EP0025748A1 - Device for transmitting digitally and for displaying graphics and/or characters to and on a screen - Google Patents

Abstract

This device comprises a terminal (5) connected to a transmission network (3), to a graphics acquisition device (4) and to a display member on a screen (6). Each terminal comprises a storage device which, according to the invention, comprises a plurality of memory plans validable in parallel, each memory plan comprising a circuit performing a logical combination between an input word and the word already written to the address indicated. Application to the production of telewriting systems or mixed telewriting and videotex systems.

Description

The present invention relates to a device for digital transmission and display of graphics and / or characters on a screen. It finds an application in the transmission and display on display devices, such as television receivers, writings, drawings, characters etc ... for any purpose of assistance with discussion, information , intelligence, identification, authentication, education or entertainment. It is a system for exchanging or receiving information through any transmission network, whether interactive or broadcast.

Telewriting devices are growing in importance and interest from day to day. It will be recalled that these devices comprise, at the end of a line or of a transmission channel, means for acquiring graphics, which may have various shapes (graphic tablets, photostyles, rolling balls, etc.) capable of periodically delivering the coordinates of the points constituting the plotted graphics, these coordinates then being coded and then transmitted over the transmission line or channel, and, at the other end, means for decoding the received signals and display organs of the decoded signals, of the cathode ray tube type, plasma panels, plotters, special printing machines, etc., these bodies reproducing the graphics plotted on the acquisition means.

• - le texte de la conférence, au Müncher Kreis, de Jean-Paul DAGNELIE (Juin 1978) intitulé "TELEBOARD SYS-TEMS" :
• - le texte de la conférence de Jean-Paul DAGNELIE (juin 1979, Paris), au congrès IFIP 79 Teleinforma- tics, intitulée "TELEWRITING" ;
• - la demande de brevet français n° 77 39395, déposée le 21/12/1977 et intitulée "Tablette graphique notamment pour système de téléécriture" ;
• - la demande de brevet français n° 77 29413, déposée le 26/9/77 et intitulée "Système de téléécriture bidirectionnelle à fonctionnement en alternat automatique sur une seule porteuse".

Such systems have already been described in particular in the following documents:

• - the text of the conference, at the Müncher Kreis, by Jean-Paul DAGNELIE (June 1978) entitled "TELEBOARD SYS-TEMS":
• - the text of Jean-Paul DAGNELIE's conference (June 1979, Paris), at the IFIP 79 Teleinformatics congress, entitled "TELEWRITING";
• - French patent application n ° 77 39395, filed on 12/21/1977 and entitled "Graphic tablet in particular for telewriting system";
• - French patent application no. 77 29413, filed on 9/29/77 and entitled "Two-way telewriting system with automatic alternating operation on a single carrier".

These systems are already widely known, we will not go into detail on their structure. We will limit ourselves to recalling the essential principles in order to facilitate understanding of the invention. For any design or production details, reference may be made to the documents cited above, which must be considered to be incorporated into the present description.

Figure 1 very schematically recalls the elements of a telewriting system. Such a system comprises telewriting sets 2, 2 ′, 2 ", etc. which exchange information through a transmission network 3. Each set includes a system for acquiring graphics 4 (such, for example, that a graphics tablet for writing, erasing, erasing, etc.), a terminal 5 which acquires the information coming from the tablet, gives them a suitable format for transmission over the network 3 and the stores, and finally, a display member 6. The terminal 5 also processes the information sent to it from the 'sets 2' and 2 "through the network 3, stores them and ensures the display thereof on the member 6 , together with those from device 4.

The transmission network 3 of FIG. 1 contains the adequate modulation and demodulation equipment. This network can be of point-to-point type: two-wire telephone line (leased or switched), four-wire telephone line, telegraph line, TRANSPAC network, CADUCEE network, TRANSMIC network, ... or broadcast type: television (with or without using the DIDON system), radio with frequency or amplitude modulation, etc. This list of networks or transmission channels is given for information only and is in no way limiting.

To set an order of magnitude, a network with a bit rate of at least 200 bits / s is currently required to transmit a write without delay. However, a more elaborate coding of the information transmitted online can be used to reduce this bit rate. In the case of a transmission channel or network having lower bit rates, the writing is transmitted with a delay which depends on the amount of data to be transmitted and on the transmission capacity of the channel or the network.

The general organization of a telewriting assembly is described in more detail in FIG. 2. Such an assembly comprises a terminal 5 associated with a graphics acquisition device 4 and with a member 6 for display on a screen. The terminal 5 is organized around a circuit 7 for processing digital data connected to the graphics acquisition device 4 via a junction 9 and to the network 3 via a junction 10. The circuit 7 receives from one or other of these junctions digital data comprising in particular the X and Y coordinates of the points making up the graphics and display codes (color, eraser, inlay, etc.) or information allowing to reconstruct them. Each terminal also includes a member 11 for storing these digital data inserted between the data processing system 7 and a display control module 12, the latter controlling the display of the corresponding points by the display unit 6.

When the data comes from the network 3, the circuit 7 decodes the information it receives, in order to reconstitute all the points of the curve of graphics or writing. These points are then stored in the image memory 11 in which each point to be displayed is represented by a memory element in systems with black and white display and by two memory elements in systems with two-color display. In the case where the information comes from the tablet 4 through the junction 9, the processing circuit 7 reconstructs the points of the graph or writing curve, and stores them in the memory 11 as indicated above. In addition, the processing circuit 7 develops the codes to be sent to the correspondent through the junction 10 and the transmission network 3.

