EP0973145A1 - Method and system for processing digital images resulting from auxiliary graphical elements blended in main images - Google Patents

Abstract

The method involve data being decoded in real time, with the data comprising an auxiliary array of data defining the auxiliary image. For each successive principle image the values of chrominance and luminance, that are to be mixed with the pixels of the principal embedded image, are supplied without having to be determined for each image.

Description

The invention relates to the development of digital images resulting from auxiliary graphic elements forming images auxiliary graphics or sub-images ("sub-pictures" in language intended to be embedded in a predetermined area of a display screen overlaying main images resulting in particular of a decoding of compressed data, in particular according to the MPEG ("Motion Pictures Experts Group") standards.

The invention relates more particularly to the decoding of these auxiliary images or sub-images and applies advantageously but not limited to the case where these sub-images result from data auxiliaries or sub-picture data stored from compressed way on a multifunction digital disc (DVD: "Digital Versatile Disk "in English).

One of the uses of these auxiliary graphic images or subpictures concerns the display of menus on the television screen or well the overlay in the main images viewed on the screen of a television, short animated sequences, or even viewing of song texts in karaoke apps.

A solution currently used for image development auxiliary graphics consists in decoding the graphic data auxiliaries compressed and stored on the digital disc so software to store images in dynamic memory auxiliary graphics thus decoded and ready to be extracted from the memory, as many times as necessary, to be displayed each time pixel by pixel.

However, such a way of operating requires a memory size. important, especially when the size of the auxiliary graphic images is important.

The invention aims to provide a solution to this problem and proposes a radically different solution for decoding and developing these auxiliary graphic images, and the development of the images resulting from their superimposition with the flow of main images.

The invention therefore provides a method for developing images numerical resulting from auxiliary graphic elements embedded in the main images.

According to a general characteristic of the invention, the method comprises reception of at least one auxiliary flow comprising a set of compressed graphical data corresponding to graphic elements forming at least one auxiliary graphic image intended to be embedded in a predetermined area of a screen display, this overlay should occur from the moment of occurrence of a predetermined initial main image and during a predetermined elementary duration, superimposed on images main. The method also includes storing the flow auxiliary in a memory and successive decoding of the data compressed graphics, these successive decodings being respectively made during the displays of successive main images, from the display of the initial main image until the expiration of said predetermined elementary duration, so as to deliver during each decoding, at the rate of display of the pixels on the screen and for each auxiliary image pixel, luminance and chrominance values as well as a mixing coefficient. The method also includes the pixel to pixel mixing in said predetermined screen area, values chrominance and luminance corresponding to the main image current being displayed and with the decoded auxiliary graphic image, taking into account said mixing coefficients.

In other words, the method according to the invention provides for a on-the-fly decoding of compressed graphic data of an image graphic, during the display of a main image (in practice at display of each frame of the main image), as well as the redecoding of the same data corresponding to the same graphic image for each main image, i.e. during the display of each main image for as long as necessary. So if for example an auxiliary graphic image needs to be embedded on the display screen overlaying an initial main image and superimposition of the following 99 main images, the data compressed graphics corresponding to each frame of this image will be successively decoded 100 times, each decoding producing in real time during the display of the main image current so that the mixer receives synchronously, for each pixel, the luminance and chrominance values of the image main one to be displayed, and those of the graphic image auxiliary decoded and intended to also be displayed as an overlay of this main image being displayed.

The invention therefore has the notable advantage of reducing the memory size required as well as the memory bandwidth used since the auxiliary graphic data of each graphic image can be kept stored in memory in a form compressed, and that the decoding of this data requires no storage in the memory of the auxiliary graphic image decoded before being display.

The auxiliary stream generally includes a header, said compressed graphical data, and at least one data set of configuration, used to configure the decoding of said image graphic. Furthermore, according to one embodiment of the invention, in which the main images are displayed line by line in two successive frames corresponding to lines of different parities, we performs an analysis processing of said configuration data between each display of a frame. That said, we could also in a other embodiment of the invention, carry out this treatment analysis of configuration data during each line feed.

In fact, in general, the analysis processing is carried out configuration data during a period during which there is no has no pixel display on the screen, so as not to disturb this display.

The compressed graphics dataset can correspond to several successive auxiliary graphic images each intended to be successively superimposed on the images main during a respective elementary duration. The auxiliary flow then includes several sets of configuration data allowing each to configure the decoding of a graphic image auxiliary. And, as long as said elementary duration corresponding to an image auxiliary graph has not elapsed, we analyze the data set setting corresponding to this image between each display of a frame, then we decode the compressed graphic data of this image based on the setting data. And, when said corresponding elementary time has elapsed, we automatically pass analysis of the configuration data set corresponding to the next auxiliary graphic image, then decoding data compressed graphics of this next image based on these new configuration data.

