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  • 1.
    Al-Naser, Mohammad
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Söderström, Ulrik
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Reconstruction of occluded facial images using asymmetrical Principal Component Analysis2012In: Integrated Computer-Aided Engineering, ISSN 1069-2509, E-ISSN 1875-8835, Vol. 19, no 3, p. 273-283Article in journal (Refereed)
    Abstract [en]

    When only non-occluded image parts are available for facial images it is difficult or impossible to correctly recognize the person in the image. The problem addressed in this work is reconstruction of the occluded parts in facial images; e. g. eyes covered with sunglasses. Asymmetrical Principal Component Analysis (aPCA) allows estimation of occluded facial parts based on the content of the facial parts which are visible. aPCA is used to estimate full non-occluded faces from 3 kinds of occlusion with 2 different reconstruction methods in this work and we present the results with both objective and subjective evaluation. The subjective evaluation shows that clear and sharp image regions are preferred even if this results in visible edges in the images. The method also performs well when a different facial expression than the one in the database is used to calculate the reconstruction parameters.

  • 2.
    Al-Naser, Mohammad
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Söderström, Ulrik
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Reconstruction of occluded facial images using asymmetrical principal component analysis2011In: 2011 18th International Conference on Systems, Signals and Image Processing (IWSSIP), IEEE , 2011, p. 276-279Conference paper (Refereed)
    Abstract [en]

    When face images are occluded it becomes difficult or impossible to make a correct recognition based on only the non-occluded parts. With asymmetrical Principal Component Analysis (aPCA) it is possible to estimate occluded regions based on the content of the non-occluded pixels. Entire faces can be reconstructed from images where some parts are occluded with the occluded region being estimated based on the relation to the non-occluded region. We show the result with 3 different occlusion cases and compare two reconstruction methods. The results are measured both objectively and subjectively and it is shown that a clear and sharp image part should be used even if the resulting image have edges in it.

  • 3.
    Darvish, Ali Mohammed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Li, Haibo
    Söderström, Ulrik
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Super-resolution facial images from single input images based on discrete wavelet transform2014In: 22nd International Conference on Pattern Recognition, 2014, p. 843-848Conference paper (Refereed)
    Abstract [en]

    In this work, we are presenting a technique that allows for accurate estimation of frequencies in higher dimensions than the original image content. This technique uses asymmetrical Principal Component Analysis together with Discrete Wavelet Transform (aPCA-DWT). For example, high quality content can be generated from low quality cameras since the necessary frequencies can be estimated through reliable methods. Within our research, we build models for interpreting facial images where super-resolution versions of human faces can be created. We have worked on several different experiments, extracting the frequency content in order to create models with aPCA-DWT. The results are presented along with experiments of deblurring and zooming beyond the original image resolution. For example, when an image is enlarged 16 times in decoding, the proposed technique outperforms interpolation with more than 7 dB on average.

  • 4.
    Khan, Muhammad Sikandar Lal
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    ur Réhman, Shafiq
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. University of East London, London, England.
    Söderström, Ulrik
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Halawani, Alaa
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Li, Haibo
    Face-off: a Face Reconstruction Technique for Virtual Reality (VR) Scenarios2016In: Computer Vision: ECCV 2016 Workshops / [ed] Hua G., Jégou H., Springer, 2016, Vol. 9913, p. 490-503Conference paper (Refereed)
    Abstract [en]

    Virtual Reality (VR) headsets occlude a significant portion of human face. The real human face is required in many VR applications, for example, video teleconferencing. This paper proposes a wearable camera setup-based solution to reconstruct the real face of a person wearing VR headset. Our solution lies in the core of asymmetrical principal component analysis (aPCA). A user-specific training model is built using aPCA with full face, lips and eye region information. During testing phase, lower face region and partial eye information is used to reconstruct the wearer face. Online testing session consists of two phases, i) calibration phase and ii) reconstruction phase. In former, a small calibration step is performed to align test information with training data, while the later uses half face information to reconstruct the full face using aPCA-based trained-data. The proposed approach is validated with qualitative and quantitative analysis.