The image memory provides the display control module 12 with information from which the latter generates baseband video signals intended for the display unit 6, of the mainstream color television type for example.

A clock signal generator 8 paces the various organs of the terminal and in particular the processing system 7 and the display control module 12. In particular, the access times to the image memory 11 are shared, thanks to the clock signals, between the processing system 7 and the module 12 in order to avoid access conflicts.

These reminders about telewriting systems having been made, it is possible now to tackle the problems which the present invention proposes to solve.

Current telewriting systems display the graphics in white on a black background, or in two-color (for example red or green) on a black background and the user has the choice to write only between two colors. In addition, he cannot keep a trace of his drawings after erasing the screen, because no temporary or final storage is possible: the life of a drawing does not exceed that of its display. These two limits lead to difficulties of use which are as follows.

The limitation to two display colors is particularly troublesome in telewriting systems because it limits their applications. Indeed, in some cases, a large amount of information must be exchanged and the color constitutes an additional datum which is particularly convenient to use since it accompanies the drawing itself. We can cite in this regard education for example. Also, the possibility of writing with more than two colors is an essential need felt by many users.

But current telewriting systems have limited performance which precisely prevents display in more than two colors. In addition, the performance limitation makes it difficult to visualize the writing. Thus, for example, the fact of passing over an already existing line with another color gives only the combination of the points of the two colors. Additional information related to what one line has been drawn after another is lost.

In current telewriting systems, access to information by the user is limited in time to the time it is present on the display device. This constitutes a serious disadvantage since the recording during the discussion or the communication of the information exchanged not possible. For example, interlocutors cannot come back to a drawing or a graphic which has already been discussed, but which has been deleted, without having to redo it entirely, at one or the other end. Likewise, users cannot prepare drawings for later use during a discussion or presentation.

In summary, the old telewriting systems are limited, both as regards the information unchanged by the interlocutors as well as that which the latter have temporarily or permanently.

The present invention proposes to remedy these drawbacks and therefore to increase the information capacity offered to users.

To this end, the terminal of the invention comprises a plurality of memory planes constituted by direct access memories of sufficient capacity to be able to each contain all the information corresponding to a complete image covering the screen, these memory plans being all validated in parallel, simultaneous access to several memory plans being possible.

Three planes can be used for example to memorize the images, each point to be displayed on the screen being associated with a point of each of the three planes, each plan being assigned to the memorization of one of the fundamental colors red, blue or green. Each point can be "lit" or not in each of the three basic colors, and therefore in all their combinations. Still by way of example, a fourth memory plan can be used to memorize the different drawings or graphics as they are developed. The memory of these drawings is retained after the screen is completely erased and this recording remains available for the rest of the conversation. Likewise, a fifth plane can be used. to obtain a flashing of the points, etc. These examples are given as an indication for the understanding of the invention, but that they do not in any way restrict the generality of the invention and its applications, other uses of the memory plans being able to be adopted according to the envisaged applications.

The fact that the various memory planes of the invention can be accessed in parallel means that it is possible to write in several or in all the planes at the same time. For example, to write in yellow, we will write in the plans corresponding to the colors red and green; similarly to obtain white lines, we will write in the three planes red, green and blue. This parallel accessibility feature increases the overall performance of the system. Indeed, a writing in white requires only one writing cycle in memory simultaneously in the three red, green and blue planes instead of three successive writing cycles in three planes taken one by one.

According to another characteristic of the invention, each memory is associated with a generator of logic functions controlled by appropriate codes and able to combine the words to be written with words already written in the memory. This combination takes place during the writing cycle of the memory plans. Thus, any logical combination of writing between two words is possible to perform complex functions and this in only two cycle times, and a single request for access to the memory, which considerably improves the overall performance of the system. In this regard, we can cite the example of drawing a line intersecting another line of different color. At the crossing point, we will observe the color of the last line drawn without modifying the adjacent points. Thus, the time information between the two plots will be preserved by having inlay one or more dots of one color between other dots of different color. This operation requires the combination of the word already written in the memory planes and containing the written point with the word to be written containing this same point, which is achieved by the circuit of the invention.

Finally, it can be added that to be effective, current telewriting systems must have identical display organs or at least of the same visual definition. However, this is not the case for example when using television receivers with European standards with 625 lines and stations with North American standards which include only 525. In this case, an image inscribed on a European standard post will give a distorted image on an American standard post. This drawback is found each time that the display device is changed. The present invention also remedies this drawback by making it possible to adapt the image supplied to the display device used.

• - la figure 1, déjà décrite, représente le schéma synoptique d'un système de téléécriture conforme à l'art antérieur ;
• - la figure 2, déjà décrite, représente le schéma synoptique d'un terminal de téléécriture conforme à l'art antérieur ;
• - la figure 3 représente le schéma synoptique d'un terminal de téléécriture selon l'invention ;
• - la figure 4 représente le schéma synoptique d'un système de calcul d'adresse en mémoire à partir de coordonnées modifiées d'un point ;
• - la figure 5 représente le schéma d'un circuit d'écriture/lecture en mémoire ;
• - la figure 6 représente le schéma d'un plan-mémoire ;
• - la figure 7 représente une variante de réalisation du terminal de l'invention adaptée à un fonctionnement en vidéotex.