According to a particularly simple mode of implementation of the invention, upon receipt of the auxiliary flow, a counter is initialized time at a predetermined initial value (e.g. time display of the first auxiliary graphic image). Each set of configuration data includes a time indication, linked to said predetermined initial value (for example the start time display of each of these auxiliary graphic images), and representative of the start time of the first decoding of the image corresponding auxiliary graphic. Before starting decoding compressed data corresponding to the first graphic image auxiliary, we store in a register the temporal indication of the image following auxiliary graph and successive decodings of the auxiliary graphic image configured by the corresponding set of setting data as long as the counter value is less than contents of the register. And, when the value of the counter becomes higher or equal to the contents of the register, it means that it is time to proceed with the decoding and display of the next auxiliary graphic image.

According to one embodiment of the invention, the processing analysis of a set of configuration data includes storage different groups of "color-mixing coefficient" pairs in different respective elementary memories (search tables; "look-up tables" in English). The number of couples per group is less than a first predetermined number (for example four when tables are addressed by 2 bits). In addition, the number of groups is less than or equal to a second predetermined number (e.g. eight, which corresponds to a maximum of eight different regions per line image). Line by line decoding of each graphic image auxiliary then includes successive data addresses decoded graphics, of the different designated elementary memories successively by so-called designation data, contained in the setup data set.

In other words, as an example, once several lookup tables were programmed during the analysis analysis of configuration data, address for the first pixels of the line a first search table then, according to a data of designation corresponding to the size of the region (number of pixels per example), we switch after the development of this number of pixels, to a other search table that we will address from the data following decoded graphics, and so on.

The subject of the invention is also a production system of digital images resulting from auxiliary graphic elements embedded in main images.

• des moyens de réception pour recevoir un flot principal comprenant des données comprimées codant des images numériques principales, et au moins un flot auxiliaire comprenant un ensemble de données graphiques comprimées correspondant à des éléments graphiques formant au moins une image graphique destinée à être incrustée dans une zone prédéterminée d'un écran d'affichage, à partir de l'instant d'occurence d'une image principale initiale pendant une durée élémentaire prédéterminée, en superposition des images principales,
• une mémoire pour stocker le flot principal et le flot auxiliaire,
• un décodeur principal (par exemple un décodeur MPEG si les images principales sont comprimées selon une norme MPEG), ce décodeur principal étant apte à décoder le flot principal de données comprimées et à délivrer pour chaque pixel d'une image principale décodée, des valeurs de luminance et de chrominance,
• un dispositif d'élaboration des images résultantes comprenant des moyens de décodage (décodeur auxiliaire ou décodeur de sous-image : "sub-picture decoder" en langue anglaise) aptes à effectuer des décodages successifs des données graphiques comprimées contenues dans la mémoire, ces décodages successifs étant respectivement effectués au cours des affichages des images principales successives, depuis l'affichage de l'image principale initiale jusqu'à l'expiration de ladite durée élémentaire prédéterminée, de façon à délivrer au cours de chaque décodage, au rythme d'affichage des pixels à l'écran et pour chaque pixel de l'image auxiliaire, des valeurs de luminance et de chrominance ainsi qu'un coefficient de mélange. Le dispositif d'élaboration comprend par ailleurs des moyens de mélange aptes à effectuer le mélange pixel à pixel dans la zone prédéterminée d'écran, des valeurs de chrominance et de luminance correspondant à l'image principale courante et à l'image graphique auxiliaire décodée, compte tenu desdits coefficients de mélange.

According to a general characteristic of the invention, this production system comprises:

• reception means for receiving a main stream comprising compressed data encoding main digital images, and at least one auxiliary stream comprising a set of compressed graphic data corresponding to graphic elements forming at least one graphic image intended to be embedded in an area predetermined display screen, from the instant of occurrence of an initial main image for a predetermined elementary duration, superimposed on the main images,
• a memory for storing the main flow and the auxiliary flow,
• a main decoder (for example an MPEG decoder if the main images are compressed according to an MPEG standard), this main decoder being capable of decoding the main stream of compressed data and of delivering for each pixel of a decoded main image, values of luminance and chrominance,
• a device for developing the resulting images comprising decoding means (auxiliary decoder or sub-image decoder: "sub-picture decoder" in English) capable of carrying out successive decodings of the compressed graphic data contained in the memory, these decodings successive being respectively carried out during the displays of the successive main images, from the display of the initial main image until the expiration of said predetermined elementary duration, so as to deliver during each decoding, at the display rate pixels on the screen and for each pixel of the auxiliary image, luminance and chrominance values as well as a mixing coefficient. The processing device also comprises mixing means able to perform pixel-to-pixel mixing in the predetermined screen area, chrominance and luminance values corresponding to the current main image and to the decoded auxiliary graphic image. , taking into account said mixing coefficients.

