The exponential growth of the technological advancements has resulted in high-resolution devices, such as digital cameras, scanners, monitors, and printers, which enable the capturing and displaying of multimedia data in high-density storage devices. Furthermore, more and more applications need to live with multimedia data. However, the gap between the characteristics of various media types and the application requirements has created the need to develop advanced techniques for multimedia data management and the extraction of relevant information from multimedia databases. At the heart of multimedia information systems lies the multimedia database management system. Everyone deals with multimedia at every walk of lives. We work with multimedia and are surrounded by multimedia. Due to the advancement of modern computer and information technology, multimedia systems play more and more impact on our lives.
Overview of Multimedia Database
Multimedia database is a kind of database like any other databases containing multimedia collections. Multimedia is defined as the combination of more than one media, they may be of two types–static and dynamic media. Text, graphics, and images are categorized as static media; on the other hand, objects like- animation, music, audio, speech, video are categorized as dynamic media. Graphic images may consist of cliparts, photographs, logos, and custom drawings. Sound consists of voice narration, speech, music etc. Video data encompasses sound as well as photos. To manage these data multimedia database management system is essential. Multimedia database management system can be defined as a software system that manages a collection of multimedia data and provides access to users to query and retrieve multimedia objects. Generally, multimedia database contains text, image, animation, video, audio, movie sound etc. But, all data are stored in the database in binary form.
Figure 1: Multimedia Database
A multimedia database is a collection of related multimedia data. Common multimedia data types that can be found in a multimedia database include the following:
- Graphics: drawing, sketches, and illustrations
- Images: color and black & white pictures, photographs, maps and paintings
- Animation sequences: Animated images or graphic objects
- Video: a sequence of images (frames), typically recording a real-life event and usually produced by a video recorder
- Audio: generated from an aural recording device
- Composite multimedia: a combination of two or more of the above data types
Figure 2: Types of Multimedia Database
Understanding Multimedia Database Characteristics
A multimedia database contains various data types such as text, images, graphic objects (including pictures, drawings and illustrations), animation sequences, video and audio. Following are the characteristic are shown below:
- Lack of structure: Multimedia data often are not quite structured; therefore, standard indexing and/content-based search and retrieval may not be available.
- Temporality: Different multimedia data types have different requirements. For example, some multimedia data types such as video, audio, and animation sequences have temporal requirements that have implications on their storage, manipulation and presentation, but images, video and graphics data have spatial constraints in terms of their content.
- Massive Volume: Usually, the data size of multimedia is large such as video; therefore, multimedia data often require a large storage device.
- Logistics: Non-standard media can complicate processing. For example, a multimedia database application requires using compression algorithms.
Why Multimedia Databases?
Following arguments will try to justify the requirements of multimedia database as explained below:
- Multimedia Database is capable of hand ling huge volume of multimedia objects which a general database fails to do effectively;
- Multimedia Database will help to create virtual museum;
- It will surely help to develop multimedia applications in various fields like teaching, medical sciences and libraries;
- Preserving decaying photographs, maps, films having got historical evidence or national importance;
- Using multimedia database, we can develop the excellent teaching packages;
- Helps multi-user operations.
Designing of Multimedia Databases
Many inherent characteristics of multimedia data have direct and indirect impacts on the design of MMDBs. These include: the huge size of MMDBs, temporal nature, richness of content, complexity of representation and subjective interpretation. The major challenges in designing multimedia databases arise from several requirements they need to satisfy such as the following:
- Manage different types of input, output, and storage devices. Data input can be from a variety of devices such as scanners, digital camera for images, microphone, MIDI devices for audio, video cameras. Typical output devices are high-resolution monitors for images and video, and speakers for audio.
- Handle a variety of data compression and storage formats. The data encoding has a variety of formats even within a single application. For instance, in medical applications, the MRI images of brain has lossless or very stringent quality of lossy coding technique, while the X-ray images of bones can be less stringent. Also, the radiological image data, the ECG data, other patient data, etc. have widely varying formats.
- Support different computing platforms and operating systems. Different users operate computers and devices suited to their needs and tastes. But they need the same kind of user-level view of the database.
- Integrate different data models. Some data such as numeric and textual data are best handled using a relational database model, while some others such as video documents are better handled using an object-oriented database model. So these two models should coexist together in MMDBs.
- Offer a variety of user-friendly query systems suited to different kinds of media. From a user point of view, easy-to-use queries and fast and accurate retrieval of information is highly desirable. The query for the same item can be in different forms. For example, a portion of interest in a video can be queried by using either
- A few sample video frames as an example,
- A clip of the corresponding audio track or
- A textual description using keywords.
The recent growth in using multimedia data in applications has been phenomenal. Multimedia databases are essential for efficient management and effective use of huge amounts of data. The diversity of applications using multimedia data, the rapidly changing technology, and the inherent complexities in the semantic representation, interpretation and comparison for similarity pose many challenges. MMDBs are still in their infancy. Today’s MMDBs are closely bound to narrow application areas. The experiences acquired from developing and using novel multimedia applications will help advance the multimedia database technology.
Challenges of Multimedia Database
There are still many challenges to multimedia databases, some of which are:
- Modelling –Working in this area can improve database versus information retrieval techniques thus, documents constitute a specialized area and deserve special consideration.
- Design –The conceptual, logical and physical design of multimedia databases has not yet been addressed fully as performance and tuning issues at each level are far more complex as they consist of a variety of formats like JPEG, GIF, PNG, MPEG which is not easy to convert from one form to another.
- Storage –Storage of multimedia database on any standard disk presents the problem of representation, compression, mapping to device hierarchies, archiving and buffering during input-output operation. In DBMS, a “BLOB” (Binary Large Object) facility allows untyped bitmaps to be stored and retrieved.
- Performance –For an application involving video playback or audio-video synchronization, physical limitations dominate. The use of parallel processing may alleviate some problems but such techniques are not yet fully developed. Apart from this multimedia database consume a lot of processing time as well as bandwidth.
- Queries and retrieval –For multimedia data like images, video, audio accessing data through query opens up many issues like efficient query formulation, query execution and optimization which need to be worked upon.
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 Samir Kumar Jalal, “Multimedia Database: Content and Structure”, Workshop on Multimedia and Internet Technologies 26th to 28th February, 2001 DRTC, Bangalore
 Chien Yu and Teri Brandenburg, “Multimedia Database Applications: Issues And Concerns For Classroom Teaching”, The International Journal of Multimedia & Its Applications (IJMA) Vol.3, No.1, February 2011
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