Abstract:
The invention concerns a device for generating mutual photometric effects and a server for delivering photometric parameters for generating mutual photometric effects and a system including such a device and such a server. The device comprises a receiver for receiving and demultiplexing the visual data sets and photometric parameters respectively associated with the data sets, a module for defining the mutual photometric effects to be generated for these photometric parameters, a compositor and a rendering module for positioning the visual data sets in the common support space and applying the effects defined for the photometric parameters from at least one of the visual data sets to at least one other of the visual data sets so that at least one visual data set influences one other visual data set in the common support space.

Description:
This application claims the benefit under 35 U.S.C. §365 of International Application PCT/EP02/04749, filed Apr. 30, 2002, which claims the benefit of European Patent Application No. 01460035.7, filed May 14, 2001. 
     FIELD OF THE INVENTION 
     The invention concerns a method and device to generate mutual photometric effects in a common support space between a plurality of visual data sets. 
     BACKGROUND OF THE INVENTION 
     Applying special effects methods has been for a long time a working field in the industry. More and more, applications, such as interactive television, or any multimedia applications bring the need of efficient data manipulation. 
     The invention concerns particularly the merging of different data sets for displaying and the mutual interaction of these different data sets. Namely, in order to improve the interaction between visual data sets, audiovisual data sets or other multi-modal data sets, it is important that some parameters of the different data sets modify the other data sets and among these parameters, the illumination and the reflection. 
     To result in a realistic or nice looking final image, mutual photometric effects between different visual data sets have to be considered. This is especially true when importing a three-dimensional object in front of a video sequence for instance. 
     Various methods exist to apply mutual photometric effects to visual data, like shading, specular reflections, cast shadows, mutual illumination. 
     In film production, professional tools are used to generate photometric special effects off-line. These tools need as input the photometric properties of the visual data as for example light sources or surface reflection properties. Before generating photometric special effects, film production experts recover the photometric properties visually or the photometric properties are measured using measuring tools during film production in the real scene. 
     In research laboratories, photometric characteristics can be recovered today off-line by automatic algorithms of very high computational cost or by semi-automatic manual interaction. 
     The off-line or interactive recovering of photometric properties does not allow a real time treatment of the visual data sets for generating photometric special effects. 
     In the MPEG-7 (MPEG standing for “Motion Picture Expert Group”) proposal n° 99 entitled “An illumination effect descriptor for video sequences”, Stauder proposes to describe illumination properties implicitly by image signal changes for content-based visual information retrieval. 
     The invention allows a real time treatment of the visual data sets for generating photometric special effects, describing illumination properties in term of light sources for special effect generation. 
     In a first aspect, the invention proposes a device to generate mutual photometric effects between a plurality of visual data sets, comprising means to position the visual data sets in a common support space characterized in that it comprises:
         means for receiving and demultiplexing said visual data sets and photometric parameters respectively associated with said data sets,   means for defining said mutual photometric effects to be generated for these photometric parameters,   composition and rendering means for positioning said visual data sets in said common support space and applying said effects defined for said photometric parameters from at least one of said visual data sets to at least one other of said visual data sets so that at least one visual data set influences one other visual data set in said common support space.       

     The invention allows the generation of mutual photometric effects by using the photometric parameters that are transmitted with the visual data sets to be displayed and so can avoid the use of complex devices or methods needed to extract the photometric properties from the visual data sets on the device. In fact the devices that could typically generate mutual photometric effects are low cost devices or consumer products which price has to be reduced. So, it is a great advantage to dissociate this functionality from the device and to provide means to treat the photometric parameters received from an outside terminal. 
     The means for defining the effects to be generated for the photometric parameters have the capability to define how meta data associated to multimedia data influence other multimedia data. It generates some information called “rendering modi” which represents this influence. This enables the composition and rendering means to display the visual data sets, while applying the photometric effects on these data sets. 
     The invention is thus particularly interesting in systems providing meta data such as systems providing MEPG-4 coded data and MPEG-7 coded data. 
     According to a second aspect, the invention proposes a server (Aj) for delivering multimedia data including visual data sets associated with respective photometric parameters for said visual data sets, characterized in that it comprises
         means for managing the storage and conditioning of photometric parameters for said visual data sets,   means for transmitting over a transmission link (Cj) said multimedia data bundled with their associated photometric parameters, said multimedia data including means to display at least one of the visual data sets with another of said visual data sets in a common support space.       