  • 5.
    Kouma, Jean-Paul
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Söderström, Ulrik
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Wyner-Ziv Video Coding using Hadamard Transform and Deep Learning2016In: International Journal of Advanced Computer Sciences and Applications, ISSN 2158-107X, E-ISSN 2156-5570, Vol. 7, no 7, p. 582-589Article in journal (Refereed)
    Abstract [en]

    Predictive schemes are current standards of video coding. Unfortunately they do not apply well for lightweight devices such as mobile phones. The high encoding complexity is the bottleneck of the Quality of Experience (QoE) of a video conversation between mobile phones. A considerable amount of research has been conducted towards tackling that bottleneck. Most of the schemes use the so-called Wyner-Ziv Video Coding Paradigm, with results still not comparable to those of predictive coding. This paper shows a novel approach for Wyner-Ziv video compression. It is based on the Reinforcement Learning and Hadamard Transform. Our Scheme shows very promising results.

  • 6.
    Li, Bo
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Halawani, Alaa
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Söderström, Ulrik
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Scale & rotation-invariant matching with curve chainManuscript (preprint) (Other academic)
    Abstract [en]

    This paper presents a new methodology that matches image geometry using a curve chain. A curve chain is defined as a 1-dimensional arrangement of curves. The idea is to match images without using local descriptors and apply this concept into applications. This paper have two contributions. First, we present a novel curve feature which is scale & rotation – invariant. Secondly, we present an efficient scale & rotational-invariant matching method which matches curve chains in the scene. The efficacy is benefited by three factors. Firstly, matching a 1-dimensional curve chain can achieve quadratic operations when dynamic programming is used.  Secondly, curves are salient features that naturally reduce the dimensionality compared with scanning all possible locations. Thirdly, curves provide stable relational cues between neighbouring curves. Such stable relational cues reduce the computation to linear operations by avoiding searching all combinations of curves in dynamic programming. The advantages of the method has good potential to benefit application including point correspondence matching, object detection, etc.  In point correspondence experiments our method yields a good total matching score on various image transformations. At the same time, the proposed method shows good potential of matching non-rigid object such as faces with scale & rotation invariance.

  • 7.
    Li, Bo
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Jevtic, Aleksandar
    Robosoft,France.
    Söderström, Ulrik
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Ur Réhman, Shafiq
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Li, Haibo
    KTH.
    Fast edge detection by center of mass2013In: The 1st IEEE/IIAE International Conference on Intelligent Systems and Image Processing 2013 (ICISIP2013), Kitakyushu, Japan, 2013, p. 103-110Conference paper (Refereed)
    Abstract [en]

    In this paper, a novel edge detection method that computes image gradient using the concept of Center of Mass (COM) is presented. The algorithm runs with a constant number of operations per pixel independently from its scale by using integral image. Compared with the conventional convolutional edge detector such as Sobel edge detector, the proposed method performs faster when region size is larger than 9×9. The proposed method can be used as framework for multi-scale edge detectors when the goal is to achieve fast performance. Experimental results show that edge detection by COM is competent with Canny edge detection.

  • 8.
    Li, Bo
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Li, Haibo
    KTH.
    Söderström, Ulrik
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Distinctive curves: unified scale-invariant detection of edges, corners, lines and curvesManuscript (preprint) (Other academic)
    Abstract [en]

    This paper aims to broaden the scope of shape related features including edges, corners, lines and curves: 1) Edges, corners, lines, curves are all shape related features. In the past, the detection of each type of feature is usually solved independently under certain hypotheses. Our proposed distinctive curve detection method (DICU) solves the detection of all these type of features together. 2) Compared to the development in scale-invariant interest point detectors which have adopted more objective robustness measures using repeatability score, the research in line and curve features is still limited to “true/false positive” measures. DICU detection utilizes the scale-space concept and proves that curve features can be as robust as scale-invariant interest points. DICU has three advantages: 1) DICU outputs multi-type features which can benefit future computer vision applications. At the same time, the computational efficiency is unaffected, after detecting edges, only 5% additional computation is needed to detect corners, lines, and curves. 2) It is robust under various image perturbations and transformations and outperforms state-of-the-art interest point detectors and line detectors. At the same time, all types of detected features are robust. 3) Curve features contains more geometric information than points. Our curve matching test shows that curve matching can outperform interest point matching. 

