Li-Wei Kang | Academia Sinica (original) (raw)

Papers by Li-Wei Kang

Rain removal from a video is a challenging problem and has been recently investigated extensively... more Rain removal from a video is a challenging problem and has been recently investigated extensively. Nevertheless, the problem of rain removal from a single image has been rarely studied in the literature, where no temporal information among successive images can be exploited, making it more challenging. In this paper, to the best of our knowledge, we are among the first to propose a single-frame-based rain removal framework via properly formulating rain removal as an image decomposition problem based on morphological component analysis (MCA). Instead of directly applying conventional image decomposition technique, we first decompose an image into the low-frequency and highfrequency parts using a bilateral filter. The high-frequency part is then decomposed into "rain component" and "nonrain component" via performing dictionary learning and sparse coding. As a result, the rain component can be successfully removed from the image while preserving most original image details. Experimental results demonstrate the efficacy of the proposed algorithm.

Journal of Visual Communication and Image Representation, 2005

For entropy-coded MPEG-2 video frames, a transmission error will not only affect the underlying c... more For entropy-coded MPEG-2 video frames, a transmission error will not only affect the underlying codeword but also may affect subsequent codewords, resulting in a great degradation of the received video frames. In this study, a hybrid error concealment scheme for MPEG-2 video transmission is proposed. The objective is to recover high-quality MPEG-2 video frames from the corresponding corrupted video frames, without increasing the transmission bit rate. In this study, transmission errors or equivalently corrupted/lost video packets in MPEG-2 video frames are detected and located by the error detection scheme proposed by Shyu and Leou [IEEE Trans. Circuits Syst. Video Technol. 10 , and then the corrupted blocks are concealed by the proposed hybrid error concealment scheme. Based on the fitness function for evaluating the candidate concealed blocks of a corrupted block, a corrupted block in an intra-coded I frame is concealed by either the spatial error concealment algorithm in H.264 or the proposed fast best neighborhood matching (BNM) algorithm. A corrupted block in an inter-coded P or B frame is concealed by the proposed fast motioncompensated BNM algorithm. Based on the simulation results obtained in this study, the proposed scheme can recover high-quality MPEG-2 video frames from the corresponding www.elsevier.com/locate/jvci (J.-J. Leou). corrupted video frames up to a packet loss rate of 20%. The performance of the proposed scheme is better than those of four existing approaches for comparison.

Journal of Electronic Imaging, 2005

Because visual data require a large amount of memory and computing power for storage and processi... more Because visual data require a large amount of memory and computing power for storage and processing, it is greatly desired to efficiently index and retrieve the visual information from image database systems. We propose efficient indexing and searching strategies for feature-based image database systems, in which uncompressed and compressed domain image features are employed. Each query or stored image is represented by a set of features extracted from the image. The weighted square sum error distance is employed to evaluate the ranks of retrieved images. Many fast clustering and searching techniques exist for the square sum error distance used in vector quantization (VQ), in which different features have identical weighting coefficients. In practice, different features may have different dynamic ranges and different importances, i.e., different features may have different weighting coefficients. We derive a set of inequalities based on the weighted square sum error distance and employ it to speed up the indexing (clustering) and searching procedures for feature-based image database systems. Good simulation results show the feasibility of the proposed approaches.

Real-time Imaging, 2005

For entropy-coded H.264 video frames, a transmission error in a codeword will not only affect the... more For entropy-coded H.264 video frames, a transmission error in a codeword will not only affect the underlying codeword but also may affect subsequent codewords, resulting in a great degradation of the received video frames. In this study, an error resilient coding scheme for H.264 video transmission is proposed. At the encoder, for an H.264 I frame, the important data for each macroblock (MB) are extracted and embedded into the next frame by the proposed MB-interleaving slice-based data embedding scheme for I frames. For an H.264 P frame, two types of important data for each MB are extracted and embedded into the next frame by the proposed MB-interleaving slice-based data embedding scheme for P frames. At the decoder, if the important data for a corrupted MB can be correctly extracted, the extracted important data for the corrupted MB will facilitate the employed error concealment scheme to conceal the corrupted MB; otherwise, the employed error concealment scheme is used to conceal the corrupted MB. Based on the simulation results obtained in this study, the proposed scheme can recover high-quality H.264 video frames from the corresponding corrupted video frames up to a video packet loss rate of 20%.

Journal of Visual Communication and Image Representation, 2006

For an entropy-coded wavelet-based image, such as a JPEG-2000 image, a transmission error in a co... more For an entropy-coded wavelet-based image, such as a JPEG-2000 image, a transmission error in a codeword will not only affect the underlying codeword but may also affect subsequent codewords, resulting in a great degradation of the received image. In this study, two error resilient coding schemes for wavelet-based image transmission based on data embedding and genetic algorithms (GA's) are proposed.

