Sung-Chang Lim

Deblocking Filtering for Illumination Compensation in Multiview Video Coding

A deblocking filtering method that reduces the blocking artifacts that result from the use of the illumination change-adaptive motion compensation method, which was already adopted in the current multiview video coding (MVC) standard, is introduced. When the macroblock (MB)-based illumination compensation method is used to compensate local illumination changes in multiview video sequences, the neighboring MBs could have different illumination values that represent the average values of the luminance MBs, horizontally and vertically. This phenomenon causes horizontal/vertical blocking artifacts on the MB boundaries due to the difference in illumination between the neighboring MBs. The proposed deblocking filtering method is designed to reduce this phenomenon by using the adequately modified boundary strength derivation process of the current H.264/AVC deblocking filtering mechanism. The proposed deblocking filtering method improves the subjective video quality and provides slightly better objective video quality in multiview video sequences.

Rate control based on linear regression for H.264/MPEG-4 AVC

An efficient rate control algorithm is required to transmit coded video sequences without abrupt changes in quality due to the limited channel bandwidth. Thus, in this paper, an efficient rate control method is proposed for the H.264/MPEG (Moving Picture Experts Group)-4 Advanced Video Coding (AVC) baseline profile that meets the above constraint by using a @r-domain source model. Firstly, a simple target bits determination method that considers the ideal buffer level is proposed, and secondly, a method of adequately determining the Quantization Parameter (QP) is presented using two kinds of linear regression. The experimental results show that the proposed rate control algorithm using the above two methods performs better than other rate control algorithms for H.264/MPEG-4 AVC in terms of the rate estimation error and the standard deviation of the Peak Signal-to- Noise Ratio (PSNR), which provides a measure of the constancy of the video quality throughout the whole video sequence.

Rate-distortion optimized adaptive transform coding

We propose a rate-distortion optimized transform coding method that adaptively employs either integer cosine transform that is an integer-approximated version of discrete cosine transform (DCT) or integer sine transform (IST) in a rate-distortion sense. The DCT that has been adopted in most video-coding standards is known as a suboptimal substitute for the Karhunen-Loeve transform. However, according to the correlation of a signal, an alternative transform can achieve higher coding efficiency. We introduce a discrete sine transform (DST) that achieves the high-energy compactness in a correlation coefficient range of −0.5 to 0.5 and is applied to the current design of H.264/AVC (advanced video coding). Moreover, to avoid the encoder and decoder mismatch and make the implementation simple, an IST that is an integer-approximated version of the DST is developed. The experimental results show that the proposed method achieves a Bjontegaard Delta-RATE gain up to 5.49% compared to Joint model 11.0.

Development of an ultra-HD HEVC encoder using SIMD implementation and fast encoding schemes for smart surveillance system

High efficiency video coding (HEVC) is the newest video coding standard that can support powerful video compression performance with increased picture resolution for ultrahigh definition (UHD). Compared to the previous standard, HEVC achieved a coding efficiency double with a tremendous increase in encoder computational complexity, making support of commercial applications for UHD video service difficult. Especially, optimized HEVC encoder for UHD is expected to be deployed as a key technology for an emerging smart surveillance system in Internet of Things environment. Single-instruction-multiple-data implementation on an Intel x86 processor and several fast encoding schemes were investigated for the complexity reduction of the HEVC reference model (HM) encoder. Fast encoding schemes included early termination processes and data-level parallel processing. The computational complexity of the proposed HEVC encoder was decreased by approximately 192 times compared with HM encoder with an acceptable coding loss.

Improving Encoder Complexity and Coding Method of the Split Information in HEVC

This paper proposes the coding method to predict the split structure of LCU in the current frame on the basis of the reference frame or temporally-previous frame. HEVC encoder determines split structure according to image characteristics in LCU which is an basic element of CU. The split structure of the current LCU is very similar to the split structure of collocated LCU in the reference frame or temporally-previous frame. Thus, this paper proposes the method to reduce the encoder computational complexity by predicting split structure of the current LCU on the basis of that of collocated LCU in the reference frame or temporally-previous frame. And it also proposes the method to reduce the BD-Bitrate by coding after the prediction of the CU split information. The simulation results of changing only encoder showed that the mean of encoder computational complexity was lower by 21.3%, the decoder computational complexity was negligible change and the BD-Bitrate increase by the maximum of 0.6%. Also, the method changing encoder, bitstream, and decoder improves the mean of encoder computational complexity was lower by 22%, the decoder computational complexity was negligible change and the BD-Bitrate is improved to the maximum of 0.3%. When compared with the conventional method, indicating that the proposed method is superior.