According to an embodiment of the invention, in which the flow auxiliary includes a header, said compressed graphic data, and at least one set of configuration data allowing configure the decoding of said graphic image, the auxiliary decoder (sub-image decoder) comprises a first memory of the type "first in first out" (FIFO) capable of storing data compressed graphics, and a second "first-in-first" memory output "suitable for storing the configuration data. Furthermore, the main images being displayed line by line and in two frames successive corresponding to different parity lines, the decoder auxiliary includes suitable analysis means, between each display of a frame, to deliver said configuration data to the second memory and to perform analysis processing of this data from setting. The auxiliary decoder also includes means for processing (including for example a variable length decoder (VLD) and a zero chain decoder (RLD)) capable of decoding compressed graphic data stored in the first memory, on the configuration data base, and to be delivered to the mixing means, for each pixel of the auxiliary graphic image, the values of luminance and chrominance, as well as a mixing coefficient.

When the compressed graphics dataset corresponds to several successive auxiliary graphic images intended to be successively superimposed on the main images for a respective elementary duration, the auxiliary flow comprises several sets of configuration data, each allowing configure the decoding of an auxiliary graphic image. And, as long as said elementary duration corresponding to an auxiliary graphic image has not elapsed, the analysis means deliver to the second memory, between each display of a frame, said configuration data corresponding and carry out an analysis processing of this data of setting. The processing means decode the graphic data compressed stored in the first memory based on data from configuration, and, when said corresponding elementary duration is elapsed, the analysis means deliver to the second memory, between each display of a frame, the image setting data following auxiliary graph and perform analysis processing of these new configuration data. The processing means decode then the compressed graphics data stored in the first memory and corresponding to this following auxiliary graphic image, on the basis of this new configuration data.

According to one embodiment of the invention, the means analysis includes a time counter and control means able to initialize the time counter to an initial value predetermined. Each setting data includes an indication temporal, related to said predetermined initial value, and representative from the start time of the first decoding of the auxiliary graphic image corresponding. The analysis means are then able to store in a register, the time indication of the next auxiliary graphic image. The processing means carry out successive decoding of the images common auxiliary graphics set by the set corresponding parameter data, as long as the counter value temporal is less than the contents of the register.

According to one embodiment of the invention, the decoder auxiliary (sub-picture decoder) has elementary memories (search tables; "look-up tables"). The means of analysis are suitable for store respectively in at least some of these memories elementary, different groups of couples "color coefficient of mixture ". The number of couples in groups is less than a prime predetermined number, while the number of elementary memories is less than or equal to a second predetermined number (for example 8). The processing means include an auxiliary decoder block (circuit VLD and RLD circuit) capable of decoding the compressed graphic data and to address elementary memories with graphic data decoded, as well as a multiplexer whose inputs are connected to outputs of the elementary memories. The auxiliary decoder includes also multiplexer control means able to select the inputs of the multiplexer according to designation data contained in the configuration data, this designation data allowing to select one of the elementary memories (table of research).

• la figure 1 est un synoptique schématique d'un système d'élaboration selon l'invention;
• la figure 2 illustre plus particulièrement une partie du système de la figure 1;
• la figure 3 illustre plus en détail mais toujours de façon schématique l'architecture interne d'un décodeur d'image auxiliaire (décodeur de sous-image);
• la figure 4 illustre le découpage en régions d'une image graphique auxiliaire destinée à être superposée à une image principale;
• la figure 5 illustre d'une façon générale l'architecture d'un flot auxiliaire correspondant à des images graphiques auxiliaires, ainsi qu'un mode de mise en oeuvre du procédé de décodage selon l'invention; et
• la figure 6 illustre, sur un cas particulier, le fonctionnement du décodeur de sous-image selon l'invention ainsi qu'une mise en oeuvre du procédé selon l'invention.

