WO2005074276A1

WO2005074276A1 - Multipage teletext decoder

Info

Publication number: WO2005074276A1
Application number: PCT/IB2005/050271
Authority: WO
Inventors: Henricus A. W. Van Gestel
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2004-01-28
Filing date: 2005-01-24
Publication date: 2005-08-11
Also published as: JP2007520953A; EP1712081A1; CN1914914A; KR20070001109A

Abstract

A teletext decoder system comprises a teletext data cache memory (17) for storing teletext data, and an input (11) for receiving a user-initiated command including a reference to a specific item in a teletext service. It is configured to maintain at least a first list, each entry in the list including information referring to an item of teletext, and to autonomously acquire and store teletext data referred to by the information included in at least the first list. The teletext decoder system is configured to add an entry to the first list including information corresponding to the reference only upon determining that teletext data referred to by the reference is absent from the teletext data cache memory (17).

Description

MULTIPAGE TELETEXT DECODER

FIELD OF THE INVENTION The invention relates to a teletext decoder system, comprising a teletext data cache memory for storing teletext data and an input for receiving a user-initiated command including a reference to a specific item in a teletext service, said teletext decoder system being configured to maintain at least a first list, each entry in the list including information referring to an item of teletext, and to autonomously acquire and store teletext data referred to by the information included in at least the first list. The invention further relates to an audiovisual device. The invention also relates to a computer program.

BACKGROUND OF THE INVENTION European patent application EP-A1-0 379252 discloses an embodiment of a television receiver comprising a multipage teletext decoder. The multipage teletext decoder comprises an acquisition circuit, which captures a number of selected pages in an autonomous manner, a page memory, in which the captured pages are stored, and a display circuit, which converts a selected stored page into elementary colour signals. The multipage teletext decoder is connected to a control circuit by means of a command bus. Furthermore, a portion of a preferably non- volatile storage medium is used for storing a number of teletext page numbers. The page numbers stored in registers of the page number memory, as well as page number 100, are passed, on to the acquisition circuit via the command bus, whereafter this circuit captures the relevant teletext pages in an autonomous manner and stores them in the page memory. Page 100 is called because this page generally comprises the main index and should be the first page to be displayed on the display screen in the teletext page. It is thus very likely that page 100 and the pages with the page numbers stored in the registers have already been found and stored if the user selects the teletext state. In response to generating a page number which is not yet stored in the page number memory, a control circuit is adapted to refrain from storing the generated page number and to assign a most recent order of precedence to the relevant page number which has already been stored. A problem of the known receiver is that page number 100 would also be entered in the page number memory if the user were to explicitly request this page at some point. Thus, a position in the teletext page number memory is needlessly occupied and a page is cached twice.

