DISTRIBUTED MULTIMEDIA SYSTEMS

Transcription

1 Components of distributed multimedia system DISTRIBUTED MULTIMEDIA SYSTEMS Application software Container object store Image and still video store Audio and component store Object directory service agent Component service agent User interface service agent. Networks. Application software: It performs, Object retrieval Object selection Object component display User initiated display Object display management and editing Document store: It is essential for applications that require storage of large volumes of documents. Image and still video store: Image and still video store is the database system optimized for storage of images. Audio and full motion video store: Audio and video objects are isochoronous and they must be played back at a constant rate. Object directory service agent: Directory service Object assignment Object status management Directory service domains Directory service server elements Network access Component service agent: Each multimedia components provides a service to the multimedia user works station and the characteristics. User interface service agent: It resides on each user work station and provides direct services to application software for management of multimedia object display windows.

2 DISTRIBUTED CLIENT SERVER OPERATION: Clients in distributed work group computing : Request specific textual data Request specific multimedia objects embedded or linked in retrieved container objects. Require activation of rendering server application Create and store multimedia object store on servers Request directory information on location of object on servers. Server in distributed work group computing : Provide storage for a variety of object classes. Transfer objects on demand to clients Provide hierarchical storage for moving unused objects to near line or offline media. Database operation Search Browse Retrieve Create and store Update middleware in distributed work group computing: middleware is used to link back end database server to front end clients in highly flexible and loosely connected networks. MULTIMEDIA OBJECT SERVERS: Types: Data processing server Document database server Document image and still video servers Audio and voice mail servers Full motion video servers Mass storage for multimedia systems: Battery powered RAM Non volatile flash memory Rotating magnetic disk drives Rotating optical disk drives Magnetic disk: Magnetic disk have long stored served as the medium of database storage. Roating magnetic disk and optical storage is used for storage of large volume information objects.

3 RAID: Redundant Array of Inexpensive Disks Levels, Level 0-Disk striping Level 1-Disk mirroring Level 2-bit interleaving of data Level 3-byte interleaving Level 4-sector interleaving Level 5-block interleaving Write once Read many: It can write only once Used in optical disk libraries Slower than magnetic drives. Rewritable optical disk: It is used as primary or secondary media for storage of large objects. Optical disk libraries: WORM disk and rewritable disk can be used in optical disk libraries to achieve very high volumes of near line storage. MULTI SERVER NETWORK TOPOLOGIES: Traditional LAN(Extended or token ring) Extended LAN(hubs,bridges and routers) High speed LAN(ATM and FDDI II) WAN(ISDN). DISTRIBUTED MULMEDIA DATABASES: Multimedia database support variety of group ware applications and it must be able to integrate and access and use information objects stored in external databases. Database organization for multimedia application: Data Independence: Storage design in independent of application Explicit data definition are independent of application Users need not know data formats. Integrity assurance is independent Recovery is independent

4 Common distributed database: Uniform distributed access by the client Single point for recovery of each database Convenient data reorganization Expandability Tenability and creation of object classes Multiple data servers When large no. of users need to access same database, then bottleneck arise and this problem is solved by multiple data server that have the copies of same database. Transaction management for multimedia systems: It is the sequence of events that starts when the user makes a request to create, render,edit or print a document. Transaction Is managed by the server that provides the storage for the data Managing hypermedia records as objects: Hypermedia documents or records are complex objects that contain multimedia information objects within them. Multimedia objects need not be embedded always, instead a reference can be embedded and the multimedia object can reside separately in its own databases. Object linking and embedding : Linking object contains only the data needed to represent the object and a pointer to an actual file that contains original data. Embedded object contains both presentation and native data. Embedded object has the object itself along with the information needed to edit the object. MANAGING DISTRIBUTED OBJECTS: The issue for distributed objects is how the objects are located,retrieval, object replication, archival and load balancing. Inter process communication: Object replication Object distribution Object recompilations Object management. Object server architecture: The key elements are, Multimedia applications Common object management API

5 Object request broker Object name server Object directory manager Object server Object manager Network manager Object data store. Object identification: Every multimedia object require a unique identity that is not compromised during the life of the object. Object identification should be treated as identical objects for the duration of time they are synchronized. Object identity: The property of object that are distinguishes from all other objects is called object identity. Identification method: Identification of object in persistent state is differ from non persistent state. An address based or variable name based identification method is implemented through various pointers to variables. When object is created its object ID must be unique across all host in n/w. Identities of copied object and merged object: Copying an object for replication purpose implies no change in the object or its object. Objects are copied for maintaining the replicated copies of the same project. Object identity in n/w: Object must be identified uniquely across the n/w which is used for maintaining database integrity. Object revision management: The new version is created not from the last version but from an older version. Optimizing n/w location of object: Multimedia objects for different classes reside on one server or multiple server. Object directory services: It is the name server for all multimedia objects LAN. The object directory list all multimedia objects and every server on which multimedia object is resident at any give time. Multimedia object retrieval:

6 Multimedia object manager performs the function of managing all request from the multimedia applications for retrieving the existing multimedia objects. ORB: Object request broker is used under CORBA. DATABASE REPLICATION TECHNIQUES: Three issues are, Sharing of all objects by all users on the n/w. Providing acceptable performance to all users Allowing all users to update the database. Types of database replication: Round robin replication Manual Scheduled Immediate Replication on demand Predictive Replicating references No replication

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