The characteristics and advantages of the present invention will become more apparent from the following description of an embodiment given by way of explanation and in no way limiting. This description refers to attached drawings in which:

• - Figure 1, already described, shows the block diagram of a telewriting system according to the prior art;
• - Figure 2, already described, shows the block diagram of a telewriting terminal according to the prior art;
• - Figure 3 shows the block diagram of a telewriting terminal according to the invention;
• - Figure 4 shows the block diagram an address calculation system in memory from modified coordinates of a point;
• - Figure 5 shows the diagram of a write / read circuit in memory;
• - Figure 6 shows the diagram of a memory plan;
• - Figure 7 shows an alternative embodiment of the terminal of the invention suitable for operation in videotex.

• a)une pluralité de plans-mémoire 18, 19, 20, 21, etc... identiques comprenant un même nombre d'éléments binaires de mémorisation ; chaque plan-mémoire est constitué par une mémoire à accès direct (en terminologie anglo-saxonne "_Random-Access-Memory") de capacité suffisante pour pouvoir contenir toute l'information correspondant à une image complète recouvrant l'écran ;
• b)un circuit 14 de calcul des adresses des éléments à écrire dans les plans-mémoire ; ce circuit reçoit, par l'intermédiaire du circuit 7 de traitement de données et pour chaque point courant écrit sur le dispositif d'acquisition de graphismes 4, les coordonnées X et Y de ce point et il délivre un mot binaire P_i comprenant un seul élément binaire à "1" et un signal numérique constituant une adresse de mémorisation pour ce mot P_i ;
• c)un circuit 15 de commande d'écriture et de lecture dans les plans-mémoires.

The device represented in FIG. 3 comprises, in addition to the means already represented in FIG. 2 and which bear, for simplicity, the same references:

• a) a plurality of identical memory planes 18, 19, 20, 21, etc., comprising the same number of binary memory elements; each memory plan is constituted by a direct access memory (in English terminology " _R andom-Access-Memory") of sufficient capacity to be able to contain all the information corresponding to a complete image covering the screen;
• b) a circuit 14 for calculating the addresses of the elements to be written in the memory planes; this circuit receives, via data processing circuit 7 and for each current point written on the graphics acquisition device 4, the X and Y coordinates of this point and it delivers a binary word P _i comprising a single binary element at "1" and a digital signal constituting a storage address for this word P _i ;
• c) a circuit 15 for writing and reading control in the memory planes.

The operation of such a device is broadly in line with that of the prior devices. Information to view by the member 6 comes from the telewriting terminal 5 which holds them either from another terminal connected to the previous one by the transmission network 3, or from the device 4 for acquiring graphics. In the latter case, the information is also sent to the other terminals of the system.

The information acquired by the terminal 5 is transformed by the circuit 7 and supplied, with the appropriate control codes, to the write and read control circuit 15. If necessary, the circuit 7 processes the information to send it through the transmission network 3. The writing / reading assembly 15 directs the information in memory, according to the commands provided by the circuit 7, in the various memory planes 18, 19, 20, 21 ... The display control module 12 reads the information in memory and routes a red, green, blue composite video television signal in baseband to the display device by the conductors 23.

The clock generator 8 supplies the various clock signals necessary for the circuit 7 and for the display control module 12. Sequencing information carried by a wire 17 intervenes in the circuit 7 and in the display module 12: to manage access to memory plans 18, 19, 20, 21, ... so as to avoid conflicts which may arise and switching parasites on the display device 6.

The various means of address calculation, write-read and storage which form part of the invention will now be described in more detail, the other circuits being of any known type.

The addressing circuit 14, first of all, is shown in FIG. 4. It includes a address calculation 50 which receives the X and Y coordinates of the point to be displayed, or, if the standards of the display member 6 are different from those of the acquisition device 4, the X 'and Y' coordinates of said point counted according to the standards of the display unit. In this case, the circuit 14 includes programmable read only memories (PROM) 56 and 56 'receiving the coordinates X and Y respectively and delivering the transformed coordinates X' and Y '. The figure corresponds to the particular case where the display device is a 525-line television set to North American standards. In this case, only the Y coordinate, corresponding to the line number, must be transformed. From the coordinates (X, Y) supplied by the connection 51, the Y coordinate is supplied to the programmable memory 56 'which delivers the modified Y' coordinate via the connection 57. For this, the memory 56 'is filled so as to match the coordinates Y and Y'. The X coordinate, for its part, remains unchanged and is supplied directly by the connection 55 to the address calculation unit 50, the memory 56 which is shown in dashes then being absent.

As for the address calculation unit 50, it comprises two memories 59 and 60 respectively receiving the coordinates X 'and Y' and an address calculator 61.

It will be assumed, to describe the operation of this circuit and for purely explanatory purposes, that the display member is a television receiver of which 512 lines are used on each of which 768 points are sampled, each line being broken down into 96 groups of 8 points. It therefore takes three bits or bits to locate a point in a group and 7 bits to locate the group in the line, or a total of 10 bits to define the address X '. Address Y specifies the rank of the line among 512 and therefore includes 9 bits. The memory 59 is therefore 10 bits and the memory 60 is 9 bits. All of the 19 bits are sent to the address calculator 61. This makes all the memories 59 and 60 play the role of shift register and delivers an address comprising 3 least significant bits making it possible to specify the place of 'a bit at "1" in a byte, P _i and 16 most significant bits, ie 2 bytes, constituting the address at which the byte P _i must be memorized in the various memory plans. Each of these plans must be able to store the equivalent of 512 lines of 96 bytes, which corresponds to a capacity of 48 K bytes (K = 1024).

In summary, the circuit 50 delivers, on an output connection 53, a byte P _i comprising a binary element at 1 at a determined location, and an address for this byte, consisting of two other bytes.