     This server enables the preparation of photometric parameters to be used for instance with a device according to the first aspect of the invention. 
     However, this server can be used with any other terminal that would need photometric parameters as input parameters. 
     This server has the great interest to deliver the multimedia data associated with photometric parameters related to them. This avoids, on a corresponding receiver, the generation of photometric parameters. 
     According to a third aspect, the invention proposes a multimedia system characterized in that it comprises
         at least one server (Aj) according to any of claim  6  to  7  for delivering multimedia data including at least two visual data sets associated with photometric parameters for visual data sets,   means (Cj) for transmitting said visual data sets and their respective photometric parameters bundled together from said server to at least one device according to any of claims  1  to  5 ,   a device according to any of claims  1  to  5  to generate mutual photometric effects for applying the effects of said delivered photometric parameters of at least one of said delivered visual data sets to at least another of said delivered visual data sets so that said visual data sets influences said other visual data set in a common support space.       

     According to a fourth aspect, the invention concerns also a method to generate mutual photometric effects between a plurality of visual data sets, wherein one positions the visual data sets in a common support space, characterized in that:
         one delivers multimedia data including at least two visual data sets respectively associated with photometric parameters for visual data sets,   one transmits, bundled together, said visual data sets and their respective photometric parameters to at least one managing means,   one defines dynamically said mutual photometric effects for the photometric parameters and their associated visual data sets,   and one applies said effects defined by said photometric parameters from at least one of said visual data sets to at least another of said visual data sets so that said visual data set influences said other visual data set.       

     The invention concerns also a television receiver, a set-top box, or any fixed or mobile terminal having the characteristics of the device to generate mutual photometric effects mentioned above, the advantages of the television receiver, the set-top box, the fixed or mobile terminal being the same as the ones of the device to generate mutual photometric effects. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other characteristics and advantages of the invention will appear through the description of a non-limiting embodiment of the invention, which will be illustrated, with the help of the enclosed drawings among which 
         FIG. 1  represents a system according to the invention, 
         FIG. 2  represents a server according to the invention, 
         FIG. 3  represents a device according to the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a system for generating mutual photometric effects according to the invention including a device  1  for generating mutual photometric effects according to the invention connected to a display  6  through a connection link  7 . Said device  1  is also connected to n servers (A 1 , A 2 , . . . , Aj, . . . , An) through transmission links (C 1 , C 2 , . . . , Cj, . . . , Cn). 
     The servers A 1 , A 2 , . . . , Aj, . . . , An are represented on  FIG. 2  and the device  1  according to the invention is represented on  FIG. 3 . 
     Transmission links C 1 , C 2 , . . . , Cj, . . . , Cn can be all of the same type or can be of different types. In a preferred embodiment, as represented on  FIG. 1 , transmission link C 1  is different from transmission links C 2 , C 3 , . . . , Cj, . . . , Cn. In this embodiment, transmission link C 1  is a broadcast link. The transmission links C 2 , C 3 , . . . , Cj, . . . , Cn are for example Internet links. This corresponds to the case when a user is watching television programs received from a broadcaster from server A 1  and wants to display on display  6  some pictures selected from an Internet web site he receives from one of the servers A 2 , A 3 , . . . , Aj, . . . , An. 
       FIG. 2  shows a bloc diagram of any of the servers A 1 , A 2 , . . . , Aj, . . . , An. Such a server includes a database  17 , a multimedia coder  9 , a meta data coder  10 , a meta data management module  18  and a transmission module  8 . 
     The database  17  contains multimedia data and meta data. Multimedia data can be audiovisual data streams, 3D scenes, hyper documents, or any kind of multi or single modal data. 
     The meta data represent the photometric properties of the stored multimedia data. It can be a single light source or several light sources of different shapes (point light, area light) and different kind of intensities (monochrome, coloured, spatially constant or spatially varying). Instead of light sources, also illumination maps or global illumination descriptors can be used. Photometric meta data can contain transparency and refraction. 
     Other meta data than illumination can be foreseen. For example, meta data can contain a sequence of reflectance maps. The sequence of reflectance maps associates one reflectance map to each video image. Each pixel of the reflectance map contains one or more parameters describing the reflection properties of the corresponding video pixel. By such a sequence of reflectance maps, special effects like specular reflections in a video can be generated. Other representations of reflection can be used, for example symbolic or numerical reflection functions or reflectance maps combined with depth maps. 
