Sharif Digital Repository

Sports video analysis and camera calibration are important applications which rely on accurate homography computation as a challenging task. Homography refinement is an important step in the task of accurate homography computation and homography tracking. Also, in certain applications (such as homography tracking) the process speed is of great importance. A robust and fast method for accurate refinement of highly inaccurate homographies in soccer video frames is proposed in this paper. To achieve that goal, a new homography model fitting method named the point-line (PL) method is proposed. It uses point-line correspondences to compute the homography, rather than point correspondences or line... 

This paper presents a novel video encoding method for cooperative Educational Dissemination Systems. Taking into consideration the inherent characteristics of distance learning video streams, existing a few moving objects in the scene and objects having slow motions, we propose a novel content-based video encoding method which is very efficient on low bandwidth channels. In the encoding process, we apply a background subtraction algorithm for motion segmentation with a novel statistical background modeling. In each frame, the moving objects are extrapolated with rectangular bounding boxes which are the only data send over the low bandwidth channel. In the decoding process, we propose a new... 

A video watermarking scheme is proposed in this paper using the concept of the secret sharing scheme. The owner's mark is split into twin shares, where the shares are inserted into the video frames in the spatial domain in a simple manner. The detection algorithm uses a linear function applied to the twin shares to reconstruct the secret. This makes the watermarked video sequence robust against pirate attacks, such as frame averaging and frame swapping. Due to the compatibility of the exploited secret sharing scheme to geometrical distortions, the watermarking system is also robust to this kind of processing schemes. On account of insertion of various marks into different frames, which are... 

The hidden, real-time sending and display of information, esp. in public places, has since long received attention and faced many challenges. Therefore, different methods have been proposed so far for hiding information in different cover media. In this paper I propose a new method for the real-time hiding of information without need to any storage cover media. This method is based on the real-time hiding of information in output screens of the instrument (such as screens shown by the monitor). This method of steganography is very similar to the two discussions of image steganography and video steganography. The idea suggested in this paper was simulated on a PC computer by using the Pascal... 

Video transcoding comprises the necessary operations for the conversion of a compressed video stream from one syntax to another one for inter-network communications, without the need of any further decoding and re-encoding process. The two most recent and popular standard video coders are H.263 and H.264. In this paper, we present tools to enable low complexity intra transcoding from H.263 to H.264 using a novel fast intra prediction mode decision algorithm that does not require extra computation. It is shown that due to basic similarities of H.263 and H.264 it is possible to reuse predictor side information, so this side information is used to simplify the mode and direction decision for... 

In this paper we propose a novel approach to insertion of watermark in the video sequences. The proposed scheme is based on visual cryptography and performs temporal scrambling for watermark embedding. Watermark, which may be a visible logo, is frequently split and inserted into video frames. Watermark detection can be verified by the human eye. Inserted watermark is expected to resist collusion attack, which is a major concern in video watermarking. Experimental results show that the proposed method provides a high resilience against some non-hostile video processing schemes, such as geometrical distortions. © 2006 IEEE  

In this paper, a new dynamic proxy solution based on overlay multicasting network for layered video streaming is presented. In our proposed approach, all clients in an Internet service provider network interested in receiving a video stream, provided by a media server in the Internet, organize themselves into an overlay tree. The root of the overlay tree acts as a proxy and receives video stream from original server and distributes it in the local overlay tree. In addition to introducing a new architecture, our main contribution in this paper is proposing a number of distributed protocols for construction and improvement of local overlay tree in video streaming applications. The experimental... 

Nowadays, deployment of peer-to-peer video streaming systems over wireless mesh networks has attained raising popularity among large number of users around the world. In this paper, we present an efficient peer-to-peer live video streaming architecture over multi-hop wireless mesh networks. In our proposed architecture, we take the physical topology of network into account and based on a distributed distributed locality-aware neighbor selection algorithm in the overlay construction phase, we generate an efficient mesh-based overlay on top of wireless mesh networks. In locality-aware neighbor selection algorithm, instead of choosing randomly, peers find their best neighbors based on their... 

Global motion estimation (GME) is an important technique in image and video processing. Whereas the direct global motion estimation techniques boast reasonable precision they tend to suffer from high computational complexity. As with indirect methods, though presenting lower computational complexity they mostly exhibit lower accuracy than their direct counterparts. In this paper, the authors introduce a robust algorithm for GME with near identical accuracy and almost 50-times faster than MPEG-4 verification model (VM). This approach entails two stages in which, first, motion vector of sampled block is employed to obtain initial GME then Levenberg-Marquardt algorithm is applied to the... 

