WO2009133498A1

WO2009133498A1 - Digital content management

Info

Publication number: WO2009133498A1
Application number: PCT/IB2009/051654
Authority: WO
Inventors: Marijn C. Damstra; Franciscus L. A. J. Kamperman
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2008-04-29
Filing date: 2009-04-22
Publication date: 2009-11-05

Abstract

Control of rendering of media content and derivative content that is associated with the media content is described. The media content is provided to a derivative content creator service, the derivative content is received from the derivative content creator service, a check is made whether or not the media content has been legitimately obtained and, in dependence on a result from the check, rendering means are applied to render the media content and the derivative content.

Description

Digital content management

TECHNICAL FIELD

The present invention relates to digital rights management.

BACKGROUND Today almost all media content is readily available in digital form - recently produced as well as older content. That is, the wide availability is now such that it also includes legacy content such as audio recordings and films that previously was available typically only in analogue form. As a consequence of the greatly enhanced availability, and the wide availability of digital media processing means, there has emerged a desire to enhance viewer/listener experience when experiencing the legacy media content.

Enhancement of viewer experience may be achieved by way of supplementing the legacy content with add-on content. One example of such enhancement is that of legacy video, i.e. films, that is supplemented with add-on content in the form of sub-titles in a desired language. Another example, which will be used in the discussion to follow, is that of legacy video content that is supplemented with digital data that enhances the visual experience. It involves the processing of legacy two-dimensional, 2D, video content by addition of a so-called depth map resulting in three-dimensional, 3D, video content. This 3D video content can be rendered on a specialized display, providing a viewer with a 3D perception of the video content. As a large amount of legacy 2D video content exists today, a scenario can be foreseen in which consumers are invited to generate depth maps for this content. For example, fans of a specific visually exciting film may wish to undertake the task to generate depth maps for all or part of the film. These depth maps can be made available to those interested in improving further, as well as those only interested in rendering them on a display. This type of scenario is typically referred to as crowd-sourcing or co-creation. An important aspect of such scenarios is that of management of the legal rights associated with the individual parts of, and the final results, of such co -creation.

For example, new video content may consist of both a 2D video and a 3D depth map. In case they are generated by the same party, they can also be protected together as a whole, e.g. by means of encrypting them. In such a situation, there is no need for consumers to generate a 3D depth map themselves. However, in many instances consumers will have legacy 2D video content for which they would like to obtain a 3D depth map.

Several license management schemes have been proposed to express rights governing the creation of such derivative works. In enterprise rights management (ERM) such as Microsoft's Rights Management Services, the publishing of documents together with such a license is intrinsically supported. Rights expressions define what parties may do with content, e.g. what rights they have and what limitations and conditions apply. Creative Commons is a set of licenses, residing in the domain between full copyright and public domain, designed to enable people to share, reuse, and remix creative works legally.

However, there is still a shortage of specific solutions in the prior art that provide digital rights owners with a flexible way of governing rights related to legacy media content in situations where the digital rights owner is not in control of the process of creation of derivative content related to the legacy content.

SUMMARY

In order to improve on the prior art there is provided, according to a first aspect, a method of controlling rendering of media content and derivative content that is associated with the media content. The method comprises checking whether or not the media content has been legitimately obtained and, in dependence on a result from the check, applying rendering means to render the media content and the derivative content.

In other words, such a method assures that a media consumer can only render derivative content when he/she holds a legitimate copy of the associated media content, for example a depth map associated with legacy two-dimensional video content. This has an advantage in that it provides owners of digital rights a flexible way of governing rights related to media content in situations where the digital rights owner is not in control of the process of creation of derivative content related to the media content.

The method may comprise providing the media content to a derivative content creator service and receiving the derivative content from the derivative content creator service before the checking takes place.

Embodiments include those where an encrypted first encryption key is obtained from an owner of the media content, the encrypted first encryption key is provided to the derivative content creator service, and the reception of the derivative content from the derivative content creator service involves reception of the first encryption key and reception of derivative content that is encrypted with the first encryption key, and the rendering of the derivative content involves decryption with the first encryption key.

Checking may be performed regarding whether or not the derivative content creator service is a trusted service and, in dependence on a result from the check, providing the media content to the derivative content creator service.

Embodiments include those where at least an identifier of the rendering means is provided to the derivative content creator service, and wherein the reception of the derivative content from the derivative content creator service involves reception of at least a rendering means identifier associated with the derivative content, and the rendering of the derivative content is further conditioned on a match at least between the received rendering means identifier and the identifier of the rendering means provided to the derivative content creator service.