     The meta data management module  18  generates and manages the meta data and associates them to the multimedia data. The meta data generation can be offline or online. It can be user assisted or automatic. Pre-calculated meta data can be used, the multimedia data can be used, or other data can be used. 
     The meta data are associated to the multimedia data. For example, a light source is associated to a video image or to a video sequence, a reflectance map is associated to a 3D object, or a reflectance map and a depth map are associated to a video image. Therefore, the meta data contain also means to display at least another visual data set with that visual data set in a common support space. These means include means to establish a relationship between meta data and multimedia data. 
     That relationship can be distance or relative position between meta data elements and multimedia data elements. The geometric relationship can be also represented by a geometric scene description. The geometric relationship defines how multimedia data elements such as video images or 3D objects and meta data such as light sources or reflection maps are positioned in a common support space. The common support space can be a plane, a 3D surface, a 3D space or any other space. 
     That relationship also describes, whether a meta data element has the capability to influence a multimedia data element or not. For example, a light source representing the illumination of a video image can influence another multimedia data element but not the video image itself. 
     That relationship can refer to multimedia data elements and meta data elements of the data base  17  or to generic data elements that are not known to the server Aj. By this, multimedia data elements from server Aj and multimedia data elements from other servers can be displayed on the display  6  of device  1  in a common support space influencing themselves mutually by consideration of their photometric properties such as illumination and reflection contained in the meta data. 
     The management module  18  manages the meta data. For example, it can decide to transmit or not a certain meta data associated to a multimedia data that is demanded by device  1 . It defines also the type of coding mode, the kind of association of the photometric parameters to multimedia data. These decisions may depend on the type and state of the transmission link Cj, on the type and state of device  1 , on the type or quality level of service, on pricing and payment mode, or on other criteria such as the profile of user using device  1 . Module  18  may also decide on spatial resolution, numerical precision or size of meta data to be generated or to be transmitted. Management module  18  can do other management tasks related to the generation of meta data, storage of meta data in the database, coding of meta data or transmission of meta data. 
     The type of the multimedia coder  9  depends on the kind of multimedia data and may be a video coder according to the MPEG-4 simple profile, a 3D data coder as MPEG-4 BIFS (standing for “Binary Information for Scene”) or any other kind of multimedia data coder. 
     The meta data coder  10  compresses the meta data and depends on the kind of meta data. In case of reflection maps, the meta data coder can contain a video coder, for example MPEG-4 simple profile, MPEG-4 core profile or JPEG (standing for “Joint Picture Expert Group”). For illumination parameters, the meta data decoder can contain an MPEG-4 BIFS module or a VRML (standing for “Virtual Reality Modeling Language”) module. The meta data decoder can contain other modules as floating point number coder, ASCII (standing for “American National Standard Code for Information Interchange”) coder, or any other kind of coder. 
     The transmission module  8  depends on the kind of transmission links C 1 , C 2 , . . . , Cj, . . . , Cn used and on the type of device  1  used. The transmission module  8  performs transmission and reception related tasks as modulation, demodulation, multiplexing, synchronization and error correction. Other transmission related operations are possible. Transmission links C 1 , C 2 , . . . , Cj, . . . , Cn transmit multimedia data, photometric meta data and signalling information. 
     On  FIG. 3 , a device  1  for generating mutual photometric effects according to the invention is represented. Said device includes a browser  2  that is connected to a memory  3 , to a composition/rendering means  4 , to an interface  5 , to a multimedia decoder  12 , a meta data decoder  13  and a meta data management module  16  through a communication bus  15 . 
     The browser  2  is an interface with a user, which allows the user to select the multimedia data he wants to display on display  6 . The selected multimedia data are requested via the interface  5  and the request is sent through communication links C 1 , C 2 , . . . , Cj, . . . , Cn, respectively, to servers A 1 , A 2 , . . . , Aj, . . . , An. The browser  2  can be accessed through a remote controller, through a keyboard or any man machine interface (not represented on the drawings). The browser can be for example a graphical interface. 
     The memory  3  stores multimedia data, meta data and browser related parameters received from the servers A 1 , A 2 , . . . , Aj, . . . , An and to be displayed on display  6 . 
