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排序方式: 共有82条查询结果,搜索用时 31 毫秒
1.
Sanghoon Lee Chris Podilchuk Vidhya Krishnan Alan C. Bovik 《The Journal of VLSI Signal Processing》2003,34(1-2):149-166
By exploiting new human-machine interface techniques, such as visual eyetrackers, it should be possible to develop more efficient visual multimedia services associated with low bandwidth, dynamic channel adaptation and robust visual data transmission. In this paper, we introduce foveation-based error resilience and unequal error protection techniques over highly error-prone mobile networks. Each frame is spatially divided into foveated and background layers according to perceptual importance. Perceptual importance is determined either through an eye tracker or by manually selecting a region of interest. We attempt to improve reconstructed visual quality by maintaining the high visual source throughput of the foveated layer using foveation-based error resilience and error correction using a combination of turbo codes and ARQ (automatic reQuest). In order to alleviate the degradation of visual quality, a foveation based bitstream partitioning is developed. In an effort to increase the source throughput of the foveated layer, we develop unequal delay-constrained ARQ (automatic reQuest) and rate compatible punctured turbo codes where the punctual pattern of RCPC (rate compatible punctured convolutional) codes in H.223 Annex C is used. In the simulation, the visual quality is significantly increased in the area of interest using foveation-based error resilience and unequal error protection; (as much as 3 dB FPSNR (foveal peak signal to noise ratio) improvement) at 40% packet error rate. Over real-fading statistics measured in the downtown area of Austin, Texas, the visual quality is increased up to 1.5 dB in PSNR and 1.8 dB in FPSNR at a channel SNR of 5 dB. 相似文献
2.
A model for texture analysis and segmentation using multiple oriented channel filters is analyzed in the general framework. Several different arguments are applied leading to the conclusion that the two-dimensional Gabor filters possess strong optimality properties for this task. Properties of the multiple-channel segmentation approach are analyzed. In particular, perturbations of textures from an ideal model are found to have important effects on the segmentation that can usually be ameliorated by simply preceding the segmentation process by a logarithmic operation and using a low-pass postfilter prior to making region assignments. The difficult problems of space-variant textures and multiple component textures are also considered. Local spatial frequency estimation approaches are suggested that use the responses as constraints in estimating the locally emergent texture frequencies. Complex texture aggregates containing multiple shared frequency components can be analyzed if the textures are distinct and few in number 相似文献
3.
Anush?Krishna?MoorthyEmail author Alan?Conrad?Bovik 《Multimedia Tools and Applications》2011,51(2):675-696
Creating algorithms capable of predicting the perceived quality of a visual stimulus defines the field of objective visual
quality assessment (QA). The field of objective QA has received tremendous attention in the recent past, with many successful
algorithms being proposed for this purpose. Our concern here is not with the past however; in this paper we discuss our vision
for the future of visual quality assessment research. We first introduce the area of quality assessment and state its relevance.
We describe current standards for gauging algorithmic performance and define terms that we will use through this paper. We
then journey through 2D image and video quality assessment. We summarize recent approaches to these problems and discuss in
detail our vision for future research on the problems of full-reference and no-reference 2D image and video quality assessment.
From there, we move on to the currently popular area of 3D QA. We discuss recent databases, algorithms and 3D quality of experience.
This yet-nascent technology provides for tremendous scope in terms of research activities and we summarize each of them. We
then move on to more esoteric topics such as algorithmic assessment of aesthetics in natural images and in art. We discuss
current research and hypothesize about possible paths to tread. Towards the end of this article, we discuss some other areas
of interest including high-definition (HD) quality assessment, immersive environments and so on before summarizing interesting
avenues for future work in multimedia (i.e., audio-visual) quality assessment. 相似文献
4.
Passive Three Dimensional Face Recognition Using Iso-Geodesic Contours and Procrustes Analysis 总被引:1,自引:0,他引:1
Sina Jahanbin Rana Jahanbin Alan C. Bovik 《International Journal of Computer Vision》2013,105(1):87-108
We introduce a new model for personal recognition based on the 3-D geometry of the face. The model is designed for application scenarios where the acquisition conditions constrain the facial position. The 3-D structure of a facial surface is compactly represented by sets of contours (facial contours) extracted around automatically pinpointed nose tip and inner eye corners. The metric used to decide whether a point on the face belongs to a facial contour is its geodesic distance from a given landmark. Iso-geodesic contours are inherently robust to head pose variations, including in-depth rotations of the face. Since these contours are extracted from rigid parts of the face, the resulting recognition algorithms are insensitive to changes in facial expressions. The facial contours are encoded using innovative pose invariant features, including Procrustean distances defined on pose-invariant curves. The extracted features are combined in a hierarchical manner to create three parallel face recognizers. Inspired by the effectiveness of region ensembles approaches, the three recognizers constructed around the nose tip and inner corners of the eyes are fused both at the feature-level and the match score-level to create a unified face recognition algorithm with boosted performance. The performances of the proposed algorithms are evaluated and compared with other algorithms from the literature on a large public database appropriate for the assumed constrained application scenario. 相似文献
5.
