Look-up Table Design Research Articles

Design and Optimization of Color Lookup Tables on a Simplex Topology

An important computational problem in color imaging is the design of color transforms that map color between devices or from a device-dependent space (e.g., RGB/CMYK) to a device-independent space (e.g., CIELAB) and vice versa. Real-time processing constraints entail that such nonlinear color transforms be implemented using multidimensional lookup tables (LUTs). Furthermore, relatively sparse LUTs (with efficient interpolation) are employed in practice because of storage and memory constraints. This paper presents a principled design methodology rooted in constrained convex optimization to design color LUTs on a simplex topology. The use of n simplexes, i.e., simplexes in n dimensions, as opposed to traditional lattices, recently has been of great interest in color LUT design for simplex topologies that allow both more analytically tractable formulations and greater efficiency in the LUT. In this framework of n-simplex interpolation, our central contribution is to develop an elegant iterative algorithm that jointly optimizes the placement of nodes of the color LUT and the output values at those nodes to minimize interpolation error in an expected sense. This is in contrast to existing work, which exclusively designs either node locations or the output values. We also develop new analytical results for the problem of node location optimization, which reduces to constrained optimization of a large but sparse interpolation matrix in our framework. We evaluate our n -simplex color LUTs against the state-of-the-art lattice (e.g., International Color Consortium profiles) and simplex-based techniques for approximating two representative multidimensional color transforms that characterize a CMYK xerographic printer and an RGB scanner, respectively. The results show that color LUTs designed on simplexes offer very significant benefits over traditional lattice-based alternatives in improving color transform accuracy even with a much smaller number of nodes.

Efficiency of Four Virtual LANs Switches with Equal Processing Times

Virtual LANs (VLANs) are introduced as some alternative switches to solve for the traffic problems of those LAN networks with Hubs. The idea is to create some collections in the whole LAN network, such collections are the so called VLANs. Appropriate switches (one switch or more of up to 24 ports) are designed to interconnect those VLANs. The design of such VLAN switches looks like the design of Look-Up tables to facilitate routing (similar to those used in CISCO networks). In this paper, an analytical model for such VLANs is proposed and then compared with single VLAN switch from the point of view of validity and speed characteristics.

Optimal look-up table-based data hiding

In this study, the authors present a novel data hiding scheme using the minimum distortion look-up table (LUT) embedding that achieves good distortion-robustness performance. LUT-based data hiding is a simple and efficient way to embed information into multimedia content for various applications, such as transaction tracking and database annotation. The authors find it possible to optimally reduce the data hiding-introduced distortion by designing the LUT according to the distribution of the host at a given robustness level. The authors first analyse the distortion introduced by LUT embedding and formulate its relationship with run constraints of LUT to construct an optimal coding problem. Subsequently, a Viterbi algorithm is presented to find the minimum distortion LUT. Then a new practical data hiding scheme using the optimal LUT is applied in the wavelet domain. Theoretical analysis and numerical results show that the new LUT design achieves not only less distortion but also more robustness than the traditional LUT-based data embedding schemes under common attacks such as Gaussian noise and JPEG compression.

The route to a defect tolerant LUT through artificial evolution

Evolutionary techniques may be applied to search for specific structures or functions, as specified in the fitness function. This paper addresses the challenge of finding an appropriate fitness function when searching for generic rather than specific structures which, when combined wiacteristic of defect tolerance on the circuit. Production defects for integrated circuits are expected to increase considerably. To avoid a corresponding drop in yield, improved defect tolerance solutions are needed. In the case of Field Programmable Gate Arrays (FPGAs), the pre-designed gate array provides a bridge between production and the application designers. Thus, introduction of defect tolerant techniques to the FPGA itself could provide a defect free gate array to the application designer, despite production defects. The search for defect tolerance presented herein is directed at finding defect tolerant structures for an important building block of FPGAs: Look-Up Tables (LUTs). Two key approaches are presented: (1) applying evolved generic building blocks to a traditional LUT design and (2) evolving the LUT design directly. The results highlight the fact that evolved generic defect tolerant structures can contribute to highly reliable circuit designs at the expense of area usage. Further, they show that applying such a technique, rather than direct evolution, has benefits with respect to evolvability of larger circuits, again at the expense of area usage.

