Patent Publication Number: US-10326662-B2

Title: System and method for managing playback of streaming digital content

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of the co-pending U.S. patent application titled, “SYSTEM AND METHOD FOR MANAGING PLAYBACK OF STREAMING DIGITAL CONTENT,” filed on Oct. 11, 2012 and having Ser. No. 13/650,072. The subject matter of this related application is hereby incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     Embodiments of the present invention relate generally to digital media and, more specifically, to a system and method for managing playback of streaming digital content. 
     Description of the Related Art 
     One popular model for consumer content delivery involves transmitting digital content files from a content server directly to a content player via a communications network. The content server is typically a computer system in a secure machine room configured to store digital content files that can be streamed to the content player via the communications network. Each digital content file is associated with metadata related to the contents of the digital content file. The metadata typically includes a specific identifying title, such as “Gone with the wind,” which is likely to be familiar to a user. A given digital content file may be discovered and selected by the user and streamed from the content server to the content player prior to or during playback. The user may discover a particular title via a metadata search, such as a title name search. 
     The content player may be implemented as an application that executes on a playback device comprising a computing platform, which may be integrated within a dedicated device such as a television panel, set-top box, or mobile device. The digital content files may comprise digitally encoded songs and sound tracks, movies, television programs, and so forth. The content player typically downloads and buffers at least a portion of the digital content file to facilitate uninterrupted playback of the title. A given device may be configured to include a content player application by the device manufacturer, or the content player may be loaded and configured by a user prior to use. 
     Oftentimes, multiple different devices capable of acting as content players may be present in a given setting. For example, a user may be in their living room with both a mobile phone and a television panel, both of which may capable of executing a suitable content player application. In this example, the television panel may be a superior option for viewing digital content; however, the mobile device may have superior user interactivity features for searching content. The user may be able to efficiently find a particular title using their mobile device, but they are still required to perform essentially the same operations using a typically cumbersome user interface implemented by the television panel remote control. This results in an inefficient playback experience. 
     One approach for improving the playback experience involves the mobile device being configured to act as a playback master and the television panel being configured to act as a playback slave. With this approach, the user may search content and select a title for playback using the mobile device, and then stream a live playback session to the television panel. While this approach allows the user to better manage playback, the mobile device is tied up acting as the playback master. If the mobile device drops off the network for any reason, such as the user taking the mobile device to a location with poor network connectivity, then the playback session to the television panel is interrupted. 
     As the foregoing illustrates, what is needed in the art is technique for enabling more efficient management of multiple content player devices. 
     SUMMARY OF THE INVENTION 
     One embodiment of the present invention sets forth a method for directing a target device to play a selected title, comprising discovering the target device with a local network, exchanging unique identifiers with the target device to establish an association with the target device, identifying to a content server the target device as an associated device, determining whether the target device includes a service application through which the target device can communicate with the content server; and if the target device includes the service application, then causing the service application to request the selected title from the content server. 
     Other embodiments include, without limitation, a computer-readable medium that includes instructions that enable a processing unit to implement one or more aspects of the disclosed methods as well as a system configured to implement one or more aspects of the disclosed methods. 
     One advantage of the disclosed systems and methods is that a control device may easily manage operations of a target playback device, including activation, installation, or any combination thereof of a corresponding service application. A second advantage is that a plurality of related devices may be associated with each other and advantageously interact using server-mediated operations based on association. This is in contrast to prior art solutions with complex, manual, and inefficient management procedures between two devices. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
         FIG. 1  illustrates a content distribution system, configured to implement one or more aspects of the present invention; 
         FIG. 2  illustrates interactions between a controller and a target, according to one embodiment of the present invention; 
         FIG. 3  is a system diagram of a playback device, according to one embodiment of the present invention; 
         FIG. 4  is a flow diagram of method steps, performed by a controller for directing a target to play a selected title, according to one embodiment of the present invention; and 
         FIG. 5  is a flow diagram of method steps, performed by a target for playing a selected title, according to one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, numerous specific details are set forth to provide a more thorough understanding of the present invention. However, it will be apparent to one of skill in the art that the present invention may be practiced without one or more of these specific details. In other instances, well-known features have not been described in order to avoid obscuring the present invention. 