Other advantages and characteristics of the invention will appear on examining the detailed description of embodiments and implementation, in no way limiting, and the appended drawings, in which:

• Figure 1 is a schematic block diagram of an elaboration system according to the invention;
• Figure 2 more particularly illustrates part of the system of Figure 1;
• FIG. 3 illustrates in more detail but still schematically the internal architecture of an auxiliary image decoder (sub-image decoder);
• FIG. 4 illustrates the division into regions of an auxiliary graphic image intended to be superimposed on a main image;
• FIG. 5 illustrates in a general manner the architecture of an auxiliary flow corresponding to auxiliary graphic images, as well as a mode of implementation of the decoding method according to the invention; and
• FIG. 6 illustrates, in a particular case, the operation of the sub-image decoder according to the invention as well as an implementation of the method according to the invention.

In FIG. 1, the reference SY generally designates a digital image processing system incorporating for example a satellite decoder and / or television.

In this SY system, IFE input means receive, by example of a multifunction digital disc (DVD disc: "Digital Versatile Disk ", in English), not shown here for the purpose of simplification, a main stream of data compressed according to, by example, MPEG standards, as well as auxiliary streams including also compressed graphic data sets, and corresponding to graphic elements forming graphic images auxiliaries intended to be embedded in a predetermined area of a AFF display screen overlaying the main images resulting decoding of the main compressed data.

To decode the main data compressed, there is a main DCD decoder, or MPEG decoder. The SY system also includes a microprocessor CPU which can for example managing the decoding of different satellite channels, as well as auxiliary DSP decoding means, more simply designated in the suite "auxiliary decoder" (sub-image decoder), intended for decode compressed graphical information corresponding to the auxiliary graphic images.

Another element of this system is dynamic memory MMP, for example an SDRAM memory, which is shared between these different elements. It is particularly interesting to be able to limit the memory size of this memory, in particular in order to limit the cost thereof and clutter. This is one of the aims of the invention.

All the elements of figure 1 dialog via a bus bidirectional BBS.

The MMP memory comprises (FIG. 2) a memory zone Z1, in which the main compressed data on standby is written of processing, as well as a ZSP zone used to store the auxiliary flows corresponding to the auxiliary graphic images. In fact, memory MMP also has at least two memory areas additional (not shown here for simplicity) and used to store main images already decoded.

Functionally, the MPEG decoder, DCD, provides output, after decoding and / or extracting the MMP memory, values of luminance Yp, and of chrominance Up and Vp, for each of the pixels of the main image to display.

Furthermore, as will be seen in more detail below, the DSP auxiliary decoder cooperates with the ZSP area of the MMP memory to decode on-the-fly, auxiliary graphics and provide, to the pixel display rate on the screen, the luminance and chrominance Ya, Ua, Va, of each pixel of the auxiliary graphic image thus decoded. The chrominance values from the MPEG decoder DCD, and the DSP auxiliary decoder, are then mixed in a MIX mixer, taking into account a mixing coefficient, to give, for the pixel considered in the resulting image, luminance values and chrominance Yr, Ur and Vr. It should be noted here that for the purpose of simplification, the MIX mixer has not been shown in FIG. 1.

If we now refer more particularly to FIG. 3, we see that the auxiliary decoder DSP has a first memory FF1, of the FIFO type, and a second memory FF2, also of the type FIFO, these two memories being capable of receiving data from auxiliary streams stored in the ZSP area of the MMP memory. Updates apart from these two memories, the auxiliary decoder is essentially implemented from doors and integrated logic circuits.

As will be seen in more detail below, the memory FF1 is dedicated to the storage of the compressed graphic data forming the or the auxiliary graphic images, while the FF2 memory is more particularly intended for the storage of DCSQ configuration data incorporated in an auxiliary flow and associated with one or more images auxiliary graphics.

Compressed graphics data in memory FF1 are decoded in an auxiliary DCDA decoder block comprising in particular a variable length decoding circuit (VLD) and a circuit decoding zero chain (RLD) well known to those skilled in the art and which are conventional for image decoding.

The DCDA auxiliary decoder block is also controlled by a CTRL controller which also receives for analysis and processing, the DCSQ configuration data stored in the memory FF2. The CTRL controller also cooperates with a time counter CTR as well as with a register RG1 which will be discussed in more detail below on function.

An LMC memory controller dialogues with the CTRL controller, as well as with the two memories FF1 and FF2 (via requests and acknowledgments), and manages the addressing of the MMP memory. This LMC memory controller is also connected to the external microprocessor CPU.

In the example described here, the auxiliary decoder DSP comprises also eight separate elementary memories (or eight memory zones distinct from the same memory) referenced LUT1-LUT8 (in practice, other elementary memories can also be provided allowing including activating highlighted geometric shapes). These elementary memories are addressed in the example described by two bits delivered by the auxiliary decoder block DCDA and resulting from the decoding compressed auxiliary graphics data. Furthermore, during a programming phase, to which we will return in more detail below, the CTRL controller can also program, i.e. load, content of at least some of these elementary memories in function of the content of the configuration data stored in the memory FF2.

