Future Multimedia Databases and Research Directions

Distributed Multimedia Databases will be a trend for future information repository. With the growing popularity of the Internet and the improvement of its bandwidth, the accessibility, diversity, mobility, and scalability of multimedia information retrieval will accelerate information exchange in our global society. Previous chapters presented in this book cover most of the recent issues in distributed multimedia systems. This final chapter points out some research issues and challenges of the underlying new technologies.

Hiding Images Using Dynamic Bit-Replacement and Human Visual System

A simple image hiding scheme in spatial domain is proposed in this chapter. The main idea is to utilize a threshold mechanism to embed as much information of the secret image into the cover image as possible. The changing of the cover image is hard to be discovered by the human eyes because the threshold mechanism is setup especially to fit the human visual system. The experimental results show that the human visual system has improved the quality in terms of perceptibility. On the hiding capacity issue, the proposed method has capability to embed two times the size of the secret image of previous work. A partial encryption strategy is used for the security of the secret image. In addition, a two-dimensional permutation function, torus automorphism, is also introduced in this chapter.

Multimedia and Multi-Stream Synchronization

Synchronization is an important aspect of the design and implementation of distributed multimedia database systems. In this chapter, we first examine the models that have been proposed in the literature to specify multimedia and multi-stream synchronization and the methods to implement synchronization mechanisms in distributed multimedia database systems. Their strengths and limitations have been compared, and the issues about time uncertainty and interactivity in multimedia and multi-stream synchronization specification and implementation are discussed. Moreover, we use an example to show how to incorporate a synchronization agent into a distributed multimedia database system. Finally, we discuss the trend of future research and development of this topic.

Watermarking on Compressed/Uncompressed Video Using Communications with Side Information Mechanism

Digital watermarking has been proposed as very useful technology in the protection of digital data such as image, audio, video, formatted documents (PDF or PS), and 3D objects. In the literature, most of the existing watermarking approaches are conducted on images. However, video is even more useful and should be protected with higher priority. In particular, video sequences usually contain rich properties that images do not have. On the other hand, the types of attacks applied on a video are much different from those applied on an image. In this chapter, we will focus ourselves specifically on video watermarking. The content of this chapter is divided into two parts. In the first part, the existing video watermarking techniques are briefly reviewed. We have pointed out their advantages and disadvantages to realize what can be done about video watermarking. In the second part, we propose a compressed domain video watermarking scheme for copyright protection. For the sake of real-time video watermark detection, our method is directly conducted in the MPEG-2 bitstream. More specifically, watermarks are inserted into the VLC domain. We shall discuss how to select proper data in a video bitstream to embed watermarks while preserving perceptual fidelity. In addition, video watermarks are embedded by a new proposed watermarking technique, which is based on the concept of communications with side information. The power of our method is reflected by its robust capability against attacks. Future work will also be pointed out to further improve the current scheme

Broadcasting Approaches for VOD Services

A VoD system is typically implemented by a client-server architecture supported by certain transport networks such as telecom, CATV, or satellite networks. The simplest scheme is to dedicate a channel to each client. Many VCR-like functions may be provided (e.g., forward, rewind, pause, search, etc.). Since video is an isochronous medium, the video server has to reserve a sufficient amount of network bandwidth and I/O bandwidth for each video stream before committing to a client’s request. Apparently, such systems may easily run out of channels because the growth of the number of channels can never keep up with the growth of the number of clients. To solve this problem, many schemes have been proposed to resolve the bandwidth problem. In this chapter, we review two kinds of broadcasting schemes. The first one is the batching scheme, in which a set of viewers arriving close in time will be collected and grouped together. Then the video server will serve them altogether with one channel. The second one is the periodic broadcasting approach. The server uses multiple dedicated channels to cooperatively broadcast one video. Each channel is responsible for broadcasting some portion of the video. Each client follows some reception rule to grab data from appropriate channels so as to play the whole video continuously. The server’s broadcasting activity is independent of the arrivals of requests. Such an approach is more appropriate for popular or “hot” videos that may interest many viewers during a certain period of time.

