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A Monte Carlo code for ocean color simulations has been developed to model in-water radiometric fields of downward and upward irradiance ([E.sub.d] and [E.sub.u]), and upwelling radiance ([L.sub.u]) in a two-dimensional domain with a high spatial resolution. The efficiency of the code has been optimized by applying state-of-the-art computing solutions, while the accuracy of simulation results has been quantified through benchmark with the widely used Hydrolight code for various values of seawater inherent optical properties and different illumination conditions. Considering a seawater single scattering albedo of 0.9, as well as surface waves of 5 m width and 0.5 m height, the study has shown that the number of photons required to quantify uncertainties induced by wave focusing effects on [E.sub.d], [E.sub.u], and [L.sub.u], data products is of the order of [10.sup.6], [10.sup.9], and [10.sup.10], respectively. On this basis, the effects of sea-surface geometries on radiometric quantities have been investigated for different surface gravity waves. Data products from simulated radiometric profiles have finally been analyzed as a function of the deployment speed and sampling frequency of current freefall systems in view of providing recommendations to improve measurement protocols. Society of America OCIS codes: 010.5620, 170.1610, 170.2655.

In this paper, we present a new approach capable of working under coherent and incoherent illumination for achieving superresolution by random coding of the object's angular information. By placing two static random masks in optically conjugate planes inside an aperture-limited imaging setup, one may obtain a transmitted image containing spatial resolution higher than the one obtained without the masks. As the most noticeable fact, the superresolution effect is obtained without imposing any restrictions either in the time domain or in the field-of-view domain but rather only in the dynamic range of the camera device. Experimental verifications for the proposed technique with incoherent illumination with a low numerical aperture (NA) lens are presented. OCIS codes: 050.1940, 100.6640, 110.0110.

Scenarios for the use of the recently approved Scalable Video Coding (SVC) extension of H.264/MPEG4-AVC in IPTV services are presented. For that, a brief technical overview of SVC when deployed in IPTV services is provided. The coding efficiency of the various scalability types of SVC is demonstrated followed by an analysis of the complexity of the various SVC tools. Based on this technical characterization, it is described how the different SVC features such as efficient methods for graceful degradation, bit rate adaptation, and format adaptation, can be mapped to application requirements of IPTV services. It is discussed how such mappings can lead to improved content portability, management and distribution as well as an improved management of access network throughput resulting in better quality of service and experience for the users of IPTV services. Index Terms--H.264, IPTV, MPEG4-AVC, SVC.

In today's hybrid video coding, Rate-Distortion Optimization (RDO) plays a critical role. It aims at minimizing the distortion under a constraint on the rate. Currently, the most popular RDO algorithm for one-pass coding is the one recommended in the H.264/AVC reference software. It, or HR-[lambda] for convenience, is actually a kind of universal method which performs the optimization only according to the quantization process while ignoring the properties of input sequences. Intuitively, it is not efficient all the time and an adaptive scheme should be better. Therefore, a new algorithm Lap-[lambda] is presented in this paper. Based on the Laplace distribution of transformed residuals, the proposed Lap-[lambda] is able to adaptively optimize the input sequences so that the overall coding efficiency is improved. Cases which cannot be well captured by the proposed models are considered via escape methods. Comprehensive simulations verify that compared with HR-[lambda], Lap-[lambda] shows a much better or similar performance in all scenarios. Particularly, significant gains of 1.79 dB and 1.60 dB in PSNR are obtained for slow sequences and B-frames, respectively. Index Terms--Hybrid video coding, Lagrange multiplier selection, rate-distortion optimization (RDO).

Integral imaging (InIm) is a highly promising technique for the delivery of three-dimensional (3D) image content. During capturing, different views of an object are recorded as an array of elemental images (EIs), which form the integral image. High-resolution InIm requires sensors with increased resolution and produces huge amounts of highly correlated data. In an efficient encoding scheme for InIm compression both inter-EI and intra-EI correlations have to be properly exploited. We present an EI traversal scheme that maximizes the performance of InIm encoders by properly rearranging EIs to increase the intra-EI correlation of jointly coded EIs. This technique can be used to augment performance of both InIm specific and properly adapted general use encoder setups, used in InIm compression. An objective quality metric is also introduced for evaluating the effects of different traversal schemes on the encoder performance. OCIS codes: 100.2000, 100.6890, 110.3000, 110.6880.