• - un circuit sélecteur 62 à une entrée reliée à la sortie du circuit 7 par une connexion 54, laquelle véhicule quatre signaux : un premier signal qui est un octet O_i pouvant être par exemple l'octet P_i lorsqu'il s'agit d'une écriture simple, engendré par le circuit 14, un second signal qui est un code de validation formé par autant d'éléments binaires qu'il y a de plans-mémoire, un troisième signal qui est un code de fonction logique et un quatrième signal qui est l'adresse de l'octet O_i formée de deux octets. Le sélecteur 62 possède quatre sorties 62', 62", 62"', et 62"" et il est apte à diriger les quatre signaux qu'il reçoit respectivement sur ces quatre sorties ;
• - une mémoire 63 à une entrée reliée à la première de ces sorties 62' d'où elle reçoit l'octet O_i, et à une sortie reliée à une connexion 71 ;
• - une mémoire 64 à une entrée reliée à la seconde sortie 62", d'où elle reçoit les éléments binaires formant le code de validation ; cette mémoire contient autant de cellules binaires de mémorisation 64', 64", 64"'... qu'il y a de plans-mémoire, ces cellules possédant chacune à une connexion de sortie, respectivement 65, 66, 67, 68 etc. ; ces connexions sont reliées aux entrées de validation de chacun desdits plans-mémoire, comme on le verra par la suite, lesquels peuvent donc tous être validés en parallèle ;
• - une mémoire 70 à une entrée reliée à la quatrième sortie 62"" d'où elle reçoit les deux octets d'adresse de l'octet 0_. et à une connexion de sortie 73.

The write-read circuit 15 in the different memory planes is shown in FIG. 5. It includes:

• a selector circuit 62 with an input connected to the output of circuit 7 by a connection 54, which conveys four signals: a first signal which is a byte O _{i which} can be for example the byte P _i when it is a question of '' a simple write, generated by circuit 14, a second signal which is a validation code formed by as many binary elements as there are memory planes, a third signal which is a logic function code and a fourth signal which is the address of byte O _i formed by two bytes. The selector 62 has four outputs 62 ', 62 ", 62"', and 62 "" and it is able to direct the four signals which it receives respectively on these four outputs;
• a memory 63 with an input connected to the first of these outputs 62 ′ from which it receives the byte O _i , and with a output connected to a connection 71;
• - a memory 64 at an input connected to the second output 62 ", from which it receives the binary elements forming the validation code; this memory contains as many binary memory cells 64 ', 64", 64 "' ... that there are memory plans, these cells each having an output connection, respectively 65, 66, 67, 68 etc.; these connections are linked to the validation inputs of each of said memory plans, as will be seen thereafter, which can therefore all be validated in parallel;
• a memory 70 with an input connected to the fourth output 62 "" from which it receives the two address bytes of byte 0 _. and to an output connection 73.

The assembly 15 may also include a programmable read-only memory 69 (PROM) for code conversion, to an input connected to the third output 62 "'of the selector circuit 62 from which it receives a logic function code, and to an output 72 delivering a code suitable for the generator of logic functions, but this memory can also be housed in this generator.

The organization of a memory plan is illustrated in FIG. 6. This memory consists of memory blocks 78 associated with buffer memories 80. Each block has a write input 77 ′, a read output 79 ′, a validation input 65 'and finally an addressing input 73'. The input 65 'is connected to the connection 65 coming from the validation memory 64, the input 77' to a connection 77, the output 79 'to a connection 79 connected to the buffer memory 80, and the input of addressing 73 'to connection 73 coming from address memory 70.

Each memory plan further comprises a logic function generator 75 having a control input 72 ′ connected to the connection 72 from the mete moire 69, a first signal input 71 'connected to the connection 71 coming from the byte memory 63, a second signal input 76' connected to a connection 76 connected to the buffer memory 80 and a signal output connected by a connection 77 to input 77 'for writing memory.

The operation of this memory is as follows.

The input byte O _i is conveyed from the memory 63 to the generator of logic functions 75 by the connection 71 while the address of this byte reaches the memory by the connection 73 coming from the memory 70. Either M _i the byte which is already in memory at this address. This byte is transmitted to the generator 75 by the connection 76, which then has two bytes to combine O _i and M. The combination which it performs is determined by a function code developed in the data processing circuit 7 from indications provided by the operator. This code, after having possibly been converted into a circuit 69, is supplied to the generator by connection 72. The byte resulting from the combination of O _i and M. is then conveyed by connection 77 to input 77 'of the memories and this byte is written. The writing will be effective in the memory plans which will have been validated by application of a validation signal on the connections 65, 66, 67, etc.

The memory is completed by a buffer register 81 and by buffer registers 82 which are connected to the outputs of blocks 78 and form a shift register. The output connection 83 is directed to the display control module 12.

• l'élément de poids fort détermine les deux temps de cycle qui sont nécessaires pour la réalisation des diverses fonctions d'effacement, d'écriture par écrasement, d'écriture par incrustation, de curseur, etc... Le premier temps correspond au bit "0" et le second au bit "1". Les bits restant définissent la fonction logique à réaliser.

The process of logical combination between the bytes O _i and M _i will now be specified. The function to be performed is defined by a 5-bit binary code:

• the most significant element determines the two cycle times which are necessary for carrying out the various functions of erasing, writing by overwriting, writing by overlay, cursor, etc. The first time corresponds to the bit "0" and the second at bit "1". The remaining bits define the logic function to be performed.