Design Optimization of High-Speed and Low-Power Operational Transconductance Amplifier Using gm/ID Lookup Table Methodology

We propose a design optimization flow for a high-speed and low-power operational transconductance amplifier (OTA) using a gm/ID lookup table design methodology in scaled CMOS. This methodology advantages from using gm/ID as a primary design parameter to consider all operation regions including strong, moderate, and weak inversion regions, and enables the lowest power design. SPICE-based lookup table approach is employed to optimize the operation region specified by the gm/ID with sufficient accuracy for short-channel transistors. The optimized design flow features 1) a proposal of the worst-case design scenario for specification and gm/ID lookup table generations from worst-case SPICE simulations, 2) an optimization procedure accomplished by the combination of analytical and simulation-based approaches in order to eliminate tweaking of circuit parameters, and 3) an additional use of gm/ID subplots to take second-order effects into account. A gain-boosted folded-cascode OTA for a switched capacitor circuit is adopted as a target topology to explore the effectiveness of the proposed design methodology for a circuit with complex topology. Analytical expressions of the gain-boosted folded-cascode OTA in terms of DC gain, frequency response and output noise are presented, and detailed optimization of gm/IDs as well as circuit parameters are illustrated. The optimization flow is verified for the application to a residue amplifier in a 10-bit 125MS/s pipeline A/D converter implemented in a 0.18µm CMOS technology. The optimized circuit satisfies the required specification for all corner simulations without additional tweaking of circuit parameters. We finally explore the possibility of applying this design methodology as a technology migration tool, and illustrate the failure analysis by comparing the differences in the gm/ID characteristics.

LUT Optimization for Memory-Based Computation

Recently, we have proposed the antisymmetric product coding (APC) and odd-multiple-storage (OMS) techniques for lookup-table (LUT) design for memory-based multipliers to be used in digital signal processing applications. Each of these techniques results in the reduction of the LUT size by a factor of two. In this brief, we present a different form of APC and a modified OMS scheme, in order to combine them for efficient memory-based multiplication. The proposed combined approach provides a reduction in LUT size to one-fourth of the conventional LUT. We have also suggested a simple technique for selective sign reversal to be used in the proposed design. It is shown that the proposed LUT design for small input sizes can be used for efficient implementation of high-precision multiplication by input operand decomposition. It is found that the proposed LUT-based multiplier involves comparable area and time complexity for a word size of 8 bits, but for higher word sizes, it involves significantly less area and less multiplication time than the canonical-signed-digit (CSD)-based multipliers. For 16- and 32-bit word sizes, respectively, it offers more than 30% and 50% of saving in area-delay product over the corresponding CSD multipliers.

A Novel Look-Up Table Design Method for Data Hiding With Reduced Distortion

Look-up table (LUT)-based data hiding is a simple and efficient technique to hide secondary information (watermark) into multimedia work for various applications such as copyright protection, transaction tracking or content annotation. This paper studies the distortion introduced by a general LUT-based data hiding. We find that designing LUT according to the distribution of host data and watermark data can greatly reduce the distortion of LUT embedding. A new practical reduced-distortion LUT design method is developed for robust data hiding. The new method is applied in a wavelet domain image data hiding system and only significant wavelet coefficients are used to embed the watermark. A Gaussian mixture model and a related expectation-maximization algorithm-based method are employed to model the statistical distribution of the host image. The statistical model is used to select significant coefficients of the host image for data hiding. The experimental results show that compared to the conventional odd-even LUT embedding method, the presented new LUT data hiding algorithm provides average 1. 5-2. 5 dB PSNR improvement and better robustness for image watermarking.

CRC Look-up Table Optimization for Single-Bit Error Correction

Many communication systems use the cyclic redundancy code (CRC) technique for protecting key data fields from transmission errors by enabling both single-bit error correction and multi-bit error detection. The look-up table design is very important for the error-correction implementation. This paper presents a CRC look-up table optimization method for single-bit error correction. The optimization method minimizes the address length of the pre-designed look-up table while satisfying certain restrictions. The circuit implementation is also presented to show the feasibility of the method in the application specific integrated circuit design. An application of the optimization method in the generic framing procedure protocol is implemented using field programmable gate arrays. The result shows that the memory address length has been minimized, while keeping a very simple circuit implementation.

Real-Time Color Matching Between Camera and LCD Based on 16-bit Lookup Table Design in Mobile Phone

Based on the concept of multimedia convergence, imag- ing devices, such as cameras, liquid crystal displays (LCDs), and beam projectors, are now built-in to mobile phones. As such, mobile cameras capture still images or moving pictures, then store them as digital files, making it possible for users to replay moving pictures and review captured still images. Increasingly, users want LCD in the mobile phone (we call it mobile LCD hereafter) to reproduce the same colors as the real scene. Accordingly, this paper proposes a method for color matching between mobile camera and mobile LCD that includes characterizing the mobile camera and mobile LCD, gamut mapping, camera noise reduction, and a 16-bit lookup table (LUT) design. First, to estimate the CIELAB values for the objects in the real scene, mobile camera characterization is achieved through polynomial regression of the optimal order determined by investigat- ing the relation between captured RGB values and measured CIELAB values for a standard color chart. Thereafter, mobile LCD characterization is conducted based on 16-bit/pixel processing be- cause of the reduced bit depth of the images displayed on a mobile LCD. In addition, a sigmoid model is used to find the luminance value corresponding to the RGB control signal, instead of using gain offset gamma and S-curve models due to the adjustment of lumi- nance curve made by a system designer for preference color repro- duction. After completing the two types of characterization, gamut mapping is performed to connect the source medium (mobile cam- era) with the target medium (mobile LCD), then a combination of sigmoid functions with different parameters to control the shape is applied to the luminance component of the gamut-mapped CIELAB values to reduce camera noise. Finally, a three-dimensional RGB LUT is constructed using 16-bit/pixel-based data to enable color matching for moving pictures and inserted into the mobile phone. Experimental results show that moving pictures transmitted by a mobile camera can be realistically reproduced on a mobile LCD without any additional computation or memory burden. © 2007 So- ciety for Imaging Science and Technology. DOI: 10.2352/J.ImagingSci.Technol.200751:4348

