• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 ITC-CSCC -1
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• pp.117-120
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• 2000

As the use of real-time multimedia applications increases, a considerable amount of “greedy” UDP traffic would easily dominate network bandwidth and packet loss. As a result, bandwidth available to TCP connections is oppressed and their performance extremely deteriorates. In or-der that both TCP and UDP sessions fairly co-exist in the Internet, it is vital that we consider the fairness among both protocols. In this work, we implement a “TCP-friendly” rate control mechanism suitable to video applications and con-sider its applicability to a real system through observation of the video quality at the receiver and the connection state. It is shown that we can achieve high-quality and stable video transfer fairly sharing the network bandwidth with TCP by applying our rate control at a control interval of 32 times as long as RTT.

• 한국통신학회논문지
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• 제41권10호
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• pp.1155-1166
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• 2016

본 논문에서는 3차원 비트율-왜곡 최적화 기반 블록 부호화를 이용하는 새로운 임베디드 비디오 압축 방법을 제안한다. 제안한 방법에서는 입력되는 비디오 프레임에 움직임 보상 시간적 필터링(Motion Compensated Temporal Filtering, MCTF)를 적용하여 비디오의 시간적 중복성을 제거한 후, 비디오 프레임에 2차원 이산 웨이브렛 변환을 수행하여 공간적 중복성을 제거한다. 이러한 방법으로 생성된 3차원 웨이브렛 계수들은 비트율-왜곡비 기댓값에 따라 정렬되며 3차원 블록분할 부호화 방법을 이용하여 부호화된다. 또한 제안한 방법은 임베디드 특징을 유지하면서도 효과적으로 컬러 비디오를 부호화하는 방법과 효율적인 비트율 제어 방법을 사용한다. 실험 결과는 제안한 방법이 임베디드 비트스트림을 생성하면서도 기존의 비디오 압축 방법과 비교하여 우수한 성능을 제공함을 보여준다.

• 한국통신학회논문지
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• 제25권1B호
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• pp.77-88
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• 2000

본 논문은 블록 단위의 비디오 코더 (Video coder)에서 최적 모드들을 적절하게 선택할 수 있는 방법을 설명한다. 비트율의 제어에 관한 문제는 버퍼가 차 있는 양에 따라 양자화 레벨이 변하는 방법이 여러 학자들로부터 연구되어 왔다. 제시된 방법은 각각의 매크로블록(macroblock)에 관한 최적 모드를 검색하지 않고 최적 결정 곡선을 검색한다는 점에서 이전의 것, 즉[4]와는 다르다. 제시된 방법은 비트율의 제어를 위하여 운동보상 또는 비 운동 보상 및 intra/inter 코딩에 관한 결정 방법까지 포함된다. 이러한 결정 방법은 주어진, 즉 고장된 결정 곡선을 이용하는 것 보다 주어진 프레임에서 설정된 비트율(bit-rate)에 따른 총체적인 왜곡을 최소화시키는 유동적인 결정 곡선을 이용하는 것이 더 바람직하다. 가열냉각 최적화기술 (annealing optimization technique)의 모의실험을 통해 곡선을 도출할 수 있다. 알고리즘은 H.261 비디오 코텍(video codec)범위에서 수행되고 모의실험 또한 그 범위에서 결과들을 보여주고 이들을 여타의 접근방법들과 비교한다.

• 한국멀티미디어학회논문지
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• 제20권6호
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• pp.853-864
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• 2017

HD padding area is essential redundancy in HD broadcasting. It is possible to use this padding area for the purpose of improving DTV broadcasting services. For utilization of this area, The bit of a service data was converted to black and white $8{\times}8$ block image. Converted block images are compressed with active video and are delivered to a receiver as only DC coefficients in a video stream. video quality is not effected by the proposed method, and service data was perfectly recovered in receiver without errors by using block average and threshold. The proposed utilization of HD essential padding area can possibly overcome the limited transmission stream rate with the bandwidth of HD broadcasting. If service data in transport or video stram were transferred using this padding area, it is possible to improve video quality with expanded video stream rate. Additionally, because the proposed methods are based on well-established standards, it is also useful for world-wide HD broadcasting systems such as ATSC, DVB, and IPTV.

• International Journal of Quality Innovation
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• 제10권1호
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• pp.115-126
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• 2009

Video transmission effectiveness in the Ad Hoc network is becoming important recently, if different routing protocols are applied. Some researchers conclude that the reactive protocols are better for file transfer protocol (FTP) and constant bit rate (CBR) or hypertext transfer protocol (HTTP) transmission in an Ad Hoc wireless network but the performance report of video transmission is not much. This study adopts Qualnet (Network Simulator) as a simulation tool for environmental designing and performance testing, and employs an experimental design with eight groups. Our experiment shows that: (1) The performance of AODV (reactive) protocol is better than DSDV, ZRP and DSR when the transmission load has only one video stream; (2) Proactive (DSDV) and Hybrid protocols (ZRP) are better for a smaller Ad Hoc network when it transmits a video stream with some applications (VoIP, FTP and CBR). We conclude that packet loss rate is sensitive to the quality of video transmission and it has negative relationship with Peak Signal-to-Noise Ratio (PSNR) value. In addition, our experiment also shows that PSNR is a simple Metric for the performance evaluation of video transmission.

