METHOD AND DEVICE FOR TRANSMITTING AND RECEIVING TELETEXT PAGES

Abstract: For novel media services such as the transmission of Electronic Program Guides (EPG), the use of teletext as a transmission medium is considered. It is efficient to refrain from the transmission, in the EPG signal, of those program data which are already present in regular teletext pages. The invention provides a method and device for assigning classification codes (program type, parental rating) to these programs. The classification is transmitted in the form of triplets in extension packets, for example packet X/26. The packets may form part of the regular teletext pages but also of the EPG data signal. In the latter case, a page linking mechanism is also provided.

Description: Method and device for transmitting and receiving teletext pages. FIELD OF THE INVENTION The invention relates to a method and device (transmitter and receiver) for transmitting and receiving teletext pages. The invention also relates to a teletext signal and to a storage medium on which such a signal is stored. BACKGROUND OF THE INVENTION A known method of transmitting teletext data is described in "World System Teletext", Technical Specification, revised March 1985, hereinafter referred to as WST specification. Said specification describes a mediod and data format for transmitting teletext pages for first-generation receivers (referred to as the Level 1 format), and a number of extensions of the Level 1 format for further facilities not yet provided for the first generation of teletext decoders. The WST specification particularly provides for the transmission of extension packets or "ghost rows" (referred to like that because they are ignored by the first- generation decoders). Extension packets are teletext data packets having a row number greater than 24. One of the known extension packets is packet X/26. With the aid of this packet, inter alia, me display facilities are further enhanced, for example the assignment of special attributes such as letter type, size, color and the like to selected text items of the teletext pages. OBJECT AND SUMMARY OF THE INVENTION It is an object of the invention to provide a method of transmitting teletext pages with which further facilities are made possible. To this end, the mediod according to the invention is characterized in that the attribute is constituted by a classification code for classifying said text item in one of a series of predetermined categories. This provides, inter alia, the possibility of classifying television programs mentioned in a television program overview into categories such as themes (sports, information, entertainment), sub-themes (soccer, news, music), parental rating and the like. The invention is particularly applicable to novel information services such as the "Electronic Program Guide" (EPG). This is a combination of an overview of television program data and a menu structure to render the information in this overview accessible to the user. The overview comprises, inter alia, an indication of the category for each program. It is true that EPG is expected to be transmitted as a teletext signal, but not in its conventional form of individually accessible teletext pages. However, in practice at least the titles of the television programs are already transmitted in die form of regular teletext pages. The non-prepublished Patent Application PHN 15.482 in me name of me Applicant describes a mechanism for providing the EPG data signal with references to these available tides. The mediod according to the invention provides die possibility of adding also classification codes to me titles which are already available. BRIEF DESCRIPTION OF THE FIGURES Fig. 1 shows diagrammatically a teletext transmission system to explain the method according to me invention. Fig. 2 shows some examples of data packets transmitted by a transmission station shown in Fig. 1. Figs. 3 and 4 show examples of a teletext broadcast to explain the mediod according to me invention. Fig. 5 shows the flow chart of a program performed by a processor shown in Fig. 1. DESCRIPTION OF EMBODIMENTS Fig. 1 shows diagrammatically a teletext transmission system to explain the method according to the invention. The system comprises a transmission station 1 , a transmission medium 2 and a receiver 3. The transmission medium may alternatively be a storage medium such as a videotape on which a television signal including teletext data is stored. The transmission station comprises a television signal generator 11 , a teletext signal generator 12, a teletext inserter 13 and a modulator 14. The television generator 11 generates a picture signal and the teletext generator 12 generates a teletext signal. The teletext signal comprises a "regular" teletext broadcast (wi news pages, sports scores, wea er forecasts, television programs). This regular teletext signal is generated in a first editing terminal 15. The teletext signal further comprises a data signal by means of which an electronic TV guide in a coded form is transmitted. This EPG data signal is composed in a second editing terminal 16. The picture signal and me teletext signal are combined in teletext inserter 13 to a video signal which is applied to the modulator 14 and is transmitted via transmission medium 2. The receiver 3 comprises a tuner 31 for demodulating the video signal. The demodulated video signal is applied for further processing and display to a television monitor 32. The video signal is also applied to a teletext decoder 33. This decoder decodes the "regular" teletext signal accommodated therein in further known manner and displays the pages on television monitor 32. The teletext decoder also receives the EPG signal and applies mis for further processing to an EPG processor 34. For each transmitted teletext page, me teletext signal comprises a plurality of data packets which are accommodated in further known manner in picture lines of the video signal during me picture flyback. Fig. 2 shows some possible forms of these data packets in greater detail. As has been attempted to show in mis Figure, each data