Pao-Chi Chang

Ming Chuan University, Hsin-chu-hsien, Taiwan, Taiwan

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Publications (60)21.66 Total impact

  • Ren-Jie Wang, Ya-Ting Yang, Pao-Chi Chang
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    ABSTRACT: Efficient multimedia retrieval has become a vital issue because more audio and video data are now available. This paper focuses on content-based image retrieval (CBIR) in the compression domain (CPD). The retrieval features are extracted based on I-frame coding information in H.264. This paper proposes using a local mode histogram as the texture feature to match images and applying the residual coefficients to filter non-confident modes. The geometrical correspondence between two images is also considered. The experimental results show that the proposed method can substantially reduce computational and memory resource consumption, and provides similar performance compared with methods that extract features from decompressed images.
    Journal of Visual Communication and Image Representation 07/2014; · 1.20 Impact Factor
  • Fourth International conference on Computer Science & Information Technology; 02/2014
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    ABSTRACT: H.264 scalable extension (H.264/SVC) is the current state-of-the-art standard of the scalable video coding. Its interlayer prediction provides higher coding efficiency than previous standards. Since the standard was proposed, several attempts have been made to improve the performance based on its coding structure. Quantization-distortion (Q-D) modeling is a fundamental issue in video coding; therefore, this paper proposes new Q-D models for three interlayer predictions in 264/SVC spatial scalability, that is, interlayer motion prediction, intraprediction, and residual prediction. An existing single layer offline Q-D model is extended to H.264/SVC spatial scalable coding. In the proposed method, the residual power from the interlayer prediction is decomposed into the coding distortion and the prediction distortion. The prediction distortion is the mean square error (MSE) between two original signals that can be obtained by preprocessing with low complexity. Therefore, the coding distortion can be estimated based on both the quantization parameter (QP) and a precalculated prediction distortion before the encoding process. Consequently, the estimated quality based on the proposed models achieved a high accuracy of over 90% for the three interlayer predictions in average.
    IEEE Transactions on Broadcasting 01/2014; 60(2):413-419. · 2.09 Impact Factor
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    ABSTRACT: Rate control is critical to time sensitive video applications over networks. However, the H.264/AVC standard takes no particularly response to the scene change which causes transmission quality deterioration significantly. In this work, we propose a robust mechanism of the rate control that can quickly respond to a scene change. In our proposed mechanism, it first allocates the remaining frames as a transition GOP. Then, according to the buffer fullness, it estimates the target bits so that a QP (quantization parameter) value can be determined. Simulation results show that our proposed method improves the average PSNR (peak signal noise ratio) about 1.1 dB with less buffer size, compared with the performance of JM in version 17.2.
    Consumer Electronics (ISCE), 2013 IEEE 17th International Symposium on; 01/2013
  • Yueh-Chuan Lu, Zong-Yi Chen, Pao-Chi Chang
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    ABSTRACT: This paper proposes a low power multi-Lane Mobile Industry Processor Interface (MIPI) Camera Serial Interface 2 (CSI-2) receiver architecture which adopts an 8-Byte parallel CSI protocol layer for hardware implementations. The proposed scheme can work in environment with 4 data Lanes and 1 Gb/s per data Lane, i.e. with maximum data rate 4 Gb/s, at 62.5 MHz which increases logic operations from 8 ns (125 MHz) to 16 ns (62.5 MHz) without throughput degradation. Therefore, the supply voltage (1.2 V) can be reduced and the power consumption can also be reduced. The proposed architecture is implemented by 0.13 μm CMOS technology and the total gate count is 32.7 K. It not only reduces the operating clock rate but also reduces more than 37%~43% logic power consumption measured in chip.
    Consumer Electronics (ISCE), 2013 IEEE 17th International Symposium on; 01/2013
  • Ren-Jie Wang, Chih-Wei Huang, Pao-Chi Chang
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    ABSTRACT: In this paper, we present the efficiency analysis of two sophisticated coding tools, multi-reference frame (MRF) and variable block size (VBS) that cost high computational complexity, in various spatial resolutions. The relationship between coding efficiency and spatial resolution is theoretically discovered. Based on the conclusion of the efficiency analysis that the efficiency improvement from sophisticated coding tools are gradually decreased in higher resolution, we propose an adaptive coding configuration for the encoding with various resolutions that yield significant complexity reduction with negligible RD performance decrease.