For an entropy-coded Joint Photographic Experts Group (JPEG) image, a transmission error in a cod... more For an entropy-coded Joint Photographic Experts Group (JPEG) image, a transmission error in a codeword will not only affect the underlying codeword but also may affect subsequent codewords, resulting in a great degradation of the received image. In this study, a new error resilient coding scheme for JPEG image transmission based on data embedding and side-match vector quantization (VQ) is proposed. To cope with the synchronization problem, the restart capability of JPEG images is enabled. The objective of the proposed scheme is to recover high-quality JPEG images from the corresponding corrupted images. At the encoder, the important data (the codebook index) for each Y (U or V) block in a JPEG image are extracted and embedded into another "masking" Y (U or V) block in the image by the odd-even data embedding scheme. At the decoder, after all the corrupted blocks within a JPEG image are detected and located, if the important data for a corrupted block can be extracted correctly from the corresponding "masking" block, the extracted important data will be used to conceal, the corrupted block; otherwise, the side-match VQ technique is employed to conceal the corrupted block. Based on the simulation results, the performance of the proposed scheme is better than that of five existing approaches for comparison. The proposed scheme can recover high-quality JPEG images from the corresponding corrupted images up to a block loss rate of 30%.

Journal of Visual Communication and Image Representation, 2004

For entropy-coded H.26L video frames, a transmission error in a codeword will not only affect the... more For entropy-coded H.26L video frames, a transmission error in a codeword will not only affect the underlying codeword but also may affect subsequent codewords, resulting in a great degradation of the received video frames. In this study, an error resilient coding scheme for H.26L video transmission based on data embedding is proposed. At the encoder, for an H.26L intra-coded I frame, the important data for each macroblock are extracted and embedded into another macroblock(s) within the I frame and the next P frame by the proposed oddeven data embedding scheme. For an H.26L inter-coded P frame, the important data for each slice are extracted and embedded into the next frame by the proposed slice-based embedding scheme for P frames. At the decoder, for each corrupted macroblock, if the important data for a corrupted macroblock can be correctly extracted, the extracted important data will facilitate the employed error concealment scheme to conceal the corrupted macroblock. Otherwise, the employed error concealment scheme is used to conceal the corrupted macroblock. Based on the simulation results, the proposed scheme can recover high-quality H.26L video frames from the corresponding corrupted video frames up to a video packet loss rate of 30%.

Journal of Visual Communication and Image Representation, 2006

For an entropy-coded Joint Photographic Experts Group (JPEG) image, a transmission error in a cod... more For an entropy-coded Joint Photographic Experts Group (JPEG) image, a transmission error in a codeword will not only affect the underlying codeword but also may affect subsequent codewords, resulting in a great degradation of the received image. In this study, an error resilient coding scheme for JPEG image transmission based on data embedding and side-match vector quantization (VQ) is proposed. To cope with the synchronization problem, the restart capability of JPEG images is enabled. The objective of the proposed scheme is to recover high-quality JPEG images from the corresponding corrupted images. At the encoder, the important data (the codebook index) for each Y (U or V) block in a JPEG image are extracted and embedded into another ''masking'' Y (U or V) block in the image by the odd-even data embedding scheme. At the decoder, after all the corrupted blocks within a JPEG image are detected and located, if the codebook index for a corrupted block can be correctly extracted from the corresponding ''masking'' block, the extracted codebook index will be used to conceal the corrupted block; otherwise, the side-match VQ technique is employed to conceal the corrupted block. Based on the simulation results obtained in this study, the performance of the proposed scheme is better than those of the five existing approaches for comparison. The proposed scheme can recover high-quality JPEG images from the corresponding corrupted images up to a block loss rate (BLR) of 30%.

In the proposed error resilient image camouflaging scheme, a secret image is camouflaged at the s... more In the proposed error resilient image camouflaging scheme, a secret image is camouflaged at the sender into multiple virtual JPEG-2000 images, resulting in multiple cipher-images. Then, instead of the secret image, only the cipher-images are transmitted to the receiver. Because both the secret and cipher-images are significant, the cipher-images do not pique the interest of illegal users who may try to get the secret image. At the receiver, if all the cipher-images are completely received, the secret image can be recovered from the cipher-images, whereas if the cipher-images are not completely received, the secret image cannot be recovered. Additionally, because the transmitted JPEG-2000 cipher-images may be corrupted by transmission errors, to enhance the degree of transmission reliability, three proposed techniques, namely, side-match vector quantization, round-robin like data embedding, and duplicate data embedding, are employed to provide error resilience for robust image transmission.

