Global Motion Parameters Research Articles

다양한 형식의 얼굴정보와 준원근 카메라 모델해석을 이용한 얼굴 특징점 및 움직임 복원

본 논문은 MPEG4 SNHC의 얼굴 모델 인코딩을 구현하기 위하여 연속된 2차원 영상으로부터 얼굴영역을 검출하고, 얼굴의 특징데이터들을 추출한 후, 얼굴의 3차원 모양 및 움직임 정보를 복원하는 알고리즘과 결과를 제시한다. 얼굴 영역 검출을 위해서 영상의 거리, 피부색상, 움직임 색상정보등을 융합시킨 멀티모달합성의 방법이 사용되었다. 결정된 얼굴영역에서는 MPEG4의 FDP(Face Definition Parameter) 에서 제시된 특징점 위치중 23개의 주요 얼굴 특징점을 추출하며 추출성능을 향상시키기 위하여 GSCD(Generalized Skin Color Distribution), BWCD(Black and White Color Distribution)등의 움직임색상 변환기법과 형태연산 방법이 제시되었다. 추출된 2차원 얼팔 특징점들로부터 얼굴의 3차원 모양, 움직임 정보를 복원하기 위하여 준원근 카메라 모델을 적용하여 SVD(Singular Value Decomposition)에 의한 인수분해연산을 수행하였다. 본 논문에서 제시된 방법들의 성능을 객관적으로 평가하기 위하여 크기와 위치가 알려진 3차원 물체에 대해 실험을 행하였으며, 복원된 얼굴의 움직임 정보는 MPEG4 FAP(Face Animation Parameter)로 변환된 후, 인터넷상에서 확인이 가능한 가상얼굴모델에 인코딩되어 실제 얼굴파 일치하는 모습을 확인하였다. Robust extraction of 3D facial features and global motion information from 2D image sequence for the MPEG-4 SNHC face model encoding is described. The facial regions are detected from image sequence using multi-modal fusion technique that combines range, color and motion information. 23 facial features among the MPEG-4 FDP (Face Definition Parameters) are extracted automatically inside the facial region using color transform (GSCD, BWCD) and morphological processing. The extracted facial features are used to recover the 3D shape and global motion of the object using paraperspective camera model and SVD (Singular Value Decomposition) factorization method. A 3D synthetic object is designed and tested to show the performance of proposed algorithm. The recovered 3D motion information is transformed into global motion parameters of FAP (Face Animation Parameters) of the MPEG-4 to synchronize a generic face model with a real face.

Digital image translational and rotational motion stabilization using optical flow technique

This paper proposes a new digital image stabilization (DIS) system based on optical flow technique. Unlike previous DIS systems developed mainly for removing the translational motion disturbance, the proposed system removes not only the translational but also the rotational motion disturbances. A computational scheme that facilitates the local motion vector field to estimate the global disturbing translational and rotational motions is developed. First, the optical flow technique is used to estimate the local motion vector field of the image, yielding the velocity of each pixel in the current image frame. Then, the global translational and rotational motion parameters are determined in terms of the least squares estimation. Finally, these motion vectors are used to generate the counterbalance signals for removing the disturbance motion. Owing to the additional ability of the rotational motion removal, the new DIS system suppresses the undesirable translational and rotational disturbances effectively and thus enhances the DIS performance significantly.

Global spinal motion in subjects with lumbar spondylolysis and spondylolisthesis: does the grade or type of slip affect global spinal motion?

This was a prospective pilot study to investigate the global motion characteristics of the spondylolysis and spondylolisthesis populations. The aim of this study is to determine the influence of a spondylolisthesis or a spondylolysis on global spinal motion and to establish whether this is dependent on the cause of the slip or the degree/grade of the slip. The condition of spondylolisthesis has been extensively discussed in the literature with respect to its etiology and management. However, the mechanics and movement of the spine in relation to pathology and the effect of this condition on function have received scant attention. The motion of the lumbar spine was investigated in 31 patients (19 men, 12 women, mean age 47.7 +/- 17.8 years) who were diagnosed as having either a lumbar spondylolysis or a spondylolisthesis. These patients were compared with a preexisting database of 203 normal subjects (100 men, 103 women, mean age 39.8 +/- 13.4 years). Patients were graded according to the type of spondylolisthesis or spondylolysis they had, and the extent of slip was rated using Meyerding's classification (1932) and measured directly using methods of Boxall et al (1979) and Wiltse et al (1983). Direct measurements of the extent of slip using Boxall et al (1979) and Wiltse et al (1983) methods were found to have no significant correlation with the resultant range of motion (ROM) or the speed of movement. This study suggests that motion parameters are influenced by the grade of slip in patients with spondylolisthesis, and the type of spondylolisthesis i.e., whether isthmic or degenerative. In the A-P flexion-extension plane, the results indicate that subjects with a defect only, i.e., a spondylolysis, and thus no slip present with a spinal hypermobility (P < 0.01). Subjects with an isthmic slip tend to be either slightly hypermobile or within the anticipated range of motion, whereas those subjects with a degenerative slip tend to be hypomobile (P < 0.05). Movements into lateral flexion were restricted in both the isthmic and degenerative spondylolisthesis patients, whereas rotation was only influenced by the level at which the defect occurred. In terms of degree of displacement, in higher grades of displacement, there was a trend towards hypermobility. The findings of this study suggest that the grade and type of spondylolisthesis do influence global motion parameters. This information may be useful in the clinical assessment of this patient group.