High coding Efficiency video codec for entertainment-quality

We present a novel video codec for supporting entertainment-quality. It has new coding tools that are intra prediction with offset, integer sine transform with adaptive quantization matrix selection, uni-directional intra prediction, and enhanced block-based adaptive loop filter. These tools are used adaptively in processing of transform, intra prediction, and loop filtering. In experiments, the proposed codec achieved high rate reduction by average 14.77% BD-rate relative to H.264/AVC for 720p sequences.1

Intra Prediction Offset Compensation for Improving Video Coding Efficiency

In this paper, an intra prediction offset compensation method is proposed to improve intra prediction in H.264/AVC. In H.264/AVC, intra prediction based on various directions improves the coding efficiency by removing spatial correlation between neighboring blocks. In details, neighboring pixels in reconstructed block can be used as intra reference block for the current block to be coded when intra prediction method is used. In order to reduce further the prediction error of the intra reference block, the proposed method introduces an intra prediction offset which is determined in the sense of the rate-distortion optimization and is added to the conventional intra prediction block. Besides the intra prediction offset compensation, the coefficient thresholding method which is used for inter coding in JM 11.0, is used for chroma component in intra block, which leads the improvement of the luma coding efficiency of the proposed method. In experiments, we show that the proposed method achieves average 2.45% in High Profile condition and maximum 4.41% of bitrate reduction relative to JM 11.0.

Constrained in-loop filtering for error resiliency in high efficiency video coding

Abstract. In error-prone environments, packets could be lost during the transmission of compressed video bitstream, and corrupted errors by the lost packets could be propagated until it meets a refresh point. To defect the error propagation, constrained intra-prediction in high efficiency video coding (HEVC) performs intra-prediction using only neighboring intra-coded samples. However, the errors could be propagated to intra-coded blocks by an in-loop filtering process, since the in-loop filtering is performed regardless of the prediction modes of blocks, even though constrained intra-prediction is used. In this paper, a constrained in-loop filtering is proposed to protect intra-coded samples from error propagation by adaptively applying filters depending on the prediction modes of reconstructed blocks. Simulation results show that the proposed method alleviates the distortion of the decoded pictures and thereby improves both subjective and objective quality compared with the HEVC standard.

Uni-directional 8X8 Intra Prediction for H.264 Coding Efficiency

This paper is ready to change a trend of a ultra high definition (UHD) video image, and it will contribute to improve the performance of the latest H.264 through the Uni-directional intra-prediction idea which is based on developing a intra prediction compression. The Uni-directional intra prediction is focused on a block intra prediction using block based prediction which is using the same direction of intra prediction. This paper describes that the uni-directional intra-prediction gets a improvement around 7.3% BDBR only in the block size, and it gets a improvement around 1.3% BDBR in the H.264 applied to the multi block size structures. In the case of a larger image size, it can be changed to a good algorithm. Because the video codec which is optimized for UHD resolution can be used a different block size which is bigger than before(currently a minimum of blocks of units).

Alternative Transform for Residual Blocks in H.264/AVC

In this paper, an alternative transform based on the correlation of the residual block is proposed for the improvement of the H.264/AVC coding efficiency. A discrete sine transform is used alternately with a discrete cosine transform in order to greatly compact the energy of the signal when the correlation coefficients of the signal are in the range of -0.5 to 0.5. Therefore, the discrete sine transform is suggested to be used in conjunction with the discrete cosine transform in H.264/AVC. The alternative transform selecting the optimal transform between two transforms by using rate-distortion optimization shows a coding gain compared with H.264/AVC. The proposed method achieves a PSNR gain of up to 1.0 dB compared to JM 10.2 at relatively high bitrates.