packet comprises 45 bytes of 8 bits each. The first 2 bytes having a fixed value 1010..10 are referred to as "clock run-in" and are denoted by CRI in d e Figure. The mird byte is a "framing code" F and has also a fixed value. The next 2 bytes comprise a 3 -bit magazine number M and a 5-bit row number R. The significance of the other 40 bytes depends on the value of the row number R. If the row number R has the value 0, as is assumed in Fig. 2A, the data packet constitutes a page header of a teletext page. The series of 40 bytes of such a page header starts with two digits T (tens) and U (units) of the page number, a sub-code SC and a plurality of control bits C. The remaining part comprises 24 character positions wi a page header HDR and 8 character positions for displaying the current time. The transmission of a teletext page starts wim, and implies, the page header of this page. The page number is constituted by d e magazine number M, tens T and units U. It is a 3-digit number and is generally between 100 and 899 in order mat me user can select it by means of a decimal keyboard. The sub-code SC is an extension of die page number MTU. The page header and the subsequent packets having d e same magazine number M constitute me relevant page. In general, a series of teletext pages is transmitted in a repetitive cycle. If me row number R has one of the values 1-24, as is assumed in Fig. 2B, dien d e 40 bytes constitute a text row of 40 characters for display on a display screen in accordance with d e Level 1 display format. If die row number R has me value 27, as is assumed in Fig. 2C, then it is a "linked page packet X/27". Such a packet starts widi a 4-bit designation code D, by means of which a maximum number of 16 packets X/27 can be distinguished, and six groups of 6 bytes. In each 6-byte group, a linked page number can be coded. In mis way, a plurality of other pages may be referred to from a teletext page by means of packets X/27. Fig. 2D shows the data format of an extension packet whose row number R has the value 26. The first of the 40 data bytes is again a 4-bit designation code D, by means of which a distinction between a plurality of packets 26 is possible. The omer 39 bytes are divided into 13 groups of 3 bytes each, referred to as triplets. Each triplet comprises 18 information bits and 6 parity bits for Hamming protection. The 18 information bits of each triplet are divided into a 6-bit address field, a 5-bit mode field and a 7-bit data field. In Fig. 2D, the bits of the address field are denoted by A, me bits of Lhe mode field are denoted by M, and me bits of the data field are denoted by D, while the protection bits are denoted by P. This division of packet 26 into triplets is known per se from me WST specification. In accordance with the invention, the significance of "classification triplet" is assigned to one of me possible values of die mode field of a triplet. In such a classification packet, die address field specifies which text item (for example, which row of the teletext page) the triplet relates to. A classification code is accommodated in the data field, for example, 0 for informative television programs, 1 for sports programs, 2 for entertainment, 3 for education, etc. If the number of bits in ie data field is insufficient, more values of me mode field may be reserved. Fig. 3 shows a first example of a teletext broadcast to explain die method according to the invention. In diis example, the packets X/26 with classification triplets form pan of the teletext page on which the corresponding text items are mentioned. The reference numerals 100 and 110 in me Figure denote two teletext pages (pages 601 and 602) wid d e television program overview of the stations BBC1 and BBC2, respectively. Bo pages comprise an extension packet X/26. The packet X/26 associated with page 601 comprises three classification triplets 101-103. The address field of triplet 101 has the value 7 and the data field has d e value 2. This means that the television program on row 7 of me page belongs to category 2 (entertainment). Similarly, triplet 102 indicates that the program on row 8 belongs to category 0 (information). Triplet 103 indicates that the program on row 9 belongs to category 2 (entertainment). Teletext page 602 comprises classification triplets 111- 113. The first triplet 111 assigns category 1 (sports) to the program on row 7, the second triplet 112 assigns category 3 (education) to the program on row 8, while in accordance with triplet 113, the program on row 9 belongs to category 0 (information). Fig. 4 shows a second example. In this example, the classification triplets in packets X/26 form pan of a separate EPG data signal. From the data in mis EPG signal, reference is made to die teletext pages wim the relevant text items. This method is more efficient because me EPG data signal is expected to be broadcast once or several times a day, while the regular teletext pages are repeated at a considerably higher frequency. The mechanism of page linking has been described in greater detail in me non-prepublished Patent Application PHN 15.482, so diat a rough description is sufficient in this case. In Fig. 4, me reference numeral 150 denotes an EPG page wi a hexadecimal page number EFO. A series of such pages constitutes the EPG data signal wim which a file of television program data (such as tide and category) of various television stations is transmitted. However, die program data of BBC1 and BBC2 are not accommodated in d e EPG data signal because they have already been mentioned on the regular text pages 601 and 602, respectively. To couple the program data of BB1 and BBC2 to the EPG file, EPG page 150 comprises references to the relevant regular teletext pages. More panicularly, page 150 comprises a linked page packet X/27 whose sixth link refers to teletext page 601 in mis example. Moreover, the EPG data signal comprises a packet X/26. The first triplet 151 in this packet is a page linking triplet (as defined by the mode field) whose address field has the value 6 and the data field has the value 0. As has been described in Patent Application