Jae-Won Suh

Error concealment based on directional interpolation

Compressed bitstreams are, in general, very sensitive to channel errors. For instance, a single bit error in a coded video bitstream may cause severe degradation on picture quality. When bit errors occur during transmission and cannot be corrected by an error correction scheme, error concealment is needed to conceal the corrupted image at the receiver. Error concealment algorithms attempt to repair damaged portions of the picture by exploiting both the spatial and the temporal redundancies in the received and reconstructed video signal. We discuss several temporal, spatial, and transform-domain error concealment techniques for MPEG coded pictures, and propose a new scheme based on directional interpolation. We also compare the performance of these techniques by computer simulation.

Error concealment techniques for digital TV

Compressed video bitstreams are intended for real-time transmission over communication networks. Most of the video coding standards employ the temporal and spatial prediction structure to reduce the transmitted video data. Therefore, the coded video bitstreams are highly sensitive to information loss and channel errors. Even a single bit error can lead to disastrous quality degradation in both time and space. This quality deterioration is exacerbated when no error resilient coding mechanism is employed to protect coded video data against the error prone environments. Error concealment is a data recovery technique that enables the decoder to conceal effects of transmission errors by predicting the lost or corrupted video data from the previously reconstructed error-free information. Motion vector recovery and motion compensation with the estimated motion vector is a good approach to conceal the corrupted macroblock data. In this paper, we develop various error concealment algorithms based on motion vector recovery, and compare their performances to those of conventional error concealment methods.

Fast coding unit decision algorithm based on inter and intra prediction unit termination for HEVC

To provide highly efficient video coding standard, the new high efficiency video coding (HEVC) standard has adopted a recursive quad-tree structured coding unit (CU) and a transform unit (TU). Although the HEVC obtains a very high coding efficiency but it considerably increases the computational complexity because the encoder tests every possible CU in order to estimate the coding performance of each CU. In this paper, we propose a fast CU decision algorithm based on Inter and Intra PU termination for the HEVC to reduce the computational complexity. The proposed algorithm checks code block flag (CBF) value and rate distortion (RD) cost for inter PU prediction. If these two values are satisfied with our present conditions, the next PU process is terminated in the current CU. Experiment result shows that the proposed algorithm reduces the encoding time average 49.56% and 37.3% according to the weighted condition of our proposed algorithm.

Walking Number Detection Algorithm using a 3-Axial Accelerometer Sensor and Activity Monitoring

The research for a 3-axial accelerometer sensor has increased dramatically in the fields of cellular phone, PDA, etc. In this paper, we develop a human walking detection algorithm using 3-axial accelerometer sensor and a user interface system to show the activity expenditure in real-time. To measure a walking number more correctly in a variety of walking activities including walking, walking in place, running, slow walking, we propose a new walking number detection algorithm using adaptive threshold value. In addition, we calculate the activity expenditure base on counted walking number and display calculated activity expenditure on UI in real-time. From the experimental results, we could obtain that the detection rate of proposal algorithm is higher than that of existing algorithm using a fixed threshold value about . Especially, it could be found out high detection rate in walking in place.

A fast intra mode skip decision algorithm based on adaptive motion vector map

A fast intra mode skip decision algorithm for H.264/AVC video encoding is proposed in this paper. Although the intra macroblock (MB) prediction algorithm, based on various prediction methods based in the pixel domain instead of in the transformed domain, increases the compression ratio, it requires a significant increase in the computational complexity. Although the intra MBs are only a small part of the whole inter frame, large computational loads occur because all MBs must be examined by the intra mode prediction process. To reduce the processing time for the inter frame mode decision, a fast intra mode skip decision scheme is proposed using an adaptive motion vector map (AMVM) algorithm for the H.264/AVC video encoder. It is verified that the proposed algorithm generates generally good performances in PSNR, bit rate, and processing time.

Fast mode decision for combined scalable video coding based on the block complexity function

Scalable Video Coding is an H.264/AVC scalable extension that is used to provide various network-friendly scalability using a single bit stream. In SVC, the newly adapted predictive coding techniques can achieve high encoding efficiency, but they increase the computational complexity. To reduce the computational complexity, we present a fast mode decision algorithm based on the block complexity function considering the degree of correlation between base layer and enhancement layer. The simulation results show that the encoding time of the proposed fast mode decision algorithm for the combined scalability is about 54.72% compared with normal method although the loss of visual quality is negligible.

Recovery of motion vectors for error concealment

A compressed bitstream generated by an MPEG-2 video coder is sensitive to channel errors. Due to the coding structure of the MPEG-2 video compression algorithm, a bit error can affect not only the current picture frame but also succeeding frames. In this paper, we propose a temporal domain error concealment algorithm to recover lost or erroneously received motion vectors. In order to estimate the motion vector of the erroneous macroblock at the decoder, we examine neighboring luminance intensity values of the lost macroblock. Simulation results show that the proposed algorithm produces reconstructed pictures of acceptable quality.

High capacity reversible data hiding using the histogram modification of block image

Reversible data hiding which can recover the original image without any distortion after extraction of the hidden data has drawn considerable attention in recent years. However, the problems of underflow and overflow have occurred occasionally in watermarked image. To overcome these problems, we propose a new reversible data hiding algorithm based on histogram modification of block image. In addition, the proposed algorithm allows for multilevel data hiding to increase the hiding capacity. Simulation results demonstrate that the proposed algorithm generates good performances in the subjective visual quality, PSNR between original image and watermarked image, and the hiding capacity.

Fragile Watermarking Based on Localized Histogram Modification

In this paper, we propose a fragile watermarking algorithm for image authentication and integrity. Existing fragile watermarking algorithms had to accept the image distortion in order to insert the watermark. To overcome this drawback, we propose a new fragile watermarking algorithm which can recover the original image after extracting the watermark. Experimental results are presented to demonstrate the validity of the proposed algorithm.

Motion vector recovery for error concealment

This paper describes an error concealment algorithm to reduce the effect of channel errors in the bitstreams generated by motion compensated video coding algorithms such as MPEG. When channel errors are introduced during transmission and cannot be corrected properly, we can apply an error concealment technique to repair damaged portions of the picture by exploiting the spatial and temporal redundancies in the received and reconstructed video signal. In motion compensated video coding, if some bits are lost or received with errors, not only the current picture will be corrupted, but also errors will propagate to succeeding frames. In this paper, we analyze the effect of channel errors in MPEG-2 bitstreams, and propose an idea for recovering lost or erroneously received motion vectors. Extended luminance intensity value of the lost block is used for motion estimation at the decoder side. Simulation results show that the proposed algorithm achieves good performance in PSNR and provides good subjective image quality.