EP0020242A2 - Method for teletext character alignment and device for carrying out this method - Google Patents

Abstract

The subject of the invention is a method for aligning teletext characters on the screen of a television receiver, the characters being organized in horizontal rows each occupying a certain number of scanning lines, the vertical dimension of the characters, and therefore rows, which can be doubled by repeating the display element from one line to the next line. The data of a row is analyzed during the scanning of the first unvisited line of this row and the alignment of the characters is adjusted according to the data obtained.

Description

The present invention relates to a method for aligning teletext characters on the screen of a television receiver. The invention also relates to a device for implementing such a method.

A teletext system is described in French patent application 2 363 949. In this system, the display of characters on the screen of the television receiver is controlled by a character generator supplied with data by an image memory.

The characters are grouped in horizontal rows, each of which is formed by a number of television scan lines, equal to 10 according to the ANTIOPE specification.

As regards the alphabetic characters, it is desirable to arrange them as low as possible in relation to the row. But as certain characters have parts located lower than the character body, or jambs, such as y, p, q, j, g, respecting the alignment between the letters jamb and the letters non jamb requires that the bodies are shifted up from the bottom of the row. In these conditions, with a row formed by 10 scanning lines, if we take into account that the first line is not displayed, the remaining 9 lines break down into 5 lines for the character body, 2 lines for the legs and 2 lines for the upper parts of the letters such as 1, d and t.

The ANTIOPE system also provides for the possibility of doubling the height of the characters, by repeating the display element from one line to the next line. If the row - which then has a double number of lines - contains single height characters (1H) and double height characters (2H), the application of the above principle will lead to a pronounced misalignment since the letters 2H legs will have a jamb of 4 lines in height and we will end up with a shift of 2 lines between the letters 1H and the letters 2H, sufficient to destroy the alignment in the eyes of the spectator.

To resolve this difficulty, the invention provides for analyzing the data of a row during the scanning of the first non-displayed line of this row and for adjusting the alignment of the characters as a function of the data obtained.

• 1) si la rangée est, ou non, composée uniquement de caractères 2H, et
• 2) si elle comporte au moins un caractère 2H jambé, et on définit alors l'alignement de la façon suivante :
  • a) si la rangée est composée uniquement de caractères 2H, on décale l'alignement de 2 lignes vers le haut par rapport à celui des caractères 1H;
  • b) si la rangée comporte à la fois des caractères 1H et des caractères 2H, et ne comporte aucun caractère 2H jambé, l'alignement est le même que dans le cas des caractères 1H;
  • c) si la rangée comporte à la fois des caractères 1H et des caractères 2H, et possède au moins un caractère 2H jambé, l'alignement des caractères 2H est décalé de 1 ligne vers le haut par rapport à l'alignement des caractères 1H, la dernière ligne des caractères 2H jambés n'étant pas répétée.

More precisely, it is determined, during the scanning of the first line of each row

• 1) whether or not the row is composed entirely of 2H characters, and
• 2) if it has at least one 2H legged character, and the alignment is then defined as follows:
  • a) if the row is composed only of 2H characters, the alignment of 2 lines is shifted upwards with respect to that of the 1H characters;
  • b) if the row contains both 1H characters and 2H characters, and has no 2H legged characters, the alignment is the same as in the case of 1H characters;
  • c) if the row comprises both 1H characters and 2H characters, and has at least one legged 2H character, the alignment of the 2H characters is shifted 1 line up relative to the alignment of the 1H characters, the last line of the 2H legged characters not being repeated.

The method according to the invention, by taking into account the parameters 1) and 2) above when scanning the first line, allows satisfactory alignment of the characters in all cases. In case c), the difference between the alignment of the characters 2H and that of the characters 1H is 1 line, and is not perceptible to the spectator.

• - les figures la à lc donnent des exemples des différents modes d'alignement obtenus selon l'invention.
• - la figure 2 est le schéma d'un dispositif permettant d'obtenir les modes d'alignement illustrés par les figures la à lc.

The invention will be clearly understood on reading the description below, made with reference to the accompanying drawings. In the drawings,

• - Figures la to lc give examples of the different alignment modes obtained according to the invention.
• - Figure 2 is a diagram of a device for obtaining the alignment modes illustrated in Figures la to lc.

Figures la to lc represent a part of the teletext display screen, on which the word LYON appears. In the ANTIOPE system, a row of characters usually occupies 10 scanning lines, but we only consider here the cases where the row comprises one or more double height characters (2H) and consequently presents a doubled height, namely 20 lines sweep. The lines are therefore numbered from 1 to 20 in each of the figures la to lc.

The alignment mode illustrated in FIG. 1 a is identical to that of the rows comprising only 1H characters, namely that the body of the characters is arranged with a deviation of 2 lines from the bottom of the row which corresponds to the height a leg of character lH. This mode of alignment corresponds to the case where the characters 1H (Y, O, N) and 2H (L) coexist in the same row, and where no character 2H contains a jamb. As can be clearly seen, the characters 2H are obtained simply by repeating the display element of one line on the next line.

The alignment mode in Figure 1b is used when the row consists exclusively of 2H characters. In this case, whether or not the row has legged characters, the alignment is offset by 2 lines compared to the previous case. In other words, the body of the characters is spaced 4 lines from the bottom of the row, this space being occupied by the legs whose height represents 4 lines (2 x 2).

Finally, the alignment mode illustrated in FIG. 1c is applied in the case where a row comprises both 1H characters and 2H characters and where at least one of the 2H characters is strung. This alignment mode consists in shifting the body of the 2H characters by 3 lines from the bottom of the row, by eliminating the repetition of the 2nd display element of the legs. It can thus be seen in FIG. 1c that the horizontal leg of the Y leg is not doubled, contrary to what is observed in FIG. 1b.