OBJECT AND SUMMARY OF THE INVENTION It is an object of the present invention to provide a teletext decoder system of the type mentioned above with a mechanism for maintaining a page number list based on past viewing behaviour in a more efficient way when used in conjunction with non- viewing related caching criteria, such as page number, content or links. This object is achieved by the teletext decoder system according to the invention, which is characterised in that the teletext decoder system is configured to add an entry to the first list including information corresponding to the reference only upon determining that teletext data referred to by the reference is absent from the teletext data cache memory. An item may be any type of identifiable complete element in a teletext service, e.g. a packet, sub-page, page or magazine. Due to the features recited above, the decoder system is configured to implement a caching algorithm based on a viewer's habits, for which reason the first list is commonly called a 'habit list'. Because the entry including information corresponding to the reference is only added upon determining that teletext data referred to by the reference is absent from the teletext data cache memory, the decoder system avoids entering superfluous entries. Where the habit list is supplemented with additional lists, based, for example, on explicit marking as a favourite by the user, the fact that it comes next in the sequence of transmission, etc., units referred to in these additional lists will not also figure on the first list. Thus, the first list is kept 'clean', and more effective use is made of it. Preferably, the teletext decoder system is configured to add the entry only upon determining that no entries including information corresponding to the reference are present in the first list. Thus, references to requested items appear only once in the first list, so that more space is available for entries including information referring to other items. Preferably, the teletext decoder system is configured to implement at least one algorithm for selecting teletext data to be autonomously acquired and stored in the teletext data cache memory on the basis of a pre-defined relationship to a previously acquired item in the teletext service. Thus, the teletext decoder system is designed to implement both a relatively fast-changing caching algorithm (based on a relationship to a previously acquired item), and a relatively slow-changing algorithm (based on a viewer's past habits). This increases the likelihood that all relevant units are cached. The invention ensures that data expressly requested by a user always results in an entry on the first list, unless it has already been cached. This is an improvement over known mechanisms for joined implementation of habit- based and relationship -based algorithms. These often result in relevant units not being cached, because the request does not fulfil the requirements for entry onto the first list, even though the requested item is not 'caught' by the relationship-based algorithm (because requested items are excluded, for instance). Other known mechanisms result in entries being added to the first list even though the requested item is already cached due to its selection on the basis of its relationship to a previously acquired item. Preferably, the teletext decoder system comprises a teletext presentation section (15,16) for decoding teletext data into a video format for a display (13,14), wherein the teletext decoder system is configured to add the entry only upon determining that the teletext data referred to by the reference has been completely acquired and decoded. Thus, accidentally entered requests are not treated as valid requests if the user immediately enters another request before the accidentally requested unit of data has been completely acquired and decoded. This is especially useful where units are requested by pressing remote control buttons corresponding to the digits of a reference number, e.g. a teletext page number, in succession. Preferably, the teletext decoder system is arranged to rank the entries in the first list in order of priority, and to autonomously acquire and store teletext data referred to by the information included in the first list in order of decreasing priority. Thus, it is possible to distinguish between very relevant previously requested items and items which have lost their relevance to the user. The very relevant ones are cached as much as possible. Preferably, the teletext decoder system is configured, upon determining that an entry including information corresponding to the reference is already present in the first list, to assign a highest level of priority to the entry already present in the first list. Thus, recently requested items are also regarded as the most relevant. Preferably, the teletext decoder system comprises a user control device adapted to allow a user to provide in a plurality of different ways a request for a specific unit of teletext data, wherein the teletext decoder system is configured to add an entry to the first list including information referring to the requested item only upon determining that teletext data corresponding to the requested item is absent from the teletext data cache memory, regardless of the way in which the request is provided. Because the user control device is adapted to allow a user to provide in a plurality of different ways a request for a specific unit of teletext data, use can be made of links in teletext pages and favourite buttons, as well as numeric keyboards for entering a request. The invention does not discriminate between the ways in which a request is entered, even when, for example, link lists or catch lists are used alongside the first list. According to another aspect of the invention, there is provided an audiovisual device, e.g. a television receiver set, comprising a teletext decoder system according to the invention. According to a further aspect of the invention, there is provided a computer program adapted, when run on a programmable processing device comprising a processor and memory, an input for receiving a user command, memory for storing teletext data and means for acquiring teletext data, to enable the programmable processing device to function as a teletext decoder system according to the invention. The programmable processing device may be a television receiver, video recorder or set-top box with a controller and memory for storing instructions. Alternatively, it may be a general-purpose computer, arranged to access teletext via the Internet, by means of a teletext decoder chip on a plug-in card, or by means of a peripheral television receiver device with a teletext decoder.