Abstract—Cloud computing allows accessing resources across

Internet transparently: requiring no expertise in, or control over the underlying infrastructure. UPnP or DLNA were not designed for media distribution beyond the boundaries of a local network. To overcome this problem, we propose Media Cloud, a home gateway service for classifying, searching and delivering media across the cloud that interoperates with UPnP and DLNA.

I. INTRODUCTION Computer communications evolved from the mainframe to

client-server and then to P2P, bringing constantly new paradigms that changed our way to use and understand computers, personal devices and consumer electronics. Cloud Computing is a new paradigm where resources are provided to other devices on demand abstracting the details of the infrastructure that supports them. The term "cloud" is a metaphor for the Internet, the network over which different organizations join to dynamically offer scalable resources [1]. The term "computing" might suggest processing power but Cloud Computing resources are not limited to CPU. In fact, multimedia management is among the most outstanding aspects of Cloud Computing, since it makes possible to retain and share large amounts of digital media.

Current state-of-the-art devices can produce, store and deliver high quality media that can be finally distributed towards social networks, communities or clouds where constituent members might be family or friends. However, there is no infrastructure to keep data under control or even find a concrete media in the home environment or outside it. UPnP [2] and DLNA alleviate the problems of sharing contents between devices in the home network but they lack of a mechanism for searching across multiple repositories in parallel. They require users to organize contents in repositories and to define rules for sharing them. Moreover, they were not designed for managing media outside the home domain.

In conclusion, familiar operations for finding and sharing media with devices over the Internet turn finally in an awful lot of clicking, typing, searching, copying, and pasting. To cope with this problem, this article describes a solution for bringing the Cloud Computing concept to the home domain. The solution describes a home gateway application, called Media Cloud, for classifying, searching and sharing media across the home domain and the cloud. The solution aligns to Cloud Computing concepts so users no longer need expertise in, or control over, the underlying technology. In fact, already deployed protocols as UPnP and DLNA can be used transparently leading also to a cost-effective solution.

This work has been partially supported by the State of Madrid (CAM), Spain under the contract number S2009/TIC-1650.

II. BACKGROUND UPnP and DLNA, the last based on the first, deal with

interoperability between networked consumer electronics permitting user-generated contents to be shared among household devices. These specifications define three functional components: Media Server (MS), Media Renderer (MR), and Control Point (CP). A device can implement several functional components (media players combine CP and MR). Control Points discover and control other devices on the network and coordinate operations among devices that yield to the desired result. Devices in DLNA expose services that provide actions. Services can be controlled via state variables or events.

UPnP AV facilitates the discovery and configuration but it does not define how contents are transferred. DLNA goes beyond UPnP defining mandatory Media Formats and Media Transport protocols as HTTP or RTP. However, distributed search operations in UPnP and DLNA are not straightforward. UPnP behaves in a P2P fashion, for instance, a CP controls a MS to render contents in a MR, but UPnP doesn’t allow to search in parallel in several repositories.

Since UPnP and DLNA were designed to operate in local networks, users rely frequently on third party services, typically web-based, to share contents beyond the boundaries of a home domain. These kinds of workarounds are orthogonal to cloud computing concepts since contents are not accessed transparently. Fortunately, there are many initiatives that allow clients to perform distributed search operations by connecting to all nodes and merging results into a unified result list. Those initiatives, as Hadoop and Lucene, employ "map and reduce" functions [3] commonly used in functional programming. Regarding security, OAuth [4] allows users to share their private resources stored in one device with others in a secure way without having to hand out usernames and passwords.

III. MEDIA CLOUD ARCHITECTURE Media Cloud services are located in a home gateway. The

gateway has access to the home network and to the Internet. Thus, it can communicate with devices located in the home environment and also provide search services, content delivery and filtering to friends and family outside home domain. Fig. 1 sketches out the architecture of Media Cloud. Media Cloud is composed by two different modules: the Home Module and the Foreign Module.

The Home Module takes care of devices within the home domain. It is composed by a CP, a MS, a MR and a Search Service. The CP discovers MSs within the home domain and obtains tags from the media offered by those MSs. The CP

�Media Cloud: Sharing Contents in the Large Daniel Diaz-Sanchez, Florina Almenares, Andrés Marin, and Davide Proserpio, Ingeniería Telemática,

Universidad Carlos III de Madrid, Avda. de la Universidad 30, 28911, Leganés, Madrid Spain.

