Showing papers by "Ravi Sankar published in 2003"
06 Apr 2003
TL;DR: Experimental results show that the compression of P-SPIHT is superior to SPIHT for all the tested images and it is comparable JPEG2000 especially in the lossless mode.
Abstract: This paper proposes an enhanced partial SPIHT (P-SPIHT) for lossless and lossy image compression. P-SPIHT uses three coding modes for each bit plane based of the probability of the significant coefficients (PI) within each bit plane as proposed by Abu-Hajar and Sankar (see ICASSP 2002, Orlando, Florida, vol.4, p.3497-3500, 2002). In this paper, P-SPIHT is extended to support both lossy and lossless compression. Also it sorts the coded data into three categories; sign bits (SB), tree bits (TB) and magnitude bits (MB). P-SPIHT sorts TB and MB into insignificant tree bits (ITB), significant tree bits (STB), insignificant magnitude bits (IMB) and significant magnitude bits (SMB). Sorting the data enhances the compression of the arithmetic coder, as each category uses its own frequency model within the coder. Sorting the data improves the compression of the arithmetic coder by a factor of two. Experimental results show that the compression of P-SPIHT is superior to SPIHT for all the tested images and it is comparable JPEG2000 especially in the lossless mode.
18 citations
TL;DR: The survey provides a quick reference to the entire spectrum of wireless technologies in use today and uses the Open System Interconnect (OSI) framework to organize the wireless landscape.
Abstract: A significant part of the growth in consumer-to-business electronic commerce is likely to originate from the increasing numbers of mobile computing devices and smart telephone devices. Most of the data from mobile computers will be carried over by emerging wireless networks. Many wireless technologies and standards are now available. As a result, it is becoming increasingly difficult for non-domain experts like managers, to sort through the maze of wireless technologies and standards to make business decisions involving these technologies. This article surveys existing and emerging wireless technologies and uses the Open System Interconnect (OSI) framework to organize the wireless landscape. The survey provides a quick reference to the entire spectrum of wireless technologies in use today.
11 citations
TL;DR: Experimental results show that the compression in bit per pixel of the proposed algorithm does not only exceed wavelet-based SPHIT and JPEG 2000 but also it exceeds the state-of-the-art context-based JPEG-LS.
Abstract: This paper presents a lossless coding that is designed for 16-bit high-resolution x-ray images. The proposed algorithm uses non-linear histogram-based mapping that eliminates the gaps in the histogram before applying wavelet transform. The mapping is designed to reduce the magnitude of the wavelet coefficients, especially in the high frequency subbands. Reducing the magnitude of the coefficients in the high frequency subbands provides more compression as the high frequency subbands occupy most of the image area. This paper shows that the energy of all the subbands is being reduced after eliminating the gaps in the histogram, and hence the magnitudes of the coefficients are being reduced. To further exploit this property, the image is segmented into 64×64 blocks, and the gaps in the histograms of each block are independently eliminated, and then each block is independently coded using SPIHT. Since the mapping is non-linear, look-up tables are transmitted to the decoder as part of the overhead information. Experimental results show that the compression in bit per pixel (bpp) of the proposed algorithm does not only exceed wavelet-based SPHIT and JPEG 2000 but also it exceeds the state-of-the-art context-based JPEG-LS.