The CTRL controller also delivers, when decoding the compressed graphics data, an SCMD control signal at MUX multiplexer so as to select one of the memories elementary LUTi. The data stored in this elementary memory selected are then delivered at the output of the multiplexer. More specifically, a first part of this data, for example on four bits, is delivered to a final memory MLUT containing, at each address designated by the four bits received as input, luminance values and chrominance Ya, Ua and Va on eight bits and corresponding to a color predefined. Another part of the data delivered by the memory elementary LUTi selected forms a mixing coefficient CM on four bits which will be delivered to the MIX mixing means so as to weight the mixture between the luminance and chrominance values of the main image pixel and luminance and chrominance values the pixel of the auxiliary graphic image.

We will now describe in more detail, referring more particularly in Figures 4 and following, an operating mode of the device according to the invention, as well as a mode of implementation of the method according to the invention.

According to a general characteristic of the invention, the steals compressed data from an auxiliary data stream defining an auxiliary image, during the display of each main image in which this auxiliary image must be embedded, so as to deliver successively during each decoding of the auxiliary image, for the successive pixels of this auxiliary image, the luminance values and of chrominance Ya, Ua, Va intended to be mixed with those Yp, Up, Vp of the homologous pixels of the main image being displayed.

An IMAX auxiliary image (Figure 4) is generally intended to be embedded in a predetermined area of the screen, in overlay with main image IMP. In fact, memories LUTi elementaries each define a lookup table ("look-up table "in English) storing, in this case, since each of these tables is addressed on two bits, at most four pairs "color-mixing coefficient". Each LUTi table is therefore associated with a region of the image within which we cannot find a maximum of four different color-coefficient pairs mixture".

Since, in this case, there are only eight memories elementary LUTi, so there can only be eight different regions possible for the IMAX auxiliary image. Of course, each line of the IMAX auxiliary image can be broken down into these eight regions. However, some lines can be broken down into less than eight regions.

Each region Ri can be of different size, having however, in the example described here, a minimum size of eight pixels.

We see in Figure 5, that an auxiliary flow stored in the area MSP memory ZSP generally has an H header, BM compressed graphic data intended in this case for form several different auxiliary graphic images, and several parameter data packets DCSQ1, DCSQ2, ..., respectively associated with each set of compressed graphical data corresponding to each auxiliary image intended to be displayed on the screen.

The header H comprises in particular the address @ 2 making it possible to locate in the ZSP memory area the start of the data packet DCSQ1 configuration of the first auxiliary graphic image. Through elsewhere, each configuration data packet contains the data binaries relating to the different color-coefficient pairs of mixture "corresponding to each of the regions of the graphic image auxiliary, as well as the size of these regions line by line, these sizes corresponding to designation data allowing, as is will see in more detail below, when decoding the images, to select this or that search table according to the line and the position of the pixel in the line.

Each DCSQi package also includes the address @ 3 corresponding to the beginning of the compressed graphic data of the image auxiliary graphic corresponding to the DCSQi package. Finally, each DCSQi packet contains a time indication (TS2 for the packet DSQ2) which actually indicates which main image the image refers to auxiliary graph corresponding to this data packet of setting.

Typically, an MPEG data stream has main streams of compressed video data corresponding to images main streams, audio data streams, and auxiliary data streams graphics corresponding to the auxiliary graphics images. These waves are transmitted multiplexed and are each preceded by PTS time presentation identifier.

When the PTS time identifier of an auxiliary flow corresponding to one or more auxiliary graphic images, is detected, the external microprocessor CPU delivers to the memory controller LMC address @ 1 allowing the address pointer to point to the start of the auxiliary flow (Figure 5).

The header H of the auxiliary flow is then for example stored in memory FF2 and analyzed by the CTRL controller. This detects the address @ 2 indicating the start of the DCSQ1 packet and provides this address @ 2 to the LMC memory controller which points to the corresponding address. The configuration data contained in the DCSQ1 package is then stored in particular in memory FF2 for analysis by the CTRL controller.

This analysis includes the programming of at least one of the LUTi elementary memories, i.e. storage in these memories binary data relating to the "color-coefficient of mixture "corresponding to the different regions of the graphic image auxiliary whose decoding will be parameterized by the data of configuration contained in the DCSQ1 package. Although, generally, the content of the MLUT memory is carried out at the start of a sequence of images, it is not excluded that its content can also be defined by the configuration data contained in the DCSQ1 package.

