• Journal of Broadcast Engineering
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• v.19 no.5
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• pp.627-630
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• 2014

The latest video coding standard, high efficiency video coding (HEVC) achieves high coding efficiency by employing a quadtree-based coding unit (CU) block partitioning structure which allows recursive splitting into four equally sized blocks. At each depth level, each CU is partitioned into variable sized blocks of prediction units (PUs). However, the determination of the best CU partition for each coding tree unit (CTU) and the best PU mode for each CU causes a dramatic increase in computational complexity. To reduce such computational complexity, we propose a fast PU decision algorithm that early terminates PU search. The proposed method skips the computation of R-D cost for certain PU modes in the current CU based on the best mode and the rate-distortion (RD) cost of the upper depth CU. Experimental results show that the proposed method reduces the computational complexity of HM12.0 to 18.1% with only 0.2% increases in BD-rate.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2013.11a
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• pp.172-173
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• 2013

최근 표준화가 완료된 HEVO(High Efficiency Video Coding)에서는 계층적 구조를 갖는 가변블록의 크기를 사용하고 재귀적으로 부호화를 수행사여, 최적의 부호화단위(CU: Coding Unit) 분할 구조와 예측단위(PU: Prediction Unit)를 결정함으로써 높은 부호화 효율을 얻을 수 있는 반면 부호화 복잡도가 증가하는 문제가 있다. 본 논문에서는 부호화기의 복잡도를 감소시키기 위한 고속 부호화 알고리즘으로 고속 모드 결정 기법을 제안한다. 제안기법은 상위 깊이(CU: Coding Unit)의 최적 모드와 부호화 율-왜곡 비용을 이용해서 현재 깊이 CU에서의 특정 모드의 율-왜곡 비용 계산을 생략함으로써 PU 탐색을 조기 종료한다. 즉, 상위 깊이 CU의 조건에 따라 화면간 예측 모드의 일부 또는 화면내 예측을 수행하지 않는다. 실험결과 제안기법은 HM 12.0대비 0.2%의 비트 증가에 22.9%의 계산시간 감소 효과를 얻을 수 있음을 확인하였다.

• Journal of Broadcast Engineering
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• v.20 no.2
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• pp.340-347
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• 2015

HEVC (High Efficiency Video Coding) achieves high coding efficiency by employing a quadtree-based coding unit (CU) block partitioning structure and various prediction units (PUs), and the determination of the best CU partition structure and the best PU mode based on rate-distortion (R-D) cost. However, the computation complexity of encoding also dramatically increases. In this paper, to reduce such encoding computational complexity, we propose three fast PU mode decision methods based on encoding information of upper depth as follows. In the first method, the search of PU mode of the current CU is early terminated based on the sub-CBF (Coded Block Flag) of upper depth. In the second method, the search of intra prediction modes of PU in the current CU is skipped based on the sub-Intra R-D cost of upper depth. In the last method, the search of intra prediction modes of PU in the lower depth's CUs is skipped based on the sub-CBF of the current depth's CU. Experimental results show that the three proposed methods reduce the computational complexity of HM 14.0 to 31.4%, 2.5%, and 23.4% with BD-rate increase of 1.2%, 0.11%, and 0.9%, respectively. The three methods can be applied in a combined way to be applied to both of inter prediction and intra prediction, which results in the complexity reduction of 34.2% with 1.9% BD-rate increase.

• Journal of Broadcast Engineering
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• v.20 no.4
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• pp.533-544
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• 2015

Recently, most of the video services are usually transmitted in wireless networks. In networks environment, a packet of video is likely to be lost during transmission. For this reason, this paper proposes a new Error Concealment (EC) algorithm. For High Efficiency Video Coding (HEVC) bitstreams, the proposed algorithm includes Adaptive Prediction Unit-based Motion Vector Extrapolation (APMVE) and Boundary Matching (BM) algorithm, which employs both the temporal and spatial correlation. APMVE adaptively decides a Error Concealment Basic Unit (ECBU) by using the PU information of the previous frame and BM employing the spatial correlation is applied to only unreliable blocks. Simulation results show that the proposed algorithm provides the higher subjective quality by reducing blocking artifacts which appear in other existing algorithms.

• IEIE Transactions on Smart Processing and Computing
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• v.4 no.1
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• pp.16-21
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• 2015

Most video services are transmitted in wireless networks. In a network environment, a packet of video is likely to be lost during transmission. For this reason, numerous error concealment (EC) algorithms have been proposed to combat channel errors. On the other hand, most existing algorithms cannot conceal the whole missing frame effectively. To resolve this problem, this paper proposes a new Adaptive Prediction Unit-based Motion Vector Extrapolation (APMVE) algorithm to restore the entire missing frame encoded by High Efficiency Video Coding (HEVC). In each missing HEVC frame, it uses the prediction unit (PU) information of the previous frame to adaptively decide the size of a basic unit for error concealment and to provide a more accurate estimation for the motion vector in that basic unit than can be achieved by any other conventional method. The simulation results showed that it is highly effective and significantly outperforms other existing frame recovery methods in terms of both objective and subjective quality.