Cardiac phase contrast gradient echo MRI: measurement of myocardial wall motion in healthy volunteers and patients.

A number of methods have been proposed for the noninvasive measurement of myocardial wall motion. The paper describes a strategy for assessing myocardial motion based on the sensitivity of the phase of the MR-signal to motion using a breath-hold phase contrast technique. A motion-sensitized and a motion-compensated MR-signal are measured during successive scans. The difference between the two MR-signals is used to calculate myocardial velocity in all three spatial dimensions. Postprocessing includes the transformation of the measured velocities into an internal coordinate system of the left ventricle. Also various presentation modes and further processing of the received velocity information are provided including calculation of global motion parameters. We examined 20 patients suffering from myocardial infarction. The overall left ventricular motion can be characterized by appropriate parameters describing the rotation and contraction or expansion, respectively. Regional motional disturbances are visualized using parametric images. Contrary to the highly consistent interindividual data in normal volunteers, patients showed significant localized motion deficits.

Fast and robust parameter estimation method for global motion compensation in the video coder

We describe a method for estimating and compensating 3D camera motion in image sequences for applications to a video coding system. To improve the estimation accuracy of the global motion parameter, we propose a robust algorithm which selects the reliable observation points adaptively and eliminates the bad observation points effectively. Unlike the existing linear recursive algorithms with an arbitrary thresholding, the proposed algorithm converges fast and is robust to feature matching error. Experimental results show that the proposed method improves the coding efficiency and reduces the computation time.

An object-oriented coder using block-based motion vectors and residual image compensation

This paper proposes a two-stage global motion parameter estimation method using block-based motion vectors and a model failure (MF) object compensation algorithm by object-oriented fractal mapping of the residual image for an object-oriented coder. In the first stage of the two-stage motion parameter estimation algorithm, coarse motion parameters are estimated by fitting block-based motion vectors computed hierarchically to a six-parameter model, and in the second stage, the estimated motion parameters are refined by the gradient method using an image reconstructed by motion parameters detected in the first stage. The local prediction error by the six-parameter method is locally reduced by blockwise motion parameter correction using the residual image. Finally, the MF object is compensated by object-oriented fractal mapping of the previous residual image into the current one, in which geometric affine mapping is followed by the massic transformation. For MF object compensation, the selection between motion parameter compensation and fractal mapping is achieved by the validity test. Computer simulation results show that the proposed method gives better performance than the conventional ones in terms of the peak signal-to-noise ratio (PSNR) and compression ratio (CR).

Global motion estimation in model-based image coding by tracking three-dimensional contour feature points

A video coding method called model-based image coding has attracted much attention as a potential candidate for low bit-rate visual communication services. This technique reconstructs the facial image with a preknown 3D human face model and its received model motion parameters. The parameters of the head motion are mainly divided into two parts: global motion parameters describe the rigid movement of the head, such as rotation and translation, and local motion parameters which deal with the nonrigid movements of facial expressions, such as the opening and closing of the mouth and eyes. In this paper, we propose a new approach which can estimate the head global motion more robustly and accurately. Comparing with the existing techniques to match only a few key points, here we extract 3-D contour feature points and use chamfer distance matching to estimate head global motion. This can improve and enhance the contour tracking performance greatly. We also develop another technique called facial normalization transform. It maps the facial region of the current input frame back to the normalized pose of the initial frame. Using this transform, we can analyze facial expressions at the same orientation and fixed region. This simplifies the analysis work a lot. Then, we do our encoding by the clip-and-paste method along with adaptive codebook technique. In the following the coder and decoder system are briefly described.

Simple method for estimation of global motion parametersusingsparse translational motion vector fields

A simple method for the estimation of global motion parameters from sparse translational vector fields is presented. Differential operations on pairs of adjacent motion vectors are used to derive local estimates of rotation and change of scale. A majority vote is then applied to identify global trends corresponding to the required estimates. Key features of the proposed technique are its low complexity and its compatibility with standardised motion estimation tools.