The provision of the media content to the derivative content creator service may involve provision of an identifier to the media content, the identifier comprising information for enabling the derivative content creator service to obtain the media content.

Other embodiments comprise calculating a hash of a description of rights that are associated with the media content, providing the hash of the description of rights to the derivative content creator service, receiving a hash value from the derivative content creator service. In such embodiments the checking whether or not the media content has been legitimately obtained comprises checking whether or not the received hash value matches the hash of the description of rights to the derivative content provided to the derivative content creator service.

This has an additional advantage when dealing with already existing, legacy media content. That is, information is used regarding rights in an existing usage license, which has already been issued with the legacy media content. That is, an advantage is that the format of the original right doesn't matter, i.e. the method is rights (DRM) format agnostic, while the properties of the original right can be maintained.

The calculation of a hash of a description of rights that are associated with the media content may involve calculation of a hash of a media content encryption key. Embodiments may comprise calculating a hash of at least an identifier of the rendering means to the derivative content creator service, providing the calculated hash of at least an identifier of the rendering means to the derivative content creator service. The reception of the derivative content from the derivative content creator service may involve reception of a hash of at least a rendering means identifier associated with the derivative content, and the rendering of the derivative content may further be conditioned on a match at least between the received hash of a rendering means identifier and the hash of the identifier of the rendering means provided to the derivative content creator service.

Some embodiments are such that the provision of the media content to the derivative content creator service involves provision of digitally watermarked media content, the reception of derivative content from the derivative content creator service involves reception of digitally watermarked derivative content, and the checking whether or not the media content has been legitimately obtained involves performing a watermark matching between the received watermarked derivative content and the watermarked media content. In a second aspect, there is provided an apparatus configured to control rendering of media content and derivative content that is associated with the media content, comprising means for providing the media content to a derivative content creator service, receiving the derivative content from the derivative content creator service, and means for checking whether or not the media content has been legitimately obtained and, in dependence on a result from the check, applying rendering means to render the media content and the derivative content.

The media content may be a two-dimensional film sequence and the derivative content may comprise a depth map.

In a third aspect, there is provided a computer program product comprising software instructions that, when executed in a computer, performs the method summarized above.

These further aspects provide corresponding effects and advantages as discussed above in connection with the first aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described with reference to the attached drawings, where: figure 1 schematically illustrates a block diagram of interconnected units, figure 2 schematically illustrates a block diagram of a media rendering apparatus, and where figure 3 is a flow chart of a first embodiment of a rendering control method, and figure 4 is a flow chart of a second embodiment of a rendering control method. DETAILED DESCRIPTION OF THE EMBODIMENTS

The following detailed description will exemplify methods and arrangements that are realized in a public key infrastructure (PKI). The examples will relate to media content in the form of two-dimensional video content and derivative content in the form of depth map data. Two-dimensional data will be abbreviated with 2D and three-dimensional information, i.e. depth map data, will be abbreviated with 3D. Other terminology and parameters will be used as summarized in table 1. Table 1 : user Consumer of video content. 2D owner Holder of the copyrights of a specific video content.

2D video Specific item of commercial 2D video that a user has bought. sk2D Symmetric key with which the 2D video has been encrypted. Typically, two layers of encryption are used to protect the 2D video content. pub2D,user Public key with which the symmetric key sk2D has been encrypted. Typically, two layers of encryption are used to protect the 2D video content. priv2D,user Private key with which the symmetric key sk2D can be decrypted by the user. Typically, this key is embedded securely in the user's device. device id A (unique) number to identify the user's rendering device, e.g. it's serial number, MAC address, IP address, etc. 2D-DRM_id A (unique) number to identify the Digital Rights

Management (DRM) client embedded in the user's rendering device for enforcing usage licenses of 2D video content, e.g. a hash of it's priv2D,user key. content id A (unique) number to identify the 2D video content, e.g. a fingerprint or watermark of the content in case of digital content distribution, or properties of the carrier in case of physical content distribution, such as a DVD or Blu-ray (BD) disc. right Rights associated with the content, e.g. to render, copy, edit, etc. the content. Rights are typically expressed in a language such as ODRL or MPEG21-REL. Rights are part of a so-called usage license. conversion service Party that converts a 2D video content into a 3D video content, by generating a depth map for that particular 2D video. sk3D Symmetric key with which the depth map has been encrypted. pub3D,service Public key with which the symmetric key sk3D has been encrypted. priv3D,service Private key with which the symmetric key sk3D can be decrypted by the service.