Cette etude specifie les contributions des processus de generation et de maintien d'image mentale intervenant lots du codage image de l'information verbale en memoire au cours du vieillissement normal. Les capacites mnesiques de 19 adultes jeunes (moyenne d'age 24 ans) et de 19 adultes eges (moyenne d'age 75 ans) sont evaluees a l'aide de taches de rappel en fonction de la valeur d'imagerie des stimuli a apprendre. Les capacites d'imagerie mentale sont evaluees et l'aide des teches de generation et de maintien temporaire d' une image mentale. L'analyse de variance indique une baisse plus importante avec l'ege de la superiorite des mots concrets sur les roots abstraits. L'apport majeur de la presente etude reside darts le fait que cette alteration du double codage de l'information verbale en memoire lors du vieillissement normal puisse provenir d'un declin des capacites de maintien et d'un ralentissement a generer des images mentales. Mots-cles : vieillissement, codage image, imagerie mentale, generation, maintien

This paper presents a rate control scheme for H.264/AVC scalable extension. Based on our previous work on H.264/AVC rate control, a switched model is proposed to predict the mean absolute difference (MAD) of the residual texture from the available MAD information of the previous frame in the same layer and the same frame in its 'base layer.' Thus, abrupt MAD fluctuations could be predicted properly in the enhancement layer. Moreover, a bit allocation scheme is proposed for the hierarchical B-frames structure by taking into consideration the relative importance of each frame. With our algorithm, the rate control for all the coarse-grain-scalability, spatial, temporal and combined enhancement layer could be realized, and the target bit rate for each layer can be achieved. Our method encodes the sequence only once and the buffer is well controlled to prevent it from overflowing and underflowing. Index Terms--H.264/AVC, rate control, scalable video coding (SVC).

Integer cosine transform (ICT) is adopted by H.264/AVC for its bit-exact implementation and significant complexity reduction compared to the discrete cosine transform (DCT) with an impact in peak sigal-to-noise ratio (PSNR) of less than 0.02 dB. In this paper, a new technique, named prescaled integer transform (PIT), is proposed. With PIT, while all the merits of ICT are kept, the implementation complexity of decoder is further reduced compared to corresponding conventional ICT, which is especially important and beneficial for implementation on low-end processors. Since not all PIT kernels are good in respect of coding efficiency, design rules that lead to good PIT kernels are considered in this paper. Different types of PIT and their target applications are examined. Both fixed block-size transform and adaptive block-size transform (ABT) schemes of PIT are also studied. Experimental results show that no penalty in performance is observed with PIT when the PIT kernels employed are derived from the design rules. Up to 0.2 dB of improvement in PSNR for all intra frame coding compared to H.264/AVC can be achieved and the subjective quality is also slightly improved when PIT scheme is carefully designed. Using the same concept, a variation of PIT, Post-scaled Integer Transform, can also be potentially designed to simplify the encoder in some special applications. PIT has been adopted in audio video coding standard (AVS), Chinese National Coding standard. Index Terms--Adaptive block-size transform (ABT), audio video coding standard (AVS), complexity reduction, discrete cosine transform (DCT), H.264/AVC, integer cosine transform (ICT), prescaled integer transform (PIT), standard, transform, video coding.

The extracted low-resolution video from a motion compensated 3-D subband/wavelet scalable video coder is unnecessarily sharp and sometimes contains significant aliasing, compared to that obtained by the MPEG4 lowpass filter. In this paper, we propose a content adaptive method for aliasing reduction in subband/wavelet scalable image and video coding. We try to make the low-resolution frame (LL subband) visually and energy-wise similar to that of the MPEG4 decimation filter through frequency roll-off. Scaling of the subbands is introduced to make the variances of the subbands comparable in these two cases. Thanks to the embedded properties of the EZBC coder, we can achieve the needed scaling of energies in each subband by subbitplane shift in the extractor and value(coefficient) scaling in the decoder. Two methods are presented which offer substantial peak signal-to-noise ratio (PSNR) gain for lower spatial resolution, as well as substantial reduction in visible aliasing, with little or no reduction in full resolution PSNR. Index Terms--Aliasing reduction, frequency roll-off, motion compensated temporal filtering, scalable image coding, scalable video coding.

