE PROGRAMMING INDICATING PERSONAL also BILLING STATUS OR BROADCAST MESSAGE 40 ACCESS EEPROM GRAB IDENTIFY INDICATED APPROPRIATE PAGE f32 EEPROM TO COMPLETEAS MEEDED ACCESS CHARACTER f34 GENERATOR DISPLAY MESSAGE (36 TEXT PROCESSING FIG. f6 U.S. Patent 4,890,321 U.S. Patent Dec. 26, 1989 Sheet 14 of 19 4,890,321 MIPIMPMIPIMPM) MEP FORWARD ERROR CORRECTION 3. MAJORITY LOGIC ters C / /(MIMel 7----- . P4gACKET 74 / / packet/M254, .4 .. .412.4%/ A IM2-4-162 MIM2's 4 ... 7,47 ZX REMOVAL OF 3: (uponocessorMAJORTY LOGIC fg:EOW packet cle's We PACKETBM as . /"62 PACKETAMMIA's M4 IM62 FIG f9 U.S. Patent Dec. 26, 1989 Sheet 15 of 19 4,890,321 FIG. 20 USE OF SYSTEM DATA 0 USE FAIL mo EVALUATE KEY KEYSOURCE 1 USETEST 5 s key KOM FIG.20C ENCRYPTED PROGRAM ENABLE DECRYPTION STORE SEGMENTD 26 EVALUATE STORED PROGRAMTIER TIER CONTROLS TO FIG, 20b U.S. Patent Dec. 26, 1989 Sheet 16 of 19 4,890,321 FIG. 20b PAY. PER VIEW YES SELECTION 266 STORE PROGRAM ID ADD CHARGETO COST OF IMPULSE CURRENT PROGRAM CHARGES COMPARE BLACKOUT CODETO STORED NUMBER DSABLE VIDEO FINGERPRINT TRIGGER ON WRITE USER ID TO SCREEN TO FIG. 20c U.S. Patent Dec. 26, 1989 Sheet 17 of 19 4,890,321 FIG.20C 280 GENERAL YES MESSAGE ON 282 REQUEST MATS TOGRABGENERAL MESSAGE PAYPER YES 286 LISTEN ON? TREAT AUDIO I AS PAYTV PROGRAM 288 SCRAMBLED YES PROGRAM ENABLE DESCRAMBLER 292 TRACKED YES 29 PROGRAM 4 ON? SAVE PROGRAM ID U.S. Patent Dec. 26, 1989 Sheet 18 of 19 4,890,321 USE OF INDIVIDUAL sesafil. NFORMATION 300 302 DATA STATUS 304 306 308 310 312 34 316 38 PAGENUMBER PAGE 320 322 MEMORY WRITE PATCH PATCH TO EEPROM U.S. Patent 4,890,321 4,890,321 1. 2 system-wide, and there is no provision made for trans COMMUNICATIONS FORMAT FOR A mission of individual messages to individual subscribers. SUBSCRIPTION TELEVISION SYSTEM Those skilled in the art will recognize that there are a PERMITTING TRANSMISSION OF INDIVIDUAL number of constraints on the operation of any successful TEXT MESSAGES TO SUBSCRIBERS 5 subscription television system. For example, there must be an extremely reliable and trustworthy method of This application is a continuation of application Ser. computing charges to be billed to the subscriber and for No. 833,310, filed July 8, 1986, now abandoned. communication of credit status updates. It is also desir able that the subscriber be permitted to prepay for cer FIELD OF THE INVENTION 10 tain classes of service, for example, to have access to a This application relates to improvements in subscrip particular broadcaster's offerings. On the other hand, it tion television systems. More particularly, the invention is also desirable that an "impulse' purchase system be relates to a communications system and format for a provided such that the viewer could purchase a particu subscription television system which permits communi lar program on a "pay-per-view' basis when desired. cation of individually addressable text messages from a 15 Similarly, it is desired that a running list of programs central location to individual subscribers. purchased by the subscriber be available, such that he can confirm that he is indeed being billed correctly. It is BACKGROUND OF THE INVENTION furthermore desired that means be provided for secur The sophistication of communications systems in ing the system against improper use, which includes volving subscription television is continually increasing. 20 both prevention of viewing of inappropriate subject The systems being installed at this time have greatly matter and purchase of fee-bearing material by persons improved communications flexibility as compared to not authorized to do so. those previously in use, while the quality of the trans The requirement that the credit status be updateable mitted signal is continually being improved, as is flexi further requires that communication be possible in both bility in the business arrangements possible between the 25 directions between the decoder and the transmitter. subscriber and the broadcaster. For example, in U.S. However, it would be inefficient to provide individual Pat. No. 4484,217 to Block et al., there is disclosed a uplink transmission facilities at each decoder in a satel subscription television system in which all billing calcu lite transmission system, for example. Therefore, it is lations are carried out at the decoder, that is, at the desirable that a two-way communications facility be individual subscriber's location.