Sharif Digital Repository

The advent of various real-time multimedia applications in high-speed networks creates a need for quality of service (QoS) based multicast routing. Two important QoS constraints are the bandwidth constraint and the end-to-end delay constraint. The QoS based multicast routing problem is a known NP-complete problem that depends on (1) bounded end-to-end delay and link bandwidth along the paths from the source to each destination, and (2) minimum cost of the multicast tree. In this paper, we presents novel centralized algorithms to solve the bandwidth-delay-constrained least-cost multicast routing problem based on the harmony search (HS) algorithm. Our first algorithm uses modified Prüfer... 

This paper presents a shape prediction algorithm in a noisy video sequence based on pixel representation in the undecimated wavelet domain. In our algorithm for tracking of user-defined shapes in a noisy sequence of images, the amplitude of coefficients in the best basis tree expansion of the undecimated wavelet packet transform are used as feature vectors (FVs). FVs robustness against noise has been achieved through inherent denoising and edge component separation in the best basis selection algorithm. The algorithm uses these FVs to track the pixels of small square blocks located at the vicinity of the object boundary. Searching for the best-matched block has been performed using... 

Nowadays, the use of multimedia services such as video sequences is constantly growing. Unfortunately, due to the lack of reliable communication channels and video data sensitivity to transmission errors, the quality of received video might decrease. Therefore, decoder error concealment methods have been developed to retrieve the damaged or lost data. In this paper, a novel temporal error concealment (TEC) algorithm based on moment invariants is presented. It includes three main stages of: designation of candidate motion vectors (MVs) set, adaptive determination of block size in the current and reference frames for feature extraction, and error function calculation based on moment... 

In some websites it is necessary to tell apart human users from computer programs which is known as CAPTCHA (Completely Automated Public Turing test to tell Computers and Human Apart). CAPTCHA methods are mainly based on the weak points of OCR systems while using them are undesirable to human users. In this paper a method has been presented for telling the human users and computer softwares apart on the basis of choice of an object shown on the screen. In this method some objects are chosen randomly and the pictures about these topics are downloaded from Internet. Then after effecting some changes such as rotating, all of the pictures are shown on the screen. Then we ask the user to choose a... 

The IP Multimedia Subsystem is a basis for a significant new architecture which offers network operators the opportunity to expand their services, integrating voice and multimedia communications and delivering them into new environments with new purposes. The IMS is an overlay network on top of IP that uses SIP as the primary signaling mechanism. Using IMS bears several new security challenges. In this paper we provide an overview of IMS and its architecture. Then we represent a secure model to overcome some of IMS security challenges. ©2009 IEEE  

Multimedia content is massively generated from various applications and devices, and processed in cloud data centers. Multimedia service providers prefer that their data are processed in data centers close to users in order to offer them high performance and reliable multimedia services that meet the requirements specified in the Service Level of Agreement (SLA). This requires transferring huge data sets of video streams, games content, images etc. across geographically distributed cloud data centers using underutilized bandwidth in backbone transport networks. As the amount of multimedia content increases, the demand to transfer big data sets across data centers increases as well. As such,... 

A Comprehensive speech database is one of the important tools for developing speech recognition systems; these tools are necessary for telephony recognition, too. Although adequate databases for direct speech recognizers exist, there is not an appropriate database for telephony speech recognizers. Most methods suggested for solving this problem are based on building new databases which tends to consume much time and many resources; or they used a filter which simulates circuit switch behavior to transform direct databases to telephony ones, in this case resulted databases have many differences with real telephony databases. In this paper we introduce a framework for creating telephony speech...