A postprocessing technique according to the maximum a posteriori (MAP) criterion is presented. Results suggest the effectiveness of the technique in achieving higher PSNR gain and in generating recovered images of good visual quality.

Recent video coding standards such as H.264 offer the flexibility to select reference frames during motion estimation for predicted frames. In this paper, we study the optimization problem of jointly selecting the best set of reference frames and their associated transport QoS levels in a multipath streaming setting. The application of traditional Lagrangian techniques to this optimization problem suffers from either bounded worst case error but high complexity or low complexity but undetermined worst case error. Instead, we present two optimization algorithms that solve the problem globally optimally with high complexity and locally optimally with lower complexity. We then present rounding methods to further reduce computation complexity of the second dynamic programming-based algorithm at the expense of degrading solution quality. Results show that our low-complexity dynamic programming algorithm achieves results comparable to the optimal but high-complexity algorithm, and that gradual tradeoff between complexity and optimization quality can be achieved by our rounding techniques. Index Terms--Communication systems, optimization methods, video signal processing.

In video transcoding, arbitrary resizing is always desired for end users with different display capabilities. In this paper, a two-stage resizing structure is proposed for arbitrary resizing. It gives a general solution for the realization of arbitrary resizing in the transform domain. Two constraints are given for the selection of parameter set to benefit the anti-aliasing and picture quality. Illustrative examples show that our proposed two-stage resizing structure, with the qualified parameter sets, can provide an appropriate solution for arbitrary resizing. Index Terms--Anti-aliasing, arbitrary resizing, two-stage implementation, video transcoding.

This paper presents an innovative algorithm for detecting all-zero discrete cosine transform (DCT) coefficient blocks prior to DCT and quantization for all block-based video coding standards. A mathematic model is established based on analyzing DCT coefficient distribution and applying Paseval energy conservation theorem. The algorithm is applied to H.264 video coding and experimental results show up to 32% higher detection ratio without degrading video quality, compared with results of the existing methods. Furthermore, up to 47% higher detection ratio is achieved by changing the threshold based on DCT coefficient distribution. For motion estimation, much less search points needed by using the proposed method as early termination criterion than that by using the existing methods. Index Terms--All-zero discrete cosine transform (DCT) coefficient blocks, DCT coefficient distribution, energy conservation theorem, video coding standard.

In this paper, we propose an adaptive and scalable soft variable length code (VLC) decoder to greatly reduce overall design complexity. Generally, a soft VLC decoder needs to maintain many states for the correct decoding when the sequence length or table size grows. We propose an adaptive sorting scheme to reduce the memory accesses and design complexity. We reduce the table size by using symbol-merging and table-merging schemes. In addition, the proposed Black-Box model improves the accuracy of performance estimation by a novel measurement of 'symbolalias' and also achieves a better tradeoff between performance and complexity. Further, no side information is transmitted and the proposed soft VLC decoder is bandwidth-efficient. The proposed design is evaluated using the model of MPEG-4/UDP-Lite/UEP/ AWGN, and hence it is standard-compliant. We averagely improve the peak signal-to-noise ratio by 0.4~2.9 dB as compared with traditional VLC decoding and standard-support reversible VLC decoding schemes. Index Terms--MPEG-4, soft-input soft-output, variable length decoder (VLD), wireless transmission.