Furthermore, the 1H characters present in the row have their normal arrangement, that is to say that the body of the 1H characters is separated by 2 lines from the bottom of the row. The resulting difference between the characters 1H and 2H is not disturbing for the spectator, because it is limited to one line.

The selection of the alignment mode therefore requires the knowledge of two elements characterizing the row considered. The first element AL1 concerns the coexistence of characters 1H and 2H, and the second element AL2 the presence of characters 2H legs.

Knowledge of the elements AL1 and AL2 is obtained by exploring the character data of the row during the scanning of the first line of the row, which is never used for display so that a clear separation is made between the characters in consecutive rows.

FIG. 2 shows a device allowing the elements AL1 and AL2 to be taken into account with a view to selecting the alignment mode.

The device shown comprises a PROM memory 1 which supplies the character generator 2 with a four-wire exploration sequence AGCl to AGC4 which controls the mode of alignment of the characters.

The memory 1 receives on four wires ADL1 to ADL4 the line address of the row considered, between 0 and 9, which is supplied by a line counter incremented by each line synchronization signal.

Memory 1 receives a signal 2H indicating that the character analyzed is double height, a signal S / I indicating that one is in the upper half row or in the lower half row of a double height row.

The memory also receives the signals AL1 and AL2 supplied respectively by flip-flops 3 and 4. The flip-flops 3 and 4 are flip-flops of the JK type.

The entry J of rocker 3 is on level "O".

Its input K receives the signal 2H indicating that the character analyzed is double height.

Its P input (Preset) is connected to an AND-NO gate 5 which receives the output signal from an AND gate 6 to which the TLG line tops are applied and the LGNIO signal which appears when the 10th line in each row is scanned.

Gate 5 also receives the inverted S / I signal, which is in the "1" state when exploring the lower half-row of a double-height row.

The signal applied to the input P therefore passes to the state "0" at the arrival of the top line of the last line of the row which precedes the row to be explored. The taking into account of the signal S / I avoids an untimely change of state of the flip-flop 3 during the passage from the upper half-row to the lower half-row of a double height row.

A clock signal H is applied to flip-flop 3 at each character time interval.

The output of flip-flop 3 is set to state "1" during the top line TLG of the last line LGN10 of the previous row, and it remains in this state if all the characters in the row are double height. But it is enough that a single character is single height for the level of the 2H signal to go to "O". The output Q then goes to state "O".

The flip-flop 4 has its input P also connected to the output of the AND-NO gate 5.

Inputs J and H are connected in the same way as on flip-flop 3.

The input K is connected to an AND-NO gate 7 receiving on one input the aforementioned 2H signal and having its other input connected to an AND gate 8 which receives a BITφ signal supplied by the character generator indicating that the analyzed character is strung , and a signal LGNφ indicating that we are exploring the first row in the row.

The Q output of flip-flop 4 is set to the "0" state by the signal from the gate 5. It goes to the "1" state when a 2H character is explored during the 1st row of the row.

When the signal AL1 is at "1", the alignment mode is that of FIG. 1b.

When the signal AL1 is at "O" and the signal AL2 is at "O", the alignment mode is that of FIG.

When finally the signal AL1 is at "0" and the signal AL2 is at "1", the alignment is that of FIG. 1c.

Claims (5)

1. Method for aligning teletext characters on the screen of a television receiver, the characters being organized in horizontal rows each occupying a certain number of scanning lines, the vertical dimension of the characters, and therefore of the rows, can be doubled by repeating the display element of one line on the next line, characterized in that the data of a row are analyzed during the scanning of the first unvisited line of this row and adjusts the alignment of characters based on the data obtained. 2. Method according to claim l, in which a row composed of single height characters (lH) occupies 10 scanning lines and a jamb of character 1H has a vertical dimension of 2 lines, characterized by the fact that during scanning the first line of each row, 1) whether or not the row is composed entirely of double height characters (2H), and 2) if it has at least one 2H legged character, and the alignment is then defined as follows: a) if the row is composed only of 2H characters, the alignment of 2 lines is shifted upwards with respect to that of the 1H characters; b) if the row contains both 1H characters and 2H characters, and has no 2H legged characters, the alignment is the same as in the case of 1H characters; c) if the row comprises both 1H characters and 2H characters, and has at least one legged 2H character, the alignment of the 2H characters is shifted 1 line up relative to the alignment of the 1H characters, the last line of the 2H legged characters not being repeated. 3. Device for implementing the method according to the claim 2, intended to provide a character generator (2) with an exploration sequence defining the alignment of the characters, characterized in that it comprises a PROM memory (1) whose outputs are connected to the character generator, and which receives a sequence (ADL1 - ADL4) from a line counter, a signal indicating that the character explored is 2H, a signal (S / I ) indicating whether one is in the upper half-row or in the lower half-row of a double-height row, an AL1 signal which is at level "1" when all the characters in the row are 2H and an AL2 signal which is at level "1" when the row includes at least one 2H leg, the PROM memory controlling an offset of the alignment by 2 lines compared to the alignment of the characters 1H when AL1 is at level "1" and an offset by 1 line when AL1 is at level "0" and AL2 at level "1", the offset being zero in the other case. 4. Device according to claim 3, in which the signal AL1 is supplied by a first flip-flop (3) the output of which is set to state "1" during the top line of the last line of the previous row, and goes to "0" if a character in the row is 1H, and the signal AL2 is supplied by a second flip-flop (4), the output of which is set to the state "1" when a 2H character has been strung in the row. 5. Device according to claim 4, wherein a signal indicating the presence of a leg is provided by the generator of (BITφ) characters (2).

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