E Encryption of message m with key k is denoted as Ek[m] or Ek {m}. sign Signing of message m with key k is denoted as signk[m]. Il Concatenation of message m with message n is denoted as {m || n}.

Turning now to the drawings, figure 1 illustrates schematically a number of interconnected entities. The connection between the entities is realized via a communication network 107, for example the Internet. A user entity 101, typically comprising a rendering apparatus as will be described with reference to figure 2, is in connection with a content owner entity 103, a derivative content creator service (DCCS) entity 105, as well as any other service entity represented with service entity 109.

The content owner entity 103 is typically a server belonging to or associated with a party who is a legal owner of media content, such as films and music. Actual media content may be present as digital files in the content owner entity 103. However, media content may also exist in a physical form such as a disk 111, e.g. DVD, BIu -ray, HD-DVD etc., on which media files are stored.

The derivative content creator service entity 105 is typically a service server, e.g. in the form of a portal, that is capable of receiving digital media content and using the media content for processing and creating derivative content. Here, the derivative content will be exemplified by 3D depth maps associated with 2D image data such as a film.

However, as the skilled person will realize, derivative content may be in many forms, such as subtitles associated with film content. The derivative content creator service entity 105 may receive media content via the network 107 directly from the user entity 101 in the form of a digital file. However, transfer of media content to the derivative content creator service entity 105 may also take place in a more indirect manner, for example by reference from the user entity 101 to any location connected to the network 107 where the media content may already be stored.

As already indicated, all entities 101, 103, 105, 107, 109, 111 will typically form part of a PKI, and the exemplifying embodiments to be described will rely on such an infrastructure. However, other infrastructures may also be used, as the skilled person will realize.

Turning now to figure 2, a user entity in the form of a rendering apparatus 201 will be described. The apparatus 201 may be, or form part of, a user entity such as the user entity 101 of figure 1. The apparatus 201, which may be a stand-alone apparatus or form part of a larger system in which it is incorporated as a subunit, comprises a processor unit 206, memory 208, input/output interface circuitry 210, and media storage units in the form of an optical media reader 212 as well as a hard disk 214. The rendering apparatus 201 is capable of data communication as indicated by the connection to a communication network 207. The processor unit 206 controls the apparatus by way of software instructions that reside in the memory 208, including software instructions that constitute programs that implement the control methods to be described below. Of course, the programs that implement the methods may be provided to the apparatus 201 by way of any known software distribution means, including optical media and network download. Visual and aural output is realized via a display 202 and a sound output unit 204. The display 202 and the sound output unit 204 may form part of the apparatus or be configured such that they are external to the apparatus 201.

Turning now to figure 3, a first embodiment of a method of controlling rendering of media content and derivative content that is associated with the media content will be described. Here, the rights associated with the media content are in the form of a license to 2D content, and it comprises the following information:

Epub2D,user[sk2D]

Playback rights etc. for 2D content sign2D_owner{Epub3D,service[sk3D] || (pub2D,user) } Conversion rights etc. for 2D to 3D content

Identifier of authorized conversion service, i.e. a derivative content creator

That is, the license stipulates the rights such that the 3D depth map conversion of the licensed media content is allowed under the constraint that the 3D depth map is issued by a trusted conversion service (e.g. with a certificate and a private key priv3D,service) and that the 3D depth map is encrypted with key sk3D. The user entity may decrypt the encrypted 3D depth map and receives Epub2D,user[sk3D] provided that a legitimate copy of the licensed content is present.

It is assumed that the user entity is able to transfer an unencrypted copy of the 2D media content and send it to the conversion service. For protection of the content the 2D media content may be transferred using a secure authenticated channel connecting to authorized parties only. Alternatively, the user entity may provide information to the conversion service by reference, i.e. refer to the 2D media content by providing an identifier of it. In such a case, the conversion service either requires access to the 2D media content, or to cache an associated depth map it has already generated during a previous request. With reference to the flow chart in figure 3 and to the entities of figure 1 , the flow of information is as follows:

The user entity 101 obtains, during an obtaining step 301, media content in the form of a 2D video from the owner 103 of the 2D content. The owner 103 of the 2D content allows the user entity 101 to generate a depth map for the 2D content according to the rights stipulated in the license, as discussed above. Although not essential, in this case the owner 103 requires the resulting depth map to be published under encryption. The required encryption key sk3D is transmitted together with the 2D content to the user entity 101. The user entity 101 then obtains a depth map that is associated with the 2D video by using the conversion service, i.e. the derivative content creation service 105. In practice, this is performed in two steps: a transmission step 303 in which the 2D content is provided to the service 105 and a reception step 305 during which the calculated depth map data is received from the service 105. The actual calculation of the depth map data by the service 105 is performed using an appropriate algorithm. Such conversion algorithms are known to the person skilled in the art. Upon providing the depth map, the service 105 ensures that the depth map is encrypted with the appropriate key sk3D. Upon receiving the encrypted depth map, the user entity 101 checks, during a checking step 307, whether a legitimate copy of the associated 2D video content is present. If this is the case, the user entity decrypts the depth map and renders it together with the 2D video content in a rendering step 309. The checking of whether a legitimate copy of the media content is present or not can be performed in any suitable manner inherent in the PKI or, in the case the media content is present on a DVD, by reading the lead-in of the disk or by measuring physical properties of the disk that can uniquely identify the disk. These properties may include (deviations of) the disk's wobble frequency. In an alternative and more extensive scheme, the user entity 101 may send

(pub2D,user), device id, 2D-DRM_id and content id to the conversion service 105, followed by the conversion service 105 returning Epub2D,user[sk3D || device id || content id || 2D- DRM id] + license stating: render only if device id, 2D-DRM_id and content id match.

Another embodiment will now be described, with reference to the flow chart in figure 4 and to figure 1. In this embodiment there is no need for an extended usage license to be issued for the 2D video content. This is advantageous when dealing with already existing, legacy, media content. Therefore, in this embodiment information is derived from an existing usage license, which has already been issued with the legacy media content. This information is then used as a condition for rendering 3D depth maps. The user entity 101 obtains a video from the owner of the 2D content. Upon generating a depth map using the derivative content creator service, the user entity 101 is requested to provide a hash H[right(sk2D)] of the right for rendering the 2D video. This right is contained in the usage license for the 2D video, the content key sk2D is located in this right as well. The advantage of using a hash over the original 2D right is in fact that the properties of the original right are copied to the 3D right. Furthermore, the hash is taken over the "in the clear" content key sk2D. This ensures that only legitimate rendering arrangements in possession of the original right can provide for this hash. Another advantage of this scheme is that the format of the original right doesn't matter, i.e. the system is rights (DRM) format agnostic, while the properties of the original 2D right are maintained.

Hence, the flow of information in the second embodiment starts with the user entity 101 obtaining, during an obtaining step 401, media content in the form of a 2D video together with a description of the rights from the owner 103 of the 2D content. As in the previous embodiment, typically, the media content is encrypted with key sk2D, which is supplied to the user entity 101 encrypted with pub2D,user. The hash of the rights is then calculated in a hash calculation step 402 and provided to the conversion service 105 together with the media content in a transmission step 403.

Upon exporting the depth map to the user entity 101, which is received in a reception step 405, the conversion service 105 has ensured that the calculated depth map is encrypted with a key sk3D. The hashed right H[right(sk2D)] is appended to the depth map and is also received during the reception step 405. Upon receiving the encrypted depth map, the user entity 101 checks in a checking step 407 whether the hashed right H[right(sk2D)] matches the hash of the right associated with the 2D video content, as received during the obtaining step 401. If this is the case, the user entity 101 decrypts the depth map and renders it in a rendering step 409 together with the 2D video content.

In an alternative and more extensive scheme, the user entity 101 securely transmits a hash of device id, 2D-DRM_id and content id to the conversion service 105, upon which the conversion service 105 returns Epub2D,user[sk3D || hash(device_id || 2D- DRM id Il content id )] + license stating: render only if hash(device_id || 2D-DRM_id || content id) matches. Optionally, the key (pub2D,user) may be included in the hash above. Alternative embodiments may involve watermarking of the media content. That is, watermarks may be used, rather than encryption to protect the 2D video and the generated 3D depth map. In this case, a compliant user entity rendering device is able to render all content containing a watermark with the identification of the rendering device. The device can render a 2D video with such a watermark. During the sequence of communication with the derivative content creator service 105, the user entity 101 sends the watermarked 2D video to the service 105. The conversion service then generates a 3D depth map, taking the watermarked 2D video as input. Provided that a robust watermark is utilized, the watermark will remain present in the generated 3D depth map. Upon detection of this watermark, the user entity 101 compares the watermark to that detected in the associated 2D video. If they match, the user entity 101 will render the depth map together with the 2D video.