Color matching that improves image quality on mobile phone displays

With digital convergence, color reproduction technology for mobile phones continues to improve. Camera technology now enables users to take both still and moving pictures, store them as digital files, and then display or project them anywhere. Color fidelity remains a challenge, however, and LCDs on mobile phones require real-time color matching between camera and cellular screen to ensure image quality. Our proposed color-matching system, shown schematically in Figure 1, comprises three steps: characterization of LCD and camera, gamut mapping, and application of a 16bit-based lookup table (LUT) design.? Device characterization defines the relationship between the tristimulus values (color spaces CIEXYZ or CIELAB) and RGB (red, green, blue) digital values. In general, characterization is modeled by polynomial regression, and as the polynomial order increases, performance improves.? However, for higher-order polynomials, most estimated tristimulus values exceed the boundary of maximum lightness and chroma. This makes implementation difficult because the relationship between tristimulus and digital RGB values has not been analyzed. We suggest a polynomial order based on investigating the relation between RGB digital values, then transformed using opponent color theory and CIELAB values. Meanwhile, for the mobile LCD characterization, we use a sigmoid function instead of a conventional method such as the GOG or S-curved model, to estimate the luminance curve made by the system designer.? This aims at better color reproduction and improved contrast. Additionally, characterization is based on the 16bit processing that controls the mobile LCD, in contrast to digital TVs or monitors, with 24bit data. Figure 1. Block-diagram of the proposed color-matching system.

A modified method of a class of recently presented cryptosystems☆

In this paper, a modified method of a class of recently proposed cryptosystems is presented. As a remedy, the piecewise linear chaotic map (PLCM) which has a uniform distribution is adopted in our method. The experimental results demonstrate that the application of PLCM can not only ensure the feasibility but also promote the encryption speed of these cryptosystems. Moreover, a new design of dynamical look-up table is used as an efficient way to ensure the security of our cryptosystem.

A modified method of a class of recently presented cryptosystems

Abstract In this paper, a modified method of a class of recently proposed cryptosystems is presented. As a remedy, the piecewise linear chaotic map (PLCM) which has a uniform distribution is adopted in our method. The experimental results demonstrate that the application of PLCM can not only ensure the feasibility but also promote the encryption speed of these cryptosystems. Moreover, a new design of dynamical look-up table is used as an efficient way to ensure the security of our cryptosystem.

Development of a new automatic calibration method for control of variable valve timing

The rising number of calibration variables and a decreasing time to market have led to the need for advanced methods of engine calibration. In this paper a new calibration method is developed for ignition timing. This calibration is based on an automated measurement and analysis method. This method enables the user to calibrate the optimal efficiency ignition angle (IA) and the torque control via the IA. The modern digital engine electronic control unit (ECU) is mainly based on look-up table methods. The combination of automatic knock detection analysis and automatic look-up table design reduces calibration time by the factor 3-4. The method was successfully applied to the low octane variation of the BMW AG 4-cylinder 2.0 l variable valve timing (VVT) spark ignition (SI) engine. The method is used in the SI combustion engine development section of the BMW AG for different types of engines. It has been shown that the application of the developed method dramatically reduces the calibration effort and time of VVT engines.

Evaluation of algorithms for ratio imaging in fluorescence microscopy.

Ratio imaging in fluorescence microscopy is used in measuring parameters such as pH, pCa, cytoplasmic porosity, and the relative concentration of fluorescent analogs within single cells. The fastest method for ratio imaging is to use lookup tables on special-purpose image processors. Since lookup tables store integers in integer addresses, using a lookup table will generate rounding errors. The magnitude of the error will depend on the transformation performed and on the number of levels used in the lookup table. We examined ratio imaging by lookup table and computed the errors generated by both inversion and log subtraction methods. Both uniformly fluorescing fields and fluorescing cell images were employed to provide data for use in confirming our calculations and illustrating both the magnitude and spatial incidence of errors. It is shown that, through proper design of lookup tables, a significant reduction can be made in the errors generated in comparison with common methods available in most image processors.

Grayscale simulation on a color display

A prescription is given for the design of (red, green, blue) lookup tables which allow pseudo-grayscale imaging on a color display.