インタラクティブ知的符号化におけるグローバル動きパラメータの検出精度

Video network is beginning to have various kinds of applications such as using a vertical blanking interval. Model-based coding is suitable for the narrow band network. Interactive model-based image coding, which had been developed for non-realtime environment, needs to be specified by the number and the precision of interactive operations. This paper first analyzes the noise in input feature points during the global motion parameter detection. Then a new structure filter for reducing the noise in the feature points on a facial wireframe model is developed. The structure filter keeps original facial shape composed of feature points and reduces variation in the mutual distance between the feature points. In evaluating the precision for applying the least-squares method for detecting depth and global motion parameters, the number of conditions of input data is considered from the point of variance of error of the estimated values. Based on the structure filter with the precision evaluation, the allowance error in the interactive operation for the encoding process is specified by the pixel accuracy for feature point position.

Global motion parameters estimation using a fast and robust algorithm

The main difficulty in global motion parameters estimation resides in the disturbance of independently moving objects. The algorithm presented in this letter exploits global motion information not only from stationary objects and the image background, but also from independently moving objects. Simulation results show that the new algorithm is computationally fast and robust to the disturbance caused by independently moving objects.

A selective coding method based on global/local motion information

A selective coding scheme is proposed that describes a method for coding image sequences, differentiating bits between background and target region. The suggested method initially estimates global motion parameters and local motion vectors. Then segmentation is performed with a hierarchical clustering scheme and a quad-tree algorithm in order to divide a given image into the background and target region. Finally, image coding is done by assigning more bits to the target region and less bits to background so that the target region may be reconstructed with a high quality. Simulations show that the suggested algorithm performs well especially in the circumstances where background changes and target region is small enough compared to the background.

Multistage motion estimation for image interpolation

Abstract In this paper we describe an algorithm for accurate motion estimation that takes into account both the motion of the camera (global motion) and the motion of the imaged objects (local motion) through the use of a multistage structure. First, global motion parameters are accurately estimated and the images are compensated for the camera motion. The local motion field is then estimated on the basis of these ‘compensated’ images. To improve the performance of this estimation, both temporal and spatial congruence constraints have been introduced. To test the performance of the proposed algorithm a motion compensated image interpolation that uses the estimated motion field has been carried out. The experimental results show the effectiveness of the proposed multistage motion estimation procedure.

Global motion compensation in video coding

AbstractAs a motion compensation method for video coding, a global motion estimation method is proposed that estimates and compensates general image motion caused by camera pan and zoom. By utilizing block displacement vectors derived from the widely utilized block‐matching method, global motion parameters are computed with a noniterative process requiring few multiply‐add operations. Parameters associated with pairs of blocks symmetrically located with respect to the center of the image are calculated, and the histogram of these parameters is then used to efficiently compute accurate motion values that depend on nothing but camera pan and zoom. A corresponding block‐by‐block ON/OFF control method is also proposed for the global motion compensation scheme. By utilizing these methods, a relatively simple and efficient coding technique with global motion estimation is realized.

CT volumetric data-based left ventricle motion estimation: an integrated approach

This paper describes a novel approach to left ventricle motion analysis via the integration of image segmentation with shape deformation analysis using computerized tomography (CT) volumetric image data. This approach is different from traditional image analysis scenario in which the image segmentation and shape analysis were considered separately. The advantage of integrating the image segmentation with the shape analysis lies in the fact that the shape characteristics of the object can be used as effective constraints in the process of segmentation while original image data can be made useful along with the segmentation results in the process of shape analysis. In the case of left ventricle motion estimation, such an integration can be applied to obtain the estimation results that are consistent with both given image data and a priori shape knowledge. The initial segmentation of the images is obtained through adaptive K-mean classification and the region-of-interest is then identified based on the initial segmentation. The shape analysis is accomplished through fitting the boundary points of the region-of-interest to the surface modeling primitives. These two processes are integrated through the feedforward and feedback channels so that the surface fitting is constrained by the confidence measures of the boundary points and segmentation refinement is guided by the result of surface modeling. Global motion parameters are obtained by comparing the parameters of the fitted surface model at consecutive time instances. The segmentation and shape analysis results obtained show that the integrated approach is capable of providing promising improvement over traditional approaches.

1.15 Mbit/s coding of video signals including global motion compensation

A coder for television video signals working at a bit-rate of 1.15 Mbit/s is presented. It uses a special coding structure facilitating trick modes and a separated global and local motion compensation. Global motion is described by a central zoom and pan model. For the estimation of global motion a frame matching algorithm is explained. The advantages of using global motion parameters are given by the reduction of the amount of coded motion information as well as the reduction of regions to be replenished in the predicted pictures. Experimental results show that for the given bit-rate of 1.15 Mbit/s the quantization step size for prediction error coding can be reduced by the factor three in case of existing global motion. Also at the decoder side global motion parameters are used for a synthesis of omitted frames resulting in a higher resolution in time for global motions.