Or, for example, to write in point a point in the memory map assigned to blue. In a first operation, this point is deleted in the three planes assigned to the three colors. For this, we form a byte O _i complementary to O _i and we combine O _i with M _i by a logical operation AND, which provides a new byte of which all the elements are zero. We note this first operation O _i . M _i → M. where the point represents the logical AND operation. The code for this AND function can be noted, for example, 0001 and since this is the first time in the cycle, a binary element of high significance "0" is associated with it, which finally gives the code 00001. The selector 62 then delivers this function code 00001 to memory 69 via connection 74, and the validation codes of the three color planes to memory 64.

In a second operation, the point in question must be written in the blue memory map. The memory 64 then validates only this plan; the function code goes to 10001, the most significant bit to "1" indicating that it is the second time of the cycle; for this second step, the code 0001 corresponds to a logical OR operation between the bytes O _i and M _i , operation noted O _i + M _i → M., the sign + indicating, depending on usage, the OR operation. This results in writing in incrustation. Of the point in the blue memory plan.

• a)incrustation avec réécriture dans un plan,
• b)incrustation d'un noir dans des plans sans réécriture (gomme),
• c)incrustation avec inversion des couleurs,
• d)écriture par octet avec écrasement.

The table below collects the codes corresponding to four functions, namely:

• a) inlay with rewriting in a plan,
• b) embedding a black in plans without rewriting (eraser),
• c) inlay with color inversion,
• d) write by byte with overwrite.

The table is divided into two parts: the upper part corresponding to the first time of the cycle (most significant binary element at "0") and the lower part corresponding to the second time of the cycle (binary element to 1). In each part, the four previous operations a), b), c) and d) are represented with the logical operations carried out. The conventions on logical operations have already been indicated, the sign ⊕ corresponding to the OR-exclusive operation. Some codes are not used and are free for other functions than those indicated.

In addition to the advantages already outlined that the invention presents, it provides another in connection with the transmission of information according to a videotex mode. This aspect of the invention will now be discussed.

We know the system called "ANTIOPE" (Digital Acquisition and Television of Image Organized in Writing Pages), and the system called "TITAN" (Interactive Teletext Terminal with Call by Dialing). It is essentially, for the first, a system of diffused videotex (therefore unidirectional) allowing to insert on television channels alphanumeric information organized in pages and magazines. For the second, it is an interactive videotex system (therefore bidirectional) compatible with the ANTIOPE system and allowing access to databases (general information, directories, etc ...) and interactive services (transactions, messages, teaching) via the telephone network.

• - l'article de Y. GUINET intitulé "Etude comparative des systèmes de télétexte en radiodiffusion. Quelques avantages de la diffusion des données par paquets appliquée au télétexte" paru dans la revue de l'U.E.R. cahier Technique, N° 165, octobre 1977, pages 242 à 253 ;
• - l'article de B. MARTI et M. MAUDUIT intitulé "ANTIOPE, service de télétexte" paru dans la revue "RADIODIFFUSION TELEVISION" 9ème année, N° 40, novembre-décembre 1975, pages 18 à 23 ;
• - la spécification du système de télétexte "ANTIOPE", éditée par le CENTRE COMMUN D'ETUDES DE TELEVISION ET TELECOMMUNICATIONS (C.C.E.T.T.) ;
• - la norme française de vidéotex interactif, éditée par la Direction Générale des Télécommunications (D.G.T.) ;
• - la demande de brevet français n° 76 27 212, déposée le 6 septembre 1976 et intitulée "Système de transmission numérique et d'affichage de texte sur un écran de télévision" ;
• - la demande de brevet français n° 76 29 034, déposée le 22 septembre 1976, et intitulée "Perfectionnements aux systèmes de transmission numérique et d'affichage de textes sur un écran de télévision" ;
• - la demande de brevet français n° 78 07 551, déposée le 10 mars 1978 et intitulée "Système de transmission numérique et d'affichage de textes et de graphiques sur un écran de télévision".

Many articles or patent applications have already described these systems and for example:

• - the article by Y. GUINET entitled "Comparative study of teletext systems in broadcasting. Some advantages of packet data dissemination applied to teletext" published in the EBU journal cahier Technique, N ° 165, October 1977, pages 242 to 253;
• - the article by B. MARTI and M. MAUDUIT entitled "ANTIOPE, teletext service" published in the review "RADIODIFFUSION TELEVISION" 9th year, N ° 40, November-December 1975, pages 18 to 23;
• - the specification of the "ANTIOPE" teletext system, published by the JOINT TELEVISION AND TELECOMMUNICATIONS STUDIES CENTER (CCETT);
• - the French standard for interactive videotex, published by the Directorate General of Telecommunications (DGT);
• - French patent application No. 76 27 212, filed on September 6, 1976 and entitled "System for digital transmission and display of text on a television screen";
• - French patent application No. 76 29 034, filed on September 22, 1976, and entitled "Improvements to digital transmission systems and text display on a television screen";
• - French patent application no. 78 07 551, filed on March 10, 1978 and entitled "System for digital transmission and display of texts and graphics on a television screen".

Videotex systems are essentially limited to the transmission and display of characters and semi-graphics.

The telewriting terminal which has been described above, can, at the cost of a few additions, also fulfill the functions of videotex terminal. In this variant embodiment, the invention makes it possible to offer a user provided with a single terminal, the two types of communications, videotex and telewriting, whereas previously, the user had to have two types of terminals. In addition, the invention allows a third type of communication by the combination of the two systems which complement each other: videotex offers possibilities for total graphics (and no longer only semi-graphics) and telewriting. opens towards the transmission of characters and graphics of the videotex type.

This variant embodiment is described in FIG. 7.