       FIG. 1  illustrates a content distribution system  100  configured to implement one or more aspects of the present invention. The content distribution system  100  includes a content server  140 , a wide area network (WAN)  130 , a router  120  coupled to a local network  122 , a controller  112  and at least one target  114 . 
     The content server  140  includes one or more server applications, implemented to execute on one or more computer servers. Each computer server may comprise a hardware computer system or a virtual computer system running on an arbitrary collection of one or more hardware computer systems. Content server  140  may implement a file server  142 , a directory server  144 , an authentication server  146 , or any combination thereof. In one embodiment, file server  142 , directory server  144 , and authentication server  146  are implemented as applications running on one or more computer systems coupled to WAN  130 . Each one of the one or more computer systems may be an independent hardware computer system, cluster of hardware systems, distributed hardware system, or a virtual computer system hosted by an arbitrary hardware configuration including one or more independent hardware computer systems. 
     File server  142  is configured to store and retrieve digital content files for download to controller  112 , targets  114 , or a combination thereof. In one embodiment, a given digital content file is downloaded via WAN  130  and router  120 . A plurality of file servers, potentially distributed to include multiple connections to WAN  130 , may be employed to scale up total download bandwidth, for example, to satisfy overall download demand. Directory server  144  implements any technically feasible mechanisms to enable a controller  112  or target  114  to locate a particular title within a catalog of titles for download of one or more corresponding digital content files from file server  142 . A particular title may have one or more associated digital content files, corresponding to different encoding formats for the title. For example, a particular title may have a plurality of associated digital content files containing video encoded in different resolutions and frame rates. As another example, a particular title may have a plurality of associated digital content files containing audio tracks dubbed in different languages. In one embodiment, directory server  144  stores metadata associated with each title, and a title search operation comprises searching for matching metadata. 
     In one embodiment, authentication server  146  is configured to provide authentication credentials to enable a particular controller  112  or target  114  to gain access to digital content files stored on file server  142 . The authentication credentials may also be used to mediate access to directory server  144 . In one embodiment, authentication server  146  queries an account database  148  for account authorization information, such as whether a particular account is authorized to access file server  142  or specific titles residing within file server  142 . Account database  148  may also include individual account data, such as viewing preferences, title access history, title selection affinities, ratings data, recommendation data, social connectivity data, and the like. In one embodiment, each account may include individualized account data for one or more users. 
     WAN  130  may be implemented using any technically feasible system configured to transport digital data between the content server  140  and router  120 . In one embodiment WAN  130  substantially comprises a switching and routing network based on the industry standard internet protocol (IP). The popular “Internet” communications network is one example of a suitable IP-based communications network. Router  120  comprises a digital packet router configured to couple WAN  130  to local network  122 . In one embodiment, router  120  includes a WAN modem, such as a cable modem or digital subscriber line (DSL) modem, as well as a digital wireless modem configured to interoperate with an institute for electrical and electronics engineers (IEEE) standard 802.11 wireless communications system. In such an embodiment, local network  122  may include an arbitrary combination of wireless and wired digital communications channels. Wired Ethernet is one example of a wired digital communications channel. 
     Controller  112  and targets  114  implement a playback application for the digital content files available from the file server  142 . A given digital content file may include data for audio playback, video playback, or combined audio and video playback. Playback of video and audio content may be synchronized via a local time signal. A digital content file may also include alternative content such as subtitles, video overlays, programmatically generated behavior, and the like. Playback of the alternative content may be synchronized to the playback video and audio content via the local time signal. In one embodiment, the playback application includes a time synchronization client configured to synchronize the local time signal to a time reference signal generated by content server  140 . Any technically feasible time synchronization technique may be implemented to synchronize the local time signal with the time reference signal, such as techniques implemented in the well-known network time protocol (NTP). 
