Soo-Wook Jang

The Quantitative Model for Optimal Threshold and Gamma of Display Using Brightness Function

We investigated physical conditions for optimum display systems on various TV viewing conditions, and found that visual brightness function could be derived from relationships between Stevens power law and Bartleson-Brenemans brightness function, and that the optimum physical contrast ratio and compensated gamma for display system with adaptation luminance level could be obtained from the proposed brightness function.

Optimal Piece Linear Segments of Gamma Correction for CMOS Image Sensors

The gamma correction for the CMOS image sensors are implemented by the method of piecewise linear approximation through a look-up table. In this paper, we propose a quantitative criterion to select the piece linear segment with the same output interval for the reduction of the error between the value of piece linear approximation and gamma correction. After the gamma correction is implemented, the average error occurred by implementing color interpolation in each segment is a basis for the optimum selecting of the piece linear segment of the gamma correction for the CMOS image sensors.

Adaptive Colorimetric Characterization of Camera for the Variation of White Balance

The RGB signals generated by different cameras are not equal for the same scene. Therefore, cameras are characterized based on a CIE standard colorimetric observer. One method of deriving a colorimetric characterization matrix between camera RGB output signals and CIE XYZ tristimulus values is least squares polynomial modeling. Yet, this involves tedious experiments to obtain a camera transfer matrix under various white balance points for the same camera. Accordingly, the current paper proposes a new method for obtaining camera transfer matrices under different white balances using a 3 x 3 camera transfer matrix under a specific white balance point.

Improvement of Gray Scale CCT for Mobile Phone LCD*This work was supported by the Sun Moon University Research Grant of 2006.

Color reproductions in most LCD are quite different from those of standard CRT (cathode ray tube) monitor display because of the nonlinear characteristic in subtractive color reproduction. Moreover, gray scale CCT (correlated color temperature) reproductions in a typical mobile phone LCD depend on the input RGB levels. A simple LUT (Look-up table) method for constant gray scale CCT and gamma characteristic of mobile phone LCD is presented in this paper. We investigate the mobile phone LCDs characteristic of compensation of CCT with using the LUT. LCDs CCT is maintaining about 7500 K, which is the target CCT of mobile phone LCD in this paper. Also LCDs gamma is similar to target gamma.

MPEG-2 test stream with static test patterns in DTV system

MPEG-2 test stream for evaluation the static picture quality of digital television (DTV) should meet both good picture quality and stable bit rate. In this paper, we present a method for generating a high quality test stream to evaluate the static picture quality in DTV receiver. The proposed method is suitable for encoding the static test pattern, such as multiburst and crosshatch, and is based on user-defined quantization and adaptive zero stuffing algorithm. The user-defined quantization is suitable for minimizing the quantization error, which is the reason of degradation of picture quality, and the adaptive zero stuffing algorithm is used to solve the overflow of video buffer verifier (VBV) buffer while encoding process by MPEG-2 encoder. Experimental results show that the average PSNR and the bit rate of the proposed method have more efficient and stable than those of the conventional.

The Design of an LCD System Based on the Quantitative Analysis for Enhancement of the Motion Picture Quality

SUMMARY The pulsed backlight system has been introduced for reducing motion blurs of LCDs in high motion pictures. But applying the pulsed backlight, full screen flicker and inconsistency of transmissivity for entire frame at a lightening time should be considered. This paper discusses the analysis of blurs in high motion pictures and proposes the design method for more suitable display terminal of LCDs.

DTV lip-sync test using time indexed audio and video signals without effect on program

The paper concentrates on a lip-sync test for DTV with respect to audio and video signals using the digital bitstream. We propose a new lip-sync test method which does not affect the current program by use of the TATS (transient effect area test signals) and an additional sub-channel audio signal. The experimental result shows that the time difference between the audio and video signals can be easily measured by a captured oscilloscope waveform at any time.

Rate control algorithm for high quality compression of static test image in digital TV system

In this paper, we propose a new algorithm for generating test bit-stream in high quality to evaluate the static image quality of DTV receiver, based on a target bit allocation in the process of rate control. In order to allocate the number of target bits, we consider the normalized complexities, which are updated or maintained according to GOP picture qualities. The proposed rate control method is suitable for the compression of static test pattern while MPEG-2 Test Model 5 is suitable for moving picture. To evaluate the performance of proposed algorithm, the test bitstream are generated by a MPEG-2 software encoder using the proposed algorithm. Experimental results show that average PSNR of the proposed method is higher than those of the conventional case. With experiment in DTV system, we have confirmed that the proposed algorithm has a stable bit rate and good video quality and it is suitable for evaluation of the DTV receiver.

Chromatic Adaptation Model Using the Relationship between the Cone Responses under Change in Illuminants

In this paper, a chromatic adaptation model (CAM) based on the dependence on LMS cone responses of the human visual system (HVS) is proposed for TV and PC monitors under a variety of viewing conditions. We derived the proposed CAM based on Brenemans corresponding color data. The results of the experiments were carried out to assess the proposed model performance in terms of color fidelity by comparing complex images on a LCD monitor. We confirmed that the proposed model performed better to predict corresponding colors under various viewing conditions. Therefore, the reproduced colors, which are viewed in real surround viewing conditions, are perceived the same as original object colors, when the proposed CAM was applied to color display devices such as CRT, LCD, and PDP.

A novel CAM for the luminance levels in the same chromaticity viewing conditions

In this paper, we propose the chromatic adaptation model (CAM) for the Variations of the Luminance Levels in the same Chromaticity Viewing Conditions. The proposed model is obtained by the transform the test colors of the high luminance into the corresponding colors of the low luminance. In the proposed model, the optimal coefficients are obtained from the corresponding colors data of the Breneman’s experiments. In the experimental results, we confirmed that the chromaticity errors between the predicted colors by the proposed model and the corresponding colors of the Breneman’s experiments are 0.004 in u ′v ′ chromaticity coordinates. The prediction performance of the proposed model is excellent because this error is the threshold value that two adjacent color patches can be distinguished.