• - un organe 100 de gestion et de mémorisation du mode de fonctionnement ; cet organe commande la jonction 10 et est relié au circuit de traitement de données 7 par une liaison 101 dont l'état électrique défini ce mode ;
• - un commutateur de mode 102 relié audit organe 100 à trois positions "téléécriture", "vidéotex" et "téléécriture-vidéotex"
• - un clavier alphanumérique à touches 104 relié au circuit de traitement de données 7 ;
• - une mémoire de formes de caractères 106, elle aussi reliée au circuit de traitement de données 7.

The terminal shown schematically in this figure comprises means already shown in Figure 3 and which bear for simplicity, the same references. It also includes:

• an organ 100 for managing and memorizing the operating mode; this member controls the junction 10 and is connected to the data processing circuit 7 by a link 101 whose electrical state defines this mode;
• a mode switch 102 connected to said member 100 with three positions "telewriting", "videotex" and "telewriting-videotex"
• - an alphanumeric keyboard with keys 104 connected to the data processing circuit 7;
• a character shape memory 106, also linked to the data processing circuit 7.

• a) un mode téléécriture dans lequel le clavier 104 et la mémoire de formes de caractères 100 sont rendus inopérants et dans lequel le circuit de traitement de données 7 et l'organe de mémorisation 11 fonctionnent comme en téléécriture ;
• b)un mode vidéotex dans lequel le clavier 104 et la mémoire de formes de caractères 106 sont mis en service et coopèrent avec le système de traitement de données 7, la jonction 10 et l'organe de mémorisation 11 comme en vidéotex classique ;
• c)un mode mixte téléécriture-vidéotex, dans lequel le terminal passe alternativement dans le mode téléécriture et dans le mode vidéotex, sous la commande de l'organe de gestion et de mémorisation 100.

These means are capable of defining three operating modes for the terminal:

• a) a telewriting mode in which the keyboard 104 and the character shape memory 100 are rendered inoperative and in which the data processing circuit 7 and the storage unit 11 operate as in telewriting;
• b) a videotex mode in which the keyboard 104 and the character shape memory 106 are put into service and cooperate with the data processing system 7, the junction 10 and the storage unit 11 as in conventional videotex;
• c) a mixed telewriting-videotex mode, in which the terminal switches alternately to telewriting mode and to videotex mode, under the control of the management and storage unit 100.

The operation of the terminal in telewriting mode only has been widely described above and will therefore not be repeated.

In videotex mode, the information coming from the transmission network 3 is coded to the videotex standards defined in the documents cited in reference. The alphanumeric keyboard 104 selects the information transmitted by the network. For this, the characters typed on this keyboard reach circuit 7 in ASCII code on 7 bits of one byte (the eighth is a parity bit). The circuit 7 transmits these characters directly to the transmission junction 10 which sends them to the network 3. The latter contains the modulation and demodulation organs, selection of the pages and adaptation of the information transmission speed.

In the case of the videotex in broadcast version, all the adaptations concerning the reception of information according to the DIDON and ANTIOPE systems are defined in the documents cited above. In the case of videotex in an interactive version, only a modulator-demodulator is necessary.

• - un état 1 où les codes transmis représentent des informations de vidéotex ;
• - un état 2 où les codes transmis représentent des informations de téléécriture.

When the rotator 20 is in the position corresponding to the mixed mode, the transmission junction 10 alternately switches to the "telewriting" mode and to the "videotex" mode as a function of the information provided by the mode management and storage circuit 100. Operating. For this, this circuit filters the data passing through the transmission junction in order to manage a state machine which can take two different states:

• - a state 1 where the transmitted codes represent videotex information;
• - a state 2 where the transmitted codes represent telewriting information.

On power-up, the PLC is in one of these states, for example always in state 1. It remains in this state as long as it does not find, in the transmitted codes, the continuation of the three bytes 9B / 25/61 ". When these three bytes occur, it goes into state 2 corresponding to telewriting. The code" telewriting code output "; this code is a byte coded" OF "sent in state" byte synchronization "of the telewriting transmission.

The mode management and storage circuit 100 therefore controls the junction 10 by indicating to it in which mode it must work. In addition, the circuit 100 dialogues with the data processing circuit 7 to indicate what type of data is transmitted to it. To this end, a link 101 indicates, by its electrical state, what type of data are passing between 10 and 7. This link 101 controls the circuit 7 and specifies the mode to be used on reception.

The control of the operating mode of circuit 7 on transmission is obtained by discrimination in the peripheral providing the data knowing that the tablet corresponds to telewriting and the alphanumeric keyboard to videotex.

In the receiving direction, the member 100, by decoding the information received by the junction 10, controls the operating mode. In addition, the member 100 eliminates the mode change codes included in the information passing between the junction 10 and the circuit 7.

In the transmission direction, each time the operating mode 7 of the circuit 7 is detected, the member 100 sends the necessary mode change codes via the junction 10.

The system has a memory for display attributes: character color, background color, character size, continuous or separate graphics, normal background, inverted, ... This memory is addressed by decoding the commands for display attributes . It provides circuit 7 with the information for filling the display memory.

Circuit 7 also has a memory for moving the cursor in coordinates (X, Y). This memory is updated as a function of the writing in the character display memory or of the cursor movement commands.

Thus, when a character to be displayed is received, the circuit 7 will draw from the character form memory 106, the bytes to be written in the various plans of the memory. These bytes are possibly modified according to the display attributes.