     As a consequence of controller  112  and targets  114  synchronizing their respective local time signals to the time reference signal, the local time signals are also synchronized to each other. Digital content playback can therefore be beneficially synchronized between or among the controller and targets  114 , for example to synchronize subtitle playback on controller  112  with video playback on target  114 - 1 . In one embodiment, subtitles in a selected language are displayed on target  114 - 1  and subtitles in a different language may be displayed on a different target, such as target  114 -N. In such a scenario, video for targets  114 - 1  and  114 -N are beneficially synchronized during playback. 
     Devices that are locally connected to local network  122  comprise a device discovery domain  110 . As shown, controller  112  and targets  114 - 1  through  114 -N are devices that comprise device discovery domain  110 . Any additional devices (not shown) connected to local network  122  may also be included in device discovery domain  110 . Devices within device discovery domain  110  implement a discovery protocol that facilitates co-discovery between and among the devices. In one embodiment, the devices implement a discovery protocol known in the art as the simple service discovery protocol (SSDP), which enables appropriately configured devices to both advertise their presence on a network and discover each other within a network. SSDP uses multicast hypertext transfer protocol (HTTP) messaging to announce establishment of a service (e.g., to announce presence on the network) and unicast signaling to reply to a multicast message. Device discovery domain  110  comprises a multicast group for the multicast HTTP messaging. One device may discover another device within device discovery domain  110  using a technique known in the art as an M-SEARCH method, whereby a device transmits a multicast message to the multicast group upon being added to device discovery domain  110 . The device may continue to transmit multicast messages to allow other devices to maintain a list of current devices within device discovery domain  110 . Each recipient of a multicast message replies to the sender with a unicast message. Over time, devices within device discovery domain  110  accumulate a current list of the current devices. In another embodiment, the devices implement a discovery protocol known in the art as universal plug and play (UPnP), modeled after SSDP, which specifically enables advertising multimedia playback capabilities. 
     After each device within device discovery domain  110  is aware of the other devices, certain of the devices may become associated, with one device designated as a controller, such as controller  112 , and another device designated as a target, such as target  114 - 1 . In one embodiment, a device explicitly performing a discover operation is designated to be controller  112  and a device being discovered by controller  112  is designated as a target  114 . For example, an Android™ mobile phone may be directed by a user to discover devices suitable to act as playback targets, and a Sony™ PS3™ may be discovered by the mobile phone. In this example, the mobile phone is controller  112  and the PS3 is a target  114 . 
     In one embodiment, two devices exchange an identifier known in the art as a universally unique identifier (UUID) to establish an association. Any technically feasible technique may be implemented to generate each UUID. In one embodiment, an Ethernet address for a device comprises at least a portion of a UUID associated with the device. In one implementation, target  114  returns a UUID as part of the discovery process. In another embodiment, devices exchange a unique service name (USN) to establish a connection. Any technically feasible technique may be implemented to generate and exchange the USN, for example target  114  may return a USN as part of the discovery process. 
       FIG. 2  illustrates interactions between controller  112  and a target  114 , according to one embodiment of the present invention. As shown, controller  112  and target  114  communicate via local network  122 . Controller  112  transmits commands  210  to target  114  and target  114  transmits events  212  back to controller  112 . Furthermore, controller  112  may establish a communication link  220  with content server  140  and target  114  may establish a separate communication link  222  with content server  140 . 
     A user may direct service application  230  to perform title searches, based on data stored within content server  140 , for example, by querying directory server  144  via communications link  220 . The user may also direct service application  230  to play content streamed via communications link  220  on controller  112 . The user may further direct service application  230  to discover target devices, such as target  114 , coupled to local network  122 . Upon discovering target  114 , service application  230  may associate with service application  232 , residing within target  114 . Once service application  230  and service application  232  are associated, service application  230  may transmit commands  210 , for example, to direct service application  232  to play content by streaming the content via communications link  222  from content server  140 . Target  114  may transmit events  212  back to controller  112  to provide, for example, playback status. In one embodiment, controller  112  comprises a mobile device and service application  230  comprises an application configured to execute on the mobile device. Additionally, target  114  may comprise a set top device or television panel with embedded network streaming capability (a “smart television”), and service application  232  comprises a streaming playback application configured to stream digital content from content server  140  via communications link  222 . 
