DE4221664A1 - Compatible transmission system for data signals within videotext data stream - has successive bits of each data signal datum inserted in different rows and-or videotext pages - Google Patents

Abstract

The transmission system allows data signals to be contained within pseudo series of videotext pages by inserting the successive bits of each datum of the data signal in different rows and/or videotext pages of a videotext data stream at an encoding side. At a decoder side the rows of the videotext data stream associated with each datum are stored temporarily, to allow the original data format to be restored. Pref. the different rows of the videotext data stream containing each datum are associated with the same videotext page or page address, the different videotext pages or page addresses and the associated videotext data stream rows transmitted in different image half frames. ADVANTAGE - Higher transmission reliability with error protection allowing reconstruction of faulty pages.

Description

The invention relates to a method according to the preamble of Claim 1 Such a method is known from DE 39 26 685 A1 known.

For the compatible transmission of data signals within a teletext data stream, it is known from DE 30 26 685 to insert the data signals as non-cyclical teletext special pages in packets into the teletext cycle. The data format in the data packets can be freely selected depending on the respective form of application. In the known method, the teletext special pages are described from left to right and from top to bottom in the same way as "normal" teletext pages. Successive data of the data stream are therefore predominantly placed side by side in a teletext row, as can be seen from FIG. 1. The teletext page shown in Fig. 1 comprises the rows l to m and the columns o to p. Each byte of the data stream is identified with its row and column address and shown as a block in FIG. 1. Each byte consists of eight bits, which are symbolized as dots within the assigned byte.

As can be seen, the teletext page is labeled with consecutive bytes from the top left (row l, column o) to the bottom right (row m, column p). The labeling direction is indicated by arrows in FIG. 1.

However, the row-oriented data transmission explained is for Error protection measures are not particularly cheap, as explained below shall be:

Each teletext page consists of an address and control frame and the actual user data, which later readable information on the screen surrender. Each user data has seven bits. For the detection of Transmission errors in the receiver become a parity bit on the transmission side added so that 8 bits = one byte is required for each user data become. An error correction is not intended for the user data. Already at 1-bit errors within a byte do not become the intended character correctly displayed on the screen. For the address and tax framework of Hamming code 4/8 is used for teletext pages. He is able to, Detect and correct 1-bit errors within a byte as well Detect multi-bit errors. The higher-value error protection for the data of the address and Control frame is useful for displayable teletext pages because Failure to receive a user data byte is just one character in a row is falsified, but in the event of reception errors in the address and control frame more serious disorders arise. For example, not at correctable error reception of a row address all in this row transmitted user data lost. It does not seem even more unfavorable correctable error reception of the page number in the head row of the teletext  Page because this means that all useful data of the relevant teletext page get lost.

So long as the teletext transmission method is only for transmission of readable information that is also transmitted cyclically, so the above-mentioned error effects have no dramatic effect, since one Correction through the reader's ability to combine or through the cyclical Repetition is made.

If, on the other hand, the user data from teletext pages are not used for direct, readable display on screens, but for the transmission of Data signals, on the one hand, is a perfect detection of Transmission errors in the receiver are imperative and secondly an error correction option advantageous to additional waiting times for avoid further enemas of the incorrectly received page, what applies in particular to multiple pages. By using a code with Error correction options can be, depending on the amount of errors and the Quality of the code, correct incorrectly received bits of an information unit. This means that the actual user data is optimal against false reception can be protected. Meanwhile, with the row-oriented Data transmission Transmission errors of more than one bit in one of the two Bytes for the "magazine and row address" of a teletext row to one Total loss of all the data arranged in this teletext row, regardless of the quality in which the user data was backed up. This proves the typical teletext backup of magazine and Row address as "bottleneck" for all high-quality error protection measures.

In contrast, the object of the invention is in a method of to achieve a higher level of transmission security.

This object is achieved by the characterizing features of Claim 1 solved.