• - l'adresse d'écriture de l'octet : pour cela il prend les coordonnées (X, Y) du curseur et les fait transformer par le système de calcul d'adresse 14 ;
• - l'octet à écrire ;
• - les plans-mémoire à valider ou non en fonction des couleurs de fond et de caractère ;
• - le code spécial de commande de l'écriture de caractères vidéotex. Ce mode correspond à une écriture avec effacement de ce qui existait auparavant.

The circuit 7 provides the memory writing device 15:

• - the write address of the byte: for this it takes the coordinates (X, Y) of the cursor and has them transformed by the address calculation system 14;
• - the byte to write;
• - the memory plans to be validated or not according to the background and character colors;
• - the special command code for writing videotex characters. This mode corresponds to a write with erasure of what existed before.

Circuit 7 restarts this procedure as many times as necessary to write a character. Thus, when a character is coded on 20 lines with 16 points per line, it is necessary to make forty writes of bytes in the visualization memory plans.

The device which has just been described allows the transmission of information intended to reveal a colored surface of any shape on a screen.

Certain known devices are equipped with means for reproducing geometric figures such as the square, the rectangle, the rhombus, the trapezoid, the triangle, the circle, the oval, etc. These surfaces have the common characteristic that they can be placed easily in equation. The limitation to these simple surfaces is naturally troublesome. For more details, see technical note No. 697 from the Communications Research Center of the Department of Communications of Canada entitled: "General description of the TELIDON Canadian proposal concerning Videotex systems" by HG BOWN, CD O'BRIEN , W. SAWCHUH and JR STOREY, from December 1978 (OTTAWA).

The present invention overcomes these drawbacks and therefore increases the information capacity offered to users, improves the image quality and limits user fatigue.

To this end, one of the memory plans of the terminal is used for temporary storage of information relating to this application. In addition, the dis positive acquisition, such as the graphic tablet, has additional facilities for the user to indicate his desire to fill the interior, exterior or both, with a surface that he has delimited. In addition, the additional memory plan is organized so as to be able to easily fill the memory plans containing the data constituting the synthetic image displayed.

The surface to be colored can be described by the curve constituting its border. The data representing this curve is transmitted by the network or the transmission channel; the coding can be of the telewriting type, equation of the curve, following the coordinates of the points constituting the curve. The data relating to the surface border, after shaping by the processing circuit, are stored in the memory plane assigned to this task and according to a particular procedure. The data processing unit searches for this information once the transmission is finished in order to store the necessary data in the plans constituting the memory of the image to be displayed. As soon as this phase is completed, the filling memory plan becomes available again for any other use.

In the description which follows, it is assumed for explanatory purposes that the data transmitted between the terminals in communication are of the telewriting type, which in no way detracts from the generality of the invention, but facilitates the description thereof.

A user of the system wishes to transmit a surface whose interior (for example) is of a chosen color. For this, he uses the graphic tablet to indicate the color and the "fill" function using any means such as a button, a button, a switch ... On this tablet he only draws the border of the surface. This border is a continuous and closed curve. Its terminal transmits it in the form of a digital code established by the processing circuit 7; transmission is via the network or channel 3. For example, the transmission code can be that of telewriting.

On reception, the terminal receives the data coming from the network 3, on the junction 10. The processing device 7 receives the data. In the data header, a positioned bit indicates that the next curve corresponds to a colored area. Taking this information into account, circuit 7 no longer writes the points of the curve in the display memories, for example the planes 18, 19 and 20, but in a special memory plane, for example the plane 21. This memory plane is organized in the same way as the others, that is to say that the same binary element corresponds to the same point to be displayed on the display device 6. This is not compulsory but greatly facilitates the work of circuit 7.

In a first phase, the circuit 7 decodes the data coming from the line and sets to 1 the binary elements of the plane 21 corresponding to the points of the border. There are several exceptions to this rule. First of all, if the corresponding point was previously written (this is the case for a double point, for example), this point must be reset to 0. You must then favor a direction, the vertical or the horizontal. We can choose the horizontal, the reasoning remaining valid if it is the vertical which is chosen. In the case where the border has a horizontal part (case of a curve having a maximum, a minimum or an inflection point) only the first point of the horizontal is set to 1, the other points being unchanged. On the other hand, the last point of the horizontal must be set to 1 in the case of an extremum (maximum or minimum), but must remain unchanged (to zero) in the case of an inflection point. For this, circuit 7 must memorize the last point before the horizontal and compare to the point following the horizontal to know whether or not there has been a change of side of the curve with respect to the horizontal.

All the points of the border being written in the plane 21 in this way, the circuit 7 passes to the phase of construction and display of the surface. For this, the plane 21 is scanned along the horizontal lines to be displayed. Along each horizontal, a binary element at 1 means that from this point we cross the border. Thus, if we started at the beginning of a horizontal from the outside, the first binary element at 1 corresponds to the passage inside and the second outside. A third binary element with 1 makes pass inside, a fourth outside, etc ... Thus, the circuit 7 can reconstitute the surface and fill the memories 18, 19 and 20 of visualization with the necessary elements according to the procedure already described.

Once all the horizontal lines have thus been scanned by the circuit 7, the colored surface is displayed and the plane 21 can be reset to zero for later use.

If the codes received from the transmission line or channel 3 are not of the telewriting type, new functions must be added to the data processing circuit 7. This circuit 7 must then interpret the codes received in order to reconstruct the sequence of coordinates (X, Y) of the points constituting the border of the surface.

The sequence of data received from network 3 may not correspond to a closed curve. The processing circuit 7 detects this anomaly because the first and the last points of the curve do not coincide. This can happen with telewriting codes. The processing circuit 7 then automatically closes the curve by joining the last point received to the first point received by a line segment. Thus, the information contained in the plane 21 will always relate to a closed curve, and therefore to the border of a surface.