     In one embodiment, controller  112  and target  114  each transmit to content server  140  UUID sets defining their association. Knowledge of this association allows content server  140  to mediate interaction between controller  112  and target  114 . For example, with the association in place between controller  112  and target  114 , content server  140  may grant a request by controller  112  to activate target  114  based on an account associated with controller  112 . 
     The association establishes a context within which target  114  may accept commands  210  from controller  112 . Commands  210  may be encrypted or signed using any technically feasible techniques to provide a secure transmission regime between controller  112  and target  114 . Similarly, events  212  may be encrypted or signed. 
     In one embodiment, commands  210  include, without limitation, play, stop, and pause. Additional commands  210  may include seeking, forwarding, and reversing. Commands  210  may be used to identify a particular piece of content, and to instruct service application  232  to stream the piece of content from content server  140 . Service application  232  streams the content via communications link  222 , which may be established using shared physical network elements, such as local network  122  and WAN  130 . Service application  230  may operate independently of service application  232 , allowing a user to perform other tasks on controller  112  while target  114  executes playback commands. Service application  230  may present a set of remote control user interface buttons within a touch-based interface to provide a user with a familiar set of commands. 
     In one embodiment, a configuration manager  234  residing within target  114  is configured to participate in device discovery. In certain implementations of target  114 , service application  232  is preinstalled by the manufacturer of target  114 . In such scenarios, configuration manager  234  would be configured to activate service application  232 . One goal of activation is to associate a particular use with account information for the user. The account information may include billing information as well as viewing preferences for individualizing a user experience. 
     In alternative embodiments of target  114 , service application  232  may not be installed by the manufacturer of target  114 . In such embodiments, configuration manager  234  would be installed to provide general configuration and installation services for target  114 . For example, a smart television may be manufactured to include configuration manager  234 , which provides installation services that enable a user to install service application  232 . 
     In one embodiment, configuration manager  234  also provides a feature known in the art as “wake on LAN,” which allows target  114  to operate in a standby mode having substantially reduced power consumption. A small set of hardware features remain active during the standby mode and listen for an arrival of a network packet having a network identifier associated with target  114 . If a data packet arrives having the network identifier associated with target  114 , then target  114  transitions to a power-on state, facilitating full interaction. For example, a smart television may remain in standby mode until discovered by controller  112 . Once the smart television is discovered, controller  112  may be associated with the smart television. At this point, the smart television may not necessarily turn fully on to display images until controller  112  instructs the smart television to turn on by transmitting one or more appropriate commands  210 . 
     If the smart television was manufactured without service application  232  being installed, then controller  112  may direct configuration manager  234  to connect to content server  140 , which may be associated with a particular service provider, to retrieve and install service application  232 . After service application  232  is installed within target  114 , the device may be independently activated or activated based on account credentials associated with controller  112 . In one embodiment, a discovery and launch (DIAL) protocol, based on SSCP, is implemented by configuration manager  234 . 
     In one embodiment, service application  230  controls playback of titles by service application  232 , but may perform other, additional actions for the user. For example, service application may present content recommendations on a display screen of controller  112 . The content recommendations may be timed close to the end of a title being played by target  114 , or based on time-correlated metadata associated with the title, such as based on current actors on-screen, or other on-screen or related information. The content recommendations may be based on recommendations derived from metadata for other user accounts associated with devices within device discovery domain  110  of  FIG. 1 . For example, in a setting where two or more individuals are carrying a device having a service application  230 , the content recommendation may be based on combined affinities for the two or more individuals. Such a recommendation is made possible and mediated by content server  140  by associations formed among devices belonging to the two or more users and reported to content server  140 , which is able to access affinity information for each user. 