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be explained in further detail with reference to the accompanying drawings. Fig. 1 shows schematically the internal layout of a television receiver equipped for implementing the invention. Fig. 2 is a flow chart illustrating the various actions undertaken by a teletext decoder system according to the invention. DESCRIPTION OF EMBODIMENTS In the television system schematically shown in Fig. 1, a radio-frequency signal is received at an input 1 of a television receiver. The received signal passes through an RF amplifier 2 to a tuning circuit 3. The tuning circuit 3 tunes to a specific carrier frequency, associated with a television channel. The output signal of the tuning circuit 3 is passed to a demodulation circuit 4. The demodulation circuit separates video, audio and teletext components from the carrier signal. A colour decoder 5 retrieves and processes the video component. A teletext data acquisition circuit 6 retrieves teletext page data. The television system is controlled by a microcontroller 7, which executes instructions stored in a Read Only Memory 8 of a known type. The microcontroller further has access to a non-volatile memory 9, for storing data that must not be erased when the television system's power is turned off. Commands and data are transferred between the microcontroller 7 and the various components operating under its control via a bus 10, for example an I²C bus. A user of the television system enters commands via a remote control (not shown), which exchanges data with a remote control interface circuit 11. The commands are passed to the microcontroller 7 via the bus 10. One command the viewer may enter is a command to change channels. This command results in a command from the microcontroller 7 to the tuner 3 directing it to tune to a different frequency. When teletext is not being viewed, the output of the colour decoder 5 is passed to a multiplexer 12, which passes it unaltered to a video amplifier 13 driving a video display unit 14. The latter may be a cathode ray tube or a plasma display for instance. When a viewer elects to view teletext pages, an appropriate signal is generated by a display section 15 to decode and display teletext page data loaded into a teletext memory 16. The output generated by the display section is used by the multiplexer 12 to replace' part (in the case of subtitles) or all of the video signal provided by the colour decoder 5. Teletext page data is transmitted in a carrousel, implying that a certain amount of time elapses between the receipt of teletext page data encoding a first page and that encoding a further page. In order to be able to provide a faster response to a viewer-initiated command selecting a specific page, the television system comprises a teletext data cache 17. If a request for a specific page is received through the remote control interface circuit 11, the teletext data cache 17 is searched for the page. If it is found, it is transferred to the teletext memory 16. If not, the teletext page data encoding the requested page will have to be provided from the teletext data acquisition circuit 6, as soon as it has been provided by the tuning circuit 3 and demodulation circuit 4. Instructions stored in the ROM 8 for execution by the microcontroller 7 configure the teletext decoder system in the television receiver to maintain at least a first list, herein to be referred to as the habit list. The habit list contains entries, each including information referring to an item in a teletext service. In the example illustrated here, it will be assumed that each entry includes information referring to a page, for example by means of its number. It will be understood that embodiments are possible in which entries include information referring to other types of entities in a teletext service, for example, magazine, sub-page or individual packet. Embodiments in which channel numbers are stored with the page number are also envisaged. In that case, each entry refers to an item in a teletext service among a plurality of receivable teletext services, each associated with a broadcast channel. The television receiver is configured to autonomously acquire and store teletext data referred to by the information included in at least the habit list. Regardless of whether a user is actually accessing a teletext service, the teletext data acquisition circuit 6 operates in the background to acquire at least the pages referred to by the entries in the habit list. The data corresponding to an acquired page is stored in the teletext data cache 17. An entry may be added to the habit list when a user submits a request for a specific page whilst accessing the teletext service. The exact manner in which the habit list is maintained will be explained in detail below. It is, however, noted that, because entries in the habit list are based on requests for viewing pages submitted by a user, the habit list reflects a user's viewing habits, hence its name. In addition to the habit list, the ROM 8 preferably also contains instructions allowing the microcontroller 7 to implement at least one further algorithm for selecting teletext data. This algorithm enables the microcontroller to establish and maintain at least one further list, in addition to the habit list. Instead of being based on a user's viewing habits, the additional list(s) is preferably based on a pre-defined relationship to a previously acquired item in the teletext service, for example the most recently viewed page. Thus, the habit list and further lists are complementary, in that the one reflects the viewer's long-term habits, whereas the other reflects short-term links between pages in a teletext service. A number of different algorithms for compiling and maintaining the further list(s) will be set out below by way of non-limitative examples. One or more of these are preferably used in conjunction with the habit list. A first example of a further list is a so-called catch list. The algorithm for selecting the pages to be referred to by the catch list includes searching a displayed page (e.g. a page of which the corresponding data is held in the teletext memory 16) for page numbers mentioned on the page. Thus, the relationship determining whether a page is selected is based on information referring to the selected page included in the previously acquired, currently or previously displayed page. This algorithm is especially useful when an index page is being displayed. Of course, the catch list may also contain entries including information referring to pages mentioned on one or more previously displayed pages, depending on the available maximum size. A second example of a further list is a so-called sequence list. This list contains entries including information referring to pages with numbers preceding and/or succeeding a currently displayed page (and/or one or more previously displayed pages if the size of the list allows it). This algorithm is especially useful if the remote control used in conjunction with the remote control interface circuit 11 comprises dedicates '+' and/or '-' keys for advancing one page forwards or backwards. Thus, the relationship between the selected pages and the previously acquired, currently displayed page is based on the order of pages in the teletext service in which they are comprised. A third example of a further list is a so-called link list. The algorithm for selecting the page numbers to be referred to by this list derives the list from editorial links contained on a currently displayed page. Page numbers are thus selected on the basis of information establishing a link, included in the teletext data corresponding to the previously acquired, currently displayed page. This algorithm is especially useful if the remote control comprises coloured keys for selecting pages editorially linked and highlighted in the appropriate colour on the currently displayed