Joint thresholding and quantizer selection for block-transform-based image coding with applications to baseline JPEG
14 Nov 1996-Vol. 2847, pp 356-364
TL;DR: A novel image-adaptive encoding scheme for the baseline JPEG standard that maximizes the decoded image quality without compromising compatibility with current JPEG decoders and may be applied to other systems that use run-length encoding, including intra- frame MPEG and subband or wavelet coding.
Abstract: We introduce a novel image-adaptive encoding scheme for the baseline JPEG standard that maximizes the decoded image quality without compromising compatibility with current JPEG decoders. Our algorithm jointly optimizes quantizer selection, coefficient 'thresholding', and entropy coding within a rate-distortion (R-D) framework. It unifies two previous approaches to image-adaptive JPEG encoding: R-D optimized quantizer selection by Wu and Gersho, and R-D optimal coefficient thresholding by Ramchandran and Vetterli. By formulating an algorithm which optimizes these two operations jointly, we have obtained performance that is the best in the reported literature for JPEG-compatible coding. In fact the performance of this JPEG coder is comparable to that of more complex 'state-of-the-art' image coding schemes: e.g., for the benchmark 512 by 512 'Lenna' image at a coding rate of 1 bit per pixel, our algorithm achieves a peak signal to noise ratio of 39.6 dB, which represents a gain of 1.7 dB over JPEG using the example Q- matrix with a customized Huffman entropy coder, and even slightly exceeds the published performance of Shapiro's celebrated embedded zerotree wavelet coding scheme. Furthermore, with the choice of appropriate visually-based error metrics, noticeable subjective improvement has been achieved as well. The reason for our algorithm's superior performance can be attributed to its conceptual equivalence to the application of entropy-constrained vector quantization design principles to a JPEG-compatible framework. Furthermore, our algorithm may be applied to other systems that use run-length encoding, including intra- frame MPEG and subband or wavelet coding.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
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01 Sep 2004
TL;DR: The objective of this work is to develop a set of quantization tables (Q tables) for compression of a specific class of medical image sequences, namely echocardiac, and to achieve a Q table that matches the specific application and can linearly change the compression rate by adjusting the gain factor.
Abstract: In this work, we propose an efficient framework for compressing and displaying medical images. Image compression for medical applications, due to available Digital Imaging and Communications in Medicine requirements, is limited to the standard discrete cosine transform-based joint picture expert group. The objective of this work is to develop a set of quantization tables (Q tables) for compression of a specific class of medical image sequences, namely echocardiac. The main issue of concern is to achieve a Q table that matches the specific application and can linearly change the compression rate by adjusting the gain factor. This goal is achieved by considering the region of interest, optimum bit allocation, human visual system constraint, and optimum coding technique. These parameters are jointly optimized to design a Q table that works robustly for a category of medical images. Application of this approach to echocardiac images shows high subjective and quantitative performance. The proposed approach exhibits objectively a 2.16-dB improvement in the peak signal-to-noise ratio and subjectively 25% improvement over the most useable compression techniques.
12 citations
Cites background from "Joint thresholding and quantizer se..."
...In this case, optimum tables as well as optimum Hufman tables can be designed based on the characteristics of the images in that particular application....
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...It exploits advantages of the available coders and compensates for their weaknesses to produce a new compression scheme that has higher compression rates with minimally noticeable distortions....
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01 Jan 2000
TL;DR: This work compares actual entropy-coding strategies and their effect on both the resulting segmentations as well as the rate-distortion performance to create an effective technique that performs significantly better than SPIHT using both objective and subjective measures.
Abstract: Joint space-frequency segmentation is a relatively new image compression technique that finds the rate-distortion optimal representation of an image from a large set of possible space-frequency partitions and quantizer combinations. As such, the method is especially effective when the images to code are statistically inhomogeneous, which is certainly the case in the ultrasound modality. Unfortunately, however, the original paper on space-frequency segmentation neglected to use an actual entropy coder, but instead relied upon the zeroth-order entropy to guide the algorithm. In this work, we fill this gap by comparing actual entropy-coding strategies and their effect on both the resulting segmentations as well as the rate-distortion performance. We then apply the resulting "complete" algorithm to representative ultrasound images. The result is an effective technique that performs significantly better than SPIHT using both objective and subjective measures.
4 citations
References
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TL;DR: The embedded zerotree wavelet algorithm (EZW) is a simple, yet remarkably effective, image compression algorithm, having the property that the bits in the bit stream are generated in order of importance, yielding a fully embedded code.
