• 제목/요약/키워드: frame-size adaptive

검색결과 56건 처리시간 0.028초

Development a simple MEMS-based astronomical adaptive optics system at laboratory

  • 유형준;박용선;채종철;양희수
    • 천문학회보
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    • 제36권2호
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    • pp.132.2-132.2
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    • 2011
  • We are developing Adaptive Optics (AO) system for astronomical use. The He-Ne laser works as an artificial light source. The tip-tilt correction servo is added to our AO system. The tip-tilt term, among the Zernike terms, is the biggest contributor of wavefront deformation caused by atmospheric turbulence at small telescopes. The tip-tilt correction servo consists of a Piezo tip-tilt platform with a mirror, a quadrant photodiode as a tip-tilt sensor, and controllers. The Shack-Hartmann wavefront sensor measures the residual wavefront errors and they are corrected by the MEMS (Micro Electro Mechanical System) deformable mirror. The MEMS deformable mirror allows the compact size at low cost compare to adaptive secondary mirror and other deformable mirrors. As the frame rates of the MEMS deformable mirror is about tens of kHz, the frame rates of the detector in wavefront sensor is the bottleneck of the wavefront correction speed. For faster performance, we replaced a CCD which provides frame rates only 70 Hz with a CMOS with frame rates up to 450 Hz.

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An efficient frame rate up-conversion method with adaptive motion estimation and compensation for mobile projection displays

  • Lee, Jong-Ok;Jang, Seul-Ki;Chen, Qiao Song;Kim, Choon-Woo
    • 한국정보디스플레이학회:학술대회논문집
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    • 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권1호
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    • pp.810-813
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    • 2007
  • Recently, mobile video communication is getting more and more popular. Visual quality and computational complexity are primary factors affecting performance of video communication. Frame rate up-conversion (FRC) is necessary for achieving high visual quality in mobile projection displays. In this paper, a FRC method using motion compensation based on block matching algorithm (BMA) with adaptive block size is proposed. In order to improve the accuracy of the estimated motion vectors, the motion vector refinement technique is proposed. Experiment results indicate that the proposed technique exhibits better performance with lower hardware complexity compared to the conventional methods.

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GOP Adaptation Coding of H.264/SVC Based on Precise Positions of Video Cuts

  • Liu, Yunpeng;Wang, Renfang;Xu, Huixia;Sun, Dechao
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • 제8권7호
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    • pp.2449-2463
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    • 2014
  • Hierarchical B-frame coding was introduced into H.264/SVC to provide temporal scalability and improve coding performance. A content analysis-based adaptive group of picture structure (AGS) can further improve the coding efficiency, but damages the inter-frame correlation and temporal scalability of hierarchical B-frame to different degrees. In this paper, we propose a group of pictures (GOP) adaptation coding method based on the positions of video cuts. First, the cut positions are accurately detected by the combination of motion coherence (MC) and mutual information (MI); then the GOP is adaptively and proportionately set by the analysis of MC in one scene. In addition, we propose a binary tree algorithm to achieve the temporal scalability of any size of GOP. The results for test sequences and real videos show that the proposed method reduces the bit rate by up to about 15%, achieves a performance gain of about 0.28-1.67 dB over a fixed GOP, and has the advantages of better transmission resilience and video summaries.

시간 적응 3차원 subband 부호화 기법 (Temporal adaptive 3D subband image sequence coding technique)

  • 김용관;김인철;이상욱
    • 한국통신학회논문지
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    • 제21권5호
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    • pp.1096-1108
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    • 1996
  • In this paper, we propose a temporal adaptive tranform 3D SBC coder with motion compensation, exploiting redundancy in the temporal domain. We propose a temporal adaptivity measure, by which the R-D optimal temporal transform can be chaosen. The base temporal subband frame is coded using H.261-like MC-DCT coder, while the higher temporal subband frames are coded using the 2D adaptive wavelet packet bases, considering the various energy distribution which results from the temporal variation. In encoding the subbands, we employ adaptive scanning methods, uniform step-size quantization with VLC, and coded/not-coded flag reduction technique using the quadtree structure. From the simulation results, the proposed adaptive 3D subband coder shows about 0.29~3.14 dB gain over the H.261 and the fixed 3D subband coder techniques.

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Adaptive Binary Negative-Exponential Backoff Algorithm Based on Contention Window Optimization in IEEE 802.11 WLAN

  • Choi, Bum-Gon;Lee, Ju-Yong;Chung, Min-Young
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • 제4권5호
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    • pp.896-909
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    • 2010
  • IEEE 802.11 medium access control (MAC) employs the distributed coordination function (DCF) as the fundamental medium access function. DCF operates with binary exponential backoff (BEB) in order to avoid frame collisions. However it may waste wireless resources because collisions occur when multiple stations are contending for frame transmissions. In order to solve this problem, a binary negative-exponential backoff (BNEB) algorithm has been proposed that uses the maximum contention window size whenever a collision occurs. However, when the number of contending stations is small, the performance of BNEB is degraded due to the unnecessarily long backoff time. In this paper, we propose the adaptive BNEB (A-BNEB) algorithm to maximize the throughput regardless of the number of contending stations. A-BNEB estimates the number of contending stations and uses this value to adjust the maximum contention window size. Simulation results show that A-BNEB significantly improves the performance of IEEE 802.11 DCF and can maintain a high throughput irrespective of the number of contending stations.

