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TRANSFER FILE FORMAT AND SYSTEM AND METHOD FOR DISTRIBUTING MEDIA CONTENT
 This application claims priority to co-pending U.S. Provisional Patent Application Serial No. 60/272,944, filed Mar. 2, 2001, with the United States Patent and Trademark Office, which is incorporated herein by reference.
FIELD OF INVENTION
 The present invention relates broadly to system, method, signal, and computer pro gram for delivery of streaming media assets over a computer network having a client server computer architecture. Specifically, the present invention relates to a file format and system that accommodates point-to-point delivery as well as point-to-multipoint delivery of streaming media assets.
 Multimedia assets such as video, audio and the other forms of content can be encoded and streamed in many different ways. Generally, streaming media assets are delivered across communication networks such as the Internet according to point-to-point or point-to-multipoint schemes. In a point-to-point distribution model, a server that administers the media assets receives a request from a client for delivery of the media asset, negotiates delivery details such as delivery time, bit rate, and other parameters that specify how delivery is to be performed for a single client. In point-to-multipoint distribution, the server streams the media asset to multiple clients that utilize similar delivery parameters so that all clients receive the media asset in a substantially simultaneous manner. However, the negotiation between the server and each of the multiple clients is still required in the point-to-multipoint distribution model, as each client must be aware of what resources such as bandwidth, processing speed and memory size must be reserved or allocated for the incoming media asset: For instances where the number of clients desiring simultaneous delivery is high, this negotiation overhead is quite high in terms of time. Additionally, there exists no single format for a file containing a media asset. This means that, depending on client demand, multiple servers are required to handle both point-to-point and point-to-multipoint distribution methods. Maintaining multiple, dedicated servers incur substantially higher operating costs and reduced profits for commercial servers.
 Thus, there is a need for a file format that can reduce the amount of negotiation required between clients and server as well as more efficient system for performing delivery of media assets.
 The present invention overcomes the problems discussed above by providing a file format and system for efficient streaming of media assets from a server to one or more clients. In one aspect, the present invention provides a transfer file format that is suitable for point-to-point or point-to-multipoint distribution of transfer files between a server and one or more clients across a computer network, wherein the transfer file includes a signature indicating the format of the file, a header containing information related to
various portions of the transfer file, asset metadata describing media content, media content that is capable of being displayed to a user, and user metadata that describes the media content and is capable of being displayed to the user. The media content may include a video object accompanied by one or more static images such as GIF images, html pages, and the like. By organizing the file format to include the asset metadata that is used by a media player program on the client side, the time consuming negotiation between client and server is eliminated and a more efficient transmission of media content is implemented.
 In another aspect, the present invention provides a server computer system and method that is capable of connection to an asset metadata database containing the asset metadata, a file system containing the media content, and a user metadata database containing the user metadata, wherein the server includes an extractor module that constructs the transfer file by receiving a request for delivery in the form of an asset identifier, writing the asset metadata associated with the asset identifier from the asset metadata database into the transfer file, writing the media content associated with the asset identifier into the transfer file, and writing the user metadata associated with the asset identifier into the transfer file. Once these portions of the file are constructed, the extractor module inserts a header that includes information about the portions into the transfer file and the transfer file is sent across the computer network to one or more clients.
 In another aspect, the present invention provides a client computer system and method for receiving transfer files as described above, wherein the client is capable of connection to a local asset metadata database, a local file system, and a local user metadata database. The client includes aparser module for processing the transfer file and allocating resources as required for the various parts of the transfer file. An installer module is included for installing the asset metadata in the local asset metadata database, the media content in the local file system, and the user metadata in the local user metadata database.
 In another aspect, the invention provides an electronic signal, generally a digital electronic signal, encoding the transfer file or parts thereof, either alone or in addition to media content.
 Other aspects of the invention will become apparent from reading the following detailed description and related drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
 FIG. 1 illustrates in block diagram form the client server architecture utilized in embodiments of the present invention.
 FIG. 2 illustrates in block diagram form an embodiment of the file format of the transfer file of the present invention.
 FIG. 3 illustrates in flow chart form an embodiment of the logical sequence of steps executed by the extractor module running on the server to assemble a media asset into a transfer file.
 FIG. 4 illustrates in flow chart form an embodiment the logical sequence of steps executed by the parser
module running on the client to receive the transfer file and allocate resources for the various parts of the transfer file.
 FIG. 5 illustrates in flow chart form an embodiment of the logical sequence of steps executed by the installer module running on the client to write the various parts of the transfer file to facilities used by the client.
 FIG. 6 illustrates in block diagram form an embodiment of the components included in a computer used by either the clients or the server.
