Haechul Choi

Generalized elastic graph matching for face recognition

Elastic graph matching (EGM) is a well-known approach in face recognition area for the robust face recognition to a rotation in depth and facial expression change. We extended the conventional EGM to the generalized EGM (G-EGM), which is afford to handle even globally warped faces, by enhancing the robustness of node descriptors to a global warping, and introducing warping-compensated edges in graph matching cost function. The improved performance of the G-EGM was evaluated through the recognition simulation based on arbitrary posed faces.

Dynamic and Interoperable Adaptation of SVC for QoS-Enabled Streaming

For seamless streaming of multimedia contents that ensures quality of service (QoS) over heterogeneous network, we propose a flexible and low-complexity adaptation scheme of scalable video coding (SVC) using MPEG-21 digital item adaptation (DIA). For adaptation, delivery, and consumption of SVC, the proposed scheme was simulated via various time-varying constraints of network condition, terminal capability, and user preference, which showed robustness and efficiency in dynamic and interoperable adaptation of SVC.

A Statistical Approach for Fast Mode Decision in Scalable Video Coding

In scalable video coding (SVC), an exhaustive mode decision is performed to search for the best mode at each macroblock. Although this method achieves an optimal trade-off between rate and distortion, it introduces an extreme computational burden on the encoder. In this letter, we propose a fast mode decision algorithm that can reduce the computational load of the mode decision for SVC. We statistically derive the expectation of the rate-distortion cost (RDcost) increase caused by skipping each mode in the mode decision. In the proposed algorithm, the encoder performs the mode decision using a small number of modes that are determined based on the expected increase of the RDcost. Experimental results show that the proposed algorithm can reduce the computational complexity significantly with negligible video quality degradation and bitrate increment.

Intra-mixture Prediction Mode and Enhanced Most Probable Mode Estimation for Intra Coding in H.264/AVC

H.264/AVC supports various block sizes for intra prediction to reduce spatial redundancy such as 4x4, 8x8 (FRExt only) and 16x16, and the blocks are predicted from neighboring reconstructed pixels by using directional prediction modes. The directional prediction mode indices are coded by using a predictive coding method, in which the most probable mode (MPM) is derived from neighboring macroblocks (MB). In this paper, we present intra-mixture prediction (IMP) mode for intra prediction and an enhanced estimation method for most probable mode (MPM). IMP mode supports more flexibility in intra prediction by mixing 4x4 blocks and 8x8 blocks in one macroblock, while the enhanced MPM estimation extends the number of referenced neighboring blocks and efficiently uses their prediction modes depending on their positions. Simulation results show that the combination of both proposed methods increases the BD-bitrate by up to -4.16% compared to H.264/AVC.

SVC Application in Advanced T-DMB

Commercial terrestrial digital multimedia broadcasting (T-DMB) service was launched in the Republic of Korea. Reflecting recent demands of high quality video, Advanced T-DMB(AT-DMB) adopting a hierarchical modulation is being developed as the way to increase the payload data. Based on the AT-DMB system, this paper proposes a method to provide increased video quality with high spatial resolution. By using the emerging H.264/MPEG-4 AVC amendment 3 scalable extension (SVC), the proposed method is able to support high spatial resolution as well as the currently serviced spatial resolution while retaining the backward compatibility to T-DMB. In the experimental results, the benefits in terms of coding efficiency and spatial scalability are proven in comparison with the conventional T-DMB and alternative methods to provide a high spatial resolution video.

Fast transform unit decision for HEVC

For the High Efficiency Video Coding (HEVC) standard, a fast transform unit (TU) decision method is proposed. HEVC defines the TU representing a region sharing the same transformation, and it supports various transform sizes from 4×4 to 32×32 by using a quadtree of TUs. The various sizes of TUs can provide good coding efficiency, whereas it may increase dramatically encoding complexity. Assuming that a TU with highly compacted energy is unlikely to be split, the proposed method determines an appropriate TU size according to the position of the last non-zero transform coefficient and the number of zero transform coefficients. Experimental results show that this reduces encoding run time by 14% with a negligible coding loss of 0.38% BD-rate from Random_access_main case.

Scalable Video Coding Using Large Block and its Performance Analysis

Recently, High-Efficiency Video Coding (HEVC) has been developed as a new video coding standard mainly focusing on the coding of ultra high definition (UHD) videos as the high resolution and high quality videos are getting more popular. Furthermore, the scalable extension of HEVC is being standardized for more efficient provision of HD and UHD services in the communications-broadcasting convergence environment. In this paper, we propose an improved scalable video coding method of H.264/AVC to achieve high coding efficiency particularly for UHD and HD videos. The basic idea is to allow large block size in H.264/AVC SVC, which results in more efficient inter-layer prediction and syntax elements coding. The experimental results show that it achieves an average 4.53% reduction in BD-rate relative to H.264/AVC SVC. Keyword : Scalable video coding (SVC), large block, ultra-high definition (UHD) (Regular Paper)

Adaptive Depth Fusion based on Reliability of Depth Cues for 2D-to-3D Video Conversion

3D video is regarded as the next generation contents in numerous applications. The 2D-to-3D video conversion technologies are strongly required to resolve a lack of 3D videos during the period of transition to the full ripe 3D video era. In 2D-to-3D conversion methods, after the depth image of each scene in 2D video is estimated, stereoscopic video is synthesized using DIBR (Depth Image Based Rendering) technologies. This paper proposes a novel depth fusion algorithm that integrates multiple depth cues contained in 2D video to generate stereoscopic video. For the proper depth fusion, it is checked whether some cues are reliable or not in current scene. Based on the result of the reliability tests, current scene is classified into one of 4 scene types and scene-adaptive depth fusion is applied to combine those reliable depth cues to generate the final depth information. Simulation results show that each depth cue is reasonably utilized according to scene types and final depth is generated by cues which can effectively represent the current scene.

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.

MPEG-21 enabled SVC Adaptation for Multi-User QoS-Adaptive Streaming

This paper presents a systematic approach to adapt a SVC bitstream to support multiple users simultaneously. Also, we show how the tools of MPEG-21 DIA can be used to enable interoperable and automatic adaptation in this case. The solution of our approach provides the users with optimal overall quality, a wide flexibility, and seamless adaptation.