In this paper, some existing perceptual encryption algorithms of MPEG videos are reviewed and some problems, especially security defects of two recently proposed MPEG-video perceptual encryption schemes, are pointed out. Then, a simpler and more effective design is suggested, which selectively encrypts fixed-length codewords in MPEG-video bit streams under the control of three perceptibility factors. The proposed design is actually an encryption configuration that can work with any stream cipher or block cipher. Compared with the previously-proposed schemes, the new design provides more useful features, such as strict size-preservation, on-the-fly encryption and multiple perceptibility, which make it possible to support more applications with different requirements. In addition, four different measures are suggested to provide better security against known/chosen-plaintext attacks. Index Terms--Cryptanalysis, fixed-length codeword (FLC), known/chosen-plaintext attack, MPEG, perceptual encryption.

The object of this paper is to present a simple and efficient algorithm for dynamic range compression and contrast enhancement of digital images under the noisy environment in the compressed domain. First, an image is separated into illumination and reflectance components. Next, the illumination component is manipulated adaptively for image dynamics by using a new content measure. Then, the reflectance component based on the measure of the spectral contents of the image is manipulated for image contrast. The spectral content measure is computed from the energy distribution across different spectral bands in a discrete cosine transform (DCT) block. The proposed approach also introduces a simple scheme for estimating and reducing noise information directly in the DCT domain. The main advantage of the proposed algorithm enhances the details in the dark and the bright areas with low computations without boosting noise information and affecting the compressibility of the original image since it performs on the images in the compressed domain. In order to evaluate the proposed scheme, several base-line approaches are described and compared using enhancement quality measures. Index Terms--Contrast enhancement, dynamic range compression, illumination, image quality metrics, noise estimation, noise reduction, reflectance.

In this paper, we address the key problem in real-time video coding, the rate-distortion (R-D) tradeoff. As most video coding applications employ color images, we analyze the R-D modeling problem of the color image sequence. We investigate that the R-D characteristics of color video signal in traditional transform-based video coding systems should be modeled for the luminance and chrominance components separately. So we propose separable R-D models for color video coding. The feedback from the encoder buffer is analyzed by a control-theoretic adaptation approach to avoid buffer overflow and underflow. To achieve smooth video quality and satisfy the delay constraints in real-time applications, a novel R-D tradeoff controller is designed. In the proposed R-D tradeoff framework, both the quality variation and buffer safety are considered. Extensive simulation results demonstrate that the proposed approach can achieve smooth video quality without sacrificing overall quality while efficiently utilize the bandwidth without buffer overflow or underflow. Index Terms--Buffer control, H.264, rate control, rate-distortion (R-D) model, R-D tradeoff, video coding.

We propose a highly efficient, look-up table-based, renormalization method that can be used by any binary arithmetic encoder with the follow-on procedure. It replaces the time-consuming branching operations in the renormalization process with table look-ups and some simple bit-wise operations. We show that our new renormalization method outperforms the currently used ones with much less memory requirement than the previously known, table-based quasi-coder. Index Terms--Arithmetic codes, optimization methods.

Most bit allocation algorithms for video are geared toward optimizing the average frame distortion. However, video sequences optimized this way may exhibit sudden changes in distortion, or 'flicker,' which can significantly affect the perceived quality of the sequence. An alternative approach is to minimize the maximum frame distortion, which aims to produce a constant-quality sequence, thus avoiding the flicker problem. In this work, we present a new algorithm for constant-quality video, called MultiStage. We first show how MultiStage works for an embedded bit plane coder, and we then demonstrate that it can be applied to traditional quantization-based coders, such as H.263 and H.264, in conjunction with a novel single-frame block-level rate-distortion optimization algorithm based on multiple-choice knapsack. We show that MultiStage achieves very good results, both in terms of maximum distortion and average distortion. Index Terms--Constant quality, H.263, H.264, rate control, rate-distortion optimization (RDO), variable bit rate (VBR), video coding.