Furthermore, before starting the actual decoding of the compressed graphic data corresponding to the graphic image auxiliary which is going to be embedded, the control means CTRL will read the time indication TS2 of the DCSQ2 packet corresponding to the image following graphic and store this indication in the register RG1. In this regard, upon receipt of the PTS time identifier of the auxiliary flow, the CTR counter has been initialized by the CTRL controller to a value predetermined initial. This initial value can for example be the time exact occurrence of the first main image in which should be embedded the first auxiliary graphic image. Alternatively, it it would also be possible to initialize the counter CTR to the value zero. Also, if the exact time is stored in the CTR counter, the indication time TS2 stored in the register RG1 could then be the time exactly where graphic image decoding should start following auxiliary corresponding to the DCSQ2 packet. If the CTR counter is initialized to zero, the time indication TS2 stored in the register RG1 could then simply be the duration of the display of the current auxiliary graphic image, in this case the graphic image auxiliary corresponding to the DCSQ1 packet.

Once the DCSQ1 packet analysis operation has been performed (this analysis being performed at the rise of the VSYNC signal during the return frame), the CTRL controller will read the address @ 3 contained in the packet DCSQ1 and corresponding to the start address of the graphic data compressed corresponding to the auxiliary graphic image which must be decoded.

On request, the compressed graphic data is then stored in memory FF1 to be decoded on the fly by the block DCDA auxiliary decoder. This DCDA decoder block delivers successively pairs of bits corresponding to the graphic data compressed. These bit pairs are delivered as addresses, to LUTi tables and these are selected by the control signal SCMD delivered by the CTRL controller according to the content of the data DCSQ1 configuration, and in particular the size of the different regions of the auxiliary graphic image. The four bits corresponding to the color, and delivered by the selected LUTi table, address the memory MLUT and this delivers three times eight bits corresponding to the values of luminance and chrominance of the pixel considered in the graphic image decoded auxiliary. At the same time, the four bits of the coefficient of CM mixture also contained in the selected LUTi table, are delivered to the MIX mixer.

In this case, the luminance and chrominance values Ya, Ua and Va are simultaneously output from the MLUT memory and are therefore delivered at the pixel display frequency, i.e. 13.5 MHz. Of course, if the luminance values, as well as the pair of chrominance values, were delivered sequentially, these would be issued on the frequency of 27 MHz.

The luminance and chrominance values thus delivered are mixed in the MIX mixer, taking into account the coefficient of blend, for each pixel and for each line of the frame the displayed image.

This decoding operation continues for all the lines of the frame of the auxiliary graphic image. During the frame return, the process which has just been described for the analysis of the packet data DCSQ1 is repeated. Then, when displaying the next frame, the decoding of the second frame of the auxiliary graphic image is performed.

These operations are carried out so on, as long as the value of the CTR time counter does not become greater than or equal to the value contained in the register RG1. If this is the case, the CTRL controller will then designate the address where the DCSQ2 data packet is located setting corresponding to the following graphic image. The same operations just described for the graphic image previous, repeat for this next auxiliary graphic image.

We now refer more particularly to FIG. 6 for describe the operating mode of the device according to the invention, in a special case of auxiliary graphic image.

This auxiliary graphic image consists of a rectangle, each LG line of which contains 30 pixels PX ₁ -PX ₃₀ . The coordinates of the start XO of the image can be defined in the DCSQ packet or else predefined by the microprocessor CPU. A first sub-region SR1 of this graphic image extends between the pixels PX ₁ and PX ₅ and consists of a yellow background to which a mixing coefficient of 80% is assigned. The second sub-region SR2 extends from pixel PX ₆ to pixel PX ₂₀ and consists of a black background assigned a mixing coefficient of 20%, on which is displayed the letter S of red color with a mixing coefficient of 50% and part of the letter T in green with a mixing coefficient of 20%.

We can therefore define in this auxiliary graphic image (for all its lines and for all its frames) a first region R1 of a size of 20 pixels, formed by the sub-regions SR1 and SR2. We can assign to this first region the table LUT1 in which we store at address 00 the couple (black; 20%), at address 01 the couple (green; 20%), at address 10 on couple (yellow; 80%) and at address 11 the couple (red; 50%). Well understood, all these couples are, as indicated above, represented each by 2 4-bit words, the first 4-bit word forming an address for MLUT memory.

The second region of the image, which extends from pixel PX ₂₁ to pixel PX ₃₀ , consists of an orange background assigned a mixing coefficient of 20%, on which is written the rest of the T bar of green color + 20%. We can therefore assign to this second region R2, the table LUT2, in which the couple at address 00 is stored (orange; 20%), and at address 01 the couple (green; 20%).