Distributed Multimedia Databases

Distributed Multimedia Database involves network technology, distributed control, security, and multimedia computing. This chapter discusses fundamental concepts and introduces issues of image database and digital libraries, video-on-demand systems, multimedia synchronization, as well as some case studies of distributed multimedia database systems. Requirements of multimedia database management systems and their functions are also presented.

Organizing Multimedia Objects Using a Class Algebra Database

This chapter considers the question of how to locate appropriate multimedia objects. The traditional use of Web search engines is limited by the fact that there are as of yet no standard XML tags describing the many various types of multimedia objects. The users would much prefer to choose from menus, especially from a classification hierarchy where subclasses are all listed. Traditional SQL relational databases are generally not flexible enough to permit dynamic addition of attribute/value pairs to describe these multimedia objects, and to display the resulting schema. The solution suggested in this chapter is the sharing of class and binary relation definitions, including the binary superclass/subclass relation of the IS-A classification hierarchy of object-oriented technology. This object-oriented database implementation is based on class algebra. Similar users can see each other’s objects, classes, and relations, and add their own objects into appropriate places in both the class hierarchy and the binary relations. The binary relations look like subdirectories, and the available binary relations and methods can be chosen from a menu. The distributed database system, therefore, looks like a typical network operating system, and it is expected that average users may be able to make database queries and updates without any need of programmers.

A Multimedia Database Supports Internet-Based English Learning

This work presents a novel English distance learning system that was developed through multimedia database and Internet technologies called English Multimedia Corpus. The system includes English articles, dialogs, and videos. A student can study English writing and reading as well as view Web browser listings to connect the Corpus server. In the system, semantic query and “Link grammar” are applied to construct the English Multimedia Corpus system. Furthermore, it promotes the query level from keyword-base and content-based query to a semantic level. The main function of this system is to query the English sentence pattern through keywords from the English Multimedia Corpus. The other function is to detect grammatical errors in written English. Thus, the system not only teaches English grammar, but also, due to its database, allows teachers to understand the most frequent mistakes.

Embedding Robust Gray-Level Watermark in an Image Using Discrete Cosine Transformation

Digital watermarking is an effective technique to protect the intellectual property rights of digital images. In general, a gray-level image can provide more perceptual information; moreover, the size of each pixel in the gray-level image is bigger. Commonly, gray-level digital watermarks are more robust. In this chapter, the proposed watermarking scheme adopts a gray-level image as the watermark. In addition, discrete cosine transformation (DCT) technique and quantization method are applied to strengthen the robustness of the watermarking system. Both original image and digital watermark, processed by DCT transformation, can build a quantization table to reduce the information size of the digital watermark. After quantized watermark is embedded into the middle frequency bands of the transformed original image, the quality of the watermarked image is always visually acceptable because of the effectiveness of the quantization technique. The experimental results show that the embedded watermark can resist image cropping, JPEG lossy compression, and destructive processes such as image blurring and sharpening.

Video Database Techniques and Video-on-Demand

Generally, a large-scale video server is composed of numerous disk striping groups. The striping policies employed by each disk striping group largely determine the performance of a video server. For storage and transmission efficiency, video data are usually compressed using variable-bit-rate (VBR) encoding algorithms, such as JPEG and MPEG. The amount of data consumed by a VBR video stream varies with time. This property, when coupled with striping, unfortunately, results in load imbalance across disks, degrading the overall server performance significantly. This chapter focuses on VBR video striping. It presents two state-of-the-art VBR striping schemes proposed in the literature: one is designed for homogeneous disks and the other is designed for heterogeneous disks. To gain insights into VBR striping, this chapter also develops performance models for the two striping policies. With these performance models, system designers can predict the maximum service capacity of a server, perform online admission control for clients, and optimize the performance of a server, without performing exhaustive tests on a real-system.