http://ivylab.kaist.ac.kr/image/demo/project_title.gif

image004

image005

Video Face Recognition Based on Face Quality Measure and Face Feature Fusion for CCTV Surveillance System

2011. 06. 01 ~

 

image007

1. Introduction

l  Recently, video face recognition (FR) has received a significant interest, due to a wide range of applications

ž   Video surveillance, biometric identification, and content-based video indexing/search.

l  Compared to the number of algorithms that do FR from stills, the research on video-based methods is relatively small.

l  Compared to a still image, a set of face images can provide rich information discriminative for FR in the face image set (see Fig. 1).

l  Face image set may contain large view-point (pose) and illumination changes and unuseful face images such as blurred face images or mis-aligned face images (see Fig. 2). These challenges could significantly degrade FR performance.

 

 

Fig. 1.  Examples of face image sequence from videos.

 

(a)

(b)

(c)

(d)

(e)

Fig. 2.  Challenges of FR in face image set: (a) Pose variation (rotation in yaw) (b) Pose variation (rotation in pitch)
(c) Expression variation (d) Illumination variation (e) Mis-aligned faces.

 

 

l  In this research, we propose a new video FR method based on weighted feature fusion approach.

l  The proposed method aims at significantly improving FR accuracy by adaptively fusing the features extracted from the multiple face images.

ž   We develop a novel weight determination solution for the purpose of attaining the best FR accuracy within our weighted-feature-fusion-based FR framework.

ž   In order to guarantee adaptive nature in determining weights, fuzzy membership function and quality measurement for face images can be used to compute weights of face features to be combined.

2. Proposed Video FR method

Fig. 3.  Overall procedure of the feature fusion based video FR.

 

l  Let  be a face sequence consisting of M face images (obtained from a video sequence) with a single and be a same identity.

l  In a typical video FR, the face features of testing images are to be extracted and to be used for a classification purpose.

l  Herein, face feature of  is denoted by . A combined face feature generated using our weighted feature fusion is defined as

(1)

ž   : the weight value of .

l  As shown in Fig. 3, given a face sequence from video frames, the proposed weight determination method largely consists of three sequential steps:

ž   Face rejection

ž   Selection of prototype face images

ž   Computation of weights using fuzzy membership function

2.1. Face Rejection

l  In practice, a number of mis-aligned face images may be present in a face sequence due to incorrect face detection and tracking result.

ž   Mis-aligned face images: incorrectly rotated or scaled face images

ž   Mis-aligned face images can significantly degrade FR performance

l  As such, mis-aligned face images need to be filtered out.

ž   For that purpose, an SVM classifier is adopted to discriminate mis-aligned face images from well-aligned face images.

l  We can select mis-aligned face images by identifying face images assigned negative confidence scores as outputs of an SVM classifier.

2.2. Selection of Prototype Face Images

l  In the proposed method, the so-called prototype face images are defined as face images with frontal lighting and small deviation from frontal pose, as well as with high sharpness.

1)    Measurement of Facial Symmetry:

ü  We assess quality degradations caused by nonfrontal lighting and inadequate facial pose (especially arising from out-of-plane rotation).

ü  The less left-right symmetric of the face image has larger distance value between the left and right half regions, and has lower image quality value.

 

Fig. 4.  Illustration of dividing a face image (based on the midline of both eyes) into the left and right half regions each denoted by  and . Note that the text enclosed in bracket below each facial image represents the value of differences between pixel values of  and  at the corresponding left-right pixel locations.

 

1)    Measurement of Face Frontal-Pose Degree:

ü  For the case of face images with variation in pose caused tilt, the facial symmetry measure may not correctly represent the drifting away from frontal pose caused by tilt.

ü  To overcome this limitation, we develop a so-called frontal-pose subspace based on the view-based reconstruction.

ü  The frontal-pose subspace model was constructed using a data set including only frontal-pose face images.

ü  The quality score for frontal-pose degree is computed as a residual reconstruction error between a test face image and its reconstruction.

Fig. 5.  Some examples of face images used to validate the reliability of frontal-pose degree measurement.

 

2)    Measurement of Face Image Sharpness:

ü  To assess the quality of facial images with respect to blurring, we make use of the Kurtosis measurement.

ü  This approach computes the energy of the high-frequency content of an image based on the statistical analysis of the Fourier transform of the image for the purpose of measuring image sharpness.

l  Using all the scores of the three different quality measurements, overall quality score of each face image is obtained by utilizing a weighted sum of the scores of the three individual quality measurements.

Fig. 6.  Overall quality scores of face images in a face sequence, computed using the proposed quality measure. Note that the three face images that correspond to the three prototype face images with highest scores are annotated by circles.

 

2.3. Weight Computation Using Fuzzy Membership Function

l  The proposed weight determination solution takes advantage of the fuzzy membership function based on the similarity view theory where membership is a notion of being similar to prototype of the category.

l  Membership function measures the degree of similarity of all element face images of a given face sequence to the associated prototype face images.

l  Notations

ž   : the face sequence (outputted by a face rejection module) can be considered to be a fuzzy set.

ž   : a set of K prototype face images selected by using the method in Section 2.2 where .