For entropy-coded H.263 video frames, a transmission error in a codeword will not only affect the... more For entropy-coded H.263 video frames, a transmission error in a codeword will not only affect the underlying codeword but also may affect subsequent codewords, resulting in a great degradation of the received video frames. In this study, a new error resilient coding scheme for H.263 video transmission is proposed. At the encoder, for an I frame, the important data of each macroblock are extracted and embedded into another macroblock within the I frame by the proposed odd-even data embedding scheme for I frames. For a P frame, a rate-distortion optimized coding mode selection approach is employed. The important data for each GOB (group of blocks) are extracted and embedded into the next frame by using the proposed macroblock-interleaving GOB-based data embedding scheme. At the decoder, after all the corrupted macroblocks within a video frame are detected and located, if the important data of a corrupted macroblock can be extracted correctly, the extracted important data will facilitate the employed error concealment scheme to conceal the corrupted macroblock; otherwise, the employed error concealment scheme is simply used to conceal the corrupted macroblock. Based on the simulation results, the proposed scheme can recover high-quality H.263 video frames from the corresponding corrupted video frames up to video packet loss rate = 30%.

Journal of Visual Communication and Image Representation, 2005

For entropy-coded H.264/AVC video frames, a transmission error in a codeword will not only affect... more For entropy-coded H.264/AVC video frames, a transmission error in a codeword will not only affect the underlying codeword but also may affect subsequent codewords, resulting in a great degradation of the received video frames. In this study, an error resilient coding scheme for H.264/AVC video transmission is proposed. At the encoder, for an H.264/AVC intra-coded I frame, the important data for each macroblock (MB) are extracted and embedded into the next frame by the proposed MB-interleaving slice-based data embedding scheme for I frames.

In this study, an image indexing and retrieval approach, using local color features and a modifie... more In this study, an image indexing and retrieval approach, using local color features and a modified weighted color distortion measure, is proposed. In the proposed approach, each image is segmented into several regions by a watershed segmentation algorithm, and then the mutual relationships between connected color regions are extracted as local color features. That is, an image can be represented as a set of connected (adjacent) color regions and the mutual relationships between connected color regions. In the image retrieval stage, the similarity between a query image and a target image will contain not only direct region correspondence but also the mutual relationships between connected color regions. A modified weighted color distortion measure is proposed, in which different color elements in the YUV color space receive different weights so that the illumination variation effect is greatly reduced.

For entropy-coded MPEG-2 video frames, a transmission error will not only affect the underlying c... more For entropy-coded MPEG-2 video frames, a transmission error will not only affect the underlying codeword but also may affect subsequent codewords, resulting in a great degradation of the received video frames. In this study, transmission errors in MPEG-2 video frames are first detected and located by the error detection scheme proposed by Shyu and Leou [1999], and then the corrupted blocks are concealed by the proposed hybrid error concealment scheme. Based on the condition of a corrupted block, a corrupted block in an intracoded I frame is concealed by either the spatial error concealment algorithm in H.26L test model long-term number 9 (TML-9) or the best neighborhood matching (BNM) algorithm followed by the proposed modified spatial anisotropic diffusion (SD) algorithm. A corrupted block in an inter-coded P or B frame is concealed by the proposed motion-compensated BNM algorithm. Based on the simulation results obtained in this study, the proposed scheme can recover high-quality MPEG-2 video frames from the corresponding corrupted video frames up to a bit error rate of 0.5%.

Wireless visual sensor networks are potentially applicable for several emerging applications. Sin... more Wireless visual sensor networks are potentially applicable for several emerging applications. Since the data size of the video captured from multiple sensors increases in proportion to the number of video sensors, the efficient compression of video data from multiple sensors is important and still challenging. However, most current multiview video coding approaches extended from single-view video coding standards perform both interview and temporal predictions at the encoder with very high computational complexity, which is not suitable for resource-limited video sensors. In this paper, a resource-scalable low-complexity multiview distributed video coding scheme is proposed. We study efficient exploitation of interview correlation by exchanging the media hash data extracted from video frames of adjacent video sensor nodes at the encoder and using the global motion parameters estimated and fed back from the decoder to improve coding efficiency. In addition, we present a power-rate-distortion (PRD) model to characterize the relationship between the available resources (e.g., power supply and target bit rate) and the RD performance. More specifically, an RD function in terms of the percentages for different coding modes of blocks and the target bit rate under the available resource constraints is derived for optimal block coding mode decision. Analytic results are provided to verify the resource scalability and accuracy of the proposed PRD model, which can provide a theoretical guideline for performance optimization in low-complexity video coding under limited resource constraints. The coding efficiency of the proposed low-complexity video codec is demonstrated via simulation results to outperform three known low-complexity video codecs, especially at high power and low bit rates.