  • 9.
    Li, Bo
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Li, Haibo
    KTH.
    Söderström, Ulrik
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Scale-invariant corner keypointsManuscript (preprint) (Other academic)
    Abstract [en]

    Effective and efficient generation of keypoints from images is the first step of many computer vision applications, such as object matching. The last decade presented us with an arms race toward faster and more robust keypoint detection, feature description and matching. This resulted in several new algorithms, for example Scale Invariant Features Transform (SIFT), Speed-up Robust Feature (SURF), Oriented FAST and Rotated BRIEF (ORB) and Binary Robust Invariant Scalable Keypoints (BRISK). The keypoint detection has been improved using various techniques in most of these algorithms. However, in the search for faster computing, the accuracy of the algorithms is decreasing. In this paper, we present SICK (Scale-Invariant Corner Keypoints), which is a novel method for fast keypoint detection. Our experiment results show that SICK is faster to compute and more robust than recent state-of-the-art methods. 

  • 10.
    Li, Bo
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Li, Haibo
    KTH.
    Söderström, Ulrik
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Scale-invariant corner keypoints2014In: 2014 IEEE INTERNATIONAL CONFERENCE ON IMAGE PROCESSING (ICIP), IEEE , 2014, p. 5741-5745Conference paper (Other academic)
    Abstract [en]

    Effective and efficient generation of keypoints from images is the first step of many computer vision applications, such as object matching. The last decade presented us with an arms race toward faster and more robust keypoint detection, feature description and matching. This resulted in several new algorithms, for example Scale Invariant Features Transform (SIFT), Speed-up Robust Feature (SURF), Oriented FAST and Rotated BRIEF (ORB) and Binary Robust Invariant Scalable Keypoints (BRISK). The keypoint detection has been improved using various techniques in most of these algorithms. However, in the search for faster computing, the accuracy of the algorithms is decreasing. In this paper, we present SICK (Scale-Invariant Corner Keypoints), which is a novel method for fast keypoint detection. Our experiment results show that SICK is faster to compute and more robust than recent state-of-the-art methods. 

  • 11.
    Li, Bo
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Söderström, Ulrik
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Ur Réhman, Shafiq
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Li, Haibo
    KTH.
    Restricted Hysteresis Reduce Redundancy in Edge Detection2013In: Journal of Signal and Information Processing, ISSN 2159-4465, E-ISSN 2159-4481, Vol. 4, no 3B, p. 158-163Article in journal (Refereed)
    Abstract [en]

    In edge detection algorithms, there is a common redundancy problem, especially when the gradient direction is close to -135°, -45°, 45°, and 135°. Double edge effect appears on the edges around these directions. This is caused by the discrete calculation of non-maximum suppression. Many algorithms use edge points as feature for further task such as line extraction, curve detection, matching and recognition. Redundancy is a very important factor of algorithm speed and accuracy. We find that most edge detection algorithms have redundancy of 50% in the worst case and 0% in the best case depending on the edge direction distribution. The common redundancy rate on natural images is approximately between 15% and 20%. Based on Canny’s framework, we propose a restriction in the hysteresis step. Our experiment shows that proposed restricted hysteresis reduce the redundancy successfully.

  • 12.
    Li, Bo
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Ur Réhman, Shafiq
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Söderström, Ulrik
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Li, Haibo
    KTH.
    Independent Thresholds on Multi-scale Gradient Images2013In: The 1st IEEE/IIAE International Conference on Intelligent Systems and Image Processing 2013 (ICISIP2013), Kitakyushu, Japan, 2013, p. 124-131Conference paper (Refereed)
    Abstract [en]

    In this paper we propose a multi-scale edge detection algorithm based on proportional scale summing. Our analysis shows that proportional scale summing successfully improves edge detection rate by applying independent thresholds on multi-scale gradient images. The proposed method improves edge detection and localization by summing gradient images with a proportional parameter cn (c < 1); which ensures that the detected edges are as close as possible to the fine scale. We employ non-maxima suppression and thinning step similar to Canny edge detection framework on the summed gradient images. The proposed method can detect edges successfully and experimental results show that it leads to better edge detection performance than Canny edge detector and scale multiplication edge detector.