We finally assume that this image must be displayed for 30 minutes from the occurrence of an initial main image.

Also, between each frame return, the CTRL controller will load LUT1 and LUT2 tables with binary values corresponding to couples indicated on figure 6. In addition, it checks by comparing the contents of the time counter CTR and of the register RG1 that the duration of 30 minutes has not expired.

The compressed graphic data stored in the memory FF1 is such that, after decoding in the auxiliary decoder block DCDA, the binary data associated with the pixels PX ₁ -PX ₅ of the line LG (for example) take the value 10. The associated binary data the pixel data PX ₆ to PX ₂₀ all take, after decoding, the value 00, except those of the pixels PX _j and PX _k which take the values 11 and 01 respectively.

For the display of pixels 1 to 20, it is therefore the LUT1 table which is selected by the control signal SCMD, the memory MLUT respectively delivering the correct color values corresponding to different pixels of the decoded auxiliary graphic image.

From pixel 21, the control signal SCMD will act on the multiplexer to select the LUT2 table. The binary data of pixels 21 to 30 of the LG line will all then have, after decoding, the value 00.

Claims (11)

Method for developing resulting digital images auxiliary graphic elements forming at least one auxiliary image embedded in main images, characterized by the fact that it decodes on-the-fly compressed data (BM) of an auxiliary data stream defining said auxiliary image (IMAX), during the display of each main image (IMP) in which this auxiliary image must be encrusted, so as to deliver successively during each decoding of the auxiliary image, for the successive pixels of this image auxiliary, luminance and chrominance values (Ya, Ua, Va) intended to be mixed with those (Yp, Up, Vp) of the pixels counterparts of the main image being displayed. Method according to claim 1, characterized in that it includes receiving the auxiliary flow comprising all of compressed graphic data (BM) corresponding to elements graphics forming at least said auxiliary graphic image intended for be embedded in a predetermined area of a display screen, from from the time of occurrence of an initial main image and during a predetermined elementary duration, superimposed on the images main, the storage of the auxiliary flow in a memory (MMP), and successive decoding of compressed graphic data respectively performed during main image displays successive, from the display of the initial main image to the expiration of said predetermined elementary duration, so as to deliver during each decoding, at the rate of display of the pixels on the screen and for each pixel of the auxiliary image, the luminance and chrominance as well as a mixing coefficient (CM), and the pixel mixing to pixel in said predetermined screen area of chrominance values and luminance corresponding to the current main image in progress display and the decoded auxiliary graphic image, taking account of said mixing coefficients (CM). Method according to claim 1 or 2, characterized in that that the auxiliary stream comprises a header (H), said data compressed graphics (BM), and at least one set of data from configuration (DCSQ) to configure the decoding of said graphic image, and by the fact that, the main images being displayed line by line and in two successive frames corresponding to lines of different parities, an analysis processing of said data is carried out setting between each display of a frame. Method according to claim 2 or 3, characterized in that that the compressed graphic dataset corresponds to several successive auxiliary graphic images each intended to be successively superimposed on the main images for a period respective elementary, by the fact that the auxiliary flow comprises several sets of configuration data (DCSQ1, DCSQ2) allowing each to configure the decoding of a graphic image auxiliary, and by the fact that, as long as said elementary duration corresponding to an auxiliary graphic image has not elapsed, we analyzes the set of configuration data corresponding to this image between each display of a frame, then we decode compressed graphic data of this image based on configuration data, and when said elementary duration has elapsed, we automatically proceed to the analysis of the configuration data set corresponding to the graphic image next auxiliary then decoding of the compressed graphic data of this next image based on this new data from setting. Method according to claim 4, characterized in that at the reception of the auxiliary flow, a time counter (CTR) is initialized a predetermined initial value, by the fact that each set of configuration data includes a time indication (TS2), linked at said predetermined initial value, and representative of the instant of start of the first decoding of the auxiliary graphic image corresponding, by the fact that before starting to decode the first auxiliary graphic image, we store in a register (RG1) the time indication of the next auxiliary graphic image and performs the successive decodings of the auxiliary graphic image set by the corresponding set of setting data both that the value of the counter is less than the content of the register. Method according to one of Claims 2 to 5, characterized by the causes the analysis processing of a set of configuration data includes storage of different groups of "color-coefficient" pairs of mixing "in respective elementary memories different (LUT1-LUT8), the number of couples per group being less than a first predetermined number, the number of groups being less than or equal to a second predetermined number, and by the fact that the line-by-line decoding of each auxiliary graphic image includes successive addressing by the decoded graphic data, different elementary memories designated successively by designation data contained in the data set of configuration (DCSQ1, DCSQ2). System for