Video on Demand
Video on Demand (VoD) is an interactive multimedia system. The fundamental process of its working is same as that of cable television. In this, the customer has the option of selecting a movie from a large video database and can watch different programs as and when required. It seems that the video rental shop is present at home. Research is going on to improve the quality of VoD-related services. Some of the VoD-related applications are providing Video Films on Demand, Local news and Weather Forecasting, Games, music and Leisure, Education and Remote Learning Facilities, Home Shopping and Other Consumer Services, Banking, etc.
This system has three main components. These are • Video server: it stores and provides access to programs. • Data delivery network: it is the linking source for subscriber. • Set-top box: It is the interface between TV equipments and VoD services. MPEG (Motion Picture Experts Group) is a group of people who work for ISO (International Standards Organization) to generate digital video standards i. e producing sequences of images in time and to generate audio compression. Various kind of MPEG are ranked on the basis of the speed (in CD-ROM data rates) at which they deliver video to consumer devices. For example, the speed of MPEG-1 was 1.
5 Mbit/s, MPEG-2 with improved resolution deliver broadcast and HDTV quality video. Over past few years, a considerable growth in the multimedia communication has been recorded due to exponential rise in consumer demands. There is a trend in allowing customers to select films/video sequences remotely and have them streamed directly to the user per specific requirements. The multimedia industry aims at developing a database system, which enables flexible and efficient acquisition, storage, access and retrieval, and distribution and presentation of large amounts of heterogeneous media data Traditional relational database model
A relational database model (RDBMS) was proposed by Dr. E. F Codd in 1970. It is composed of several rows and columns, which are interrelated. SQL (structured query language) is used as DDL (data definition language) and DML (data manipulation language) by RDBMS. Due to introduction of SQL, users can easily migrate their database applications between database systems. Other advantages of this system is that data stored in two or more RDBMSs can be easily accessed without changing database sub-language ( SQL ), rapid data access and large storage capacity. Failure of one file affects only a single program.
Some of the examples of this model are Oracle (by Oracle Corp. ), Microsoft Access (by Microsoft), and Sybase Inc. etc. It facilitates users and application developers with processing and retrieval of large object within an SQL-based operating environment. The major disadvantages of using this system are that it cannot handle application areas like spatial databases (eg CAD), involving images and special type databases (eg complex numbers, arrays). Separate data files are created for each application, which results in data duplication, which conflicts with data integrity. RDBMSs such as the TERADATA.
RTM system are very popular but existing RDBMSs are not appropriate to handle large multimedia objects. There is no doubt that RDBMS database features and functions apply equally well to alphanumeric or multimedia data types but multimedia objects give rise to new semantics problems, and require new strategies for manipulating and moving extremely large objects. This could block RDBMS computational capacity and the I/O capability of the computer implementing the RDBMS. Therefore, in order to overcome the limitations of Relational Database model, a more advanced system has been incorporated- Object-Oriented Database model.
Object-Oriented Database Model The development of object-oriented system made it possible to represent complex objects and store binary content such as images, video and audio. It is based on object-oriented programming language. This system is composed of Graphical User Interface (GUI) component objects, which enables the manipulation of complicated data visibly, while constructing and updating facilities data on the map. It plays an important role in integrating structural and temporal aspects of different multimedia data (eg integer, real and character strings integrated with textual, visual and audio information).
It reduces the complexity required to manage multimedia information, and is used for real time applications because it can extend memory beyond the operating systems own virtual memory. Access to data is faster as compared to relational database because object retrieval can be done without a search, by following pointers. Application data model and the database data model are directly related which, results in less code, more natural data structures, and better maintainability and reusability of code. Examples of Object-Oriented databases are Object Store (www. progress. com/ real time) and Versant VDS (www.
versant. com). However, Object-oriented database management systems are unpopular as they require a large capital investment and are incompatible with existing RDBMSs. Further, maintaining two separate data repositories in a RDBMS and an OODBMS is inconsistent with the database management philosophy of maintaining a secure consistent. In addition, it lacks mathematical foundation (as found in relational model). Object-oriented models lack in standardized approach; therefore, they are hardly understandable by those designers, who are not an expert of the used, specific notation.
To avoid this problem, Object Data Management Group has proposed a standard ODMG 1. 0 (revised to ODMG 2. 0) which is composed of object model, ODL (object defining language), OQL (object query language) and other object-oriented programming language. Besides this, Object-oriented model is not widely acceptable because of scalability problems and it cannot support large-scale systems. Object Relational Database Model (ORDBMS) The main aim of launching this model was to avail the benefits of both object-oriented and relational models.
For example, getting scalability and rich data types, both in the same system. It has been developed by incorporation of the object-oriented features in the relational database model; some data are stored in tables and some as abstract data types (ADTs). The management of traditional fielded data, complex objects such as time-series and geospatial data and diverse binary media such as audio, video, images, and applets are integrated under such a system. The important features of ORDBMS are base data type extension, support complex objects, inheritance and rule systems.
For example, it gives student identity by his first name, last name, sex, major, address, father’s name, location and picture. The current examples of ORDBMS are Oracle8 (from Oracle Corporation) and Universal database (UDB, from IBM). Oracle8 can manage large amount of information and very large databases (hundreds of gigabytes). These qualities are required by traders to examine trends on stock data. The most important achievement of ORDBMSs is their massive scalability. The database market is conquered by its feature like large storage capacity, high access speed and manipulation power of object databases.
Still, there are many spheres in which ORDBMS lacks behind such as high-speed web applications. Nevertheless, the support from Data Base Management system vendors ensure that these drawbacks will be overcome and ORDBMS will become the market leader in next three years. As per the results of database market, IDC (International Data Corporation) has given the same opinion. RDBMS vs ODBMS vs ORDBMS The data model used in RDBMS is SQL2, ODBMS is ODMG-2. 0 and in ORDBMS, SQL3 is used. Object-oriented features are extensively supported by ODBMS, limited by ORDBMS and not at all by RDBMS.
Relational model does not support abstract data types and object model supports complex relationships but both the data types are supported by object relational model. The advantages of relational model is its dependence on SQL, it has quiet simple query optimization and therefore gives good performance and has good market record, those of object model is its ability to handle all types of complex applications, reusability of code and less coding but the market reputation is extremely poor. Ability to query and handle large complex applications is the advantage of object relational model, which makes it a market leader. Conclusion
Dr. Michael Stonebraker, Chief Technology Officer of Informix Software, in his paper, “Object-Relational DBMS: The Next Wave,” has categorized the DBMS applications which are: simple data without query( it corresponds to Relational DBMSs), simple data with query( corresponds to Object-Oriented DBMSs), complex data without query( corresponds to object-Relational DBMS), and complex data with query( corresponds to Universal Server, developed by Informix). Stonebraker has also predicted that applications from Relational DBMSs (simple data with query) will slowly move towards the Object-Relational DBMSs (complex data with query).
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Topic- Enhancement of Processing Efficiency in Multimedia Database Management Systems and Video Servers supported by the Use of Meta-Data Written by Dr. Dip. Inf. Harald KOSCH
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