• 전자공학회논문지
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• 제50권8호
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• pp.245-249
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• 2013

In this paper, we propose two rate control algorithms for multi-view extension of HEVC with two rate control algorithms adopted in HEVC and analyze the multi-view rate control performance. The proposed multi-view rate controls are designed on HEVC-based multi-view video coding (MV-HEVC) platform with consideration of high-level syntax, inter-view prediction, etc. not only for the base view but also for the extended views using the rate control algorithms based on URQ (Unified Rate-Quantization) and R-lambda model adopted in HEVC. The proposed multi-view rate controls also contain view-wise target bit allocation for providing the compatibility to the base view. By allocating the target bitrates for each view, the proposed multi-view rate control based on URQ model achieved about 1.83% of average bitrate accuracy and 1.73dB of average PSNR degradation. In addition, about 2.97% of average bitrate accuracy and 0.31dB of average PSNR degradation are achieved with the proposed multi-view rate control based on R-lambda model.

• 대한전자공학회논문지SD
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• 제44권6호
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• pp.77-82
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• 2007

기존 H.264 프레임 단위 데이터율 제어는 버퍼 상태와 영상의 복잡도를 효율적으로 사용치 못하여 움직임이 많은 영상에 있어 영상 품질의 변화가 심한 단점이 있다. 특히 인코딩시 설정된 비트율이 낮고 (19.2 kbps 이하) 프레임율이 높아 (30 fps), 영상 프레임당 사용할 수 있는 비트가 작아지면 영상 품질의 변화는 더욱 심해진다. 본 논문에서는 안정된 영상품질과 버퍼상태를 얻기 위해 향상된 H.264 프레임 단위 데이터율 제어 알고리즘을 제안한다. 실험 결과, 제안한 알고리즘은 기존 알고리즘에 비해 향상된 결과를 보였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권11호
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• pp.2103-2120
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• 2011

In this research, we consider the replication strategy for the applications of video streaming in wireless mesh networks (WMNs). In particular, we propose a closed-form of optimal replication densities for a set of frames of a video streaming by exploiting not only the skewed access probability of each frame but also the skewed loss probability and skewed encoding rate-distortion information. The simulation results demonstrate that our method improves the replication performance in terms of user-perceived quality (UPQ) which includes: 1) minimum average maximum reconstructed distortion for high peak signal-to-noise ratio (PSNR), 2) small reconstructed distortion fluctuation among frames for smooth playback, and 3) reasonable average maximum transmission distance for continuous playback. Furthermore, the proposed strategy consumes smaller storage capacity compared to other existing optimal replication strategies. More importantly, the effect of encoding rate is carefully investigated to show that high encoding rate does not always gain high performance of replication for video streaming.

• Journal of Information Processing Systems
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• 제5권3호
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• pp.151-158
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• 2009

This paper proposes a utility-based data rate allocation algorithm to provide high-quality mobile video streaming over femtocell networks. We first derive a utility function to calculate the optimal data rates for maximizing the aggregate utilities of all mobile users in the femtocell. The total sum of optimal data rates is limited by the link capacity of the backhaul connections. Furthermore, electromagnetic cross-talk poses a serious problem for the backhaul connections, and its influence passes on to mobile users, as well as causing data rate degradation in the femtocell networks. We also have studied a fixed margin iterative water-filling algorithm to achieve the target data rate of each backhaul connection as a counter-measure to the cross-talk problem. The results of our simulation show that the algorithm is capable of minimizing the transmission power of backhaul connections while guaranteeing a high overall quality of service for all users of the same binder. In particular, it can provide the target data rate required to maximize user satisfaction with the mobile video streaming service over the femtocell networks.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 신호처리소사이어티 추계학술대회 논문집
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• pp.133-136
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• 2003

In this paper, we propose a low bit-rate embedded video coding scheme with 3-D block partition in the wavelet domain. The proposed video coding scheme includes multi-level three dimensional dyadic wavelet decomposition, raster scanning within each subband, partitioning of blocks, and adaptive arithmetic entropy coding. Although the proposed video coding scheme is quite simple, it produces bit-streams with good features, including SNR scalability from the embedded nature. Experimental results demonstrate that the proposed video coding scheme is quite competitive to other good wavelet-based video coders in the literature.