Advantageous refinements and developments of the invention Transfer procedures result from the subclaims.

In the method according to the invention, the one mentioned at the beginning Weak point "magazine and row address" due to a different distribution of the User data bypassed what is briefly called data splitting in different rows referred to as. With this data splitting, the individual, successive bits of each date in different rows and / or Pages of the teletext data stream inserted. As a result of this series or page-by-page division in the incorrect transmission of a row address are only one bit at a time in the information units concerned disturbed, which can be reconstructed due to the error protection. So that's it it makes sense to provide error protection mechanisms for the information units, which offer a higher level of error protection than that of teletext for magazine, Page and row addresses used Hamming code. In the event of a disturbance Page address offers the insertion of successive bits of each data stream in different pages of the teletext data stream the particular advantage that again only 1 bit per affected information unit is disturbed and thus if an appropriate error protection is used, the disturbed Information units and thus the complete, disturbed page completely can be reconstructed.

The invention is explained in more detail with reference to the drawings. It shows:

Figure 1 is a schematic representation of the row-oriented data distribution on a teletext page.

Fig. 2 is a schematic representation of the row splitting according to the invention of bits according to the inventive method;

Fig. 3 is a schematic representation of the page splitting of consecutive bits of each data in accordance with an alternative of the method according to the invention,

Fig. 4 is a schematic representation of the page splitting of consecutive bits of each data in accordance with another alternative of the method according to the invention;

Fig. 5 is a schematic representation of the row splitting of successive bits of each date in the transmission of coded traffic information, and

Fig. 6 is a schematic representation of the page splitting of successive bits of each date in the transmission of coded traffic information.

As can be seen from FIG. 2, the teletext page shown there consists of the byte columns o to p, of which each byte column has 8 bit columns. Furthermore, each side has m rows. The successive bits of each information unit (date) of the data signals are inserted into a bit column, so that successive information units are transmitted in successive bit columns, as indicated by the arrow directions in FIG. 2. However, the insertion of an information unit in a bit column is not mandatory; when using an n-bit error correction code, it is possible to use n consecutive bit columns for one information unit.

In the page splitting shown in FIG. 3, successive bits of each information unit are transmitted on the same row, byte column and bit column address of different pages q to r. Successive units of information are transmitted in successive bit columns of the same rows of pages q to r. This results in a 3-dimensional transmission scheme.

The row splitting according to FIG. 2 is carried out as follows:

Starting with row No. 1, byte column No. o, bit column No. 1, the first information bit is written into the selected 1-bit memory location. Then a row counter is incremented to 1 + 1 and the second information bit is written into the memory location addressed in this way. The incrementing of the row counter and the writing of the information bits are repeated up to and including row m. By transferring the row counter, a bit column counter is incremented to the value 2 and the row counter is reset to the value 1. Now the writing and addressing processes for bit column 2 begin, then for bit column 3 , etc. The bit column counter counts up to the value 8. The bit column counter is then used to increment a byte column counter that Bit column counter reset to 1 and the row counter to the initial value 1. The byte column counter runs up to the byte column p.

This is the area of the teletext page that is used to transmit data is being completed. This teletext page can then in the usual way Teletext data stream are inserted. If the data signal to be transmitted If a teletext page does not fit, a subsequent page can follow the same scheme be written with the remaining part of the data signal.

As already mentioned, the failure of a row address only leads to Loss of a single bit per unit of information, provided that the number of bits of an information unit is smaller than the number of Series n. By using a 1-bit correctable code, it is possible to to correct the loss of the relevant single bit per information unit and thus to completely reconstruct the disturbed row.

The row splitting according to FIG. 2 fails, however, if an uncorrectable error occurs in the address and control frame of the head row (row no. 0), since then the page in question and thus all information units of this page are lost. This fault case can, however, be corrected with the side splitting according to FIG. 3 or FIG. 4.