 The present invention provides a file format and data structure that can be used for either point-to-point or point-to-multipoint distribution of media assets. Transfer of metadata associated with the media assets is supported. User defined metadata associated with video objects can be transferred using this file format, as well as one or more content and auxiliary files. The file format of the present invention supports transfer of necessary information for network-backed-assets. Because the file format is textbased, the file format allows pluggability of metadata in different formats such as plain text, XML, and the like.
 Directing attention to FIG. 1, the present invention utilizes a client-server computer architecture 100 communicating over a network, such as a large public computer network such as the Internet. Server 102 is responsible for distributing streaming media assets such as video, audio, static images, graphics, or a combination thereof to clients 104-1, 104-2, . . . , 104-m, where n is the number of clients requiring streaming media assets, via public computer network 106. Media assets are streamed by transmitting a sequence of packets from the server 102 to the client 104. Once the client has the media asset it can later serve the media asset to other media players. These media players may then decrypt, decode, or otherwise process the media asset (or allow the player to process the media asset after receipt) to play or render the media asset on a suitable device using a media player program that decompresses, decodes, and performs any necessary processing on the sequence of packets received from the server 102 to present aural or visual presentation contained in the packets to a user. Examples of streaming media assets include movies, newscasts, music, graphics, animation, slide presentations, and the like, all of which are capable of being presented in a serial fashion to a human user. Server 102 may be a source of the streaming media assets. Optionally, one or more third party content providers such as content provider 108 may be in communication with server 102, and provide the streaming media assets to the server 102 over network 106. Media assets are typically stored in files in the memory of the server 102 and distributed to clients on demand or according to a schedule.
 Server 102 includes an extractor module 110 which includes instructions executed to assemble a media asset into a file format that is easily transferred over computer network 106 to clients 104 in a multicast transmission model. In order to assemble the media asset into a transfer file, the extractor module 110 reads data from asset metadata database 112, user metadata database 114, and asset file system 116. Client 104 includes a media player program 117 such as Media Base, available from Kasenna, Inc. of Mountain View, Calif., which is capable of playing out a media asset
in a manner which is observable by a user. For example, the media player program 117 can display media assets having an MPEG format on a computer monitor. Client 104 incorporates a parser module 118 which reads the transfer file containing the media asset and associated data and installer module 120 installs various portions of the transfer file into local asset metadata database 122, user metadata database 123, and files system 126.
 FIG. 2 illustrates the structure of an embodiment of the file format of transfer file 130 of the present invention. Transfer file 130 includes a signature 132, which identifies to a client that the transfer file contains a media asset organized according to file format of transfer file 130. Header 134 follows signature 132, and defines such information as the format(s) of the media content 138, such as MPEG, PGM, RMTP, and the like, the size, duration and bit rate of the media content 138, the size of the asset metadata 136 and user metadata 140, and other information. Asset metadata 136 follows header 134, and may include such information as the name or ID of the source of the media content 138, the creation time and/or modification time of the media content, which is useful if multiple versions of the media asset exist, keywords such as metatags, number of plays for the media content 138, fast forward or reverse file size, a unique media asset identifier, and other information. Asset metadata 136 is stored on the server side in asset metadata database 112. Once the transfer file 130 is received by the client 104, the asset metadata 136 is stored in asset metadata database 122. Following the asset metadata 136 is the media content 138. The media content 138 includes the media asset to be played by the user, as well as any additional or enhanced content, such as alternative views from multiple camera angles used for sporting events and the like. Media content 138 can thus include multiple files, such that for example, an MPEG file is accompanied by JPEG files, GIF images, html pages, and the like. Media content 138 is stored on the server side in asset file system 116. Once the transfer file 130 is received by the client 104, the media content 138 is stored in file system 126. Following the media content 138 is user metadata 140, which may contain information related to media content 138 that can be displayed to a user. For example, if the media asset is a movie, user metadata 140 can optionally include one or more of a director name, actor names, ratings information, duration of the movie, plot synopsis, and the like. User metadata 140 is stored on the server side in user metadata database 114. Once the transfer file 130 is received by the client 104, the user metadata is stored in user metadata database 124.
 An example of header 134 follows. The header 134 consists of a list of name-value pairs separated by newline characters. The following name-value pairs for the header are exemplary and others may be defined. Note that the value part follows the colon ":" separator. The type of the value field is specified below. A string representation of the value is used in an embodiment. In cases where multiple forward slash ("/")-seParated fields are specified, the various fields represent the various possible values for that item. Of course, other field differentiation than ":" or "/" may alternatively be used. The values of these fields are defined in a file, such as in the mbase/lib/mbtransferff/nvpair_defs.h header file in one embodiment. An exemplary embodiment of this file is shown in Table I. An example of the asset metadata 136 is shown in Table II.