METHOD AND SYSTEM FOR CONTROLLING ACCESS TO COMPONENTS OF A MULTIMEDIA SCENE

Abstract: An apparatus (100) presenting a multimedia scene that is represented in an electronic form. The apparatus has a retrieval module (120) for retrieving a scene description (134), possibly from a remote server (128). The scene description includes a component identification (140), identifying a component (136) comprising content for the scene, and a conditional access identification (144), for determining access rights to the component. The conditional access module (122) of the apparatus determines the access rights to the component. If the determined access rights allow, the apparatus retrieves the content of the component and presents the scene including the content of the retrieved component.

Description: METHOD AND SYSTEM FOR CONTROLLING ACCESS TO COMPONENTS OF A MULTIMEDIA SCENE The invention relates to an apparatus for presenting a scene that is represented in an electronic form. The invention further relates to a method of presenting a scene that is represented in an electronic form. The invention further relates to a computer program product for carrying out such a method and a storage medium carrying such a computer program product. The invention further relates to an apparatus for producing a scene description. The invention further relates to a method of producing a scene description. The invention further relates to a storage medium carrying such a scene description. The reproduction of a multimedia presentation on a computer or the like may involve several elements. The presentation may comprise various pieces of video and/or images, possibly combined with audio fragments. It is known to specify such a multimedia presentation in a so-called scene description. The Synchronized Multimedia Integration Language (SMIL 1.0 Specification, REC-smil-19980615), defined by the World Wide Web Consortium, is a suitable language to define such a scene description. The scene description specifies a number of components of which the content contributes to the content of the scene, e.g. some images that are to be displayed on the screen and an audio fragment that is to be played back. Furthermore, the scene description specifies the mutual relationships between these components, e.g. where and how certain images are to be positioned on the screen and when certain audio fragments must be played. In an implementation using SMIL, the content description is a file in the SMIL format and the individual components are other respective files in the appropriate formats, e.g. images in GIF and JPEG and audio fragments in MP3. A presentation engine parses the scene description file and retrieves a component file when this becomes necessary during the presentation of the scene. A typical example of a system organization includes a server computer on which the scene description file and the component files reside and a client computer on which the presentation engine is executed. The client computer can access the server computer via a network connection, e.g. via the Internet. International Patent Application WO 99/39272 describes a system for presenting a scene based on such a client-server architecture. This system provides for user interaction with the presented scene, allowing the user to select a particular sub-scene. The selection is sent from the client to the server as a command to start a new presentation. Content is regarded of value and may be protected by a conditional access system. Such a system allows usage of content in conformance with the rights that the user has obtained for that content. This means that certain component files may be accessed by certain users and not by certain other users. When a file is requested, the conditional access system that has control over the file verifies the current user rights and only supplies the file if those rights allow that. Alternatively, the component file may be encrypted and a decryption key is necessary to properly reproduce the content. The conditional access system will then supply that key if the user rights allow this. In the case of encrypted files, the file itself may be freely available to everyone, since it is of no use as long as the decryption key is not available. It is an object of the invention to provide an apparatus for presenting a scene with an efficient handling of access rights. This object is achieved according to the invention in an apparatus comprising: retrieval means for retrieving a scene description, the scene description including a component identification, identifying a component comprising content for the scene, and a conditional access identification, for determining access rights to the component; conditional access determining means for determining the access rights to the component; and presenting means for presenting the scene including the content of the component in conformance with the access rights. Due to the fact that the conditional access identification of a given component is included in the scene description, the user rights to the content of that component can be determined without accessing the component itself or its multiplex. Furthermore, the fact that the user rights to a component can be directly established when parsing the scene description is advantageous because the presentation can immediately be adapted if it appears that a component's content is not available. Such adaptation may be replacing the intended content of the component by a stub, re-positioning other components, scaling other components to fill a larger part of the screen, or disguising the missing of content in some other way. The advantage of the apparatus according to the invention is that such adaptation can be done without having to obtain the conditional access identification of the component from outside the scene description. An embodiment of the apparatus according to the invention is described in claim 2. By specifying the identification of the conditional access system in the scene description, the apparatus can operate with more than one conditional access system. Different scene descriptions and constituent components may then be protected