• 한국통신학회:학술대회논문집
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• 한국통신학회 1991년도 추계종합학술발표회논문집
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• pp.111-114
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• 1991

This paper proposes an efficient adaptive echo canceller using pilot filter approach to achieve improved convergence speed. The pilot filter is an adaptive filter with only a few filter coefficients to filter the received signal for the purpose of whitening the signal. Thus the convergence speed of the main LMS-TDL filter combined with the pilot filter is improved. In the proposed echo canceller, an adaptive lattice predictor as the pilot filter is used and its inverse filter is used to equalize the distorted near end talker signal. Simulation results for colored signal show that the convergence speed of the proposed echo cancellation algorithm is faster than that of the conventional LMS-TDL echo cancellation algorithm.

• 전자공학회논문지B
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• 제32B권11호
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• pp.1405-1416
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• 1995

An effective algorithm for implementation of unmanned surveillance system which detects moving object from image sequences, predicts the direction of it, and drives the camera in real time is proposed. Outputs of proposed algorithm are coordinates of location of moving object, and they are converted to the values according to camera model. As a pre- processing, extraction of moving object and shape discrimination are performed. Existence of the moving object or scene change is detected by computing the temporal derivatives of consecutive two or more images in a sequence, and this result of derivatives is combined with the edge map from one original gray level image to obtain the position of moving object. Shape discri-mination(Target identification) is performed by analysis of distribution of projection profiles in x and y directions. To reduce the prediction error due to the fact that the motion cha- racteristic of walking man may have an abrupt change of moving direction, an order adaptive lattice structured linear predictor is proposed.

• 전자공학회논문지B
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• 제30B권12호
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• pp.12-20
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• 1993

In a conventional adaptive echo canceller, an ADF(Adaptive Digital Filter) with TDL(Tapped-Delay Line) structure modelling the echo path uses the LMS(Least Mean Square) algorithm to compute the coefficients, and NET detector using energy comparison method prevents the ADF to update the coefficients during the periods of the NET signal presence. The convergence speed of the LMS algorithm depends on the eigenvalue spread ratio of the reference signal and NET detector using the energy comparison method yields poor detection performance if the magnitude of the NET signal is small. This paper presents a new adaptive echo canceller which uses the pre-whitening filter to improve the convergence speed of the LMS algorithm. The pre-whitening filter is realized by using a low-order lattice predictor. Also, a new NET signal detection algorithm is presented, where the start point of the NET signal is detected by computing the cross-correlation coefficient between the primary input and the ADF output while the end point is detected by using the energy comparison method. The simulation results show that the convergence speed of the proposed adaptive echo canceller is faster than that of the conventional echo canceller and the cross-correlation coefficient yields more accurate detection of the start point of the NET signal.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1992년도 학술논문발표회 논문집 제11권 1호
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• pp.23-28
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• 1992

The purpose of this paper is to develop a new adaptive echo canceller improving convergence speed and near-end-talker detection performance of the conventional echo canceller. In a conventional adaptive echo canceller, an adaptive digital filter with TDL(Tapped-Delay Line) structure modelling the echo path uses the LMS(Least Mean Square) algorithm to cote the coefficients, and NET detector using energy comparison method prevents the adaptive digital filter to update the coefficients during the periods of the NET signal presence. The convergence speed of the LMS algorithm depends on the eigenvalue spread ratio of the reference signal and NET detector using the energy comparison method yields poor detection performance if the magnitude of the NET signal is small. This paper presents a new adaptive echo canceller which uses the pre-whitening filter to improve the convergence speed of the LMS algorithm. The pre-whitening filter is realized by using a low-order lattice predictor. Also, a new NET signal detection algorithm is presented, where the start point of the NET signal is detected by computing the cross-correlation coefficient between the primary input and the ADF(Adaptive Digital Filter) output while the end point is detected by using the energy comparison method. The simulation results show that the convergence speed of the proposed adaptive echo canceller is faster than that of the conventional echo canceller and the cross-correlation coefficient yield more accurate detection of the start point of the NET signal.

• 한국정보통신학회논문지
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• 제7권2호
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• pp.344-352
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• 2003

본 논문에서는 CCD 카메라를 통해 전송되는 영상 시퀀스를 대상으로 움직이는 물체의 형태가 보행중인 사람, 혹은 자동차인지를 식별하고 이의 이동 방향을 판단하여, 이를 추적하는 무인 감시 시스템을 위한 효율적인 알고리즘을 제안한다. 고정 카메라 환경에서 유동적인 배경으로부터 안정된 움직임 추출을 위하여 배경과 이동 물체를 통계적 매개 변수로 모델링하고 배경만이 존재하는 초기 연속 영상 중 일부에 대하여 통계적으로 학습한다. 또한, 능동카메라 환경에서는 카메라 움직임에 의하여 배경에서도 움직임 에너지가 발생하므로 예측된 이동 궤적정보를 이용함으로써 연산량의 감소와 정확성을 기하였다. 본 논문에서 제안한 알고리즘을 고정카메라 및 능동카메라 환경에서 취득한 연속 영상에 적용한 결과 안정된 추적 결과를 얻었다. 제안한 알고리즘은 제한된 지역내의 무인 감시 시스템 도로 환경에서 교통흐름의 모니터링 시스템 및 나아가서 지능형 도로망을 위한 자가 주행 시스템에 적용이 기대된다.

• 한국통신학회논문지
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• 제23권8호
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• pp.1998-2009
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• 1998

본 논문에서는 배경의 움직임이 유발되는 능동 CCD 카메라를 통하여 실시간으로 포착되는 영상 데이터를 대상으로 카메라의 사전 설치 정보나 좌표 보정(calibration) 없이 강체(rigid body) 혹은 비 강체(non-rigid body)의 움직이는 물체를 추출하고 이의 이동 방향을 판단하여, 추적하는 효율적인 알고리즘을 제안한다. 이동 물체의 영역분할을 위하여 동체의 형태를 규정하는 특징 점을 추출하고, 시간에 따른 특징 점의 이동 벡터로 구성된 특정 플로우 필드(feature flow field)를 구한 후 이들을 다차원 특정 공간상에서 군집화(clustering)함으로써 동체를 추출한다. 제안하는 IRMAS(lncremenatal Rotational Minimum Angle Search)에 의하여 군집화된 특정점들의 볼록 다각형(convex hull)올 구함으로써 이동 물체의 개괄적인 외곽 형태를 재 구성한다. 또한, 이동 궤적의 갑작스러운 변화를 가져올 수 있는 동작 특성을 가지는 이동 물체의 효과적인 추적을 목적으로 개선된 선형 예측기를 사용하였다. 이동 궤적 예측기는 기존의 선형 예측기의 차수를 이동의 변화도에 따라 적응적으로 조정함으로써 예측 오차를 감소시켜, 빠른 속도로 이동 궤적에 수렴한다.