    Consumer Electronics (ISCE), 2013 IEEE 17th International Symposium on; 01/2013
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    ABSTRACT: Video quality under rate constraint is mainly controlled by the frame rate and the quantization parameter. This work proposes a mechanism to obtain the optimal frame rate that maximizes video quality under rate constraint. Based on an objective metric of video quality that can reflect subjective quality, this work first proposes a video quality—frame rate—rate constraint model. Second, the relationship between model parameters and video characteristics is formulized. Finally, this work proposes an efficient frame rate optimization mechanism. Experimental results show that the optimal frame rate estimated by our mechanism is identical to the actual optimal frame rate under most bit rate constraints for both training sequences and new test sequences. In addition, the quality loss caused by the estimation error is generally limited within 0.8 dB in our experiments.
    IEEE Transactions on Broadcasting 01/2012; 58(2):200-208. · 2.09 Impact Factor
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    Hua-Chang Chung, Zong-Yi Chen, Pao-Chi Chang
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    ABSTRACT: This paper proposes a low power deblocking filter (DF) architecture with Horizontal Edge Skip Processing Architecture (HESPA) scheme that offers an intelligent edge skip aware mechanism in filtering the horizontal edges by adopting a four-stage pipeline and adaptive hybrid filtering order to boost the speed of DF process. The proposed architecture not only reduces more than 34% logic power consumption measured in FPGA but also saves the filtering processes down to 100 clock cycles per macroblock (MB). The system throughput can easily support 1080HD video format at 30 fps with 70MHz clock frequency for low power and high definition video applications. It is implemented on 0.18μm standardized cell library, which consumes only 19.8K gates at a clock frequency of 200 MHz.
    Consumer Electronics (ICCE), 2011 IEEE International Conference on; 02/2011
  • Ming-Chen Chien, Pao-Chi Chang
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    ABSTRACT: Real-Time Complexity Control for H.264 Video Encoding by Coding Gain Maximization
    IEICE Transactions. 01/2011; 94-B:2181-2184.
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    ABSTRACT: Scalable Video Coding (SVC) provides an efficient compression for the video bitstream equipped with various scalable configurations. H.264 scalable extension (H.264/SVC) is the most recent scalable coding standard. It involves the state-of-the-art inter-layer prediction to provide higher coding efficiency than previous standards. Moreover, the requirements for the video quality on distinct situations like link conditions or video contents are usually different. Therefore, it is very desirable to be able to construct a model so that the target quality can be estimated in advance. This work proposes a Quantization-Distortion (Q-D) model for H.264/SVC spatial scalability, and then we can estimate video quality before the actual encoding is performed. In particular, we further decompose the residual from the inter-layer residual prediction into the previous distortion and Prior-Residual so that the residual can be estimated. In simulations, based on the proposed model, we estimate the actual Q-D curves, and its average accuracy is 88.79%.
    Advances in Image and Video Technology - 5th Pacific Rim Symposium, PSIVT 2011, Gwangju, South Korea, November 20-23, 2011, Proceedings, Part II; 01/2011
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    Zong-Yi Chen, Jhe-Wei Syu, Pao-Chi Chang
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    ABSTRACT: This paper proposes a fast inter-layer motion estimation algorithm on spatial scalability for scalable video coding extension of H.264/AVC. In the enhancement layer motion estimation, we utilize the relation between two motion vector predictors from the base layer and the enhancement layer respectively to reduce the number of searches. Additionally, we utilize the mode correlations of temporal direction motion estimation to save more encoding time. The simulation results show that the proposed algorithm can save the computation time up to 67.4% compared with JSVM9.12 with less than 0.0476dB video quality degradation.
    Multimedia and Expo (ICME), 2010 IEEE International Conference on; 08/2010
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    Ren-Jie Wang, Ming-Chen Chien, Pao-Chi Chang