by different conditional access systems, while they still may be presented on the apparatus according to the invention. An embodiment of the apparatus according to the invention is described in claim 3. In this embodiment it is particular advantageous to determine the access right to the component from the scene description, since it avoids retrieving the component in the case that no access rights exist. If the component resides on a remote computer connected to the apparatus via a network, avoiding a useless retrieval of the component saves valuable bandwidth of the network. An embodiment of the apparatus according to the invention is described in claim 4. It is advantageous to have another component available as alternative in case the particular user of the scene description has no (longer) access rights to the original component. The apparatus determines this situation directly by verifying the access rights on the basis of the conditional access identification present in the scene description and subsequently decides to retrieve the alternative component. An example of this is where the original component is a high resolution image protected by conditional access rights and the further component is a freely available image in lower resolution. It is a further object of the invention to provide a method of presenting a scene with an efficient handling of access rights. This object is achieved according to the invention in a method comprising the steps of: retrieving a scene description, the scene description including a component identification, identifying a component comprising content for the scene, and a conditional access identification, for determining access rights to the component; determining the access rights to the component; and presenting the scene including the content of the component in conformance with the access rights. Since the conditional access identification of a given component is available from the scene description itself, any actions based on the presence or absence of access rights can be immediately taken. This avoids consulting the component at some possibly remote location or consulting the multiplex of the component.. It is a further object of the invention to provide a program for carrying out the method of presenting a scene with an efficient handling of access rights. This object is achieved according to the invention in a computer program product loadable into the internal memory of a digital computer, comprising software code portions for executing the steps of the method according to the invention when said product is run on the digital computer. Such a program may be obtained in the local computer by downloading it via a network connection from a remote computer having the program available on its storage devices. This process of downloading may be the process of storing the program on a local storage device, from where it can be loaded for later execution, or the process of loading the program into the memory of the local computer for immediate execution. Furthermore, the program may be obtained by retrieving it from a storage medium carrying the program, which storage medium has been purchased for this purpose. It is a further object of the invention to provide an apparatus for producing a scene description that allows presenting the scene with an efficient handling of access rights. This object is achieved according to the invention in an apparatus comprising: description means for preparing a scene description, the scene description including a first component identification, identifying a first component comprising content for the scene, and a conditional access identification, for determining access rights to the first component; and output means for outputting the scene description in the form of a computer program product. It is a further object of the invention to provide a method of producing a scene description that allows presenting the scene with an efficient handling of access rights. This object is achieved according to the invention in a method comprising the steps of: preparing a scene description, the scene description including a first component identification, identifying a first component comprising content for the scene, and a conditional access identification, for determining access rights to the first component; and outputting the scene description in the form of a computer program product. The invention and its attendant advantages will be further elucidated with the aid of exemplary embodiments and the accompanying schematic drawing, wherein: Figure 1 schematically shows an apparatus for presenting a scene according to the invention and Figure 2 schematically shows an apparatus for producing a scene description according to the invention. Corresponding features in the Figures are denoted by the same reference symbols. Figure 1 schematically shows an apparatus for presenting a scene according to the invention. The apparatus 100 is implemented according to a known computer architecture. The apparatus has a processor 102 for carrying out the machine instructions of a program loaded into working memory 104. The system further has an interface 106 for communication with peripheral devices. There is a bus 108 for the exchange of data and commands between the various components of the apparatus. The peripheral devices of the apparatus include a storage medium 110 containing the program to be executed. The storage medium 110 may be a hard disk or any other suitable medium, like an optical disk, a chip card or a tape. As an alternative to loading the program from the storage medium 110, the program may be downloaded via a network connection 112. The peripheral devices of the apparatus further include a display 114 for, among other things, displaying the images of the scene and speakers 116 for playing the audio of the scene. Furthermore, the apparatus has an input device 118, e.g. a keyboard, for the user to enter commands. The apparatus is capable of performing various functions which are realized by respective software modules. These software modules are part of the program that is loaded into working memory 104 when the apparatus is activated