EP0020242B1 - Method for teletext character alignment and device for carrying out this method - Google Patents

Description

The present invention firstly relates to a method for aligning teletext characters on the screen of a television receiver, as defined in the preamble of claim 1. The invention also relates to a device for setting up implements such a process.

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 body of the character, or legs, 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. Under 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 lines and 2 lines for the upper parts of the letters such as l, d and t.

The ANTIOPE system, as described in the document "All Electronics", No. 439 (Jan. 1979) "The ANTIOPE System", p. IV-IX, also provides 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 - includes single height characters 1 H 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 leg of 4 lines in height and we will end up with a 2 line offset between the letters 1H and the letters 2H, sufficient to destroy the alignment in the eyes of the spectator.

The present invention aims to solve this difficulty. To this end, the method of the invention is characterized according to the characterizing part of claim 1.

The method according to the invention, thanks to the taking into account during the scanning of the first line, of the parameters determining whether or not the row is composed solely of 2H characters and if it comprises at least one 2H character which is cuffed, allows satisfactory alignment characters in any case. In the case where the row comprises both 1H characters and 2H characters, and has at least one legged 2H character, the difference between the alignment of the 2H characters and that of the 1H characters is 1 line, and n is not noticeable to the viewer.

The invention also relates to a device for implementing the method of the invention, intended to provide a character generator with an exploration sequence defining the alignment of the characters, characterized in that it comprises a PROM memory whose outputs are connected to the character generator, and which receives a sequence (ADL1 to ADL4) from a line counter, a signal indicating that the character explored is 2H, a signal (Sii) indicating whether one is in the half upper 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 has at least one 2H legged character, the PROM memory controlling an offset of the alignment of 2 lines with respect to the alignment of the characters 1 H when AL1 is at level "1" and an offset of 1 line when AL1 is at level " 0 "and AL2 at level" 1 ", the offset é so much null in the other case.

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

• les figures 1 a à 1 c donnent des exemples des différents modes d'alignement obtenus selon l'invention;

In the drawings:

• Figures 1 a to 1 c 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 by Figures 1 a to 1 c.

FIGS. 1 a to 1 c 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 Figures 1 a to 1 c.

The alignment mode illustrated in FIG. 1 a is identical to that of the rows comprising only 1 H 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 of a 1 H character string. This alignment mode corresponds to the case where the characters 1 H (Y, O, N) and 2H (L) coexist in the same row, and where no 2H character contains 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 by FIG. 1 c is applied in the case where a row comprises at the times 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 is thus observed in FIG. 1 c that the horizontal leg of the Y leg is not doubled, contrary to what is observed in FIG. 1 b.

In addition, the 1 H characters present in the row have their normal arrangement, that is to say that the body of the 1 H characters is separated by 2 lines from the bottom of the row. The resulting difference between the characters 1 H and 2 H is not annoying 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 with 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 memory PROM 1 which supplies the character generator 2 with a four-wire exploration sequence AGC1 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.

The 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 "0".

Its input K receives the signal 2H indicating that the character analyzed is double height. Its input P (Preset) is connected to an AND-NO gate 5 which receives the output signal from an AND gate 6 which is applied the TLG line tops and the LGN signal 10 which appears during the scanning of the 1st O line of each row.

Gate 5 also receives the inverted S / I signal, which is in state "1" 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 LGN 10 of the previous row, and it remains in this state if all the characters in the row are double height But it suffices a single character is single height so that the level of the 2H signal goes to "0". The Q output then goes to state "0".

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.

fourni par le générateur de caractères indiquant le caractère analysé est jambé, et un signal LGN

indiquant que l'on explore la première ligne de la rangée.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 BIT signal

provided by the character generator indicating the analyzed character is strung, and an LGN signal

indicating that we are exploring the first line of the row.

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

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

When the signal AL1 is at “0” and the signal AL2 is at “0”, the alignment mode is that of FIG. 1 a.

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

Claims (4)

1. Method of aligning videotex characters on the screen of a television set, the characters being arranged in horizontal rows each occupying a number of scanning lines, wherein a row composed of single height 1 H characters occupies 10 scanning lines and a downstroke of a 1 H character has a vertical dimension of 2 lines, the vertical dimension of the characters, and therefore of the rows, may be doubled by repetition of the display element of a line over the following line, characterized by the steps of analysing the data of a row during the scanning of the first, not displayed, line of this row ascertaining, during the scanning time of the first line of each row,

1 ) whether the row is only composed of doubles height 2H characters, or not, and

2) whetheritincludesatleastone2Hcharacterwith downstroke, and defining then the alignment as follows:

a) if the row only contains 2H characters, the alignment is offset upwards by 2 lines with respect to the alignment of 1H characters;

b) if the row contains both 1 H and 2H characters, and contains no 2H character with downstroke, the alignment is the same as in the case of 1 H characters;

c) if the row contains both 1 H and 2H characters, and has at least one 2H character with downstroke, the alignment of the 2H characters is offset upwards by 1 line with respect to the alignment of 1 H characters, and the last line of the 2H characters with downstroke is not repeated.

2. Device for carrying out the method according to claim 1, intended to supply to a character generator (2) a reading sequence defining the alignment of the characters, characterized in that it comprises a PROM memory (1) having its output connected to the character generator and receiving a sequence ADL1-ADL4 from a line counter, a signal indicating whether the read character is 2H, a signal (S/I) indicating whether the upper half or the lower half of a double height row is concerned, a signal AL1 which is at level « 1 » when all of the characters of the row are 2H and a signal AL2 which is at level «1 » when the row includes at least one 2H character with downstroke, the PROM memory controlling a 2-line offset of the alignment with respectto the alignment of the 1 H characters when signal AL1 is at level « 1 » and a 1-line offset when AL1 is at level «0» and AL2 is at level « 1 », the offset being nil otherwise.

3. Device according to claim 2, wherein signal AL1 is supplied by a first flip-flop (3) the output of which is set to level « 1 »at the occurrance of the line synchronization pulse of the last line of the preceding row, and is changed to level «O» if one character of the row is 1 H, and signal AL2 is supplied by a second flip-flop (4) the output of which is set to level «1 when a 2H character with downstroke contained within the row.

4. Device according to claim 3, wherein a signal (BIT⌀) indicative of a downstroke is supplied by the character generator (2).

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