     In one embodiment, users form social connections and user metadata may be shared with others within a connected social group. When individuals within the social group are physically co-located, their devices may be associated, enabling server mediated recommendations to be generated. One form of metadata is a recommendation, where a user rates a particular title. In one embodiment, a collection of ratings is used to generate a statistical affinity for one or more users based on certain metadata associated with different titles. From the statistical affinity, server mediated individual recommendations may be generated, and server mediated group recommendations may be generated, for example, when different users gather within a device discovery domain  110 . 
     In one embodiment, service application  230  is configured to provide a synchronized playback on controller  112  of a current title being played by target  114 . Rather than simply mirroring the content being displayed by target  114 , controller  112  is configured to show additional information such as subtitles and time-correlated metadata, such as on-screen actors. Additionally, service application  230  may be configured to enable a user to rate the current title by asserting to a user interface control, such as a button. When service application  230  receives user input in the form of a rating, the rating, along with identifying title information, may be transmitted to account database  148  to be stored along with other user data. 
     As the foregoing illustrates, decoupling playback responsibilities of service application  230 , within controller  112 , from those of service application  232 , within target  114 , enables greater flexibility. Additionally, allowing one or more service applications to form associations within device discovery domain  110  advantageously enables server-mediated features related to user proximity. 
     In one embodiment, controller  112  is configured to temporarily activate a target  114  based on a user account associated with controller  112 . For example, a user may temporarily activate a hotel television configured to act as a target. In such a scenario, an activation duration may be specified based to a hotel stay duration or based on the controller  112  remaining within proximity to the hotel television. 
       FIG. 3  is a system diagram of a playback device  300 , according to one embodiment of the present invention. Playback device  300  may comprise controller  112  and target  114 . Playback device  300  may include, without limitation, a central processing unit (CPU)  310 , a graphics subsystem  312 , an audio subsystem  314 , an input/output (I/O) device interface  315 , a network interface  318 , an interconnect  320 , and a memory subsystem  330 . Playback device  300  may also include a mass storage unit  316 . 
     CPU  310  is configured to retrieve and execute programming instructions stored in a memory subsystem  330 . CPU  310  retrieves the programming instructions from the memory subsystem  330  via interconnect  320 , which is configured to facilitate transmission of data, such as the programming instructions and application data, between CPU  310  and other subsystems. The other subsystems may include, without limitation, graphics subsystem  312 , audio subsystem  314 , I/O devices interface  315 , mass storage unit  316 , network interface  318 , and memory subsystem  330 . 
     Graphics subsystem  312  is configured to generate frames of video data, such as a sequence of graphics images, and to transmit the frames of video data to display device  360 . Graphics subsystem  312  is coupled to CPU  310  via interconnect  320 . In one embodiment, graphics subsystem  312  is embedded into an integrated circuit, along with CPU  310 . Display device  360  may comprise any technically feasible means for generating an image for display. For example, display device  360  may utilize liquid crystal display (LCD) technology, cathode-ray technology, or light-emitting diode (LED) display technology (either organic or inorganic) to produce a visual representation of the frames of video data. 
     Audio subsystem  314  is configured to generate one or more electrical audio signals corresponding to a digital audio stream. For example, audio subsystem  314  may receive a sequence of binary digital values comprising the digital audio stream and generate one or more analog electrical audio signals that correspond to the binary digital values. Audio device  362  includes a speaker or earphone configured to generate an acoustic output in response to the electrical audio signals. In alternative embodiments, display device  360  may include audio device  362  within in a single unit. A television is an example of a device known in the art that incorporates both a display device such as display device  360 , and an audio device, such as audio device  362 . 
     Input/output (I/O) device interface  315  is configured to receive input data from user I/O devices  364  and transmit at least a portion of the input data to CPU  310  via interconnect  320 . For example, user I/O devices  364  may include one or more buttons, a keyboard, and a mouse, a touch screen, or any other pointing device. User I/O devices  364  may also include indicator devices such as light emitting diodes, liquid crystal display indicators, and the like. 