  • 13.
    Mejtoft, Thomas
    et al.
    Umeå University.
    Cripps, Helen
    Edith Cowan University.
    Bahtiri, Blerand
    Umeå University.
    Söderström, Ulrik
    Umeå University.
    Use of Image Recognition of Social Media2017In: ANZMAC 2017: Marketing for Impact: Conference Proceedings / [ed] Linda Robinson, Linda Brennan, Mike Reid, Melbourne: RMIT University , 2017, p. 271-278Conference paper (Refereed)
    Abstract [en]

    Images are central to firms in their use of social media platforms as part of their marketing strategy. Images are a powerful online marketing tool as they allow for engagement and personalisation of marketing content for individual customers. However, images can be a double edge sword in the web 2.0 world, where consumers are able to post content to branded social media sites. This study evaluates the benefits of integrating image recognition into social media from the users perspective. The pilot study undertaken found the majority of the participants thought the possibilities presented for image recognition technology are useful, however they showed concern in relation to their privacy if this technology were to be in social media networks. The results also showed that prior familiarity with this technology does not have any significant impact in how social media users feel about having this technology in social media.

  • 14.
    Mejtoft, Thomas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Hellman, David
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Söderström, Ulrik
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Reclaiming control over personal data with blockchain technology: An exploratory study2019In: 32nd Bled eConference: Humanizing Technology for a Sustainable Society: Conference Proceedings / [ed] A. Pucihar, M. Kljajić Borštnar, R. Bons, J. Seitz, H. Cripps & D. Vidmar, Maribor, Slovenia: University of Maribor Press , 2019, p. 411-425Conference paper (Refereed)
    Abstract [en]

    With the digitalization and increasing number of Internet users,more and more personal data breaches occur. Many people are not awareof their personal data rights and have not received any instructions on howto act in situations such as when their personal data is abused. This issomething that illustrates the flaws of the Internet. A technology thatprovides solutions to some of these problems, such as trust andtransparency, is the blockchain technology. Hence, the objective of thispaper is to investigate knowledge about personal data rights and to explorethe design of a prototype of a blockchain application for increased securityand transparency. User tests were conducted, highlighting the greatestneeds for users to feel secure and in control over their personal data. Thisknowledge provide the foundation for a prototype based on blockchaintechnology that gives the users increased security and forces those whostore personal data to be more transparent with the usage.

  • 15.
    Mejtoft, Thomas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Lindberg, Lena
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Söderström, Ulrik
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Mårell-Olsson, Eva
    Umeå University, Faculty of Social Sciences, Department of applied educational science.
    Feedback in commercial educational applications: Guidelines and conceptual framework2017In: Proceedings of the European Conference on Cognitive Ergonomics 2017 (ECCE 2017), ACM Digital Library, 2017, p. 113-120Conference paper (Refereed)
    Abstract [en]

    In recent years, schools made large investments to increase the integration and use of contemporary technologies in teaching and learning.Today iPads and educational applications are growing in popularity and are commonly used. These technologies have a potential beneficial effect on the learning, but studies show that some applications have flaws that hinder these positive effects, for example regarding the feedback provided to the user. This study has determined a number of guidelines for effective feedback in a learning situation and has further shown how well these guidelines can be reached in an educational application today. The study shows that there are both advantages and disadvantages of feedback in an application compared to giving feedback in a more traditional learning situation. Many of the guidelines for effective feedback were found to be possible to reach in an application, and the greatest advantage found in applications is that they can provide feedback timely on each action taken by the pupils.