by a user. The apparatus has a first retrieval module 120 for retrieving the scene description of the scene that is to be presented and a conditional access module 122 for determining the access rights of the various components of the scene description. Furthermore, the apparatus has a second retrieval module 124 for retrieving the components that are necessary according to the scene description. The apparatus also has a presentation module 126 to actually present the content of the scene description and of the retrieved components. There are various ways to distribute the functions over the various software modules and the distribution described above is just one example. It is for instance possible to combine the first retrieval module and the second retrieval module into one module capable of retrieving both the scene description and the various components. In the embodiment shown in Figure 1, the scene description and the components reside on a remote server computer 128 to which the apparatus is connected via network connection 130. This server has a storage device 132 containing scene description files, e.g. scene description file 134, and component files, e.g. component file 136 and component file 138. The example scene description contains a first component identification 140, identifying a first component whose content is to be retrieved and included in the scene, and a second component identification 142, identifying a second component whose content is to be retrieved and included in the scene. Furthermore, the scene description contains for the first component a conditional access identification 144, identifying the first component for the conditional access system. The operation of apparatus 100 is as follows. The software modules 120-126 are loaded into the memory 104, whereby not all modules need to be loaded initially but loading may be postponed until needed for some of them. Then, typically on the basis of some user input, the first retrieval module 120 retrieves the scene description 134 from server 128. During processing the scene description, it is determined that the content of component 'CMPT is part of the content of the scene. It is also determined that the content of 'CMP 1' is protected and that it has the conditional access identification 144. So it appears that access to the component is under control of the conditional access system 'CA1' and that the component is identified in that system by number '123'. The conditional access module 122 determines the access rights to the first component 136 on the basis of this information. If the access rights allow, the second retrieval module 124 retrieves the first component 136 from the server 128. If the access rights do not allow access, the first component is not retrieved and the apparatus may take an appropriate action to cope with this situation, e.g. replacing it by an alternative component or rearranging the other components in the scene. The fact that the access rights can be established on the basis of information in the scene description itself makes it possible to decide on such corrective actions without delay and without consulting other sources for finding the conditional access identification. In a system where the conditional access identification is available at the level of the server, e.g. in the component itself, a retrieval of the component is required even if there are no access rights, namely to find out that there are no such rights. The invention avoids such an unnecessary component retrieval, thus saving time and bandwidth of the network. These savings can be considerable since a component file usually has a relatively large size. The scene description in the embodiment of the invention is prepared according to the SMIL 1.0 specification. This multimedia language is defined by the World Wide Web Consortium (SMIL 1.0 Specification, REC-smil-19980615). In that language the conditional access identification of a component can easily be represented by a dedicated test attribute that SMIL allows to be added to a component. Furthermore, SMIL has a <switch> element that allows the selection between two components on the basis of the evaluation of the test attribute. Section 4.3 of the SMIL 1.0 Specification describes the <switch> element and section 4.4 of the SMIL 1.0 Specification describes the test attribute. Below are some lines of an example showing an audio component protected by a conditional access system and an alternative audio component if the current user does not have rights to the original audio component. <smil> <head> </head> <body> <switch> <audio src- 'audiol" system-access-id="CAl:123"/> <audio src— 'audio 1 -replacement" system-access-id="free:0"/> </switch> </body> </smil> If the first test attribute system-access-id evaluates to true, the presentation engine knows that there are access rights to the audio 1 component and retrieves this component for play back. If the first test attribute system-access-id evaluates to false, there are no access rights and the audio 1 -replacement component is retrieved. Figure 2 schematically shows an apparatus for producing a scene description according to the invention. The apparatus 200 is implemented according to a similar architecture as apparatus 100. The apparatus 200 has a description module 202 for preparing a scene description 134. This scene description contains a first component identification 140, identifying a first component whose content is part of the scene, and a second component identification 142, identifying a second component whose content is part of the scene. Furthermore, the scene description contains for the first component a conditional access identification 144, identifying the first component for the conditional access system. The apparatus 200 further has an outputting module 204 for outputting the prepared scene description. The outputted scene description may be sent via a network connection to another computer, where it may be executed or stored. Furthermore, the outputted scene description may be stored on a local storage medium, e.g. on storage medium 110. The scene description contains the specification of a scene. It