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Three-dimensional (3-D) ray-tracing and analysis is used to characterize the path angles in a rectangular building in which all interior walls are parallel or perpendicular to the exterior walls. Path angles are recorded for 500 random transmitter and receiver locations, maintaining constant range throughout a particular building model. The main contribution of this paper is the observation that when all of the path angles from all 500 trials are measured relative to one building wall and collectively analyzed in a signal strength distribution, clustering is clearly apparent. While this angle clustering in the ensemble of channels is not the same as clustering in a single channel trial, it may partially account for the clusters observed in single trials. As a practical matter, these results may impact the use and placement of directional antennas for wireless LANs in buildings of this type. Index Terms--Indoor radio communication, local area networks, multipath channels, propagation.

A study on the use of post-processing in video compression proposes a novel, postprocessing algorithm to enhance the visual quality of low bit-rate, MC-block-discrete cosine transform-based image and video compression systems. The algorithm minimizes the unwanted blocking effects and mosquito noise artifacts while maintaining image sharpness and naturalness. It is relatively simple yet performs quite well in different situations.

A postprocessing algorithm that enhances video picture quality adapts itself to pixel characteristics in a video sequence to filter out noise and preserve image detail. The system puts video signals into different classes and uses separate nonlinear filters matched to each class. The most general version of the algorithm uses motion-compensated frame averaging to improve picture quality. A suboptimal, spatial version of the adaptive postfilter enhances picture quality in a 384 kbps 3-D subband coder.

A three-dimensional spatio-temporal subband decomposition method developed for video coding functions by arranging the image sequence into various spatio-temporal frequency bands and then separating the information into spatio-temporal subbands. The method yields a 1-Mbps coder using an adaptive differential pulse code modulation scheme and adaptive bit allocation. A new vector quantization scheme is suitable for data in higher frequency bands.

The delivery of high quality video to multiple viewers accessing the content from various devices and networks with varying conditions is a challenging task. Transferring the same content (often with large volume) to multiple viewers drives unicast transmission inefficient. Furthermore, traditional multicasting is not an optimal solution for heterogeneous networks since it either overwhelms slow receivers or starves the fast ones. Hence, new delivery solutions with the goal of reducing the output rate of the source and tailored to heterogeneous networks is necessary. In this paper, we present a novel scheme for layered video multicasting to viewers with the flexibility to access the content from various devices (in a heterogeneous network) and loss/erasure prone networks. In this scheme, the source node uses Scalable Video Coding (SVC) to obtain scalability together with modern elastic Forward Error Correction (FEC) for loss protection. There exists a non-trivial advantage in using elastic FEC in conjunction with SVC which enables us to introduce a new architecture that brings considerable savings in required source output bandwidth. Our solution adapts to the specific needs of viewers, shows resilience against packet loss, e.g. less than 5dB drop in Peak Signal-to-Noise Ratio (PSNR) for up to 30% loss rate, and especially, can reduce the source output rate by half for typical 3-layer SVC. [ABSTRACT FROM PUBLISHER]

The article focuses on the subjective viewing developments linked with the delivery of stereoscopic three-dimensional television (3DTV) to the home stressing on video artifact visibility and applications of 3DTV technology in the U.S. It gives a description of the initial results of a subjective testing using stereoscopic 3DTV video containing artifacts. The initial subjective results from the work indicate compression and network artifacts in stereoscopic 3DTV technology.

In real-time remote diagnosis of emergency medical events, mobility can be enabled by wireless video communications. However, clinical use of this potential advance will depend on definitive and compelling demonstrations of the reliability of diagnostic quality video. Because the medical domain has its own fidelity criteria, it is important to incorporate diagnostic video quality criteria into any video compression system design. To this end, we used flexible algorithms for region-of-interest (ROI) video compression and obtained feedback from medical experts to develop criteria for diagnostically lossless (DL) quality. The design of the system occurred in three steps-measurement of bit rate at which DL quality is achieved through evaluation of videos by medical experts, incorporation of that information into a flexible video encoder through the notion of encoder states, and an encoder state update option based on a built-in quality criterion. Medical experts then evaluated our system for the diagnostic quality of the video, allowing us to verify that it is possible to realize DL quality in the ROI at practical communication data transfer rates, enabling mobile medical assessment over bit-rate limited wireless channels. This work lays the scientific foundation for additional validation through prototyped technology, field testing, and clinical trials. [ABSTRACT FROM AUTHOR]

Three-dimensional (3-D) ray-tracing and analysis is used to characterize the path angles in a rectangular building in which all interior walls are parallel or perpendicular to the exterior walls. Path angles are recorded for 500 random transmitter and receiver locations, maintaining constant range throughout a particular building model. The main contribution of this paper is the observation that when all of the path angles from all 500 trials are measured relative to one building wall and collectively analyzed in a signal strength distribution, clustering is clearly apparent. While this angle clustering in the ensemble of channels is not the same as clustering in a single channel trial, it may partially account for the clusters observed in single trials. As a practical matter, these results may impact the use and placement of directional antennas for wireless LANs in buildings of this type. [ABSTRACT FROM AUTHOR]

Describes the capabilities of multimedia technologies and the future challenges in terms of quantitative metrics and tradeoffs. Overview of multimedia; Audiovisual signal processing; Speech recognition and understanding; Communication technologies; Digital signal processing and computing.