developing digital images resulting from auxiliary graphic elements embedded in main images, characterized in that it comprises receiving means (IFE) for receiving a main stream comprising compressed data encoding main digital images, and at least one auxiliary stream comprising a set of compressed graphic data corresponding to graphic elements forming at least one graphic image intended to be embedded in a predetermined area of a display screen (AFF), from the instant of occurrence of an initial main image and for a predetermined elementary duration, in superposition of the main images, a memory (MMP) for storing the main flow and the auxiliary flow, a main decoder (DCD) capable of decoding the main stream of compressed data and of delivering for each pixel of a decoded main image, luminance and chrominance values, a device for developing the resulting images comprising an auxiliary decoder (DSP) capable of carrying out successive decodings of the compressed graphic data contained in the memory, these successive decodings being respectively carried out during the displays of the successive main images, from the display of the initial main image until the expiration of said predetermined elementary duration, so as to deliver during each decoding, at the rate of display of the pixels on the screen and for each pixel of the auxiliary image, values of luminance and chrominance as well as a mixing coefficient, and mixing means (MIX) able to perform pixel-to-pixel mixing in said predetermined screen area of the chrominance and luminance values corresponding to the current main image being displayed and the decoded auxiliary graphic image, taking into account said mixing coefficients (CM). System according to claim 7, characterized in that the auxiliary flow includes a header (H), said graphic data compressed (BM), and at least one set of configuration data (DCSQ) used to configure the decoding of said graphic image, by the fact that the auxiliary decoder (DSP) comprises a first memory (FF1) of the "first in first out" type capable of storing the compressed graphic data, a second memory (FF2) of the type "first in-first out" able to store the configuration data, by the fact that, the main images being displayed line by line and in two successive frames corresponding to lines of different parities, the auxiliary decoder (DSP) includes analysis means (CTRL) capable, between each display of a frame, of delivering said data from setting in the second memory and performing analysis processing of this configuration data, and suitable processing means (DCDA) to decode the compressed graphic data stored in the first memory, on the basis of the configuration data, and to be delivered to the means mixing (MIX), for each pixel of the auxiliary graphic image, the luminance and chrominance values, as well as a coefficient of mixed. System according to claim 8, characterized in that the compressed graphic dataset (BM) corresponds to several successive auxiliary graphic images intended to be successively superimposed on the main images for a period respective elementary, by the fact that the auxiliary flow comprises several sets of configuration data, each allowing configure the decoding of an auxiliary graphic image, and thereby that, as long as said elementary duration corresponding to an image auxiliary graph has not elapsed, the analysis means deliver to the second memory (FF2), between each display of a frame, said corresponding parameter data (DCSQ1) and perform a analysis processing of this configuration data, and the means of processing (DCDA) decode compressed graphics data stored in the first memory, based on data from configuration, and when said corresponding elementary duration is elapsed, the analysis means deliver to the second memory, between each display of a frame, the configuration data (DCSQ2) of the following auxiliary graphic image and perform processing analysis of this configuration data, and the processing means decode the compressed graphics data stored in the first memory and corresponding to this following auxiliary graphic image, on the database of new configuration data (DCSQ2). System according to claim 9, characterized in that the analysis means include a time counter (CTR) and control means (CTRL) capable of initializing the time counter at a predetermined initial value, by the fact that each set of data configuration includes a time indication (TS2), linked to said predetermined initial value, and representative of the start time of the first decoding of the corresponding auxiliary graphic image, by the fact that the analysis means are able to store in a register (BG1) the time indication of the next auxiliary graphic image and by the fact that the processing means carry out successive decodings of the current auxiliary graphic image configured by the set setting data correspondent as long as the counter value temporal is less than the contents of the register. System according to one of Claims 7 to 10, characterized by the fact that the auxiliary decoder (DSP) has memories elementary (LUT1-LUT8), by the fact that the means of analysis are able to store respectively in at least some of these memories elementary, different groups of couples "color-coefficient of mixture ", the number of couples per group being less than a first predetermined number, the number of elementary memories being lower or equal to a second predetermined number, and by the fact that the means processing include an auxiliary decoder block (DCDA) capable of decode compressed graphics data and address memories basic with decoded graphic data, as well as a multiplexer (MUX) whose inputs are connected to the outputs of elementary memories, and by the fact that the auxiliary decoder (DSP) comprises control means (CTRL) of the multiplexer suitable for select the inputs of the multiplexer according to data from designation contained in the configuration data.

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