  • 16.
    Mejtoft, Thomas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Nanyang Technological University, Singapore.
    Långström, Arvid
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Söderström, Ulrik
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    The effect of skeleton screens: Users’ perception of speed and ease of navigation2018In: Proceedings of the 36th European Conference on Cognitive Ergonomics, New York, NY: ACM Press, 2018, article id 22Conference paper (Refereed)
    Abstract [en]

    Progression bars and spinners have long been the norm when providing feedback during wait times on the web. However, a more recent trend is the use of skeleton screens. This paper aims to evaluate the usefulness of skeleton screens as an alternative to spinners. This is done user testing a fictional news site with two variations, one showing skeleton screens before content is loaded, and another utilizing spinners. Both a questionnaire and measuring timing while finding a specified article when entering a website for the first time was used. The results show that the page using skeleton screens, scored higher on average on both perceived speed and ease of navigation. However, people using the page with spinners were faster at finding the article when entering the site for the first time. The results of this paper cannot show any significant differences in any of the comparisons between the web pages.

  • 17.
    Mejtoft, Thomas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Ristiniemi, Charlotte
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Söderström, Ulrik
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Mårell-Olsson, Eva
    Umeå University, Faculty of Social Sciences, Department of applied educational science, Interactive Media and Learning (IML).
    User experience design and digital nudging in a decision making process2019In: 32nd Bled eConference: Humanizing Technology for a Sustainable Societ: Conference Proceedings / [ed] A. Pucihar, M. Kljajić Borštnar, R. Bons, J. Seitz, H. Cripps & D. Vidmar, Maribor, Slovenia: University of Maribor Press , 2019, p. 427-442Conference paper (Refereed)
    Abstract [en]

    When using online nudges to steer people in the right directionwhile they are making a decision, there is usually one preferable outcome.What might happen if the user experience is inadequate, will the nudgesstill work or might they be undermined? In this paper we investigate thecorrelation between user experience and digital nudges in a decisionmaking process. A user A/B test was conducted to investigate theproblem. The test participants visited one of two websites that includedthe same nudges where they were nudged to choose option (a) instead of(b). The only difference in the websites was the quality of the userexperience, one website design had a good user experience while the otherone offered an inadequate user experience. The results showed thateveryone who was assigned the good user experience chose (a), while twoof the inadequate experience participants chose (b). The results indicatethat user experience design can be used for digital nudging.

  • 18.
    Mejtoft, Thomas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Söderström, Ulrik
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Intressentfokuserade oberoende longitudinella utvärderingar2018In: Proceedings från 6:e Utvecklingskonferensen för Sveriges ingenjörsutbildningar / [ed] Lena Peterson, Kristina Edström, Oskar Gedda, Fredrik Georgsson, Liselott Lycke och Marie Arehag, Göteborg: Chalmers tekniska högskola , 2018, p. 94-96Conference paper (Refereed)
    Abstract [sv]

    Utbildningskvalité är en mycket viktig fråga som diskuteras frekvent inom universitetsvärlden. Såväl kontroll som förbättring av utbildningskvalité är i många lägen starkt kopplat till olika former av utvärderingar. Denna artikel syftar till att illustrera och analysera en utvärderingsmodell som har använts på ett civilingenjörsprogram vid Umeå universitet. Målsättningen med utvärderingsmodellen är att skapa mer holistiska utvärderingar med ett starkare fokus på de intressenter som finns för kvalitetsutveckling - studenter och lärare.

  • 19.
    Son, Le-Hung
    et al.
    Umeå University, Faculty of Science and Technology, Applied Physics and Electronics.
    Söderström, Ulrik
    Umeå University, Faculty of Science and Technology, Applied Physics and Electronics.
    Li, Haibo
    Umeå University, Faculty of Science and Technology, Applied Physics and Electronics.
    Ultra low bit-rate video communication: video coding = pattern recognition2006In: Proceedings of the 25th Picture Coding Symposium, 2006Conference paper (Refereed)
  • 20.
    Söderström, Ulrik
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Personal Internet-driven maps based on time distances2011In: 2011 IEEE International Conferences on Internet of Things, and Cyber, Physical and Social Computing, Los Alamitos: IEEE Computer Society, 2011, p. 683-686Conference paper (Refereed)
    Abstract [en]

    New ways for map creation are presented. Instead of using the physical distance between locations the distance is measured in time, cost, environmental effect or as a weighted version between the different parameters. The maps will be personal and changed based on the user preferences so the map appearance will be different for different users. In closed-up version the standard map with physical distance should still be used since it is very important that the map resembles the actual surrounding when you are using a map in a local environment. As devices are connected to the Internet the calculation of distance can be made on-line and follow train/flight departures and delays.

