Ely K. Tsern

Portable video-on-demand in wireless communication

Our present ability to work with video has been confined to a wired environment, requiring both the video encoder and decoder to be physically connected to a power supply and a wired communication link. This paper describes an integrated approach to the design of a portable video-on-demand system capable of delivering high-quality image and video data in a wireless communication environment. The discussion will focus on both the algorithm and circuit design techniques developed for implementing a low-power video compression/decompression system at power levels that are two orders of magnitude below existing solutions. This low-power video compression system not only provides a compression efficiency similar to industry standards, but also maintains a high degree of error tolerance to guard against transmission errors often encountered in wireless communication. The required power reduction can best be attained through reformulating compression algorithms for energy conservation. We developed an intra-frame compression algorithm that requires minimal computation energy in its hardware implementations. >

A low-power video-rate pyramid VQ decoder

Battery-operated portable video devices require compression schemes and hardware with low-complexity, low-power implementations. This pyramid vector quantization (PVQ) decoder chip is used for real-time video decompression with low-power operation. The chip performs decompression by converting PVQ codewords into data values and integrates all functionality on one die, requiring no external hardware or memory.

Error-resilient pyramid vector quantization for image compression

Pyramid vector quantization (PVQ) uses the lattice points of a pyramidal shape in multidimensional space as the quantizer codebook. It is a fixed-rate quantization technique that can be used for the compression of Laplacian-like sources arising from transform and subband image coding, where its performance approaches the optimal entropy-coded scalar quantizer without the necessity of variable length codes. In this paper, we investigate the use of PVQ for compressed image transmission over noisy channels, where the fixed-rate quantization reduces the susceptibility to bit-error corruption. We propose a new method of deriving the indices of the lattice points of the multidimensional pyramid and describe how these techniques can also improve the channel noise immunity of general symmetric lattice quantizers. Our new indexing scheme improves channel robustness by up to 3 dB over previous indexing methods, and can be performed with similar computational cost. The final fixed-rate coding algorithm surpasses the performance of typical Joint Photographic Experts Group (JPEG) implementations and exhibits much greater error resilience.

Low-power signal processing system design for wireless applications

Our ability to work with most multimedia data has been confined to a wired environment, requiring both the data source and the receiver to be physically connected to a power supply and a wired communication link. This article describes the design principles applicable to wireless signal processing systems, using a portable video-on-demand system as an example. The discussion focuses on both the algorithm and circuit design techniques developed for implementing a low-power video compression/decompression system at power levels that are two orders of magnitude below existing solutions. This low-power video compression system not only provides a compression efficiency similar to industry standards, but also maintains a high degree of error tolerance to guard against the transmission errors often encountered in wireless communication.

Design of a low power video decompression chip set for portable applications

This paper describes the design process of a chip set which performs real-time video decompression for wireless portable applications and concentrates on four critical aspects of the design: compression algorithm development, control complexity, programmability, and throughput. For each of these design areas, this paper evaluates the design trade-offs between low power, compression efficiency, and throughput, which are the three main requirements for wireless portable video. The chip set consists of a subband reconstruction chip and a pyramid vector quantization (PVQ) decoder chip and requires no external memory support or frame buffer. For portable applications with a resolution of 176 pixels wide, 240 lines, and 30 frames per second color video, the chip set, operating at a 1.35 V supply, dissipates less than 9 mW.

Video compression for portable communication using pyramid vector quantization of subband coefficients

The authors describes a video compression scheme that performs pyramid vector quantization (PVQ) of subband coefficients and a VLSI architecture for the PVQ decoder. This algorithm not only provides good compression performance, but also results in a low complexity, low power VLSI implementation. Furthermore, this algorithm demonstrates good error resiliency under severe channel distortion without the use of error correction codes. PVQ also allows encoding and decoding to be computation-based instead of memory-based, as in standard VQ, thus allowing for real-time video coding and eliminating the need for large memories. The algorithm and its performance are described in detail, and the chip architecture of the PVQ decoder is presented.<<ETX>>

Image coding using pyramid vector quantization of subband coefficients

This paper presents an improved algorithm using pyramid vector quantization with subband decomposed images. Specifically, the use of large vector dimensions and different dimensions for each subband yields significant improvement over previously reported results. Simulations reveal compression performance comparable to JPEG using a purely fixed-rate code, which has less hardware complexity and greater error resiliency. A comparison between product and inner pyramid VQ using statistical analysis of subband data and simulations demonstrates that product pyramid VQ is better suited for subband coding.<<ETX>>

Video Compression for Wireless Communications

This research centers on providing digital video on demand to portable receivers through wireless communications. The three main technological issues for wireless video communication are compression efficiency, error recovery, and low-power implementation. The algorithmic goal is to develop compression algorithms that maintain consistent visual quality for image and video signals transmitted over a noisy channel. These algorithms must therefore provide efficient compression and provisions for recovery in situations of severely degraded transmission. The hardware goal is to demonstrate low-power decoder modules that implement the decompression algorithms with recovery capability for lost information.

A low-power portable digital video-on-demand system

This paper describes the implementation of a real-time encoding/decoding digital system based on the pyramid vector quantization (PVQ) of subband coefficients. The implementation demonstrates a fast-prototyping approach to the design of portable systems, and addresses engineering trade-offs encountered in building a working system. Low power consumption is the most critical performance criterion in this implementation, which dictates both the hardware and software design choices. We conclude with an assessment of the strength and weakness of the chosen approach as well as possible improvements of the system.