PHN 15.482, mis constitutes a reference to a regular teletext page whose page number has an offset 0 with respect to the sixth link in packet X/27. In this way, a reference is made to page 601 +0 = 601. The next mree triplets 152-154 are classification triplets. They correspond to the triplets 101-103 shown in Fig. 3. On the one hand, they define the program title because the address field comprises the relevant row number, and on me o er hand, they classify die category of d e program by means of the data field. As is apparent from the mode field, the next triplet 155 is a page linking triplet again. It refers to a regular teletext page whose page number has an offset 1 with respect to me sixth link in packet X/27. In this way, a reference is made to page 601 + 1 = 602. The next three triplets 156-158 are classification triplets. They correspond to the triplets 111-113 in Fig. 3 and mus define die program tides and categories of the BBC2 programs. Fig. 5 shows the flow chart of a program performed by EPG processor 34 (Fig. 1). In a step 200, the EPG data signal is received and decoded, and the decoded program data such as station, title, category, parental rating, and die like are stored in a local memory. In a step 201, it is checked whether me EPG signal comprises one or more links to regular teletext pages. If this is the case, the relevant teletext page is acquired in a step 202. In a step 203, it is checked whedier the EPG data signal and/or regular teletext page comprise classification triplets. If this is the case, the address field and the data field of mis triplet are decoded in a step 204. The address field is representative of a row number in the regular teletext page, and die data field represents a given category. In a step 205, me program title on the relevant row is read and added, together widi the conesponding category, to die omer program data in the local memory. Subsequendy, the program returns to step 203 so as to check whether mere are more classification triplets to be processed. The invention may be summarized as follows. For novel media services such as the transmission of Electronic Program Guides (EPG), the use of teletext as a transmission medium is considered. It is efficient to refrain from the transmission, in the EPG signal, of those program data which are already available in regular teletext pages. The invention provides a method and device for assigning classification codes (program type, parental rating) to these programs. The classification is transmitted in the form of triplets in extension packets, for example packet X/26. The packets may form pan of the regular teletext pages, but also of the EPG data signal. In the latter case, a page linking mechanism is also provided.

Claims: CLAIMS: 1. A method of transmitting a teletext signal, in which an extension packet comprising address data is added to the teletext signal for addressing a text item in a selected teletext page, and attribute data for assigning an attribute to said text item, characterized in diat said attribute is constituted by a classification code for classifying said text item in a predetermmed category. 2. A method as claimed in Claim 1, in which d e address data and attribute data are transmitted in the form of triplets with an address field, a mode field and a data field, characterized in uiat a predetermined value of the mode field indicates diat the classification code is incorporated in the data field. 3. A mediod of receiving a teletext signal to which an extension packet comprising address data is added for addressing a text item in a selected teletext page, and attribute data for assigning an attribute to said text item, characterized in mat said attribute is constituted by a classification code for classifying said text item in one of a series of predetermined categories, d e memod comprising the step of receiving, decoding and coupled storage of said text item with d e assigned classification code. 4. A transmitter for transmitting a teletext signal, in which an extension packet comprising address data is added to d e teletext signal for addressing a text item in a selected teletext page, and attribute data for assigning an attribute to said text items, characterized in that said attribute is constituted by a classification code for classifying said text item in a predetermined category. 5. A transmitter as claimed in Claim 4, adapted to transmit address data and attribute data in die form of triplets with an address field, a mode field and a data field, characterized in that a predetermined value of the mode field indicates that the classification is incorporated in the data field. 6. A receiver for receiving a teletext signal to which an extension packet comprising address data is added for addressing a text item in a selected teletext page, and attribute data for assigning an attribute to said text item, characterized in d at said attribute is constituted by a classification code for classifying said text item in a predetermined category, and in diat die receiver is adapted to receive, decode and coupled-store said text item with the assigned classification code in a memory. 7. A teletext signal to which an extension packet comprising address data is added for addressing a text item in a selected teletext page, and attribute data for assigning an attribute to said text item, characterized in that said attribute is constituted by a classification code classifying said text item in a predetermined category. 8. A signal as claimed in Claim 7, in which the address data and attribute data are incorporated in die form of triplets with an address field, a mode field and a data field, characterized in uiat a predetermined value of the mode field indicates that die classification code is incorporated in the data field. 9. A storage medium on which a teletext signal as claimed in Claim 7 or 8 is stored.

Inventors: VAN GESTEL HENRICUS ANTONIUS W, VAN GESTEL, HENRICUS, ANTONIUS, WILHELMUS
Applicants: PHILIPS ELECTRONICS NV, PHILIPS NORDEN AB, PHILIPS ELECTRONICS N.V.
Application year: 1996
Main classification: H04N7
IPC codes: H04N7