     Mass storage unit  316  is configured to store non-volatile data. Mass storage unit  316  may be implemented using a single storage device or an array of storage devices. Each storage device may comprise a magnetic hard disk drive, a flash drive, or any other technically feasible non-volatile storage device. The non-volatile data may include, without limitation, a boot image of an operating system, applications, application data, and locally stored digital content files. Mass storage unit  316  is coupled to CPU  310  via interconnect  320 . Network interface  318  is configured to transmit and receive packets of data via local network  122 . In one embodiment, network interface  318  is configured to communicate using the well-known Ethernet standard. Network interface  318  is coupled to CPU  310  via interconnect  320 . 
     Memory subsystem  330  includes programming instructions and data that comprise an operating system  332  and applications, such as playback application  340 . Operating system  332  performs system management functions, such as functions to manage hardware devices including network interface  318 , mass storage unit  316 , I/O device interface  315 , audio subsystem  314 , and graphics subsystem  312 . Operating system  332  also provides a run time model for a user interface  334 , playback application  340 , and configuration manager  234  of  FIG. 2 . User interface  334  provides a specific structure, such as a window and object metaphor, for user interaction with features of playback device  300 . Persons skilled in the art will recognize the various operating systems and run time models known in the art are suitable for incorporation into playback device  300 , or may serve as exemplary models for operating system  332 . 
     In one embodiment, user interface  334  is configured to generate a graphical user interface on display device  360 . The user operates user I/O devices  364 , in conjunction with user interface  334 , to select the one or more titles for playback. Playback application  340  then retrieves digital content data associated with the selected titles for playback. The digital content is downloaded, decoded, and played to display device  360  via graphics subsystem  312  and the audio device  362  via audio subsystem  314 . In one embodiment, graphics subsystem  312  is configured to generate subtitles, which may be synchronized to video and audio playback. 
     Playback application  340  is configured to retrieve digital content data from file server  142  of  FIG. 1  via the network interface  318  and to play the digital content data to display device  360  and audio device  362 . Playback application  340  includes, without limitation, a management interface  342  and a content stream decoder  344 . In one embodiment, management interface  342  implements features to facilitate playback of content locally on playback device  300 . In another embodiment, management interface  342  implements features to facilitate playback of content locally, as well as playback of content on other devices acting as targets  114 . 
     Content stream decoder  344  implements a decoder for encoded video streams and a decoder for encoded audio streams. In one embodiment, the digital content streamed from content server  140  comprises an encoded video stream and an encoded audio stream, both structured for synchronized decoding by content stream decoder  344 , which generates corresponding video frames from the encoded video stream and audio samples from the encoded audio stream. 
     In one embodiment, playback application  340  comprises service application  230  of  FIG. 2  and playback device  300  operates as controller  112 . In this embodiment, playback application  340  may request title and catalog information from directory server  144  and present the information to the user via the user interface  334 . The user is able to interact with user interface  334  to select a title for playback. Service application  230  may play content back locally, or transmit commands  210  to service application  232 , instructing service application  232  to retrieve and play the selected title. 
     In a different embodiment, playback application  340  comprises service application  232  and playback device  300  operates as target  114 . In this embodiment, playback application  340  receives commands  210  from service application  230  that identify a title for playback and commands  210  for initiating playback of the title. In response to commands  210 , playback application  340  retrieves data associated with the title for playback. 
       FIG. 4  is a flow diagram of method  400 , performed by a controller for directing a target to play a selected title, according to one embodiment of the present invention. Although the method steps are described in conjunction with the systems of  FIGS. 1-3 , persons skilled in the art will understand that any system configured to perform the method steps, in any order, is within the scope of the invention. 