Real-Time Digital Image Stabilization for Cell Phone Cameras in Low-Light Environments without Frame Memory

  • Luo, Lin-Bo;Chong, Jong-Wha
    • ETRI Journal
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    • 제34권1호
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    • pp.138-141
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    • 2012
  • This letter proposes a real-time digital image stabilization system for cell phone cameras without the need for frame memory. The system post-processes an image captured with a safe shutter speed using an adaptive denoising filter and a global color correction algorithm. This system can transfer the normal brightness of an image previewed under long exposure to the captured image making it bright and crisp with low noise. It is even possible to take photos in low-light conditions. By not needing frame memory, the approach is feasible for integration into the size-constrained image sensors of cell phone cameras.

고속 분산 비디오 복호화 기법에서 패리티 비트 예측방식에 대한 LDPCA 프레임 크기 효과 (Effects of LDPCA Frame Size for Parity Bit Estimation Methods in Fast Distributed Video Decoding Scheme)

  • 김만재;김진수
    • 한국정보통신학회논문지
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    • 제16권8호
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    • pp.1675-1685
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    • 2012
  • 분산 비디오 부호화 기법(DVC)은 매우 낮은 복잡도를 갖는 비디오 부호화기를 제공하는데 중요한 역할을 담당하고 있다. 그러나 우수한 비트율-왜곡 성능을 얻기 위해 기존의 대부분의 DVC 기법은 피드백 채널을 통해 패리티 비트 제어를 수행하고 있으며, 이것은 비디오 복호화에 있어 많은 시간을 초래하여 실시간 구현을 위해 꼭 극복해야 할 문제점으로 남아 있다. 이러한 문제점을 해결하고 상업화를 촉진하기 위해, 본 논문에서는 LDPCA 프레임 크기가 복호화 지연 및 전체적인 부호화 성능에 미치는 영향을 분석한다. 먼저 화소 영역 위너-지브 부호화 기법에서 각 비디오 프레임을 일정한 크기의 LDPCA 프레임으로 분할하고, 분할된 LDPCA 프레임별로 시간적 상관성을 이용한 예측 방식과 공간적 상관성을 갖는 예측 방식에 따른 성능을 비교 분석한다. 모의실험을 통하여, 현재 가장 많이 연구되고 있는 QCIF크기의 영상에 대해서는 LDPCA 프레임 크기가 3168크기일 때, 가장 우수한 부호화 성능 및 고속화에 유리함을 보인다.

적응 DPCM에 의한 영상정보 감축 (Image Information Compression by Adaptive Differential Pulse Code Modulation)

  • 조병걸;한영오;오진성;이세현;장인호;이웅천;박상희
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 1988년도 전기.전자공학 학술대회 논문집
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    • pp.229-231
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    • 1988
  • In this paper, we design adaptive DPCM by the two dimensional linear prediction using the covariance method and propose adaptive algorithm which determines analysis frame size by the compassion of the local standard deviation and the global standard deviation of images.

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실시간 배경갱신 및 이를 이용한 객체추적 (Real time Background Estimation and Object Tracking)

  • 이완주
    • 정보학연구
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    • 제10권4호
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    • pp.27-39
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    • 2007
  • Object tracking in a real time environment is one of challenging subjects in computer vision area during past couple of years. This paper proposes a method of object detection and tracking using adaptive background estimation in real time environment. To obtain a stable and adaptive background, we combine 3-frame differential method and running average single gaussian background model. Using this background model, we can successfully detect moving objects while minimizing false moving objects caused by noise. In the tracking phase, we propose a matching criteria where the weight of position and inner brightness distribution can be controlled by the size of objects. Also, we adopt a Kalman Filter to overcome the occlusion of tracked objects. By experiments, we can successfully detect and track objects in real time environment.

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기존 전술 무전기를 이용한 전술 데이터 통신 성능 실험 (The Performance Experiments on the Tactical Data Communication over the Legacy Radio Systems)

  • 심동섭;강경성;김기형
    • 한국군사과학기술학회지
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    • 제13권2호
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    • pp.243-251
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    • 2010
  • The military has been putting great efforts into applying data communication on existing voice communication systems being used in NCW(Network Centric Warfare). Data communication will be an effective choice in one of many effort to yield a minimum kill chain, comparing to legacy voice communications, when tactical units conduct their missions. However, the required budget will be enormous, in case of the replacement of a lot of legacy communication systems with new one. As a cost-effective alternative, the tactical data communication systems using the conventional radio systems instead of the development of new radio systems has been proposed. It is mandatory, though, to ensure QoS while maintaining data communication by making use of legacy radio systems already in use. This paper focuses on the performance issues experimented and analyzed for tactical data communication through the legacy radio systems as the first step towards guaranteed QoS. We have conducted various experiments such as the transmission error rate on certain tactical messages, performance evaluation of redundant transfers, the relationship between the transmission frame size and rate of error, the identification of error points in the transmission frame, and techniques to reduce the errors in both hopping and non-hopping modes. As a result of the performance experiments, The adaptive communication module which decides the redundant transmission or the Forward Error Correction(FEC) technique by analyzing channel status and current transmission status(hopping/non-hopping) of the legacy radio should be designed. the FEC technique in non-hopping, and the redundant transmission technique in hopping mode was recommended from the result of experiment with the frame size is 20bytes in non-hopping and 10Bytes frame size in hopping mode.