describes what is to be presented and how this is to be presented. In that respect, it contains instructions for the presentation program regarding the presentation to be made. The presentation engine parses the scene description in a way that is similar to an interpreter parsing a file with program instructions. Therefore, it can be said that the scene description can be executed on a computer that is loaded with the appropriate presentation program. There are several ways for sending the content from the server to the client. It may be on the basis of request and transmission of individual files In this case, application of the invention makes that for determining the access rights, it is not necessary to access the component file on the server. Another way of sending the content to the client is to send it as a multiplexed signal. This may a broadcast multiplex signal, where many clients receive the same signal, or a direct multiplex signal where an individual client may request certain information. In the broadcast implementation, application of the invention makes that for determining the access rights, it is not necessary to access the multiplex of the component. This saves resources because that multiplex then need not be decoded and evaluated. In the direct implementation, application of the invention makes that for determining the access rights, it is not necessary to request for the multiplex of the component. This saves resources in a similar way and bandwidth of the network connection. It should be noted that the above-mentioned embodiments illustrate rather than limit the invention and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word 'comprising' does not exclude the presence of elements or steps other than those listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention can be implemented by means of hardware comprising several distinct elements and by means of a suitably programmed computer. In the device claim enumerating several means, several of these means can be embodied by one and the same item of hardware.

Claims: CLAIMS: 1. An apparatus for presenting a scene that is represented in an electronic form, the apparatus comprising: retrieval means for retrieving a scene description, the scene description including a component identification, identifying a component comprising content for the scene, and a conditional access identification, for determining access rights to the component; conditional access determining means for determining the access rights to the component; and presenting means for presenting the scene including the content of the component in conformance with the access rights. 2. An apparatus as claimed in Claim 1, wherein the conditional access identification includes a system identification identifying a conditional access system controlling the access rights of the component. 3. An apparatus as claimed in Claim 1, comprising further retrieval means for retrieving the content of the component in conformance with the access rights. 4. An apparatus as claimed in Claim 3, wherein the further retrieval means are arranged to retrieve, in the case that the conditional access determining means determine that no access rights exist to the component, content of a further component as an alternative, the scene description including a further component identification, identifying the further component comprising content for the scene. 5. A method of presenting a scene that is represented in an electronic form, the method comprising the steps of: retrieving a scene description, the scene description including a component identification, identifying a component comprising content for the scene, and a conditional access identification, for determining access rights to the component; determining the access rights to the component; and presenting the scene including the content of the component in conformance with the access rights. 6. A computer program product loadable into the internal memory of a digital computer, comprising software code portions for executing the steps of Claim 5 when said product is run on the digital computer. 7. A storage medium comprising the computer program product claimed in Claim 6. 8. An apparatus for producing a scene description, the apparatus comprising: - description means for preparing a scene description, the scene description including a component identification, identifying a component comprising content for the scene, and a conditional access identification, for determining access rights to the component; and output means for outputting the scene description in the form of a computer program product. 9. An apparatus as claimed in Claim 8, wherein the description means are arranged to prepare the scene description in the SMIL language, whereby the conditional access identification is described by a test attribute of SMIL. 10. An apparatus as claimed in Claim 9, wherein the scene description includes in addition to the component identification a further component identification, identifying a further component comprising content for the scene, and wherein the two component identifications are included as respective alternatives in a SMIL switch element. 11. A method of producing a scene description, the method comprising the steps of: preparing a scene description, the scene description including a component identification, identifying a component comprising content for the scene, and a conditional access identification, for determining access rights to the component; and outputting the scene description in the form of a computer program product. 12. A computer program product comprising a scene description, the scene description including a component identification, identifying a component comprising content for the scene, and a conditional access identification, for determining access rights to the component. 13. A storage medium comprising the computer program product claimed in Claim 12.

Inventors: VAN RIJNSOEVER BARTHOLOMEUS J, VAN RIJNSOEVER, BARTHOLOMEUS, J.
Applicants: KONINKL PHILIPS ELECTRONICS NV, KONINKLIJKE PHILIPS ELECTRONICS N.V.
Application year: 2000
Main classification: G06F1
IPC codes: G06F1, G06F12, G06F21, H04N7