DE4133496A1 - Adaptive teletext transmission method - Google Patents

Abstract

Special data blocks or parts of data blocks are transmitted in redundant intervals or a heading is transmitted before the corresponding data block, after a suitable time interval, and another data block is inserted. By setting suitable bit errors or a parallel mode bit, premature interruption of data reeipt of the decoder is avoided. During transmission, teletext standared control bit for separating the type of magazine transmission is transmitted with the parallel mode code word.

Description

The present invention relates to a method for transmission gen alphanumeric data according to the generic term of the An claim 1. Such a method is known from DE 34 18 068 C1 known.

After in Germany, Great Britain and in other European countries States used by television broadcasters or proposed teletext standards (teletext standards) for example according to the so-called "Level 1 Teletext" standard, the encoded, alphanumeric data is in vertical Blanking gaps of a television signal cyclically or quasi-zy cliché. The transferred data is played back collected on one side and page by page as a standing television picture (= Teletext page). Represent one side each sent user data are combined into a block, which is preceded by a data packet as a header, the identifies the page number of the block in question.

According to DE 34 18 068 C1 it is provided that each header another data packet (header line) the length of one TV line is prefixed, this pre-header the Page number of the page after the next in the transmission cycle identified. In a variant according to this document can also be provided that within a line of the End of the television broadcasting the previous block field a preamble the length of a television line is transmitted, and that immediately behind the header repeats the header of the block currently being transferred becomes. A header repeated in this way is also called Intermediate header.  

The playback-side collection of the data takes place at a well-known decoder (company brochure "Valvo Technische Infor mations for industry ", No. TI 840314) in one page storage arrangement, the storage volume of the maximum data amount of eight pages corresponds. Because of the "adaptive over carrying principle "forces this limitation of the storage volu mens that before displaying a user selected page the memory must be cleared before the Data of the selected page - as soon as it is in the transmission cycle occur klus - can be invited. The "adaptive Transmission principle "states that a teletext line without Information content ("empty") is not transferred to the Shorten transmission cycle. The deletion follows only when the header of the selected page decodes becomes.

Since this deletion occurs with a considerable number of Teletext deco previously used in television receivers which takes about 20 milliseconds, must be for compatibility between the transfer of the header and the transfer a waiting interval of about 20 milliseconds. The same applies if instead of one New selection of a page in the header a special deletion is incorrectly included, for example in so-called more technical sides of the transmission cycle (several different with the same page number) is the case. The Einhal tion of this waiting interval takes place in that the header le and the following user data in separate television halves images are transmitted.

While usually in the television field, in which the Header is transferred, if necessary, remaining text line len can be filled in by repeating the header according to DE 34 18 068 C1 provided that the deletion of the Page memory already during the transfer of the ge desired page immediately preceding page, so that repeating the headers is unnecessary.  

In practice, when carrying out the However, DE 34 18 068 C1 previously known pre-header method Problems have occurred that have led to such Transfers had to be stopped.

For a better understanding of the teletext transmission method, reference is made to the document "Technical Guideline ARD / ZDF, No. 8 R 4, television text specification", published by IRT Institute for Broadcasting Technology GmbH, Munich, June 1986. Then there are up to eight magazines, the respective number of which is symbolically followed by the letter "m" (m = 1, 2,...,
8) is provided, to which the teletext pages can be assigned. Each magazine can have up to 100 pages, the respective number of which is shown symbolically below with the letter "n" (n = 00, 01, 02,..., 99). A complete addressing of a teletext page can therefore be done by a three-digit decimal number (m, n), the first position of which indicates the magazine number and the second and third number of which the page number within this magazine.

For example, the teletext page 103 represents page number 03 in magazine number 1. An extension to hexadecimal numbers is provided for expansion stages of the teletext service.

The difficulties encountered with the pre-header method The main reason for this is that an asyn Chrone request of any page depending on internal control processes of the teletext decoder used may result in this page not being complete or is not read at all.