     Method  400  begins in step  410 , where the controller, such as controller  112 , discovers targets within a device discovery domain, such as device discovery domain  110 . In one embodiment an SSDP-based protocol, such as UPnP, is implemented to perform discovery as discussed previously in  FIGS. 1 and 2 . In step  412 , the controller associates with a target, such as target  114 . A UUID or USN may be exchanged between the controller and each one of the discovered targets to establish a unique context for interaction between the controller and each target. In step  414 , the controller transmits information describing a set of associations established between the controller and discovered targets to a content server, such as content server  140 . In one embodiment, the associations comprise UUID or USN pairs, which are transmitted to the content server. These associations enable the content server to perform mediated operations between the controller and associated (co-located) targets. In step  416 , a user selects a target to control. In one embodiment, the controller displays a list representing discovered targets, and the user selects a target from the list to control. In other embodiments, a set of targets may be selected. 
     If, in step  420 , an appropriate playback application is installed on a selected target, then the method proceeds to step  430 . In one embodiment, the controller queries the selected target to determine whether the playback application is installed and available. Any technically feasible query mechanism may be implemented without departing the scope and spirit of embodiments of the present invention. 
     If, in step  430 , an appropriate playback application is activated on the selected target, then the method proceeds to step  440 , where the controller receives a user interface (UI) command from a user. The command may include, without limitation, search commands to be executed by the content server, playback commands to be executed by either the controller or the selected target. In step  442 , the controller processes the command. For example, the controller may transmit a search query to the content server, or the controller may transmit a play command to the target. In one scenario, the controller transmits a command to request the selected title for playback. 
     If, in step  450 , an event is received, then the method proceeds to step  452 , where the controller processes the event. The event may be received from the content server or the target. One exemplary event originating from the content server is a play command for displaying a recommendation on the controller prior to a current title concluding on the target. One exemplary event originating from the target is a playback status indicator. 
     If, in step  460 , the controller receives an exit command, then the method terminates in step  490 . Otherwise, the method proceeds back to step  440 . 
     Returning to step  420 , if an appropriate playback application is not installed on a selected target, then the method proceeds to step  422 . In one embodiment, the controller transmits installation information to that target to begin downloading an appropriate playback application. The installation information may include, without limitation, a uniform resource locator, web address, IP number, or other address information for a server, such as the content server, configured to provide the playback application for download. In this embodiment, the target acts on the installation information because the target and controller are currently associated with each other. 
     Returning to step  430 , if appropriate playback application is not activated on the selected target, then the method proceeds to step  432 . In one embodiment, the controller transmits an activation credential to the target based on associated account information. The target then presents the activation credential to the content server to become activated. 
     Returning to step  450 , if an event is not received, then the method proceeds to step  460 . 
       FIG. 5  is a flow diagram of method  500 , performed by a target for playing a selected title, according to one embodiment of the present invention. Although the method steps are described in conjunction with the systems of  FIGS. 1-3 , persons skilled in the art will understand that any system configured to perform the method steps, in any order, is within the scope of the invention. 
     Method  500  begins in step  510 , where that target, such as target  114 , discovers devices within a device discovery domain, such as device discovery domain  110 . In one embodiment an SSDP-based protocol, such as UPnP, is implemented to perform discovery as discussed previously in  FIGS. 1 and 2 . In step  512 , the target associates with a controller, such as controller  112 . A unique identifier, such as a UUID or a USN, may be exchanged between the target and the controller to establish a unique association and context for interaction between the target and the controller. In step  514 , the target determines availability of a specified service application from a list of available applications on the target device. Any technically feasible technique may be implemented to maintain a list of available applications. In step  516 , the target receives a command. In one scenario, the command is received from the controller. In another scenario, the command is received from the content server. 
     If, in step  520 , the command is an install command, then the method proceeds to step  522 , where the target downloads and installs the specified service application, such as service application  232 . In one embodiment, a configuration manager, such as configuration manager  234 , within the target downloads an installation package from the content server and extracts an executable service application from the installation package and stores the service application within the target. The configuration manager then adds the service application to the list of available applications. In one embodiment, details related to specifying the service application are included in the command or in a related command. 