page. As mentioned, other types of lists may be used, such as lists compiled by express user commands marking a page as a 'favourite'. It is observed that the algorithms used in addition to the algorithm for compiling and maintaining the habit list need not necessarily result in data corresponding to the actual list being stored physically in the nonvolatile memory. The algorithm may also be used to instruct the teletext data acquisition circuit to acquire certain pages without the actual page numbers first being stored in the nonvolatile memory 9 as a list. An example of an algorithm used to compile and maintain the habit list will be explained with reference to Fig. 2. It has the advantage of covering up flaws in the other algorithms used to select teletext data to be cached. In particular, one of its merits is that it avoids pages being 'caught' or 'missed' by both algorithms together. The algorithm assumes that the user of the television receiver is actually accessing pages in a teletext service. Thus, data corresponding to a requested page is present or being loaded into the teletext memory 16 for decoding into a video format for the video display unit 14 by the display section 15. The algorithm starts by receiving a user's request for a specific page in a first step 18. It is noted that the television receiver may advantageously allow for a page request to be submitted in several different ways. This includes selection of a page by entering a three- digit number of the desired page, the use of a coloured button on a remote control device to request a page linked to the currently displayed page and the use of '+' or '-' buttons to request a page immediately succeeding or preceding the currently displayed page. Regardless of the way in which the request is provided, and of the specific command provided to the microcontroller 7 via the bus 10, each request is treated in the same way, and potentially results in a modification of the habit list. Thus, even if a page is requested using the '+' or '-' buttons and the sequence list, or a favourites button and a list of favourites, an entry may still be made in the habit list. Thus, it is assured that no requested page is missed. As will be explained further below, page numbers referring to page data already cached through a different algorithm are not added to the habit list, so that superfluous additions are avoided. Thus, in a step 19 following the receipt of a request for a specific page, the microcontroller 7 determines whether or not data corresponding to the requested page is absent from the teletext data cache 17. This determination may be carried out by actually analysing the contents of the teletext data cache 17 or by consulting a register of the current contents of the teletext data cache 17, for example. If it is determined that data corresponding to the requested page is absent from the teletext data cache 17, four steps 20-23 are carried out. In a first step 20, the microcontroller instructs the teletext data acquisition circuit to acquire the data corresponding to the requested page. Subsequently (step 21), the display section 15 decodes the acquired data, which is loaded into the teletext memory 16, into a format suitable for the video display unit 14. Only upon determining that the teletext data corresponding to the requested page has been completely acquired and decoded does the microcontroller add an entry including information referring to the requested page to the habit list (step 22). Thus, page numbers entered by the user by mistake do not result in the addition of an entry to the habit list, as these do not represent a true request. The same holds true when a page is requested by rapidly pressing the '+' button a number of times in succession. This feature thus aids in making effective use of the available space in the habit list. Preferably, the entries in the habit list are ranked in order of priority. The teletext data acquisition circuit 6 normally also acquires and caches the teletext pages referred to in the habit list in order of descending priority, thus assuring that the most important pages have the highest chance of being cached. To ensure that the habit list evolves with the habits of user's, the entry added in step 22 is moved to the top of the habit list in a subsequent step 23, i.e. assigned the highest level of priority upon addition to the habit list. Thus, the most recently requested page is also the one of which the data is most likely to be present in the teletext data cache 17, and the first to be updated. If, in step 19, it is determined that teletext data corresponding to the page requested in step 18 is present in the teletext data cache 17, no entry is added to the habit list. This keeps the habit list free of superfluous entries. If data corresponding to the requested page is already present, this means that the page has already been selected by means of one of the additional selection algorithms, or that the habit list already contains an entry including information referring to that page. In either case, no new entry in the habit list is called for. Instead, the data corresponding to the requested page is retrieved from the teletext data cache 17, loaded into the teletext memory 16 and formatted for display by the video display unit 14 by the display section 15, in a step 24. As mentioned above, the habit list may already contain an entry referring to the requested page. In that case, the entry already present in the habit list is assigned the highest level of priority in a subsequent step 25. Thus, even when a requested page is not absent from the teletext data cache 17, the habit list still evolves to reflect changing user habits. It is observed that, in a preferred variant of the example of Fig. 2, the habit list is also checked prior to the addition of a new entry into the habit list in step 22. If the habit list contains an entry including information to a page of which the corresponding data has been determined to be absent from the teletext data cache 17 in step 19, no new entry is added, but the existing entry is assigned the highest level of priority. Thus, in this variant, the entry is added only upon determining that no entries including information referring to the requested item are present in the habit list. It should be noted that the above-mentioned embodiment illustrates rather than limits the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps other than those listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention can be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device claim enumerating several means, several of these means can be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Thus, for example, the method according to the invention may also be carried out by a computer, for example a personal computer, operatively connected to a television tuner and teletext data acquisition circuit. The latter may be installed on a tuner card installed in the computer, or in an external tuner, connected to the computer by means of, for example a USB link. In this setting, the method may be used to manage the caching of teletext page data in a memory circuit of the tuner or the personal computer, in order to achieve the same advantages as are achieved in the embodiment described in more detail herein above.