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    ABSTRACT: Down-sampling coding, which sub-samples the image and encodes the smaller sized images, is one of the solutions to raise the image quality at insufficiently high rates. In this work, we propose an Adaptive Down-Sampling (ADS) coding for H.264/AVC. The overall system distortion can be analyzed as the sum of the down-sampling distortion and the coding distortion. The down-sampling distortion is mainly the loss of the high frequency components that is highly dependent of the spatial difference. The coding distortion can be derived from the classical Rate-Distortion theory. For a given rate and a video sequence, the optimum down-sampling resolution-ratio can be derived by utilizing the optimum theory toward minimizing the system distortion based on the models of the two distortions. This optimal resolution-ratio is used in both down-sampling and up-sampling processes in ADS coding scheme. As a result, the rate-distortion performance of ADS coding is always higher than the fixed ratio coding or H.264/AVC by 2 to 4 dB at low to medium rates.
    Proc SPIE 02/2010;
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    Zong-Yi Chen, Tien-Hsu Lee, Pao-Chi Chang
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    ABSTRACT: Systematic Lossy Error Protection (SLEP) is a robust error resilient mechanism which uses Wyner-Ziv coding to protect the video bitstream. In this paper, we propose a low overhead adaptive lossy error protection (ALEP) mechanism that provides a good trade-off between the error resilience and decoded video quality. The proposed method can generate appropriate redundant slices to provide proper error correction capability for varying channel conditions. The proposed method maintains good video quality at low packet loss rate compared to original SLEP and still provides sufficient error correction capability at high packet loss rate in our simulation results. It achieves 2-3 dB PSNR improvement at 5% packet loss rate for various video sequences in our simulations.
    Communications and Information Technology, 2009. ISCIT 2009. 9th International Symposium on; 10/2009
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    ABSTRACT: In this paper, we propose an estimated high frequency compensated (EHFC) algorithm for super resolution images. It is based on iterative back projection (IBP) method combined with compensated high frequency models according to different applications. The proposed algorithm not only improves the quality of enlarged images produced by zero-order, bilinear, or bicubic interpolation methods, but also accelerates the convergence speed of IBP. In experiments with general tested images, EHFC method can increase the speed by 1 ~ 6.5 times and gets 0.4 ~ 0.7 dB PSNR gain. In text image tests, EHFC method can increase 1.5 ~ 6.5 times in speed and 1.2 ~ 8.3 dB improvement in PSNR.
    Communications and Information Technology, 2009. ISCIT 2009. 9th International Symposium on; 10/2009
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    ABSTRACT: This work proposes a complexity-control algorithm that efficiently utilizes encoding tools of an H.264 video coding system under different power status. Experiments performed on a power-scalable embedded system reveal the excellent rate-distortion performance with various power constraints. Specifically, the power consumption can be adjusted around 77% to 100% with PSNR degradation within 1.08 dB at the same bit rate.
    Consumer Electronics, 2009. ISCE '09. IEEE 13th International Symposium on; 06/2009
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    Yu-Shin Cheng, Zong-Yi Chen, Pao-Chi Chang
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    ABSTRACT: In the advanced H.264 video coding, the computation complexity is much higher than the previous video coding standards due to the variable block size and multi-reference frame features which are used in the motion compensation process. This paper proposes a hierarchical H.264 fast motion estimation algorithm to decrease the coding complexity in both spatial and temporal domains for encoding high-definition videos. In the spatial domain, we utilize the fast search method with a hierarchical-subsampling structure to decrease the memory access bandwidth of search points. In the temporal domain, we employ the linear motion model to further reduce the search ranges of multiple reference frames. This search algorithm is particularly suitable for being implemented in the parallel-processing architecture with the limited hardware resources. Simulation results show that the proposed algorithm can reduce up to 98.2% computation complexity of full search in JM with less than 0.1 dB video quality degradation.
    International Symposium on Circuits and Systems (ISCAS 2009), 24-17 May 2009, Taipei, Taiwan; 01/2009
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    ABSTRACT: Media encryption technologies actively play the first line of defense in securing the access of multimedia data. Traditional cryptographic encryption can achieve provable security but is unfortunately sensitive to a single bit error, which will cause an unreliable packet to be dropped creating packet loss. In order to achieve robust media encryption, the requirement of error resilience can be achieved with error-resilient media transmission. This study proposes a video joint encryption and transmission (video JET) scheme by exploiting media hash-embedded residual data to achieve motion estimation and compensation for recovering lost packets, while maintaining format compliance and cryptographic provable security. Interestingly, since video block hash preserves the condensed content to facilitate search of similar blocks, motion estimation is implicitly performed through robust media hash matching - which is the unique characteristic of our method. We analyze and compare the performance of resilience to (bursty) packet loss between the proposed method and forward error correction (FEC), which has been extensively employed to protect video packets over error-prone networks. The feasibility of our packet loss- resilient video JET approach is further demonstrated through experimental results.
