James Oliver Normile

Image compression using coarse grain parallel processing

The architecture and application of a multiprocessor system based on a homogeneous array of DSP processors are discussed. The system consists of floating point digital signal processors connected to each other via fast serial links. Each processor has access to a globally shared memory, and a multiple bus architecture in combination with a dual ported memory allows communication with a host controller. The architecture has been implemented and applied to the prototyping of video compression algorithms. The algorithms implemented include JPEG still-frame compression, CCITT H.261, and MPEG coding. These techniques may be decomposed into variable length encode or decode portions in tandem with a compute intensive element. This decomposition and its mapping into parallel processors is described.<<ETX>>

A real time software-only H.261 codec

Video and audio conferencing over networks is becoming increasingly popular due to the availability of video and audio I/O as standard equipment on many computer systems. So far, many algorithms have concentrated on playback only capability. This generally results in unacceptable real-time performance with respect to latency and encoder complexity. We describe a software-only system that allows full duplex video communication. For our analysis and implementation we chose a DCT based method that uses motion estimation and is modelled on the CCITT H.261 standard. We discuss the algorithm, followed by an analysis of the computational requirements for each major block. The results presented show the effect of computational simplifications on signal to noise ratio and image quality. We also examine the processing needs for full resolution coding and project when this will become available.

Multimedia databases and information systems

presented by the networks of today and even more importantly What are the possible applications? Would people really pay for the networks that could emerge from merging cable and telethem? How to bill someone? Per minute, per item, per search, phone companies in the near future. One of the most important by distance, combination? Copyright issues and how to enforce challenges for continued success and growth of multimedia is them? the ability to easily manage and access the information: storing gigabytes of data, organizing the information such that it is easily obtainable, searching capabilities to allow for convenient access, presenting and delivering the requestedinformation with appropriatequality of service, controlling access, and preserving copyrights. These functions are typically associated with databases which can easily be performed on text-based information; however, multimedia databases containing text, video, images, and audio present novel problems that must be addressed and resolved. This panel will discusss three of these issues that need to be resolved in order for multimedia databases and information systems to become a reality: information and data representation, query specification, and user interfaces. Other important issues. such as networking and storage, which will not be addressed.

Vector-quantization-based video codes for software-only playback on personal computers

This paper discusses a video compression and decompression method based on vector quantization (VQ) for use on general purpose computer systems without specialized hardware. After describing basic VQ coding, we survey common VQ variations and discuss their impediments in light of the target application. We discuss how the proposed video codec was designed to reduce computational complexity in every principal task of the video codec process. We propose a classified VQ scheme that satisfies the data rate, image quality, decoding speed, and encoding speed objectives for software-only video playback. The functional components of the proposed VQ method are covered in detail. The method employs a pseudo-YUV color space and criteria to detect temporal redundancy and low spatial frequency regions. A treestructured-codebook generation algorithm is proposed to reduce encoding execution time while preserving image quality. Two separate vector codebooks, each generated with the treestructured search, are employed for detail and low spatial frequency blocks. Codebook updating and sharing are proposed to further improve encoder speed and compression.

High-performance video codec for CD-ROM-based video playback

This paper discusses video compression and decompression strategies for use on general purpose computer systems where no specialized hardware is available. We first examine the alternatives and describe the performance and limitations of the first generation of such methods. A brief description is given of the possible algorithmic approaches. We introduce requirements for the encoder/decoder, and show that a vector quantization based scheme with image preprocessing and classification can provide the required performance. The remainder of the paper deals with the algorithm design and the tradeoffs made to meet the goals of realtime decode capability, compression ratio and image quality. Finally, we present results for the optimized algorithm and indicate areas which appear to be most promising for further work.

Performance of real-time software-only H.261 codec on the Power Macintosh

The widespread use of teleconferencing as a major role of remote communication has until now been stymied by the costs associated with deploying specialized hardware required to achieve good performance. Another constraint has been the incompatibility among the various systems that are available. These facts coupled with the rapid increase in computational power available on desktop systems convinced us of the value of a standards-based software solution. Leveraging the performance of the PowerPC RISC processors, we have implemented a software-only realization of the CCITT H.261 video coding standard. In this paper, we will discuss the performance of the software codec which has been optimized for the Power Macintosh 8100. Over ISDN and loaded Ethernet, the codec provides good visual quality in terms of spatial quality and frame rate over a range of bit rates (less than 64 to 384 Kbits/s). We will outline the structure of the software codec and discuss its performance.

Quantization and truncation effects in the design of adaptive digital filters

This paper presents an implementation of an adaptive digital filter. The hardware is outlined and the limitations of the design discussed. The effect of rounding on the filter characteristics is described. A method of improving filter performance, when using low adaptive gains, by means of the addition of a dither signal to the coefficient updates is described. Experimental results from the implementation are presented. These results concur with trends predicted by computer simulations, results of which are also included. Potential applications are suggested as are methods for improving the design.

Analysis and application of adaptive noise reduction using sparse filters

Summary form only given. The analysis of a sparse adaptive filtering technique and its application to the problem of system identification and noise reduction are discussed. In conventional adaptive filtering, modeling of systems whose impulse responses have clusters of nonzero coefficients, separated by samples that are small or zero, requires that the adaptive filter be sufficiently long to match the system. Consequently, in its converged state, the adaptive filter has many impulse response samples which are close to zero. These small coefficients contribute to residual filter misadjustment. Additionally, the convergence rate of the filter is determined by the total length. A sparse method that circumvents these problems by avoiding the calculations associated with the near-zero coefficients has been developed. As a result, the final mean square error attained is reduced, as is the convergence time.<<ETX>>

Parallel processing approach to transform-based image coding

This paper describes a flexible parallel processing architecture designed for use in real time video processing. The system consists of floating point DSP processors connected to each other via fast serial links, each processor has access to a globally shared memory. A multiple bus architecture in combination with a dual ported memory allows communication with a host control processor. The system has been applied to prototyping of video compression and decompression algorithms. The decomposition of transform based algorithms for decompression into a form suitable for parallel processing is described. A technique for automatic load balancing among the processors is developed and discussed, results ar presented with image statistics and data rates. Finally techniques for accelerating the system throughput are analyzed and results from the application of one such modification described.