Claims

CLAIMS:

1. Teletext decoder system, comprising a teletext data cache memory (17) for storing teletext data and an input (11) for receiving a user-initiated command including a reference to a specific item in a teletext service, said teletext decoder system being configured to maintain at least a first list, each entry in the list including information referring to an item of teletext, and to autonomously acquire and store teletext data referred to by the information included in at least the first list, characterised in that the teletext decoder system is configured to add an entry to the first list including information corresponding to the reference only upon determining that teletext data referred to by the reference is absent from the teletext data cache memory (17).

2. Teletext decoder system according to claim 1 , configured to add the entry only upon determining that no entries including information corresponding to the reference are present in the first list.

3. Teletext decoder system according to claim 1 or 2, configured to implement at least one algorithm for selecting teletext data to be autonomously acquired and stored in the teletext data cache memory (17) on the basis of a pre-defined relationship to a previously acquired item in the teletext service.

4. Teletext decoder system according to claim 3 , configured to select the teletext data on the basis of information referring to the teletext data, included in the teletext data corresponding to the previously acquired item.

5. Teletext decoder system according to any one of the preceding claims, comprising a teletext presentation section (15,16) for decoding teletext data into a video format for a display (13,14), wherein the teletext decoder system is configured to add the entry only upon determining that the teletext data referred to by the reference has been completely acquired and decoded.

6. Teletext decoder system according to any one of the preceding claims, arranged to rank the entries in the first list in order of priority, and to autonomously acquire and store teletext data referred to by the information included in the first list in order of decreasing priority.

7. Teletext decoder system according to claim 6, configured to assign a highest level of priority to the entry upon adding it to the list.

8. Teletext decoder system according to claim 6 or 7, configured, upon determining that an entry including information corresponding to the reference is already present in the first list, to assign a highest level of priority to the entry already present in the first list.

9. Teletext decoder system according to any one of the preceding claims, comprising a user control device adapted to allow a user to provide in a plurality of different ways a request for a specific unit of teletext data, wherein the teletext decoder system is configured to add an entry to the first list including information referring to the requested item only upon determining that teletext data corresponding to the requested item is absent from the teletext data cache memory, regardless of the way in which the request is provided.

10. Audiovisual device, e.g. a television receiver set, comprising a teletext decoder system according to any one of claims 1 -9.

11. Computer program adapted, when run on a programmable processing device comprising a processor (7) and memory (8,9), an input (11) for receiving a user command, memory (17) for storing teletext data and means (6) for acquiring teletext data, to enable the programmable processing device to function as a teletext decoder system according to any one of claims 1-9.