  • 21.
    Söderström, Ulrik
    Umeå University, Faculty of Science and Technology, Applied Physics and Electronics.
    Very low bitrate facial video coding: based on principal component analysis2006Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis introduces a coding scheme for very low bitrate video coding through the aid of principal component analysis. Principal information of the facial mimic for a person can be extracted and stored in an Eigenspace. Entire video frames of this persons face can then be compressed with the Eigenspace to only a few projection coefficients. Principal component video coding encodes entire frames at once and increased frame size does not increase the necessary bitrate for encoding, as standard coding schemes do. This enables video communication with high frame rate, spatial resolution and visual quality at very low bitrates. No standard video coding technique provides these four features at the same time.

    Theoretical bounds for using principal components to encode facial video sequences are presented. Two different theoretical bounds are derived. One that describes the minimal distortion when a certain number of Eigenimages are used and one that describes the minimum distortion when a minimum number of bits are used.

    We investigate how the reconstruction quality for the coding scheme is affected when the Eigenspace, mean image and coefficients are compressed to enable efficient transmission. The Eigenspace and mean image are compressed through JPEG-compression while the while the coefficients are quantized. We show that high compression ratios can be used almost without any decrease in reconstruction quality for the coding scheme.

    Different ways of re-using the Eigenspace for a person extracted from one video sequence to encode other video sequences are examined. The most important factor is the positioning of the facial features in the video frames.

    Through a user test we find that it is extremely important to consider secondary workloads and how users make use of video when experimental setups are designed.

  • 22.
    Söderström, Ulrik
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Very Low Bitrate Video Communication: A Principal Component Analysis Approach2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    A large amount of the information in conversations come from non-verbal cues such as facial expressions and body gesture. These cues are lost when we don't communicate face-to-face. But face-to-face communication doesn't have to happen in person. With video communication we can at least deliver information about the facial mimic and some gestures. This thesis is about video communication over distances; communication that can be available over networks with low capacity since the bitrate needed for video communication is low.

    A visual image needs to have high quality and resolution to be semantically meaningful for communication. To deliver such video over networks require that the video is compressed. The standard way to compress video images, used by H.264 and MPEG-4, is to divide the image into blocks and represent each block with mathematical waveforms; usually frequency features. These mathematical waveforms are quite good at representing any kind of video since they do not resemble anything; they are just frequency features. But since they are completely arbitrary they cannot compress video enough to enable use over networks with limited capacity, such as GSM and GPRS.

    Another issue is that such codecs have a high complexity because of the redundancy removal with positional shift of the blocks. High complexity and bitrate means that a device has to consume a large amount of energy for encoding, decoding and transmission of such video; with energy being a very important factor for battery-driven devices.

    Drawbacks of standard video coding mean that it isn't possible to deliver video anywhere and anytime when it is compressed with such codecs. To resolve these issues we have developed a totally new type of video coding. Instead of using mathematical waveforms for representation we use faces to represent faces. This makes the compression much more efficient than if waveforms are used even though the faces are person-dependent.

    By building a model of the changes in the face, the facial mimic, this model can be used to encode the images. The model consists of representative facial images and we use a powerful mathematical tool to extract this model; namely principal component analysis (PCA). This coding has very low complexity since encoding and decoding only consist of multiplication operations. The faces are treated as single encoding entities and all operations are performed on full images; no block processing is needed. These features mean that PCA coding can deliver high quality video at very low bitrates with low complexity for encoding and decoding.

    With the use of asymmetrical PCA (aPCA) it is possible to use only semantically important areas for encoding while decoding full frames or a different part of the frames.