     The bus  15  is used for interconnecting the different modules of the device  1 . 
     A module  11  includes said multimedia decoding module  12 , said meta data decoding module  13 , said interface  5  and a transmission module  14 . 
     Multimedia decoder  12  decodes the multimedia data coded by the multimedia data coder  9  of one of the servers A 1 , . . . , Aj, . . . , An. 
     Meta data decoder  13  decodes the meta data coded by the meta data coder  10  of one of the servers A 1 , . . . , Aj, . . . , An. 
     The transmission module  14  depends on the kind of transmission links C 1 , C 2 , . . . , Cj, . . . , Cn and kind of servers A 1 , . . . , Aj, . . . , An used. The transmission module  14  performs transmission and reception related tasks as modulation, demodulation, multiplexing, demultiplexing, synchronization and error correction. Other transmission related operations are possible. 
     The meta data management module  16  manages the meta data received by the communication links C 1 , C 2 , . . . , Cj, . . . , Cn and stored in the memory  3 . Management tasks are for example the spatial resolution and numerical precision of the stored meta data, the decision whether meta data is received and stored or not, the selection of meta data to be transmitted to the composition/rendering module  4 . 
     A number of rendering modi  19  are determined by meta data management module  16  for the multimedia data elements and the meta data elements. The rendering modi determine by which meta data elements a multimedia data element is influenced and which meta data elements have no effect on it. 
     The rendering modi  19  is explained by the following example. If a user selects via the browser  2  the transmission of a video sequence from server A 1  and a 3D object from server A 2 , and if the server A 1  associates a light source to the video sequence and the server A 2  associates a reflectance map to the 3D object, knowing that said light source and said reflectance map are transmitted respectively together with said video sequence and said 3D object to the device  1 , the rendering mode may be to let the light source illuminate only the 3D object and not the video sequence and, furthermore, to prevent from reflections from the 3D object onto the video sequence. 
     Furthermore, the rendering modi  19  may not only determine whether there is an influence between meta data and multimedia data, but may also determine how a meta data element influences a multimedia data element during composition/rendering. Therefore, the rendering modi  19  may define the spatial resolution of meta data used, the type and numerical precision of used light distribution or colour models, or any other parameters defining the influence of a meta data to a multimedia data element. 
     Composition/rendering module  4  positions the multimedia data in a common support space assisted by the user thanks to the browser  2 . The common support space can be a 2D plane, a 3D space or any other common space. The visual parts of the multimedia data are rendered considering the photometric meta data and the rendering modi  19  determined by meta data management module  16 . Audio data are composed of at least one audio signal. 
     We are going now to describe through a non-limitative embodiment the treatment of the request of a user. 
     When a user wants to display an object on display  6  while watching a video movie for example, he selects the requested object thanks to the browser  2 . The requested object is issued from one of the remote server A 1 , A 2 , . . . , Aj, . . . , An. The request is sent from browser  2  to the interface module  5  and through the transmission links C 1 , C 2 , . . . , Cj, . . . , Cn. Depending on the type of networks it is a broadcast request or a unicast request and the interface module depends also on the type of network. The interface module can also include several sub-modules if the links C 1 , C 2 , . . . , Cj, . . . , Cn are of different types as explained earlier. 
     Then the request is received by the transmission module  8  of one of the servers A 1 , A 2 , . . . , Aj, . . . , An. The requested data is then extracted from the database with its associated meta data. These meta data have been generated by the meta data management module  18  or is stored in the data base  17 . Then the requested data and their associated meta data are respectively sent to the multimedia coder  9  and to the meta data coder  10 . Once coded, both are associated together in the transmission module  8 . The type of association depends on the protocol used on the links C 1 , C 2 , . . . , Cj, Cn. They can be associated for instance according to TCP/IP protocol if the links are internet links. 
     The coded data are transmitted to the device  1  through the transmission links Cj and received on the transmission module  14  of device  1 . The transmission module demultiplexes the received data and meta data according to the protocol used on the links. Then the data and the associated meta data are respectively decoded by the multimedia decoder  12  and the meta data decoder  13 . The data are then sent to the memory  3  and treated by the meta data management module  16 . This meta data management module  16  determines the rendering modi to be used by the composition rendering module. 
     Then the composition and rendering module  4  treats the data and the modi and sends the composed data to the display  6 .