A novel mechanism that flexibly adapts data flows and configures computational units is proposed to establish an application-specific data path in the digital signal processor (DSP) that can efficiently perform multistandard video codecs. Based on this mechanism, the proposed application-specific data path, using the very long instruction word (VLIW) architecture with eight computational units of five arithmetic logic units (ALUs), one multiplier and two load/store units, is designed to perform five adaptive operations according to the characteristics of the low-level functions of MPEG-2, MPEG-4 and H.264/AVC video codecs. Using these adaptive operations, the proposed application-specific data path reduces the number of clock cycles required by the TI TMS320C64x data path to perform the low-level functions of the MPEG-2 video encoder and the H.264/AVC video decoder by 23.10% and 28.43%, respectively, for 30 352 x 288-pixel Foreman frames. Additionally, considering the operating frequency, the proposed application-specific data path reduces the computation time required by the TI TMS320C64x data path to realize the abovementioned encoder and decoder by 19.86% and 25.41%, respectively. Based on the TSMC 0.18-[micro]m CMOS cell library, the proposed application-specific data path is implemented, and exhibits the highest ratio of computational power to hardware cost among all of the data paths associated with the conventional DSPs in implementing the low-level functions of video codecs. Index Terms--Digital-signal-processing-chips, parallel-processing, pipeline-processing, video-coding, VLSI.

The MPEG-4 Part-10 AVC/H.264 standard employs several powerful coding methods to obtain high compression efficiency. To reduce the temporal and spatial redundancy more effectively, motion compensation uses variable block sizes, and directional intra prediction investigates all available coding modes to decide the best one. When the rate-distortion (R-D) optimization technique is used, an encoder finds the coding mode having minimum R-D cost. Due to the large number of combinations of coding modes, the decision process requires extremely high computation. To reduce the complexity, we propose two methods: early SKIP mode decision and selective intra mode decision. In the simulation results, the proposed methods are verified to significantly reduce the entire encoding time by about 60% with only negligible coding loss. Index Terms--Coding mode selection, early SKIP detection, fast algorithm, mode decision, MPEG-4 Part-10 AVC/H.264, selective intra coding.

Long Reed-Solomon codes over the prime field GF([2.sup.16] + 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 is long delay due to long codes. However, the incurred delay is justifiable for Internet low bit video transmission and in high quality video broadcasting systems like streaming MPEG2 video where each encoder and decoder may have three frames delay. The proposed method surpasses the previous works for video transmission over binary symmetric channels, bursty channels, and packet loss channels. Also we propose a nearly error free transmission system for Gaussian channels for completeness of the work. We have also proposed short codes, which with larger overhead provide nearly error free transmission, and still outperform the previous works. Index Terms--Channel coding, error correction codes, Reed-Solomon codes over prime fields, video coding.

Subpixel motion estimation plays an important role in compression efficiency within modern video codecs such as MPEG2, MPEG4, and H.264. Subpixel motion estimation is implemented within these standards using interpolated values at 1/2 or 1/4 pixei accuracy. Such interpolation gives a good reduction in residual energy for each predicted macroblock and, therefore, improves compression. However, this leads to a significant increase in computational complexity at the encoder. This is especially true for H.264 where the cost of an exhaustive set of macroblock segmentations need to be estimated in order to obtain an optimal mode for prediction. This paper presents a novel interpolation-free scheme for subpixei motion estimation using the result of the full pixel sum of absolute difference distribution of each motion compensated block applied to an H.264 encoder. This system produces reduced complexity motion estimation with a controllable tradeoff between compression performance and encoder speed. These methods facilitate the generation of a real time software H.264 encoder. Index Terms--Motion estimation, video coding.

In the upcoming video coding standard MPEG-4 AVC/JVT/H.264, motion estimation is allowed to use multiple references and multiple block sizes to improve the rate-distortion performance. However, full exhaustive search of all block sizes is computational intensive with complexity increasing linearly to the number of allowed reference frames and block sizes. In block motion estimation, a search pattern with a different shape or size has a very important impact on search speed and distortion performance. Based on an in-depth examination for the influence of search pattern on speed performance, a novel search algorithm, three-dimensional predict hexagon search (3DPHS), is proposed in this paper. The 3DPHS depends on the characteristics of motion vector distribution; it can predict the object movement in horizontal and vertical direction with a novel search pattern. The proposed algorithm also considers the characteristics of multiple reference frames and multiple block sizes in H.264. The analysis results show that the speed improvement of 3DPHS over some popular fast search algorithms is about 25%-75%. The compression quality is almost the same compared with Full Search. Index Terms--Fast block matching algorithm, H.264, motion estimation.