Gregory W. Cook

Renal Cysts of inv/inv Mice Resemble Early Infantile Nephronophthisis

Cystic kidney disease has been linked to mutations in the Invs gene in mice with inversion of embryonic turning (inv/inv) and the INVS (NPHP2) gene in infants with nephronophthisis type 2 (NPHP2). The inv mouse model features multiorgan defects including renal cysts, altered left-right laterality, and hepatobiliary duct malformations transmitted in an autosomal recessive manner. Affected mice usually die of renal and liver failure by postnatal day 7. Although cardiopulmonary and liver anomalies have been carefully detailed, renal cysts have yet to be fully characterized in inv/inv. By use of three-dimensional visualization by two-photon microscopy, this study provides the first comprehensive analysis of in situ cyst formation and progression in inv/inv kidneys. At embryonic day 15, there is dilatation of Bowmans capsule followed temporally by corticomedullary cysts involving collecting ducts, proximal tubules, and thick ascending limbs. Collecting ducts of newborn inv/inv mice are uniformly and diffusely cystic from medulla to cortex, with normal diameters found only at their most proximal tips. Proximal tubules form fusiform cysts that alternate with segments of normal or narrowed caliber along torturous convolutions. Because defective cilia have been linked to situs inversus and cystogenesis, we examined inv/inv cilia by scanning and transmission electron microscopy. The former detected monocilia of expected length in cystic collecting ducts and proximal tubules; the latter demonstrated the usual 9 + 2 pattern in respiratory cilia. The inv mutant mouse has renal cysts resembling infantile NPHP2 and will provide broader insight into the role cilia play in renal cystogenesis.

Multiresolution sequential edge linking

We describe a multiresolution approach to edge detection using a sequential search algorithm. The use of a multiresolution image pyramid allows the integration of global edge information contained in lower resolutions to guide the sequential search at higher resolutions. As a consequence, the dependence on a priori knowledge of the image edges is greatly reduced. Estimating the sequential search parameters from lower resolution images provides for a more accurate and less costly search of edge paths in the image.

Overview of parallel processing approaches to image and video compression

In this paper we present an overview of techniques used to implement various image and video compression algorithms using parallel processing. Approaches used can largely be divided into four areas. The first is the use of special purpose architectures designed specifically for image and video compression. An example of this is the use of an array of DSP chips to implement a version of MPEG1. The second approach is the use of VLSI techniques. These include various chip sets for JPEG and MPEG1. The third approach is algorithm driven, in which the structure of the compression algorithm describes the architecture, e.g. pyramid algorithms. The fourth approach is the implementation of algorithms on high performance parallel computers. Examples of this approach are the use of a massively parallel computer such as the MasPar MP-1 or the use of a coarse-grained machine such as the Intel Touchstone Delta.

Rate control for fully fine-grained scalable video coders

In this paper we study two rate control strategies for fully fine-grained scalable (FFGS) video coders. Usually, in scalable coders the bitstream is divided into a base layer, which is decoded by all the decoders, and one or more enhancement layers which can improve the quality provided by the base layer. In Internet video streaming it is important that the bitstream be scalable in rate, which allows a server to adapt the bitstream to changes in the available bandwidth in the network. FFGS coders allow the maximum degree of rate scalability by using scalable encoding in both the base and enhancement layers. In this paper, we propose a rate control algorithm which is based on the rate distortion characteristics of the encoded bitstream and prevents large jumps in quality. We show that due to the embedding property of FFGS encoders, we can properly select the number of bits of every layer and frame by taking into account the quality of the video sequence. In addition, by allowing a controlled amount of prediction drift, we can set the rate control of the base layer much higher and gain in some cases several dB of PSNR performance at the highest rate. Experimental comparisons are made using SAMCoW, a FFGS video coder based on the wavelet transform and motion compensated prediction, and the MPEG-4/FGS coder using the TM-5 rate control algorithm.