ž   : a set of face features each corresponding to the nth prototype face image.

l  Given the face features  and  of  and , respectively, the distance metric (Minkowski metric) is used to measure the distance:

(2)

ž   : the kth element of the feature vector  and  is the dimension of the feature vectors.

l  For the , the sum of distances with all the selected prototype features is the distance criterion:

(3)

ž   K: the number of prototype face images selected.

l  The membership value for the  is determined as follows:

(4)

ž   where  and  are parameters to be determined.

ž   The value of  is used to adjust the weighting effect of the membership function, and  is a weight scale threshold.

l  The weight to be assigned to each image  within a face sequence is computed as follows:

(5)

ž    and

l  The results in Fig. 7 validate the effectiveness of the proposed method for determining weights.

Fig. 7.  Weight values computed for each face image within a face sequence to show the effectiveness of determining weights using the proposed method. Note that the three face images that correspond to the three prototype face images with highest overall quality scores are annotated by circles.

3. Experiment

<Experimental setup>

l  Used video face DBs: the VidTIMIT, YouTube celebrity, Honda/UCSD, and CMU MoBo.

l  The Viola-Jones face detection and the Lucas-Kanade face tracking techniques were run on all video frames.

l  The detected and tracked face images were rescaled to 44 x 44 pixels (refer to Fig. 8).

l  Three popular feature extraction techniques were used to construct feature extractors for computing face features:

ž   Fishers linear discriminant analysis (FLDA)

ž   Regularized linear discriminant analysis (RLDA)

ž   Eigenfeature regularization and extraction (ERE). In addition

l  Gabor wavelet face representation was used in conjunction with the aforementioned low-dimensional feature extraction techniques.

(a)

(b)

(c)

(d)

Fig. 8.  Example of face sequences used in our experiments, which show a variety of different lighting, pose and occlusion conditions, and misaligned face images. (a) VidTIMIT DB. (b) YouTube celebrity DB. (C) Honda/UCSD DB. (d) CMU MoBo DB.

3.1. Results on VidTIMIT Data set and YouTube Celebrity Data set

<Comparison methods>

l  Baseline: A conventional still-image-based FR solution (only using a single face image)

l  FR using majority vote: Integrates the recognition result in each frame using majority voting

l  Proposed (uniform weighting): all face features have the same weights

l  Proposed (fuzzy weighting): weights are determined using fuzzy membership function

 

Table 1.  Effectiveness of the proposed method on the VidTIMIT DB. K represents the number of selected prototype face images.

Table 2.  Effectiveness of the proposed method on the YouTube celebrity DB.

<Results>

l  Compared to baseline method, the rank-one identification rate can be substantially improved with around 40% for all feature extraction methods.

l  The proposed fuzzy weighting scheme considerably outperforms the approach using uniform weights.

ž   This demonstrates the effectiveness of the proposed weight determination solution in terms of achieving the best possible recognition accuracy via the proposed weighted feature fusion method.

l  The proposed method can achieve the FR performance of up to about 91% for YouTube celebrity DB.

ž   This results show that the proposed method can achieve acceptable recognition accuracy over challenging and real-life face images.

3.2. Comparisons with other video FR methods

<References for comparison methods>

[1] A. Hamid and M. Pietikainen, From still image to video-based face recognition: An experimental analysis, in Proc, IEEE Int. Conf. AFGR 2004.

[2] A. Hamid and M. Pietikainen, Combining appearance and motion for face and gender recognition from videos, Pattern Recognition, 2009.

[3] R. Wang, S. Shan, X. Chen, and W. Gao, Manifold-manifold distance with application to face recognition based on image set, in proc. IEEE Int. Conf. CVPR, 2008.

[4] K. C. Lee, J. Ho, M. H. Yang, and D. Kriegman, Video-based face recognition using probabilistic appearance manifolds, in Proc. IEEE Int. Conf. CVPR, 2003.

[5] G. Aggarwal, A. K. Roy-Chowdhury, and R. Chellapa, A system identification approach for video-based face recognition, in Proc. IEEE ICPR 2004.

 

* Contact Person: Prof. Yong Man Ro (ymro@kaist.ac.kr)

http://ivylab.kaist.ac.kr/image/demo/project_publication.gif

1.     J. Y. Choi, K. N. Plataniotis, and Y. M. Ro, Face Feature Weighted Fusion Based Fuzzy Membership Degree for Video Face Recognition, IEEE Transactions on Systems, Man, and Cybernetics-Part B, 2012.

2.     J. Y. Choi, W. D. Neve, Y. M. Ro, and K. N. Plataniotis, Automatic Face Annotation in Personal Photo Collections Using Context-Based Unsupervised Clustering and Face Information Fusion, IEEE Transactions on Circuits and Systems for Video Technology, 2011.

3.     J. Y. Choi, W. D. Neve, and Y. M. Ro, Towards an Automatic Face Indexing System for Actor-based Video Services in an IPTV Environment, IEEE Transactions on Consumer Electronics, 2010.

 

http://ivylab.kaist.ac.kr/image/demo/project_demo.gif

l  Video1: Real-time face detection and recognition in CCTV video.

 

l  Video2: Effectiveness of fusing multiple face features for FR.