Browsing by Author "Chen, Fu-Chuang"

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A NOVEL VARIANCE-BASED INTRA-FRAME RATE CONTROL ALGORITHM FOR H.264/AVC
(2011)
Chen, Fu-Chuang
;
Hsu, Yi-Pin
;
電控工程研究所
;
Institute of Electrical and Control Engineering
To enhance image quality and retain a limited bit budget, intra-frame in the frame type selection plays a significant role in video coding systems because the frame is treated as a key frame for temporal domain reference. This paper presents an algorithm to predict accurate quantization parameters by developing variance-based distortion measurements. Firstly, the intra-frame rate control in JVT-G012 is analyzed before discussing possible drawbacks. Current algorithms includes JVT-G012 and Yan's algorithm based on mean square error metrics for intra-frame rate controls are compared to show that the proposed distortion metric is useful to estimate quantization parameters. Experimental results show that the proposed algorithm can significantly improve video quality up 10 0.19 dB and 1.28 dB, compared with the algorithm JVT-G012, which is implemented in the H.264 reference software JM 15.0 and Yan's algorithm.
An adaptive content based H.264/AVC rate control in low bit rate video
(2011)
Chen, Fu-Chuang
;
Hsu, Yi-Pin
;
電控工程研究所
;
Institute of Electrical and Control Engineering
In this paper, we analyze a rate control formula, which is Laplacian based model, then propose a content based equation for an enhanced JVT-G012 algorithm. Based on the simple and fast characteristics of the JVT-G012 algorithm, which is very suitable for real time embedded systems, we integrate the equation into the JVT-G012 algorithm to create an efficient quantizer. However, active local motion will produce error distortion and influence the determination of the quantization parameter. To solve this problem, a modified histogram based detector is proposed. Combining this detector with the equation refines the predicted quantization parameter more precisely. It is shown both theoretically and experimentally that a well-designed quantizer not only improves video quality, but also maintains the designed bit rate budget. In addition, our algorithm can achieve superior results to existing algorithms-up to 0.72 dB without large computation loading. (C) 2010 Elsevier GmbH. All rights reserved.
Analytical Settling Noise Models of Single-Loop Sigma-Delta ADCs
(2009-10-01)
Chen, Fu-Chuang
;
Huang, Chun-Chieh
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Switched-capacitor integrators are the basic building components for sigma-delta (Sigma Delta) modulators, and their incomplete charge transfer (settling problem) constitutes one of the dominant error sources in Sigma Delta modulators. Due to the complexity of the settling problem, analytic models for related noises are nonexistent. In this brief, closed forms of settling error models are obtained and represented as functions of Sigma Delta modulator system parameters. Both behavioral simulations and transistor-level circuit simulations are employed to verify these analytical models, and the results show that our analytical models are sufficiently accurate.
Modeling Harmonic Distortions Caused by Nonlinear Op-Amp DC Gain for Switched-Capacitor Sigma-Delta Modulators
(2009-09-01)
Chen, Fu-Chuang
;
Hsieh, Chih-Lung
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Op-amps are crucial components in sigma-delta modulators (SDMs). As device dimensions and supply voltages continue to scale down, it is increasingly critical to determine a suitable op-amp dc gain. If the dc gain is set too high, then the op-amp consumes too much power; if the dc gain is too small, then nonlinear distortion becomes serious. However, there exists no efficient approach for selecting dc gains. In this brief, we propose to use a nonlinear function to model nonlinear op-amp dc gain curves. Then, this nonlinear function is employed to derive an SDM nonlinear distortion model as a function of SDM system parameters. The obtained SDM nonlinear distortion model can subsequently be used to compute the minimum required op-amp dc gain such that nonlinear distortions are kept under a tolerable value. The nonlinear dc gain curve model and the SDM nonlinear distortion model proposed in this brief are verified by behavior simulations and transistor-level simulations.
Rate-Distortion Optimization of H.264/AVC Rate Control with Novel Distortion Prediction Equation
(2011-08-01)
Chen, Fu-Chuang
;
Hsu, Yi-Pin
;
交大名義發表
;
National Chiao Tung University
This study proposes a joint rate-distortion optimization for the H.264 rate control algorithm with a novel distortion prediction equation. First, based on the original distortion theorem, we produced a novel, analytically derived equation for the prediction of distortion. This novel distortion predictor avoids linear regression employed in other distortion predictors, and therefore can considerably speed up rate estimation. Then, this work constructed an optimal quantization parameter selection for encoder processing on the new distortion prediction equation and the JVT-G012 rate estimation equation at block level. Simulations demonstrated that the proposed algorithm had achieved an improvement in image quality and a computational saving of at least 34% over two existing algorithms, including the JVT-G012, which was the recommended rate control algorithm in the H.264 reference software JM15.0.
Rate-Distortion Optimization of H.264/AVC Rate Control with Novel Distortion Prediction Equation
(2011-08-01)
Chen, Fu-Chuang
;
Hsu, Yi-Pin
;
電控工程研究所
;
Institute of Electrical and Control Engineering
This study proposes a joint rate-distortion optimization for the H.264 rate control algorithm with a novel distortion prediction equation. First, based on the original distortion theorem, we produced a novel, analytically derived equation for the prediction of distortion. This novel distortion predictor avoids linear regression employed in other distortion predictors, and therefore can considerably speed up rate estimation. Then, this work constructed an optimal quantization parameter selection for encoder processing on the new distortion prediction equation and the JVT-G012 rate estimation equation at block level. Simulations demonstrated that the proposed algorithm had achieved an improvement in image quality and a computational saving of at least 34% over two existing algorithms, including the JVT-G012, which was the recommended rate control algorithm in the H.264 reference software JM15.0.
Suppression of Electromagnetic Interference of DC-DC Power Converters by Chaos Generators
(2010-01-01)
Chen, Fu-Chuang
;
Shen, Po-Nien
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Power DC-DC converters are notorious sources of electromagnetic interference in electronic products; therefore, suppression of EMI is an important topic in the design of switch-mode power converters. Conventional EMI suppression methods may employ LC filters and metal shielding, but this can significantly increase cost, size, and weight. In this paper we propose a chaos-based method to reduce peak EMI magnitude and spread the energy to a wide range of frequencies. This method is to add a chaos-modulation clock to a converter maintaining in regular period state, in order to create chaotic behaviors in the converter. Our results show that this method is effective in suppressing EMI in DC-DC converters without much impact on the performance of converters. System stability is also analyzed and discussed. Moreover, compared with conventional methods, this method can be easily implemented in CMOS technology.