The latter can happen, for example, when the recipient requested a desired teletext page (m, (n + 1)) before the pre-header assigned to this page (m, (n + 1)) VK, the same information as that of this page assigned header (m, (n + 1)) K, is received. in the Connection to the header (m, (n + 1)) VK follows after the be  did the header (m, n) K know what was mentioned in the internal control sequence of the teletext decoder also as Completion of data acquisition for the teletext page (m, n + 1) is evaluated, so that after the transfer for the teletext page (m, n) receiving the header (m, (n + 1)) K no longer relates the decoder for data acquisition the (m, (n + 1)) page opens. The side (m, (n + 1)) "applies" yes as already received and therefore no longer needs to be read in. Is between the header (m, (n + 1)) VK and the header (m, n) K still an intermediate header (m, n) ZK with remaining assigned to the teletext page (m, n) Data lines contained in the transmission cycle, is from For the same reasons, the page (m, n) was only partially fed chert.

Especially when requested from the side, the important information tion for internal decoder sorting and / or management gangs ben included, for example the "TOP" (= Table of Pages) mentioned system tables (see DE 36 34 757 C1), this can lead to considerable problems, quite apart from opti inconsistencies that "norma le "can affect teletext pages anyway.

The invention is based on the object mentioned at the outset te procedures so that the transfer of the above pre-header lines and intermediate header lines explained can be, without thereby extending the cycle duration it has to be accepted.

This object is achieved by the in claim 1 specified features solved.

The inventive method has the advantage that the shortening associated with the principle of the pre-header method the cycle duration continues to be used and over this compares to a further shortening of the cycle time it is achieved.  

The invention is based on the knowledge of teletext decoders so-called parallel mode to operate, so that after Reception of a header the subsequent reception of header len does not yet complete the data acquisition.

In a development of the method according to the invention when teletext data is broadcast, it is also in tele text standard to distinguish the magazine transmission ar ten - serial or parallel magazine transmission - provided ne control bit C11 with the characteristic of the parallel mode Transfer value. According to the above-mentioned ARD / ZDF specifications On, the control bit C11 is set to the value "zero" transfer.

This has the additional advantage that the principle shortening the cycle associated with the pre-header method is made usable in a compatible manner.

The operating mode "parallel mode" was for one at the time completely different purpose included in the ARD / ZDF specification been. By assigning individual magazines to each a particular line or group of lines should be for the within the vertical blanking interval of television fields lines available multiple independent transmission cycles let set up. Depending on the used Number of pages within the individual transmission cycles of all However, different access times to the pages of the individual cycles are accepted.

The training mentioned is based on the knowledge existing control devices in teletext decoders to take advantage of the fact that after receiving a header the subsequent receiving headers not yet data acquisition completes. The decoder is received with the help of the relevant operating mode "Parallel mode" signals, so the decoder side Data acquisition not completed until after receiving a  a header identifying a requested page Header of the same magazine is received.

With this knowledge, everyone on the market can be sensitive decoders, the ARD / ZDF specifics mentioned above tion are sufficient, for example for those under the type designation "TPU 2732" and "TPU 2735" known teletext processors ren of the company ITT Semiconductors, the readiness for data acquisition of a desired one requested by the user Teletext page from the one following the request The corresponding header is automatically received for this time continue until a same magazine as this header assigned other header is received correctly.

Further features, advantages and details of the invention are described below using an exemplary embodiment Drawing explained in more detail. Show:

Fig. 1 is a schematic illustration of a cycle of teletext pages according to the prior art using Vorkopfzeilen,

Fig. 2 is a schematic representation of a cycle 'of teletext pages according to the transmission method according to the invention.

The transmission cycle of teletext pages shown schematically in FIG. 1 contains blocks 100 , 102 , 103 , 205 , 210 , 300 , 505 and 520 , each of which has a header 100 K, 102 K, identifying them. . ., 520 K precedes. Before each of these headers, a pre-header line 102 VK, 103 VK. . ., 100 VK transmitted. The 520 K and the block 520 preceding pre-header in Fig. 1 of the header line 100 VK into account the fact that repeats the transmission cycle after the transmission of the block 520, as indicated by the arrow P1.

The useful data of each of the blocks mentioned represent in total including a teletext page. The number of the tele concerned The text page is identified by the header (m, n) assigned to it identified.

Using the pre-header (m, n) VK, the recipient receives Decoder already at the start of transmission of a page or one Blocks or "in between" the information which page as next page is transmitted so that when the pages number (m, n) of this next page selected by the user was already moving forward immediately during the transfer outgoing page ((m-1), n-1)) with the deletion of the page memory can be started in the decoder. When the Header (m, n) K of the desired page (m, n) can then incoming user data of this page immediately from the empty pages memory are taken over.