Abstract: The embedded zerotree wavelet algorithm (EZW) is a simple, yet remarkably effective, image compression algorithm, having the property that the bits in the bit stream are generated in order of importance, yielding a fully embedded code The embedded code represents a sequence of binary decisions that distinguish an image from the "null" image Using an embedded coding algorithm, an encoder can terminate the encoding at any point thereby allowing a target rate or target distortion metric to be met exactly Also, given a bit stream, the decoder can cease decoding at any point in the bit stream and still produce exactly the same image that would have been encoded at the bit rate corresponding to the truncated bit stream In addition to producing a fully embedded bit stream, the EZW consistently produces compression results that are competitive with virtually all known compression algorithms on standard test images Yet this performance is achieved with a technique that requires absolutely no training, no pre-stored tables or codebooks, and requires no prior knowledge of the image source The EZW algorithm is based on four key concepts: (1) a discrete wavelet transform or hierarchical subband decomposition, (2) prediction of the absence of significant information across scales by exploiting the self-similarity inherent in images, (3) entropy-coded successive-approximation quantization, and (4) universal lossless data compression which is achieved via adaptive arithmetic coding >
5,559 citations
TL;DR: The author provides an overview of the JPEG standard, and focuses in detail on the Baseline method, which has been by far the most widely implemented JPEG method to date, and is sufficient in its own right for a large number of applications.
Abstract: A joint ISO/CCITT committee known as JPEG (Joint Photographic Experts Group) has been working to establish the first international compression standard for continuous-tone still images, both grayscale and color. JPEG's proposed standard aims to be generic, to support a wide variety of applications for continuous-tone images. To meet the differing needs of many applications, the JPEG standard includes two basic compression methods, each with various modes of operation. A DCT (discrete cosine transform)-based method is specified for 'lossy' compression, and a predictive method for 'lossless' compression. JPEG features a simple lossy technique known as the Baseline method, a subset of the other DCT-based modes of operation. The Baseline method has been by far the most widely implemented JPEG method to date, and is sufficient in its own right for a large number of applications. The author provides an overview of the JPEG standard, and focuses in detail on the Baseline method. >
3,425 citations
"Joint thresholding and quantizer se..." refers background or methods in this paper
...This is equivalent to solving (1) with a fixed Huffman table and the added constraint that Q = k * Q,, where Q is the "example" JPEG matrix....
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...The scheme oP may be interpreted as minimizing (1) as a function of Qj, with H constant and 7j = 1, Vi, j, b....
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...The key to the algorithm is using Lagrange multipliers to convert the constrained problem in (1) to the following unconstrained minimization = D(T , Q) + A * R(1 , , H)] (2)...
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...With appropriate choice of A, achieved by iteration, solutions to (2) provide solutions to (1)....
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...Also, to obtain solutions to the rate-constrained problem(1), a root-solver requiring minimizations at different )'s may be used to find ) such that the rate constraint is best satisfied....
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TL;DR: Design of the MPEG algorithm presents a difficult challenge since quality requirements demand high compression that cannot be achieved with only intraframe coding, and the algorithm’s random access requirement is best satisfied with pure intraframes coding.
Abstract: The Moving Picture Experts Group (MPEG) standard addresses compression of video signals at approximately 1.5M-bits. MPEG is a generic standard and is independent of any particular applications. Applications of compressed video on digital storage media include asymmetric applications such as electronic publishing, games and entertainment. Symmetric applications of digital video include video mail, video conferencing, videotelephone and production of electronic publishing. Design of the MPEG algorithm presents a difficult challenge since quality requirements demand high compression that cannot be achieved with only intraframe coding. The algorithm’s random access requirement, however, is best satisfied with pure intraframe coding. MPEG uses predictive and interpolative coding techniques to answer this challenge. Extensive details are presented.
2,447 citations
TL;DR: A rate-distortion optimal way to threshold or drop the DCT coefficients of the JPEG and MPEG compression standards using a fast dynamic programming recursive structure.
Abstract: We show a rate-distortion optimal way to threshold or drop the DCT coefficients of the JPEG and MPEG compression standards. Our optimal algorithm uses a fast dynamic programming recursive structure. The primary advantage of our approach lies in its complete compatibility with standard JPEG and MPEG decoders. >
190 citations
27 Apr 1993
TL;DR: Simulation results demonstrate that, with picture-adaptive quantization tables designed by the proposed algorithm, the JPEG DCT (discrete cosine transform) coder is able to compress images with better rate-distortion performance than that achievable with conventional empirically designed quantization table.
Abstract: A recursive algorithm is presented for generating quantization tables in JPEG (Joint Photographic Experts Group) baseline coders from the actual statistics of the input image. Starting from a quantization table with large step sizes, corresponding to low bit rate and high distortion, one entry of the quantization table is updated at a time so that, at each step, the ratio of decrease in distortion to increase in bit rate is approximately maximized. This procedure is repeated until a target bit rate is reached. Simulation results demonstrate that, with picture-adaptive quantization tables designed by the proposed algorithm, the JPEG DCT (discrete cosine transform) coder is able to compress images with better rate-distortion performance than that achievable with conventional empirically designed quantization tables. >
130 citations