2011 IEEE International Conference on Consumer Electronics (ICCE)

978-1-4244-8712-7/11/$26.00©2011 IEEE 227

builds a text based index for each media using tags, information about the device where the media is stored, the date, the owner of the device, access control information and any other optional attribute. This index is stored in the Home Media Indexes (HMI) database. The Home Module redirects any search operation originated in home domain to the Content Server that will perform a distributed search over other gateways. The MS at the gateway is able to deliver content obtained from outside to home devices. The MR shall receive content from home devices and redirect it to outside when requested by an authorized foreign gateway.

Fig. 1. Media Cloud architecture.

The Foreign Module handles inter domain communications. It is in charge of making home media available to other gateways, for instance, those owned by family and friends. The module is composed by a Content Server, an OAuth module and an Access Control System. The Content Server facilitates foreign clients to search within the HMI database and delivers content to foreign clients when necessary. It uses secure versions of HTTP and RTP to cope with the search operations and content delivery operations. The authentication is handled by the OAuth module that authenticates and authorizes foreign clients using a security token. The Access Control System uses the security token to filter HMI database contents preventing information leakage.

IV. MEDIA CLOUD OPERATION

A. HMI database building The Home Module discovers and interrogates home domain

MSs for media description. Nowadays multimedia devices allow users to annotate content. For instance, typing a comment and configuring a camera to embed that comment would make every media produced by the camera to be appropriately annotated.

The Home Module assumes the existence of a simple UPnP action called TagIt, which returns tag identifiers and tag values for a given media stored in the device. The Home Module uses that information for building the HMI tag database that includes also information for accessing the content.

B. Searching and accessing media in the home domain Devices in the home domain can use the Home Module to

search across the home domain and outside it. The search service consumes text as input and produces a result that can be classified by score and refined by media type, quality, format, size and any other attribute. Once the desired media is found, the home gateway can use the CP to link media renderers and media servers transparently to normal DLNA UPnP AV operation.

Home Device

Home Module

Controller Point

Home ModuleMedia

Renderer

Foreign ModuleSearch System

Foreign ModuleContent Delivery

Foreign ModuleAccessControl

DiscoveryDevice 123

Action TagIt: media 1

List MediaResponse

Response...

Action TagIt: media nResponse

Home Media

Indexes

Home Media

Indexes

Get indexes for “wedding photos”OauthKey: nc2j82cjn924nf

Aunt Anna’sSet top

box

filter for Nc2j8...Filtered indexes Media1, media8...

Get media1Request media1 to device 123

DLNA/UPnP AV request for media1

Request Media1to

device 123

Streaming StreamingGet

Encryptionkeys Secure

delivery Fig. 2. Media Cloud operation.

C. Searching and accessing media in large Foreign devices can search within an index by connecting

to all gateways offering this service and merging results from all nodes into a unified result list. The Foreign Module checks for a valid OAuth token before letting foreign clients to search across the home domain and if they are authorized to do so it applies filters according to a policy.

V. IMPLEMENTATION AND CONCLUSIONS We have developed Media Cloud including the UPnP

services for tag exchange. We used Cling open source UPnP library for the UPnP modules. The Home Media Indexes database has been built using the Apache Lucence open source project. The distributed search uses a distributed search library from the Katta project compliant with Lucene.

Media Cloud provides a cost-effective solution for cloud computing service provision among federated gateways. It uses well known protocols as HTTP, UPnP, and OAuth. Resources are presented to UPnP and DLNA as if they were local. Thus, it is compatible with already deployed protocols.

REFERENCES [1] A. Weiss, "Computing in the clouds," in Networker Journal, vol. 11,

Issue 4, ACM. New York, 2007, pp, 16-25. [2] Contributing members of UpnP Forum, “UpnP Device Architecture

Version 1.1", UpnP Forum, October 2008. [3] J. Dean and S. Ghemawat, “Mapreduce: Simplified data processing on

large clusters,” in OSDI’04, 6th Symposium on Operating Systems Design and Implementation, 2004, pp. 137–150.

[4] E. Hammer-Lahav, "The OAuth 1.0 Protocol", Internet Engineering Task Force, RFC 5849, April 2010.

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