    Multimedia Tools and Applications 01/2009; 44:249-278. · 1.01 Impact Factor
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    Shih-Wei Sun, Chun-Shien Lu, Pao-Chi Chang
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    ABSTRACT: In this paper, a new multimedia joint encryption and fingerprinting (JEF) scheme embedded into the advanced access content system (AACS) is proposed for multimedia transmission over networks. AACS is selected because it has been jointly developed by many famous companies and has been considered as the leading technology in content access control and multimedia distribution. In this framework, many attack points exist and can be exploited to defeat it. Furthermore, multiple attack points can be combined to form multi-point collusion attacks, which also endanger the proposed system. In this paper, we address the security concerns toward AACS-compatible JEF system in its entirety and propose solutions to cope with some security threats. The contributions of this paper include: (i) applying multimedia encryption at different points to resist some attacks points; (ii) proposing rewritable fingerprint embedding (RFE) to deal with some multi-point collusion attacks; (iii) designing a perceptual security spectrum metric (PSSM) to evaluate the degree of security when multiple encryptions are applied. The feasibility of the proposed AACS-compatible JEF method is further demonstrated through simulation results.
    Signal Processing Image Communication 03/2008; · 1.29 Impact Factor
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    Wei-Di Hong, Tien-Hsu Lee, Pao-Chi Chang
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    ABSTRACT: Foreground segmentation for video frames has played an important role in many video applications, such as video surveillance, video indexing, etc. Due to most videos are compressed, foreground segmentation can benefit from utilizing such coding information and save much processing time. In this paper, we propose a real-time foreground segmentation algorithm for the moving camera based on the H.264 video coding information. In the proposed algorithm, we first utilize the relative global motion model to calculate the approximate global motion vector and get the motion vector difference of each block. Then, according to the block partition modes, we assign different weightings and apply spatio-temporal refinement to these motion vector differences for further improving the accuracy of segmentation results. Finally, we segment out the foreground blocks by an adaptive threshold. With the aid of H.264 video coding information, the proposed segmentation algorithm is more practical than many other methods based on spatial domain information in computational complexity.
    Future generation communication and networking (fgcn 2007); 01/2008
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    Ming-Chen Chien, Zong-Yi Chen, Pao-Chi Chang
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    ABSTRACT: The allowable computational complexity of video encoding is limited in a power-constrained system. Different video frames are associated with different motions and contexts, and so are associated with different computational complexities if no complexity control is utilized. Variation in computational complexity leads to encoding delay jittering. Typically motion estimation (ME) consumes much more computational complexity than other encoding tools. This work proposes a practical complexity control method based on the complexity analysis of an H.264 video encoder to determine the coding gain of each encoding tool in the video encoder. Experiments performed on a programming optimized source code show that the computational complexity associated with each frame is
    Proceedings of the International Conference on Image Processing, ICIP 2008, October 12-15, 2008, San Diego, California, USA; 01/2008

Publication Stats

229 Citations
21.66 Total Impact Points

Institutions

  • 2011
    • Ming Chuan University
      Hsin-chu-hsien, Taiwan, Taiwan
  • 1999–2010
    • National Central University
      • • Department of Communication Engineering
      • • Department of Electrical Engineering
      Taoyuan City, Taiwan, Taiwan
  • 2009
    • Telecommunication Laboratories, Chunghwa Telecom Co., Ltd.
      Hsin-chu-hsien, Taiwan, Taiwan
    • Jinwen University of Science and Technology
      Taiwan
  • 2004–2007
    • Academia Sinica
      • Institute of Earth Sciences
      Taipei, Taipei, Taiwan
  • 2006
    • Ching Yun University
      Taoyuan City, Taiwan, Taiwan
  • 1998
    • Central University of Venezuela
      Caracas, Distrito Federal, Venezuela