    We show that a codec based on PCA can compress facial video to a bitrate below 5 kbps and still provide high quality. This bitrate can be delivered on a GSM network. We also show the possibility of extending PCA coding to encoding of high definition video.

  • 23.
    Söderström, Ulrik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Bååth, Martin
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Mejtoft, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Nanyang Technological University, Singapore.
    The Users’ Time Perception: The effect of various animation speeds on loading screens2018In: Proceedings of the 36th European Conference on Cognitive Ergonomics, New York, NY: ACM Press, 2018, article id 21Conference paper (Refereed)
    Abstract [en]

    Loading screens are still important in 2018, and there is a reason for that: they provide a great way to give feedback to the user in the interface during wait times after a user's action. Previous research shows that it is essential for a well designed interface and it is a well established way to increase and maintain a user's satisfaction. This study specifically examine the looped, passive animation screen with regards to how the animation speed affects the user. Results suggests that with faster animation, perceived wait time gets shorter and the user is more satisfied.

  • 24.
    Söderström, Ulrik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Freidovich, Leonid B.Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Proceedings of the 16th Student Conference in Interaction Technology and Design and the 5th Student Conference in Electronics and Mechatronics2019Conference proceedings (editor) (Refereed)
    Abstract [en]

    The joint Student Conference in Interaction Technology and Design and Student Conference in Electronics and Mechatronics is the annual grand finale of the courses Current Topic in Interaction Technology and Design and Student Conference in Electronics and Mechatronics at the Department of Applied Physics and Electronics, Umeå University. The idea and objective of the two courses are to give the students a forum where they can actively participate in scientific research and development through their own ideas and interests.  The course introduces students to independently researching an interesting topic, using a foreign language orally and in writing, writing a scientific article, peer-review and presenting their work at a conference. The conference format was chosen to provide a realistic environment for the presentation of the results. The work has been reviewed both by other participant on the course and members of the department. If the reviews are favorable, the paper is accepted as a full paper at the conference and included in the proceedings. Research that has an interesting topic and potential for future publication is presented as work-in-progress at the conference and the abstract is included in the conference proceedings. This year 10 full papers and 2 work-in-progress papers were accepted at the conference and all included in this proceedings as full papers and extended abstracts, respectively.

  • 25.
    Söderström, Ulrik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Li, Haibo
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Anonymous video processing for live street view2011In: 2011 IEEE International Conferences on Internet of Things, and Cyber, Physical and Social Computing, Los Alamitos: IEEE Computer Society, 2011, p. 109-113Conference paper (Refereed)
    Abstract [en]

    We propose a method for hiding the identity of persons and objects in video sequences. This type of video sequence will be used in applications where the scene is important but the identity of persons should be unrecognizable, e.g., street view applications. Other parts, such as company logos, names on house doors or license plates on parked cars should not be recognizable as well. This is today solved in street view by blurring out parts of images that are compressed with standard encoding techniques. We propose a method that automatically will blur out parts that are moving but still show the motion. Our technique requires very low bitrates for video transmission; almost as low as for a still image. The low bitrate and the low computational complexity will enable video views of streets at the same costs as for still images.

  • 26.
    Söderström, Ulrik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Li, Haibo
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Asymmetrical Principal Component Analysis: Theory and Its Applications to Facial Video Coding2011In: Effective Video Coding for Multimedia Applications / [ed] Sudhakar Radhakrishnan, InTech Open , 2011, p. 95-110Chapter in book (Refereed)
  • 27.
    Söderström, Ulrik
    et al.
    Umeå University, Faculty of Science and Technology, Applied Physics and Electronics.
    Li, Haibo
    Umeå University, Faculty of Science and Technology, Applied Physics and Electronics.
    Eigenspace compression for very low bitrate transmission of facial video2007In: IASTED International conference on Signal Processing, Pattern Recognition and ApplicationsArticle in journal (Refereed)
  • 28.
    Söderström, Ulrik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Li, Haibo
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    HD video communication at very low bitrates2009In: Recent Advances in Multimedia Signal Processing and Communications / [ed] Mislav Grgic, Kresimir Delac, Mohammed Ghanbari, Berlin, Heidelberg: Springer Berlin/Heidelberg, 2009, p. 295-314Chapter in book (Other academic)
    Abstract [en]

    This chapter describes compression of facial video, i.e., video where the face or head-and-shoulders of a person is the important information. This kind of video is used for communication between people and HD quality of this video makes it much more useful. When it is wearable so that the user is free to move it becomes an even more appealing application.