This article is an introduction to a special issue on signal coding and compression. We begin by defining the concepts of digital coding and audiovisual signal compression. We then describe the four dimensions of coding performance: bit rate, signal quality, processing delay and complexity. We illustrate the two basic principles of audiovisual coding, removal of signal redundancy and the matching of the quantizing system to the properties of the human perceptual system, with specific recent examples of coding algorithms. We then summarize standards for, and applications of audiovisual signal compression. A fast-emerging application is the internetworking of audiovisual information, a field that is too recent to be covered in the articles in this collection. We conclude our article by presenting our views about future research directions in the field. [ABSTRACT FROM AUTHOR]

At the 38th International Conference on Acoustics, Speech, and Signal Processing (ICASSP) in Vancouver, Canada, Jos? M.F. Moura, in his acceptance speech for the IEEE Signal Processing Society Award, shared a number of thoughts that I found worthy of further reflection because they are an intricate part of the identity of signal processing as a technical discipline. The first of these thoughts was the difficulties many of us have experienced trying to explain what signal processing is to someone with no significant background in technical disciplines. The second of these thoughts was a recollection of the idea of ?Signal Processing Inside,? presented in his column by then editor-in-chief of IEEE Signal Processing Magazine and current IEEE Signal Processing Society president, K.J. Ray Liu, [S1], and highlighted during ICASSP 2007 as a motto describing signal processing as a ?phantom technology,? that was pervasive but at the same time a key contributor to technological advances from a position that is not readily apparent to the general public. [ABSTRACT FROM PUBLISHER]

The papers in this collection are diverse, and address multiple application genres: entertainment, collaboration, surveillance, and healthcare, all powered by new combinations of enablers - scientific, technological, and standards driven. The expositions are generally too multifaceted to permit simple categorization. However, we have arranged these contributions in a sequence that the reader may find useful. [ABSTRACT FROM AUTHOR]

This paper describes the design and implementation of a multimedia home gateway for threescreen television (3STV) service. The proposed in-home wireless network uses scalable video coding (SVC) and unequal error protection with Raptor forward error correction (FEC) for maximizing the quality of experience (QoE) over the variable-bandwidth, error-prone wireless network. The gateway incorporates (a) dynamic SVC layerswitching, which enables the server to perform selecting appropriate layers from SVC bitstreams, (b) adaptive Raptor FEC, which controls the overhead of Raptor FEC according to packet loss rate (PLR), (c) an efficient combination of (a) and (b), and (d) slice group-based selective streaming in the overall gateway architecture. The paper explains the home gateway architecture as well as experiments for performance evaluation as compared to that of traditional SVC streaming. In the experiments conducted, gains in video quality vary from 2 to 5dB in peak signal-to-noise ratio (PSNR), with corresponding subjective improvements. Overall reductions of bit rate at the input to the home gateway vary from 28% to 36%1. [ABSTRACT FROM AUTHOR]

Modern imaging technology permits obtaining images at varying depths along the thickness, or the Z-axis of the sample being imaged. A stack of multiple such images is called a Z-stack image. The focus capability offered by Z-stack images is critical for many digital pathology applications. A single Z-stack image may result in several hundred gigabytes of data, and needs to be compressed for archival and distribution purposes. Currently, the existing methods for compression of Z-stack images such as JPEG and JPEG 2000 compress each focal plane independently, and do not take advantage of the Z-signal redundancy. It is possible to achieve additional compression efficiency over the existing methods, by exploiting the high Z-signal correlation during image compression. In this paper, we propose a novel algorithm for compression of Z-stack images, which we term as ZPEG. ZPEG extends the popular discrete-cosine transform (DCT) based image encoder to compress Z-stack images. This is achieved by decorrelating the neighboring layers of the Z-stack image using differential pulse-code modulation (DPCM). PSNR measurements, as well as subjective evaluations by experts indicate that ZPEG can encode Z-stack images at a higher quality as compared to JPEG, JPEG 2000 and JP3D at compression ratios below 50∶1.