In soccer matches, 3D reconstruction is a main part of many applications including free-viewpoint broadcasting, match analysis, augmented reality, and refereeing examination. The main challenge of 3D reconstruction in soccer scenes is the human body reconstruction. Although 3D reconstruction methods have been improved to a high extent in controlled condition, still there are lots of uncovered issues in outdoor scene reconstructions with uncontrolled conditions. In this paper, a view-dependent depth optimization method is presented which addresses two of these issues in soccer scenes. These issues include inaccurate camera calibrations and limited number of input cameras. This method will... 

Reciprocal interaction and facial expression are some of the most interesting topics in the fields of social and cognitive robotics. On the other hand, children with autism show a particular interest toward robots, and facial expression recognition can improve these children’s social interaction abilities in real life. In this research, a robotic platform has been developed for reciprocal interaction consisting of two main phases, namely as Non-structured and Structured interaction modes. In the Non-structured interaction mode, a vision system recognizes the facial expressions of the user through a fuzzy clustering method. The interaction decision-making unit is combined with a fuzzy finite... 

In this paper, we propose a new peer-to-peer (P2P) video streaming protocol which presents an implementation of network coding with a new caching mechanism. It employs a push-pull mechanism for sending the video chunks between peers. More specifically, this push-pull mechanism gives priority to the video chunks according to their video layers. The video base layer is transmitted through a pushing mechanism while the enhancement layers employ a pulling mechanism. Moreover, in the network coding algorithm of this protocol, we introduce a caching mechanism to improve the network's performance as well as the video streaming quality. The comprehensive simulations show that the proposed protocol... 

Rapidly improving video-editing software tools and algorithms have made video content manipulation and modification feasible even by inexpert users. Detecting video tampering and recovering the original content of the tampered videos is, thus, a major need in many applications. Although detection and localization of the tampering in certain types of video editing have successfully been addressed in the literature, attempts for recovering the tampered videos are bound to methods using watermarks. In this paper, a scheme for the reconstruction of the tampered video through watermarking is proposed. The watermark payload, which consists of highly compressed versions of keyframes of the video... 

This paper presents a novel method for cooperative educational dissemination systems. Taking into consideration the inherent characteristics of distance learning video streams (existence of a few slow moving objects in a classroom), we have proposed a novel content-based video coding method that is very efficient at low bitrate channels. On the encoding side, we have applied a background subtraction algorithm for motion segmentation using a novel statistical background modeling approach. At each frame, the moving objects are extrapolated with a rectangular model and tracked frame by frame (which forms the only data needed to be sent over the channel). On the decoding side, we have used a new... 

Motion patterns in traffic video can be directly exploited to generate high-level descriptions of video content, which can be used for rule mining and abnormal event detection. The most recent and successful unsupervised methods for complex traffic scene analysis are based on topic models. In this paper, a topic related sparse topical coding framework is proposed for more effectively discovering motion patterns in traffic videos. © 2001-2011 IEEE  

This paper aims to present a novel accurate moving object detection method based on the conditional random field (CRF) for high efficiency video coding/H.265 compressed domain video sequences. For each block, the number of consumed bits, motion vectors (MVs), and partitioning modes for a given block is extracted from the compressed bitstream. After removing outlier MVs, compensating MVs are assigned to the I-blocks based on their neighboring blocks. The information, such as MV, partitioning mode, and bit consumption, is used in the potential functions of a CRF model which is updated for every frame to detect the objects. Then, a number of standard test video sequences are used to verify the... 

Recovering low-rank and sparse components from missing observations is an essential problem in various fields. In this paper, we have proposed a method to address the missing low-rank and sparse decomposition problem. We have used the smoothed nuclear norm and the L1 norm to impose the low-rankness and sparsity constraints on the components, respectively. Furthermore, we have suggested a linear modeling for the corrupted observations. The problem has been solved with the aid of alternating minimization. Moreover, some simplifications have been applied to the relations to reduce the computational complexity, which makes the algorithm suitable for large-scale problems. To evaluate the proposed... 

Long Reed-Solomon codes over the prime field GF(216 + 1) are proposed as a low overhead channel code for reliable transmission of video over noisy and lossy channels. The added redundancy is near optimal from the information theoretic point of view contrary to the conventionally used intra-coding and sync (marker) insertion in video transmission that are not justified theoretically. Compared to known source-channel coding methods, we have achieved the quality of the output of source coder by providing nearly error free transmission. (By nearly error free we mean an arbitrarily small error probability.) The price paid for such remarkable video quality improvement and relatively low complexity...