Hyang-Mi Yoo

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.

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.

Improved reversible data hiding based on histogram modification of difference images

In this paper, we propose a new reversible data hiding algorithm using the histogram modification of difference images. The histogram modification method has been used for reversible data hiding remarkably. However, this method has the underflow/overflow problems. To overcome these problems, we embed the compressed location map to identify the points of underflow and overflow. Therefore, the proposed algorithm can recover the original image quite simply without the overhead information. In addition, because we use the multilevel data hiding scheme, we can get a large amount of embedding data while keeping low distortion. Experimental results are presented to demonstrate the validity of the proposed algorithm.

Reversible data hiding without side information

Reversible data hiding algorithms based on histogram shift generate side information in the process of data embedding. The side information can be regarded as a secret key to extract the embedded data but its size generally increases proportionally to the amount of embedded data. To overcome this problem, the side information is included as some parts of embedded data in the proposed reversible data hiding algorithm. Experimental results demonstrate that the proposed scheme can embed a large amount of pure data while keeping high visual quality without the side information.

Reversible Data Hiding Using the Histogram Modification of Block Image

Reversible data hiding has drawn considerable attention in recent years. Reversible data hiding recover the original image without any distortion after the hidden data have been extracted. However, one of drawbacks for existing reversible data hiding is underflow and overflow. To overcome these problems, we propose a new reversible data hiding algorithm based on histogram modification of block image. The experimental results and performance comparisons with other reversible data hiding schemes are presented to demonstrate the validity of our proposed algorithm.

Fast CU Decision Algorithm using the Initial CU Size Estimation and PU modes' RD Cost

High Efficiency Video Coding(HEVC) obtains high compression ratio by applying recursive quad-tree structured coding unit(CU). However, this recursive quad-tree structure brings very high computational complexity to HEVC encoder. In this paper, we present fast CU decision algorithm in recursive quad-tree structure. The proposed algorithm estimates initial CU size before CTU encoding and checks the proposed condition using Coded Block Flag(CBF) and Rate-distortion cost to achieve the fast encoding time saving. And, intra mode estimation is also possible to be skipped using the CBF values acquired during the inter PU mode estimations. Experiment results shows that the proposed algorithm saved about 49.91% and 37.97% of encoding time according to the weighting condition.

Reversible data hiding employing histogram shifting using a rotated even–odd difference image

Reversible data hiding, a technique that can recover an undistorted original image from a watermarked one, has drawn considerable attention in recent years. However, most of the current reversible data-hiding algorithms based on histogram modification have underflow and overflow problems with regard to the watermarked image. In order to overcome these problems in the proposed algorithm, we implement a location map that indicates the positions of the underflow and overflow problems and include the compressed location map in the hidden data. In addition, the proposed algorithm allows multi-level data hiding in order to increase the data-hiding capacity. The simulation results demonstrate that the proposed algorithm generates a superior performance in the peak signal to noise ratio (PSNR) values and the embedding capacity.

Reversible watermarking without underflow and overflow problems

Reversible watermarking, a technique that can recover an undistorted original image from a watermarked one, has drawn considerable attention in recent years. However, most of the current reversible watermarking algorithms based on histogram shifting have underflow and overflow problems in regards to the watermarked image due to the histogram shift. In order to nip these problems in the bud, in the proposed algorithm the lower and upper bound pixel levels are modified into the nearest neighbor pixel levels and the position information of the modified pixel levels are embedded in the watermarked image. In addition, to increase the data hiding capacity while keeping high visual quality of the watermarked image we allows multi-level data hiding using a rotated even-odd difference image. The simulation results demonstrate that the proposed algorithm generates a superior performance in the PSNR values and the embedding capacity.