Danda Pani Paudel

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Research Scholar at University of Strasbourg

  • Sliced Wasserstein Generative Models

    In generative modeling, the Wasserstein distance (WD) has emerged as a useful metric to measure the discrepancy between generated and real data distributions. Unfortunately, it is challenging to approximate the WD of high-dimensional distributions. In contrast, the sliced Wasserstein distance (SWD) factorizes high-dimensional distributions into their multiple one-dimensional marginal distributions and is thus easier to approximate. In this paper, we introduce novel approximations of the primal and dual SWD. Instead of using a large number of random projections, as it is done by conventional SWD approximation methods, we propose to approximate SWDs with a small number of parameterized orthogonal projections in an end-to-end deep learning fashion. As concrete applications of our SWD approximations, we design two types of differentiable SWD blocks to equip modern generative frameworks---Auto-Encoders (AE) and Generative Adversarial Networks (GAN). In the experiments, we not only show the superiority of the proposed generative models on standard image synthesis benchmarks, but also demonstrate the state-of-the-art performance on challenging high resolution image and video generation in an unsupervised manner.

    04/10/2019 ∙ by Jiqing Wu, et al. ∙ 46 share

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  • Model-free Consensus Maximization for Non-Rigid Shapes

    Many computer vision methods rely on consensus maximization to relate measurements containing outliers with a reliable transformation model. In the context of matching rigid shapes, this is typically done using Random Sampling and Consensus (RANSAC) to estimate an analytical model that agrees with the largest number of measurements, which make the inliers. However, such models are either not available or too complex for non-rigid shapes. In this paper, we formulate the model-free consensus maximization problem as an Integer Program in a graph using 'rules' on measurements. We then provide a method to solve such a formulation optimally using the Branch and Bound (BnB) paradigm. In the context of non-rigid shapes, we apply the method to filter out outlier 3D correspondences and achieve performance superior to the state-of-the-art. Our method works with outlier ratio as high as 80 formulation for 3D template to image correspondences. Our approach achieves similar or better performance compared to the state-of-the-art.

    07/05/2018 ∙ by Thomas Probst, et al. ∙ 4 share

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  • Image-based Navigation using Visual Features and Map

    Building on progress in feature representations for image retrieval, image-based localization has seen a surge of research interest. Image-based localization has the advantage of being inexpensive and efficient, often avoiding the use of 3D metric maps altogether. This said, the need to maintain a large number of reference images as an effective support of localization in a scene, nonetheless calls for them to be organized in a map structure of some kind. The problem of localization often arises as part of a navigation process. We are, therefore, interested in summarizing the reference images as a set of landmarks, which meet the requirements for image-based navigation. A contribution of the paper is to formulate such a set of requirements for the two sub-tasks involved: map construction and self localization. These requirements are then exploited for compact map representation and accurate self-localization, using the framework of a network flow problem. During this process, we formulate the map construction and self-localization problems as convex quadratic and second-order cone programs, respectively. We evaluate our methods on publicly available indoor and outdoor datasets, where they outperform existing methods significantly.

    12/10/2018 ∙ by Janine Thoma, et al. ∙ 4 share

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  • Face Translation between Images and Videos using Identity-aware CycleGAN

    This paper presents a new problem of unpaired face translation between images and videos, which can be applied to facial video prediction and enhancement. In this problem there exist two major technical challenges: 1) designing a robust translation model between static images and dynamic videos, and 2) preserving facial identity during image-video translation. To address such two problems, we generalize the state-of-the-art image-to-image translation network (Cycle-Consistent Adversarial Networks) to the image-to-video/video-to-image translation context by exploiting a image-video translation model and an identity preservation model. In particular, we apply the state-of-the-art Wasserstein GAN technique to the setting of image-video translation for better convergence, and we meanwhile introduce a face verificator to ensure the identity. Experiments on standard image/video face datasets demonstrate the effectiveness of the proposed model in both terms of qualitative and quantitative evaluations.

    12/04/2017 ∙ by Zhiwu Huang, et al. ∙ 0 share

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  • Towards an Understanding of Our World by GANing Videos in the Wild

    Existing generative video models work well only for videos with a static background. For dynamic scenes, applications of these models demand an extra pre-processing step of background stabilization. In fact, the task of background stabilization may very often prove impossible for videos in the wild. To the best of our knowledge, we present the first video generation framework that works in the wild, without making any assumption on the videos' content. This allows us to avoid the background stabilization step, completely. The proposed method also outperforms the state-of-the-art methods even when the static background assumption is valid. This is achieved by designing a robust one-stream video generation architecture by exploiting Wasserstein GAN frameworks for better convergence. Since the proposed architecture is one-stream, which does not formally distinguish between fore- and background, it can generate - and learn from - videos with dynamic backgrounds. The superiority of our model is demonstrated by successfully applying it to three challenging problems: video colorization, video inpainting, and future prediction.

    11/30/2017 ∙ by Bernhard Kratzwald, et al. ∙ 0 share

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  • Incremental Non-Rigid Structure-from-Motion with Unknown Focal Length

    The perspective camera and the isometric surface prior have recently gathered increased attention for Non-Rigid Structure-from-Motion (NRSfM). Despite the recent progress, several challenges remain, particularly the computational complexity and the unknown camera focal length. In this paper we present a method for incremental Non-Rigid Structure-from-Motion (NRSfM) with the perspective camera model and the isometric surface prior with unknown focal length. In the template-based case, we provide a method to estimate four parameters of the camera intrinsics. For the template-less scenario of NRSfM, we propose a method to upgrade reconstructions obtained for one focal length to another based on local rigidity and the so-called Maximum Depth Heuristics (MDH). On its basis we propose a method to simultaneously recover the focal length and the non-rigid shapes. We further solve the problem of incorporating a large number of points and adding more views in MDH-based NRSfM and efficiently solve them with Second-Order Cone Programming (SOCP). This does not require any shape initialization and produces results orders of times faster than many methods. We provide evaluations on standard sequences with ground-truth and qualitative reconstructions on challenging YouTube videos. These evaluations show that our method performs better in both speed and accuracy than the state of the art.

    08/13/2018 ∙ by Thomas Probst, et al. ∙ 0 share

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  • Towards High Resolution Video Generation with Progressive Growing of Sliced Wasserstein GANs

    The extension of image generation to video generation turns out to be a very difficult task, since the temporal dimension of videos introduces an extra challenge during the generation process. Besides, due to the limitation of memory and training stability, the generation becomes increasingly challenging with the increase of the resolution/duration of videos. In this work, we exploit the idea of progressive growing of Generative Adversarial Networks (GANs) for higher resolution video generation. In particular, we begin to produce video samples of low-resolution and short-duration, and then progressively increase both resolution and duration alone (or jointly) by adding new spatiotemporal convolutional layers to the current networks. Starting from the learning on a very raw-level spatial appearance and temporal movement of the video distribution, the proposed progressive method learns spatiotemporal information incrementally to generate higher resolution videos. Furthermore, we introduce a sliced version of Wasserstein GAN (SWGAN) loss to improve the distribution learning on the video data of high-dimension and mixed-spatiotemporal distribution. SWGAN loss replaces the distance between joint distributions by that of one-dimensional marginal distributions, making the loss easier to compute. We evaluate the proposed model on our collected face video dataset of 10,900 videos to generate photorealistic face videos of 256x256x32 resolution. In addition, our model also reaches a record inception score of 14.57 in unsupervised action recognition dataset UCF-101.

    10/04/2018 ∙ by Dinesh Acharya, et al. ∙ 0 share

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