In distributed video coding, individual frames are encoded independently but decoded conditionall... more In distributed video coding, individual frames are encoded independently but decoded conditionally. The Wyner-Ziv theorem-based source coding with side information only available at the decoder states that an intraframe encoder with interframe decoder system can approach the efficiency of a conventional interframe encoder and decoder system. In this paper, a new block discrete cosine transform (DCT)based Wyner-Ziv video codec with coding mode-aided motion compensation at the decoder is proposed. The key is that for each block, a large amount of candidate blocks are evaluated based on some criteria derived from Reed-Solomon (RS) decoding and best neighborhood matching to find the best candidate block as the side information. Another characteristic is that error correction code (ECC) decoding is proposed to participate in generating side information. Compared with some known Wyner-Ziv video coding systems, in the proposed video codec, no extra information should be transmitted and feedback channel is unnecessary. The coding performance of our method has been verified through simulations.

Compressive sensing (CS) has recently attracted much attention due to its unique feature of direc... more Compressive sensing (CS) has recently attracted much attention due to its unique feature of directly and simultaneously acquiring compressed and encrypted data based on their sparse or compressible properties. To securely transmit compressively sensed multimedia data over networks, it is required to support transcoder to securely convert compressed multimedia into several different types for diverse receivers. In this paper, a secure transcoding scheme for compressive multimedia sensing is proposed. We focus on securely converting compressively sensed multimedia data (not data compressed via standard codec) with a certain number of measurements into other different numbers of measurements without resorting to reconstruct the original data. We show that the security can be achieved via transforming multimedia re-sensing process into another secure domain at the transcoder. We also show that the computational security can be achieved while transmitting compressively sensed data between the sender (or each receiver) and the transcoder over networks.

To meet the requirements of resource-limited video sensors, lowcomplexity video encoding techniqu... more To meet the requirements of resource-limited video sensors, lowcomplexity video encoding technique is highly desired. In this paper, we propose a low-complexity power-scalable multi-view distributed video encoding scheme by using the correlations among video frames from adjacent video sensor nodes via robust media hashing extracted at encoder and using the global motion parameters estimated and fed back from the decoder. In addition, the proposed method is power-scalable, which is adaptive based on the available power supply of the video sensor. The powerrate-distortion behavior of the proposed scheme is also analyzed in order to maximize the video quality under limited sensor resource allocation. Index Terms-Low-complexity video coding, multi-view distributed video coding, power-scalable video coding, wireless video sensor networks

Journal of Visual Communication and Image Representation, 2005

Journal of Electronic Imaging, 2005

Real-time Imaging, 2005

Journal of Visual Communication and Image Representation, 2006

Journal of Visual Communication and Image Representation, 2004

Journal of Visual Communication and Image Representation, 2006

For an entropy-coded Joint Photographic Experts Group (JPEG) image, a transmission error in a cod... more For an entropy-coded Joint Photographic Experts Group (JPEG) image, a transmission error in a codeword will not only affect the underlying codeword but also may affect subsequent codewords, resulting in a great degradation of the received image. In this study, an error resilient coding scheme for JPEG image transmission based on data embedding and side-match vector quantization (VQ) is proposed. To cope with the synchronization problem, the restart capability of JPEG images is enabled. The objective of the proposed scheme is to recover high-quality JPEG images from the corresponding corrupted images. At the encoder, the important data (the codebook index) for each Y (U or V) block in a JPEG image are extracted and embedded into another ''masking'' Y (U or V) block in the image by the odd-even data embedding scheme. At the decoder, after all the corrupted blocks within a JPEG image are detected and located, if the codebook index for a corrupted block can be correctly extracted from the corresponding ''masking'' block, the extracted codebook index will be used to conceal the corrupted block; otherwise, the side-match VQ technique is employed to conceal the corrupted block. Based on the simulation results obtained in this study, the performance of the proposed scheme is better than those of the five existing approaches for comparison. The proposed scheme can recover high-quality JPEG images from the corresponding corrupted images up to a block loss rate (BLR) of 30%.

Journal of Visual Communication and Image Representation, 2005

For entropy-coded MPEG-2 video frames, a transmission error will not only affect the underlying c... more For entropy-coded MPEG-2 video frames, a transmission error will not only affect the underlying codeword but also may affect subsequent codewords, resulting in a great degradation of the received video frames. In this study, transmission errors in MPEG-2 video frames are first detected and located by the error detection scheme proposed by Shyu and Leou [1999], and then the corrupted blocks are concealed by the proposed hybrid error concealment scheme. Based on the condition of a corrupted block, a corrupted block in an intracoded I frame is concealed by either the spatial error concealment algorithm in H.26L test model long-term number 9 (TML-9) or the best neighborhood matching (BNM) algorithm followed by the proposed modified spatial anisotropic diffusion (SD) algorithm. A corrupted block in an inter-coded P or B frame is concealed by the proposed motion-compensated BNM algorithm. Based on the simulation results obtained in this study, the proposed scheme can recover high-quality MPEG-2 video frames from the corresponding corrupted video frames up to a bit error rate of 0.5%.