Quality-aware images. 总被引:4,自引:0,他引:4
Zhou Wang Guixing Wu Hamid Rahim Sheikh Eero P Simoncelli En-Hui Yang Alan Conrad Bovik 《IEEE transactions on image processing》2006,15(6):1680-1689
We propose the concept of quality-aware image, in which certain extracted features of the original (high-quality) image are embedded into the image data as invisible hidden messages. When a distorted version of such an image is received, users can decode the hidden messages and use them to provide an objective measure of the quality of the distorted image. To demonstrate the idea, we build a practical quality-aware image encoding, decoding and quality analysis system, which employs: 1) a novel reduced-reference image quality assessment algorithm based on a statistical model of natural images and 2) a previously developed quantization watermarking-based data hiding technique in the wavelet transform domain. 相似文献
6.
Foveated video quality assessment 总被引:2,自引:0,他引:2
Most image and video compression algorithms that have been proposed to improve picture quality relative to compression efficiency have either been designed based on objective criteria such as signal-to-noise-ratio (SNR) or have been evaluated, post-design, against competing methods using an objective sample measure. However, existing quantitative design criteria and numerical measurements of image and video quality both fail to adequately capture those attributes deemed important by the human visual system, except, perhaps, at very low error rates. We present a framework for assessing the quality of and determining the efficiency of foveated and compressed images and video streams. Image foveation is a process of nonuniform sampling that accords with the acquisition of visual information at the human retina. Foveated image/video compression algorithms seek to exploit this reduction of sensed information by nonuniformly reducing the resolution of the visual data. We develop unique algorithms for assessing the quality of foveated image/video data using a model of human visual response. We demonstrate these concepts on foveated, compressed video streams using modified (foveated) versions of H.263 that are standard-compliant. We rind that quality vs. compression is enhanced considerably by the foveation approach 相似文献
7.
A novel framework for digital image compression called visual pattern image coding, or VPIC, is presented. In VPIC, set of visual-patterns is defined independent of the images to be coded. Each visual pattern is a subimage of limited spatial support that is visually meaningful to a normal human observer. The patterns are used as a basis for efficient image representation; since it is assumed that the images to be coded are natural optical images to be viewed by human observers, visual pattern design is developed using relevant psychophysical and physiological data. Although VPIC bears certain resemblances to block truncation (BTC) and vector quantification (VQ) image coding, there are important differences. First, there is no training phase required: the visual patterns derive from models of perceptual mechanisms; second, the assignment of patterns to image regions is not based on a standard (norm) error criterion; expensive search operations are eliminated 相似文献
8.
9.
Sampat M.P. Zhou Wang Gupta S. Bovik A.C. Markey M.K. 《IEEE transactions on image processing》2009,18(11):2385-2401
We introduce a new measure of image similarity called the complex wavelet structural similarity (CW-SSIM) index and show its applicability as a general purpose image similarity index. The key idea behind CW-SSIM is that certain image distortions lead to consistent phase changes in the local wavelet coefficients, and that a consistent phase shift of the coefficients does not change the structural content of the image. By conducting four case studies, we have demonstrated the superiority of the CW-SSIM index against other indices (e.g., Dice, Hausdorff distance) commonly used for assessing the similarity of a given pair of images. In addition, we show that the CW-SSIM index has a number of advantages. It is robust to small rotations and translations. It provides useful comparisons even without a preprocessing image registration step, which is essential for other indices. Moreover, it is computationally less expensive. 相似文献
10.
A very fast high-compression, high-fidelity, image coding technique termed visual pattern image coding (VPIC) was recently introduced by the authors (1990). A hierarchical version of VPIC termed hierarchical VPIC (HVPIC) is developed here. In HVPIC, coded images of improved visual fidelity relative to VPIC are generated, with increased compressions (routinely exceeding 20:1). Significantly, the computational efficiency of simple VPIC is retained by HVPIC, which utilizes simple VPIC at each resolution level 相似文献