Moreover, it is possible that, before the user entity 101 sends the 2D video to the conversion service 105 to obtain the 3D depth map, it first downscales the 2D video content. Several types of downscaling will not hamper depth map generation, for example converting the color 2D video to a grayscale 2D video.

Furthermore, it is also possible for the conversion service 105 to operate on the 2D video under encryption, i.e. without decrypting the content. Techniques exist that can achieve this, such as homomorphic encryption. It is known how to implement a number of basic operations on encrypted data.

Hence, in summary, control of rendering of media content and derivative content that is associated with the media content is described. The media content is provided to a derivative content creator service, the derivative content is received from the derivative content creator service, a check is made whether or not the media content has been legitimately obtained and, in dependence on a result from the check, rendering means are applied to render the media content and the derivative content.

Claims

CLAIMS:

1. A method of controlling rendering of media content and derivative content that is associated with the media content, comprising checking (307,407) whether or not the media content has been legitimately obtained and, in dependence on a result from the check, applying rendering means to render (309,409) the media content and the derivative content.

2. The method of claim 1, comprising: providing (303,403) the media content to a derivative content creator service (105), receiving (305,405) the derivative content from the derivative content creator service.

3. The method of claim 2, comprising: obtaining an encrypted first encryption key from an owner (103) of the media content, - providing the encrypted first encryption key to the derivative content creator service, and wherein: the reception of the derivative content from the derivative content creator service involves reception of the first encryption key and reception of derivative content that is encrypted with the first encryption key, and - the rendering of the derivative content involves decryption with the first encryption key.

4. The method of claim 2 or 3, comprising: checking whether or not the derivative content creator service is a trusted service and, in dependence on a result from the check, providing the media content to the derivative content creator service.

5. The method of any of claims 2 to 4, comprising: providing at least an identifier of the rendering means to the derivative content creator service, and wherein: the reception of the derivative content from the derivative content creator service involves reception of at least a rendering means identifier associated with the derivative content, and - the rendering of the derivative content is further conditioned on a match at least between the received rendering means identifier and the identifier of the rendering means provided to the derivative content creator service.

6. The method of any of claims 2 to 5, wherein the provision of the media content to the derivative content creator service involves provision of an identifier to the media content, the identifier comprising information for enabling the derivative content creator service to obtain the media content.

7. The method of claim 2, comprising: - calculating (402) a hash of a description of rights that are associated with the media content, providing (403) the hash of the description of rights to the derivative content creator service, receiving (405) a hash value from the derivative content creator service, and wherein the checking whether or not the media content has been legitimately obtained comprises: checking whether or not the received hash value matches the hash of the description of rights to the derivative content provided to the derivative content creator service.

8. The method of claim 7, wherein the calculation of a hash of a description of rights that are associated with the media content involves calculation of a hash of a media content encryption key.

9. The method of claim 7 or 8, comprising: calculating a hash of at least an identifier of the rendering means to the derivative content creator service, providing the calculated hash of at least an identifier of the rendering means to the derivative content creator service, and wherein: the reception of the derivative content from the derivative content creator service involves reception of a hash of at least a rendering means identifier associated with the derivative content, and the rendering of the derivative content is further conditioned on a match at least between the received hash of a rendering means identifier and the hash of the identifier of the rendering means provided to the derivative content creator service.

10. The method of claim 2, wherein: the provision of the media content to the derivative content creator service involves provision of digitally watermarked media content, the reception of derivative content from the derivative content creator service involves reception of digitally watermarked derivative content, and the checking whether or not the media content has been legitimately obtained involves performing a watermark matching between the received watermarked derivative content and the watermarked media content.

11. An apparatus (201) configured to control rendering of media content and derivative content that is associated with the media content, comprising means for checking whether or not the media content has been legitimately obtained and, in dependence on a result from the check, applying rendering means to render the media content and the derivative content.

12. The apparatus of claim 11, comprising means for: providing the media content to a derivative content creator service, - receiving the derivative content from the derivative content creator service.

13. The apparatus of claim 10 or 11, where the media content is a two- dimensional film sequence and the derivative content comprises a depth map.

14. A computer program product comprising software instructions that, when executed in a computer, performs the method of any of claims 1 to 10.