• Journal of Information Processing Systems
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• v.18 no.2
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• pp.235-244
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• 2022

Many new techniques have been adopted in HEVC (High efficiency video coding) standard, such as quadtree-structured coding unit (CU), prediction unit (PU) partition, 35 intra-mode, and so on. To reduce computational complexity, the paper proposes two optimization algorithms which include fast CU depth range decision and fast PU partition mode decision. Firstly, depth range of CU is predicted according to spatial-temporal correlation. Secondly, we utilize the depth difference between the current CU and CU corresponding to the same position of adjacent frame for PU mode range selection. The number of traversal candidate modes is reduced. The experiment result shows the proposed algorithm obtains a lot of time reducing, and the loss of coding efficiency is inappreciable.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.11
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• pp.41-47
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• 2016

High efficiency video coding (HEVC) employs a coding tree unit (CTU) to improve the coding efficiency. A CTU consists of coding units (CU), prediction units (PU), and transform units (TU). All possible block partitions should be performed on each depth level to obtain the best combination of CUs, PUs, and TUs. To reduce the complexity of block partitioning process, this paper proposes the PU mode skip algorithm with region of interest (RoI) selection using motion vector. In addition, this paper presents the CU depth level skip algorithm using the co-located block information in the previously encoded frames. First, the RoI selection algorithm distinguishes between dynamic CTUs and static CTUs and then, asymmetric motion partitioning (AMP) blocks are skipped in the static CTUs. Second, the depth level skip algorithm predicts the most probable target depth level from average depth in one CTU. The experimental results show that the proposed fast CU decision algorithm can reduce the total encoding time up to 44.8% compared to the HEVC test model (HM) 14.0 reference software encoder. Moreover, the proposed algorithm shows only 2.5% Bjontegaard delta bit rate (BDBR) loss.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.49 no.3
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• pp.40-50
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• 2012

In this paper we propose the fast CU (Coding Unit) mode decision method. To reduce computational complexity and save encoding time of HEVC, we divided CU, PU (Prediction Unit) and TU (Transform Unit) decision process into two stages. In the first stage, because $2N{\times}2N$ PU mode is mostly selected among $2N{\times}2N$, $N{\times}2N$, $2N{\times}N$, $N{\times}N$ PU modes, proposed algorithm uses only $2N{\times}2N$ PU mode deciding depth of each CU in the LCU (Largest CU). And then, proposed method decides exact PU and TU modes at the depth level which is decided in the first stage. In addition, early skip decision rule is applied to the proposed method to obtain more efficient computational complexity reduction. The proposed method reduces computational complexity of the HEVC encoder by simplifying a CU depth decision method. We could obtain about 50% computational complexity reduction in comparison with HM 3.3 HEVC reference software while bitrate compressed by the proposed algorithm increases only 2%.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2014.11a
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• pp.194-196
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• 2014

HEVC(High Efficiency Video Coding)는 재귀적 쿼드트리 분할 구조의 부호화단위(CU: Coding Unit)와 각 CU에서 다양한 예측단위(PU: Prediction Unit)를 제공하고, 율-왜곡 기반으로 최적의 CU와 PU를 결정함으로써 높은 부호화 효율을 얻을 수 있는 반면 부호화 복잡도 또한 크게 증가하는 문제가 있다. 본 논문에서는 부호화기의 복잡도를 감소시키기 위해 상위깊이의 부호화 정보를 이용한 고속 부호화 기법을 제안한다. 제안기법은 상위깊이 CU의 Sub-CBF(coded block flag)를 이용하여 현재깊이 CU에서의 PU를 조기 결정하여 PU 탐색을 고속화 한다. 또한 화면내(Intra) 예측 고속화를 위하여 현재 CU의 sub-CBF를 함께 사용하여 하위깊이에서의 화면내 예측을 생략한다. 실험결과 제안기법은 HM 14.0 대비 1.2%의 BD-rate 증가에 31.4%의 부호화 시간 감소 효과를 얻을 수 있었다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2014.06a
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• pp.209-210
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• 2014

최근 인터넷 상에서 제공되는 영상 서비스에 대한 요구가 증가하고 있다. 하지만 네트워크 환경에서 전송되는 데이터는 오류로 인하여 쉽게 손실될 수 있다. 특히 HEVC(High Efficiency Video Coding)와 같이 높은 압축률로 압축된 정보에 대한 전송 오류는 영상 복원에 심각한 영향을 끼친다. 따라서 네트워크 환경에서 일정한 화질을 유지하기 위한 오류 은닉(Error Concealment : EC) 방법이 필요하다. 본 논문은 HEVC EC 를 위한 PU(Prediction Unit) 기반 움직임 벡터 외삽법(Motion Vector Extrapolation : MVE) 모델을 제안한다. PU 는 예측의 기본 단위로써 PU 내에 동일한 물체가 포함될 확률이 높다. 따라서, 이 모델은 손실된 프레임의 이전 프레임이 갖는 PU 정보를 이용하여 PU 단위로 외삽(extrapolation)을 실시한다. 또한, 손실된 블록과 외삽 블록간의 관계를 고려하여 겹쳐진(overlapped) 외삽 블록 중 가장 작은 PU 크기를 EC 기본 단위로 결정한다. 이 방법은 PU 정보를 반영함으로써 블록 경계 오류(block artifact)를 감소시킨다.