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AllwaysAllowed indicator for out-of-band DRM permissions Disclosure Number: IPCOM000022494D
Publication Date: 2004-Mar-18
Document File: 2 page(s) / 24K

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AllwaysAllowed indicator for out-of-band DRM permissions

The UPnP ContentDirectory Service (CDS) is a standard that allows devices to advertise the content they store on the home network. Other devices, called Control Points (CP) can send browse and query actions to the CDS and thus look through the collection, obtaining meta-data about content like title, authors, media type and supported formats. CPs can set up streams to play the content from the CDS on other devices (for example on a UPnP TV). It is not unlikely for a future UPnP version that the CDS will be extended with digital rights management (DRM) support.

Assuming that this extension is to support multiple types of DRM systems, one approach is to make the actual DRM standards “out-of-band”. Thereby, CPs need not understand the actual DRM systems, but invoke a set of generic actions.

DRM systems usually limit to which devices content can be streamed. Typically, a minimum requirement is that the receiving device supports the same DRM system. However, there are often additional restrictions, and these can vary from DRM system to DRM system. Some are as simple as a copy-once bit, while others support a rights language, to specify additional restrictions under specific conditions (e.g. no playing of content on queen’s birthday). Furthermore there can be additional restrictions on the kind of devices and interconnections for certain operations (e.g., only reduced quality play allowed via wireless and no (full) copy).

CDS meta-data is often shown to end-users by CPs. Preferably, a CP should be capable to show to the user only that content that can really be handled by an anticipated sink device (e.g., a UPnP TV). However, because the actual DRM system is out-of-band for UPnP, a CP can only make use of the standardized part of the meta-data for selection purposes. As part of this, a CP may be able to check that the source and sink device support the same DRM system, and that the anticipated content transfer (copying, moving or streaming) belongs to the allowed transfer types of the sink device. If these are different, then it is guaranteed that no stream can be set-up. However, the specific restrictions that hold for specific DRM systems (see above) are not guaranteed to be part of the standardized meta-data. For example, it might be the case that copying over wired links is allowed but not over wireless. Therefore, there are still cases in which the DRM systems match and the anticipated content transfer type seems to be allowed, but the content transfer is prohibited by the DRM system. When a user invokes such a content transfer, an error will occur.

Now a sink device can provide an explicit test action. A CP can invoke this action to check whether a specific piece of content can be transmitted between source and sink device. The test action checks whether the desired c...