Claims (8)

1. Device for digital transmission and display of graphics on a screen, comprising at least two telewriting terminals connected by a transmission network (3), each terminal (5) being associated with a graphics acquisition device (4 ) and to a member (6) for displaying on a screen, each terminal being organized around a circuit (7) for processing digital data connected to the graphics acquisition device (4) via a junction (9) and to the network (3) by means of a junction (10), the circuit (7) receiving digital data from one or the other junction comprising in particular the X and Y coordinates of the component points the graphics and display codes or information making it possible to reconstruct them, each terminal further comprising a member (11) for storing this digital data inserted between the data processing system (7) and a display control module ( 12), this module controlling the display d es corresponding points by the display member (6); this device being characterized in that each terminal comprises: a) a plurality of memory planes (18, 19, 20, 21, etc.) comprising the same number of binary memory elements, each memory plan being constituted by a direct access memory of sufficient capacity to be able contain all the information corresponding to a complete image covering the screen, this memory having a write input, a read output, a validation input (65) and an address input (73), each memory plane being associated with a logic function generator (75) pos having a control input (72), a first signal input (71), a second signal input (76) connected to the memory read output and a signal output (77) connected to the input writing of the memory, this output conveying a word to be written which is a logical function of the words applied to the two inputs (71) and (76); b) a circuit (14) for calculating the addresses of the elements to be written in the memory plans, this circuit receiving, via the circuit (7) for data processing, for each current point written on the acquisition device graphics (4), the X and Y coordinates of this point and delivering a binary word P _i comprising a single binary element at "1", this word being applied to the first input 71 of the generator 75, and a digital signal constituting a address for this word P _i ; c) a circuit (15) for writing and reading control in the memory planes comprising: c ₁ ) a selector circuit (62) with an input connected to the output of the data processing circuit (13) from which it receives four signals: a first signal which is a word O _i possibly being the word P., a second signal which is a validation code formed by as many binary elements as there are memory maps, a third signal which is a logic function code and a fourth signal which is the address of said word O _i , the selector (62) having four outputs and being able to direct the four signals which it receives respectively on these four outputs, c ₂ ) a memory (63) with an input connected to the first of these outputs, from which it receives the word O _i , and with an output connected to the signal input of the logic function generator (75), c ₃ ) a memory (64) at an input connected to the second output, from which it receives the binary elements forming the validation code, this memory containing as many binary memory cells as there are memory plans, these cells being each connected to an output connection, respectively (65), (66), (67), (68), ... themselves connected to the validation inputs of each of said memory plans, these memory plans can therefore all be validated in parallel, C ₄ ) a memory (70) with an input connected to the fourth output from which it receives the address of the word 0 _i and with an output (73) connected to the addressing inputs of the memory plans, these means a) , b), and c) allowing simultaneous access to several memory plans validated in parallel to write binary information to the desired address, taking into account the information already written to this address according to predetermined functions. 2. Device according to claim 1, characterized in that the display member (6) is a television receiver with 512 lines of 768 viewable points and in that each memory plane has a capacity of 48K bytes (K = 1024), the words O _i and M _i entering and writing in the memory plans being bytes comprising a single binary element at "1", the address of such a byte in the memory being identified by a word of 16 elements binary (2 bytes). 3. Device according to claim 1, characterized in that the standards of the display member (6) being different from those of the acquisition device (4), the address calculation circuit comprises a programmable read only memory (56 , 56 ') which receives the X and Y coordinates of the points written in the acquisition device and which delivers transformed coordinates X 'and Y' corresponding to the standards of the display unit, the address being calculated from said coordinates X 'and Y'. 4. Device according to claim 1, characterized in that it further comprises, either in the assembly (15) for writing and reading, or in the generator of logic functions (75), a programmable read only memory (69 ) code conversion, to an input connected to the third output of the selector circuit (62) from which it receives a logic function code, and to an output (72) delivering a code adapted to the logic function generator (75) . 5. Device according to any one of claims 1 to 4, characterized in that three of the memory planes are assigned to the storage of data corresponding to graphics respectively in the three primary colors red, green, blue. 6. Device according to claim 5, characterized in that a fourth memory plane is assigned to the memorization of the graphics even after complete erasure of the screen. 7. Device for digital transmission and display of graphics and / or characters according to any one of claims 1 to 6, characterized in that each terminal further comprises: a member (100) for managing and memorizing the operating mode, this member controlling the junction (10) and being connected to the data processing circuit (7) by a link whose electrical state depends on this mode, - a three-position mode switch (102) connected to said member (100), - an alphanumeric keyboard with keys (104) connected to the data processing circuit (7), - a character form memory (106) connected to the data processing circuit (7), these means being able to define three operating modes for the terminal: a) a telewriting mode in which the keyboard (104) and the character shape memory (106) are rendered inoperative and in which the data processing circuit and the storage unit (11) operate as in telewriting, b) a videotex mode in which the keyboard (104) and the character shape memory (106) are put into service and cooperate with the data processing system, the junction (10) and the storage unit (11) as in conventional videotex, c) a mixed telewriting-videotex mode in which the terminal alternately switches to telewriting mode and to videotex mode under the control of the management and storage unit (100) which filters the data passing through the junction (10) and determines, from the nature of this data, the operating state of the terminal. 8. Device according to claim 5, characterized in that an additional memory plane is assigned to the storage of information relating to the definition of a closed curve delimiting a surface, the data processing system (7) being able to process this information to control the display of the interior and / or exterior of this curve according to a specific color.

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