Rate-distortion analysis of motion-compensated rate scalable video

Generally speaking, rate scalable video systems today are evaluated operationally, meaning that the algorithm is implemented and the rate-distortion performance is evaluated for an example set of inputs. However, in these cases it is difficult to separate the artifacts caused by the compression algorithm and data set with general trends associated with scalability. In this paper, we derive and evaluate theoretical rate-distortion performance bounds for both layered and continuously rate scalable video compression algorithms which use a single motion-compensated prediction (MCP) loop. These bounds are derived using rate-distortion theory based on an optimum mean-square error (MSE) quantizer, and are thus applicable to all methods of intraframe encoding which use MSE as a distortion measure. By specifying translatory motion and using an approximation of the predicted error frame power spectral density, it is possible to derive parametric versions of the rate-distortion functions which are based solely on the input power spectral density and the accuracy of the motion-compensated prediction. The theory is applicable to systems which allow prediction drift, such as the data-partitioning and SNR-scalability schemes in MPEG-2, as well as those with zero prediction drift such as fine granularity scalability MPEG-4. For systems which allow prediction drift we show that optimum motion compensation is a sufficient condition for stability of the decoding system

An Investigation of Scalable SIMD I/O Techniques with Application to Parallel JPEG Compression

The problem inherent with any digital image or digital video system is the large amount of bandwidth required for transmission or storage. This has driven the research area of image compression to develop more complex algorithms that compress images to lower data rates with better fidelity. One approach that can be used to increase the execution speed of these complex algorithms is through the use of parallel processing. In this paper, we address the parallel implementation of the JPEG still-image compression standard on the MasPar MP-1, a massively parallel SIMD computer. We develop two novel byte alignment algorithms which are used to efficiently input and output compressed data from the parallel system, and present results which show real-time performance is possible. We also discuss several applications, such as motion JPEG, that can be used in multimedia systems.

An investigation of JPEG image and video compression using parallel processing

The problem inherent with any digital image (or digital video) system is the large amount of bandwidth required for transmission or storage. This has driven the research area of image compression to develop more complex algorithms that compress images to lower data rates with better fidelity. One approach that can be used to increase the execution speed of these complex algorithms is through the use of parallel processing. In this paper we address one aspect of the parallel implementation of the JPEG still image compression standard on the MasPar MP-1, a massively parallel SIMD computer. We develop a novel byte alignment algorithm used to efficiently output compressed data from the parallel system.<<ETX>>

The use of high performance computing in JPEG image compression

The problem inherent to any digital image (or digital video) system is the large amount of bandwidth required for transmission or storage. This has driven the research area of image compression to develop more complex algorithms that compress images to lower data rates with better fidelity. One approach that can be used to increase the execution speed of these complex algorithms is to implement the algorithms on a parallel supercomputer. The authors address the parallel implementation of the JPEG still image compression standard on the MasPar MP-1, a massively parallel SIMD computer. They demonstrate that the greatest difficulty lies not with the compression algorithm per se, but with the speed bottleneck that arises in the output of the compressed image. They develop a parallel output algorithm which addresses this problem and present results which show real-time performance on 1024/spl times/1024 images.<<ETX>>

Analysis of the efficiency of SNR-scalable strategies for motion compensated video coders

In this paper, an analysis of the efficiency of three signal-to-noise ratio (SNR) scalable strategies for motion compensated video coders and their non-scalable counterpart is presented. After assuming some models and hypotheses with respect to the signals and systems involved, we have obtained the SNR of each coding strategy as a function of the decoding rate. To validate our analysis, we have compared our theoretical results with data from encodings of real video sequences. Results show that our analysis describes qualitatively the performance of each scalable strategy, and therefore, it can be useful to understand main features of each scalable technique and what factors influence their efficiency.

An analysis of the efficiency of different SNR-scalable strategies for video coders

In this paper, we analyze the efficiency of three signal-to-noise scalable strategies for video coders using single-loop motion-compensated prediction (MCP). In our analysis, we assume the video sequences have uniform and constant translational motion and we model MCP as a stochastic filter. We also assume an exponential model for the distortion-rate function of the intraframe coding. The analysis is divided into two parts: the steady-state analysis and the transient analysis. In the first part, only the steady-state response of the coders is taken into account, and, thus, this analysis allows us to asses approximately the efficiency of coders with long input sequences. The transitory analysis considers both the transient and the steady-state responses of the coders, which makes it appropriate to analyze coders using periodic intraframes or with short input sequences. To validate our analysis, theoretical results have been compared to results from encodings of real video sequences using the scalable adaptive motion compensated wavelet video coder. We show that our theoretical analysis effectively describes qualitatively the main trends of every video coding strategy.