Typically, the vertical blanking interval is each TV field a limited transmission range, the can include, for example, five television lines for which Transmission of teletext data available. In extreme cases can also all lines of the television field for this Are available, for example with a so-called video Text channel of cable television.

Because of the waiting interval of approx. 20 explained at the beginning According to the prior art, milliseconds must be between each Pre-header and the first user data line of the assigned ten blocks, there is also a minimum time interval of approx for about 20 milliseconds.

Differentiate the pre-header lines and the intermediate header lines - apart from their position in the teletext data cycle - by the known method described so far none of the associated headers. Therefore led the users This method also applies to a number of teletext de coder also for incorrect playback of teletext pages.  

The affected decoders had received by vorkopf lines of advertised intermediate headers or headers the arrival of a new teletext page closed. The Decoder control evaluated the reading of those already started and now actually to be continued or actually now page to be imported as already completed.

With teletext decoders with appropriate control facilities, such as those under the type drawings "TPU 2732" and "TPU 2735" well-known Teletext-Pro ITT Semiconductors, the Tele Control text decoder according to the transmitter so that it Data acquisition not undesired prematurely as complete evaluates. The one with these processors and everyone else who mentioned ARD / ZDF specification corresponding decoders Control bit detection device can be seen to such Use control purposes.

Is namely when receiving teletext pages using the Tax set accordingly on the transmitter side to the value "zero" bits C11 recognized on the decoder side that the operating mode "Par allel mode "is present, so the decoder-side data clock quisition not completed until after receipt of a requested header again Header of the same magazine is received.

In the transmission cycle of teletext pages, shown schematically in FIG. 2, according to an embodiment of the method according to the invention, the blocks 100 , 205 , 102 , 210 , 103 , 505 described for FIG. 1 follow relative to one another at another point in the transmission cycle . 300 and 520 , each of which has a 100 K, 205 K,. . ., 520 K precedes. The pre-header lines transmitted according to the method shown in FIG. 2 are, however, inserted into the teletext data stream in such a way that between each header line and the block assigned to it a sufficient minimum time interval for deleting the page memory provided for the data to be acquired, for example about 20 milliseconds, is observed.

The pre-header 100 K preceding the block 520 in the illustration in FIG. 2 takes into account the fact that after the transmission of the block 520 the transmission cycle is repeated with the transmission of the header 205 K, the block 100, etc., as indicated by the arrow P2 is indicated.

The prior art lines required so far in the prior art can be omitted without replacement in the transmission method described in FIG. 2, whereby this method, in addition to the compatibility with the decoders on the market, also has the additional advantage that the cycle time is compared shortened even further to the state of the pre-head technology.

Claims (4)

1. A method for cyclic or quasi-cyclic transmission of coded, alphanumeric data in television lines, which are collected on the playback side and displayed page by page as a standing television picture (teletext page), the at least two teletext pages being provided, each representing one page User data as one or more data packets (lines) each having the length of a television line are combined to form a block, which is preceded by a data package (header) identifying the magazine and page number of this block and the length of a television line, characterized in that in each data packet of each block the magazine number assigned to this block is transmitted, so that not all teletext pages are assigned to a single magazine, that between each block ( 505 ) and the header line ( 505 K) assigned to it a different block ( 103 ) and / or one another header ( 300 K) can be inserted, where de r other block ( 103 ) contains only data packets that are assigned to a single teletext page ( 03 ) and have a magazine number ( 1 ) that is different from the magazine number ( 5 ) of the first-mentioned block ( 505 ), and which in the data packet containing another header ( 300 K) has a magazine number ( 3 ) which is different from the magazine number ( 5 ) of the first-mentioned header ( 505 K). 2. The method according to claim 1, characterized in that when broadcasting the teletext pages at the same time an Teletext standard to differentiate between magazine transmissions control bit provided with the parallel Mode characteristic value is transmitted.   3. The method according to claim 1 or 2, characterized net that the data packets of each block on the one hand and the header assigned to him on the other hand in time len different television fields transmitted will. 4. The method according to any one of claims 1 to 3, characterized characterized in that between the data packet each head line and the data packets of the block assigned to it a minimum interval of about 20 milliseconds is observed.