     In step  524 , the target transmits an association established between the target and the controller to a content server, such as content server  140 . This association enables the content server to perform mediated operations between the controller and the target, such as granting activation permission to the target based on account credentials for the controller. 
     If, in step  530 , the command is an activate command, then the method proceeds to step  532 , where the target performs an activation procedure with the content server based on association with the controller. In one embodiment, the association is based on exchanged unique identifiers. Association with the controller enables the target to use account credentials for activation with the content server. The account credentials may be associated with the controller, the target, other discovered devices within device discovery domain  110 , or any combination thereof. In one embodiment, account credentials specifically associated with the controller are used for activation of the target. 
     If, in step  540 , the command is a playback command, then the method proceeds to step  542 , where the target executes the playback command. Exemplary playback commands include specifying a particular title for playback, initiating playback, pausing playback, aborting playback, fast forwarding, and seeking based on time or content organization, such as scenes. Upon initiating execution of the playback command, the method proceeds back to step  516 . 
     If, in step  550 , an exit signal is not received, then the method proceeds to step  552 , where the target executes the command, which may be a house-keeping command, control command, activity synchronization command, or any other technically feasible command that should be executed by the target. 
     Returning to step  520 , if the command is not an install command, then the method proceeds to step  524 . 
     Returning to step  530 , if the command is not an activate command, then the method proceeds to step  540 . If, in step  540 , the command is not a playback command, then the method proceeds to step  550 . If, in step  550 , an exit signal is received, then the method terminates in step  590 . 
     One embodiment of the present invention is implemented as a program product stored on at least one computer-readable storage medium residing within the playback device  300 . In such an embodiment, the playback device  300  comprises a general purpose computing platform, such as a smart phone computing platform, or an embedded computer platform such as a set top box or “smart television.” The stored program product enables methods  400  and  500  to be implemented by the playback device  300 . In an alternative embodiment, a program product is downloaded to a memory within playback device  300 . For example, the downloaded program product may be executable instructions embedded within an Internet web site, such as content server  140 , or an on-line application store. In such an embodiment, the downloaded program product enables methods  400  and  500  to be implemented by the playback device  300 . 
     In sum, a technique for managing playback of digital content is disclosed. A controller device and a target device discover each other on a local network using a local discovery protocol. Devices that discover each other are able to associate with each other and to report their association to a content server that is then able to mediate interactions between the controller and the target. For example, the target is able to initiate installation, activation, or any combination thereof of a related service application through a server mediated download operation based on device association. Explicit association between co-located devices enables certain other server mediated operations, such as content recommendations based on blended affinity metadata for co-located users. 
     One advantage of the disclosed systems and methods is that a control device may easily manage operations of a target playback device, including activation, installation, or any combination thereof of a corresponding service application. A second advantage is that a plurality of related devices may be associated with each other and advantageously interact using server-mediated operations based on association. This is in contrast to prior art solutions with complex, manual, and inefficient management procedures between two devices. 
     While the forgoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. For example, aspects of the present invention may be implemented in hardware or software or in a combination of hardware and software. One embodiment of the invention may be implemented as a program product for use with a computer system. The program(s) of the program product define functions of the embodiments (including the methods described herein) and can be contained on a variety of computer-readable storage media. Illustrative computer-readable storage media include, but are not limited to: (i) non-writable storage media (e.g., read-only memory devices within a computer such as CD-ROM disks readable by a CD-ROM drive, flash memory, ROM chips or any type of solid-state non-volatile semiconductor memory) on which information is permanently stored; and (ii) writable storage media (e.g., floppy disks within a diskette drive or hard-disk drive or any type of solid-state random-access semiconductor memory) on which alterable information is stored. Such computer-readable storage media, when carrying computer-readable instructions that direct the functions of the present invention, are embodiments of the present invention. 
     In view of the foregoing, the scope of the present invention is determined by the claims that follow.