KEYWORDS: Video, Internet, Video processing, Local area networks, Sun, Visual communications, Image processing, Electronic imaging, Data communications, Multimedia
There are great challenges in streaming variable-bit-rate video over wide-area networks due to the significant variation
of network conditions. The utilization of the precious bandwidth of wide-area networks is often low in such streaming
systems. In this paper, we propose a novel framework to improve the bandwidth utilization from a new perspective.
Instead of focusing on the performance of each single media stream, we aim to improve the overall bandwidth utilization
for video streaming systems. We try to exploit the unoccupied bandwidth in ongoing streams and using it to deliver
some prefetched data which can be used to facilitate future streaming. Preliminary results show that our mechanism has
great potential to improve both the overall bandwidth utilization and the caching performance of the proxy servers in the
streaming systems.
Efficient delivery of streaming media content over the Internet becomes an important area of research as such content is rapidly gaining its popularity. Many research works studied this problem based on the client-proxy-server structure and proposed various mechanisms to address this problem such as proxy caching and prefetching. While the existing techniques can improve the performance of accesses to reused media objects, they are not so effective in reducing the startup delay for first-time accessed objects. In this paper, we try to address this issue by proposing a more aggressive prefetching scheme to reduce the startup delay of first-time accesses. In our proposed scheme, proxy servers aggressively prefetch media objects before they are requested. We make use of servers' knowledge about access patterns to ensure the accuracy of prefetching, and we try to minimize the prefetched data size by prefetching only the initial segments of media objects. Results of trace-driven simulations show that our proposed prefetching scheme can effectively reduce the ratio of delayed requests by up to 38% with very marginal increase in traffic.
Delivering streaming media content over the Internet is a very challenging problem. Proxy servers has been introduced into the streaming media delivery systems over the Internet, and many mechanisms have been proposed based on this structure, such as proxy caching and prefetching. While the existing techniques can improve the performance of accesses to reused media objects, they are not effective in reducing the startup delay for first-time accesses. In this paper, we propose a more aggressive server-assisted prefetching mechanism to reduce the startup delay of first-time accesses. In this aggressive prefetching mechanism, proxy servers prefetch media objects before they are requested. To ensure the accuracy of this beforehand prefetching, we make use of server's knowledge about access patterns to locate the most popular media objects and provide such information to proxy servers as hint for prefetching. A proxy server makes decision based on the hint and its users' profile and prefetches suitable objects before they are accessed. Results of trace-driven simulations show that our proposed mechanism can effectively reduce the ratio of delayed requests by up to 38% with very marginal increase in traffic.
An automatic synchronization system of the popular song and its lyrics is presented in the paper. The system includes two main components: a) automatically detecting vocal/non-vocal in the audio signal and b) automatically aligning the acoustic signal of the song with its lyric using speech recognition techniques and positioning the boundaries of the lyrics in its acoustic realization at the multiple levels simultaneously (e.g. the word / syllable level and phrase level). The GMM models and a set of HMM-based acoustic model units are carefully designed and trained for the detection and alignment. To eliminate the severe mismatch due to the diversity of musical signal and sparse training data available, the unsupervised adaptation technique such as maximum likelihood linear regression (MLLR) is exploited for tailoring the models to the real environment, which improves robustness of the synchronization system. To further reduce the effect of the missed non-vocal music on alignment, a novel grammar net is build to direct the alignment. As we know, this is the first automatic synchronization system only based on the low-level acoustic feature such as MFCC. We evaluate the system on a Chinese song dataset collecting from 3 popular singers. We obtain 76.1% for the boundary accuracy at the syllable level (BAS) and 81.5% for the boundary accuracy at the phrase level (BAP) using fully automatic vocal/non-vocal detection and alignment. The synchronization system has many applications such as multi-modality (audio and textual) content-based popular song browsing and retrieval. Through the study, we would like to open up the discussion of some challenging problems when developing a robust synchronization system for largescale database.
Semi-fragile watermarking methods aim at detecting unacceptable image manipulations, while allowing acceptable manipulations such as lossy compression. In this paper, we propose new semi-fragile authentication watermarking techniques using random bias and non-uniform quantization, to improve the performance of the methods proposed by Lin and Chang. Specifically, the objective is to improve the performance tradeoff between the alteration detection sensitivity and the false detection rate.
The need to authenticate multimedia content (audio, image and video) brings new challenges to the traditional digital signature schema. Unavoidable transmission distortion of multimedia data, such as noises introduced in printing a certificate, demands new authentication techniques that are resistant to reasonable modifications. In this paper, a novel approach to multimedia authentication based on the vector quantization (VQ) technique is presented. Its security is guaranteed by adopting a typical digital signature scheme and a hierarchical authentication procedure. The flexibility of this approach is achieved by the scalability of VQ. In addition, a feature-based registration procedure is used to pre-filter and restore the received media with reference to the original one. Using this method, a continuous measure of the authenticity can be computed based on the proposed registration and authentication procedure. This measure is helpful for setting a proper threshold for some specific authentication applications. Our experimental results with audio, image, and video have shown that the scheme is robust and practical.
KEYWORDS: Digital watermarking, Signal processing, Signal detection, Image registration, Distortion, Image processing, Medical imaging, Nonlinear optics, Lithium, Image segmentation
An audio registration method based on dynamic time-warping (DTW) technique was described in this paper. DTW technique can register two audio signals whose type of misalignment in time domain is unknown. By measuring the frame dissimilarities in two audio signals, the best alignment between a pair of audio signals can be obtained to register the two audio signals. This method can solve the registration problem for audio signal which is processed by re-scaling in the time domain. It is useful in many audio applications and has been applied to digital audio watermarking detection.
While most researchers are focusing on how to develop a robust and imperceptible watermarking technology, in this paper, we would stress a little in error analysis on recovering modified (attacked) watermarked images with reference to their original images. Here 'recovering' means that firstly we must find out the modification parameters of these images and then transform them back with maximum similar to the original images. We argue that correctly and accurately estimating the transform parameters of the modified watermarked images based on the given original image or some invariant parameters extracted from original image is very useful, helpful even essential for watermarking detection and verification. In this paper, firstly we will briefly introduce several basic image registration techniques. Then we evaluate the availability and limits of which they are directly used for recovering modified watermarked images considering some common attacks on image watermark. Furthermore we propose a method of estimating the transform parameters of modified watermarked image with reference to original image (Or its invariant feature parameters), and then analysis the recovering errors based on the proposed method. After reviewing several typical image watermarking schemes and systems based on different purposes, we outline some quantities for each system in condition that the embedded watermark could be extracted without error. We believe that a slight modification version of the proposed method could be used as a module of image authentication.
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