In the method outlined by FIG. 3, the first information bit is written into the selected 1-bit memory location, starting at page q, row 1, byte column o, bit column 1 . The page counter is then incremented to q + 1 and the second information bit is written into the 1-bit memory location addressed in this way. The incrementing of the page counter and the writing of the next information bits are repeated up to and including the maximum page counter reading r. The subsequent incrementation creates a carry that increments the bit column counter to the value 2 and resets the page counter to the value q. Now the writing and addressing processes for the page sequences q to r, each row l, byte column o, bit column 2 , then bit column 3 etc. to bit column No. 8 begin in the manner described above. By transferring the bit column counter, the byte column counter is then incremented to the value o + 1 and the bit column counter is reset to the value 1. The byte columns o + 1 to p are, as before, for the byte column o explained, described with the other information bits.

If the address "page r, row l, byte column p, bit column 8 " is described, then a carry is carried out next, which increments the row counter to l + 1 and the page counter, the bit column counter and the byte column counter reset to their initial values. Now rows no. 1 + 1 and the following - as previously explained for row no. 1 - are addressed and described until row m, byte column p, bit column no. 8 on side r is reached.

This is the area of the teletext pages that is used to transmit data is being completed. The pages of this sequence can be viewed in the Teletext data stream inserted in the usual way and in the order q, q + 1, q + 2 bis r are sent. The parts of the After a time T, the data signal can either be on the same teletext page or transmitted on other teletext pages.

The failure of a complete teletext page of an information sequence only leads to the loss of one bit of each information unit of this sequence in the case of page splitting according to FIG. 3. When using a 1-bit error-correcting code, the disturbed bit per information unit and thus the complete, disturbed page can be reconstructed. As an alternative to the failure of a complete page of the sequence, the failure of up to [(rq) +] rows with different row addresses still leads to correct results.

In addition to the previously described division of the information bits, further divisions are also possible. Another alternative of side splitting is outlined in FIG. 4.

With this alternative, the page counter is first incremented as before. His Carryover now causes the row counter to increment. The carry over of the row counter incrementing the bit column counter and ultimately the Carry the bit column counter incrementing the byte column counter.

A practical embodiment of the methods described above consists in the protected transmission of coded traffic information. Such one The method carries, as with RDS, TMC-encoded traffic information according to the invention in teletext special pages. The coded Traffic information consists of data blocks of 37 bits each. One undergoes expand these to 40 bits (e.g. by appending "0" bits) Information units of a Haming 4/8 coding, so data blocks arise 80 bits or 10 bytes each, which have a higher-quality error protection. At The described row splitting can be used here n 32 of these Transfer traffic information. n then typically has the values 1 or 2, so that 9- or 17-line teletext special pages are created.  

When using the side splitting described, eight n + 1-line Build teletext special pages. Each block of 8 of these teletext Special pages can transmit 32 traffic information.

In contrast to row splitting, n can have values between 1 and 23 to have. This allows the choice of one for the transmission of teletext in the Blanking of the television signal favorable value. There are m lines in this Blanking gaps for the transmission of teletext are available for n favorable values as km-1, where km must be <24 and k = 1, 2 etc.

Claims (5)

1. A method for transmitting data signals within a teletext data stream, for example within pseudo-rows of teletext pages or within special teletext pages, characterized in that encoder-side successive bits of each date of the data signals in different rows and / or teletext pages of the teletext Data stream are inserted and that the rows belonging to a date of the received teletext data stream are temporarily stored on the decoder side and converted back into their original data format. 2. The method according to claim 1, characterized in that the different rows of the teletext data stream of a common one Teletext page or teletext special page address are assigned.   3. The method according to claim 1, characterized in that the different rows of the teletext data stream different Teletext page or teletext special page addresses are assigned. 4. The method according to claim 3, characterized in that the various teletext page or teletext special page addresses and the different rows of teletext assigned to them Data streams are transmitted in different fields. 5. The method according to any one of claims 1 to 4, characterized in that the data signals contain encoded traffic information.