  • 29.
    Söderström, Ulrik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Li, Haibo
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    High definition wearable video communication2009In: Image analysis: 16th Scandinavian Conference, SCIA 2009, Oslo, Norway, June 15-18, 2009. Proceedings / [ed] Arnt-Børre Salberg, Jon Yngve Hardeberg, Robert Jenssen, Heidelberg: Springer Berlin , 2009, p. 500-512Conference paper (Refereed)
    Abstract [en]

    High definition (HD) video can provide video communication which is as crisp and sharp as face-to-face communication. Wearable video equipment also provide the user with mobility; the freedom to move. HD video requires high bandwidth and yields high encoding and decoding complexity when encoding based on DCT and motion estimation is used. We propose a solution that can drastically lower the bandwidth and complexity for video transmission. Asymmetrical principal component analysis can initially encode HD video into bitrates which are low considering the type of video (< 300 kbps) and after a startup phase the bitrate can be reduced to less than 5 kbps. The complexity for encoding and decoding of this video is very low; something that will save battery power for mobile devices. All of this is done only at the cost of lower quality in frame areas which aren’t considered semantically important.

  • 30.
    Söderström, Ulrik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Li, Haibo
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Representation bound for human facial mimic with the aid of principal component analysis2010In: International Journal of Image and Graphics, ISSN 0219-4678, Vol. 10, no 3, p. 343-363Article in journal (Refereed)
    Abstract [en]

    In this paper, we examine how much information is needed to represent the facial mimic, based on Paul Ekman's assumption that the facial mimic can be represented with a few basic emotions. Principal component analysis is used to compact the important facial expressions. Theoretical bounds for facial mimic representation are presented both for using a certain number of principal components and a certain number of bits. When 10 principal components are used to reconstruct color image video at a resolution of 240 × 176 pixels the representation bound is on average 36.8 dB, measured in peak signal-to-noise ratio. Practical confirmation of the theoretical bounds is demonstrated. Quantization of projection coefficients affects the representation, but a quantization with approximately 7-8 bits is found to match an exact representation, measured in mean square error.

  • 31.
    Söderström, Ulrik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Li, Haibo
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Side view driven facial video coding2013In: Advanced Video Coding for Next-Generation Multimedia Services / [ed] Yo-Sung Ho, InTech, 2013, p. 139-154Chapter in book (Refereed)
    Abstract [en]

    A video can be decoded from an encoded version of another video when there is correspondence between the pixels in the two videos. Asymmetrical principal component analysis allows decoding of the frontal view of a face based on an encoded version the side view, or the profile of the side, of the same face. If the side view is used for encoding instead of the frontal view the reconstruction quality is only lowered slightly ($\approx$ 1,5 dB PSNR). If the profile of the side of view is used to encode the video the complexity for the encoding is lowered with more than 99\% but the largest benefit of this coding is that the side view can be used for encoding instead of the frontal view. Filming the side view is far easier from a use-friendly point of view. This is a new kind of video coding where the information that is decoded does not have to be available for the encoding phase.

  • 32.
    Wikstrand, Greger
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Söderström, Ulrik
    Umeå University, Faculty of Science and Technology, Applied Physics and Electronics.
    Internet card play with video conferencing2006In: Proceedings SSBA 2006: Symposium on Image Analysis, Umeå, March 16-17, 2006 / [ed] Fredrik Georgsson, Niclas Börlin, Umeå: Umeå universitet , 2006, p. 93-96Chapter in book (Other academic)
    Abstract [en]

    In an experiment, groups of four participants played “bluffstopp” — a card game based on deception — over the Internet while communicating through multicast video and audio. Higher frame rates lead to lower video quality ratings. The result is explained as an effect of increasing visual workload.

1 - 32 of 32
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