Alan C. Bovik

Bio: Alan C. Bovik is an academic researcher from University of Texas at Austin. The author has contributed to research in topics: Image quality & Video quality. The author has an hindex of 102, co-authored 837 publications receiving 96088 citations. Previous affiliations of Alan C. Bovik include University of Illinois at Urbana–Champaign & University of Sydney.

A fast and memory efficient video transcoder for low bit rate wireless communications

Abstract: Wireless video is one of the important applications supported by upcoming 3G mobile communication systems. In this paper, we propose a fast and memory efficient DCT-domain video transcoder to convert a high quality MPEG2 video bit stream into a low bit rate MPEG4 stream with low spatial resolution for wireless video access. Compared to existing approaches, the proposed video transcoder can save more than 50% of required memory. Furthermore, the computational complexity of the proposed method is less than 30% of that required by existing methods. However, the video quality achieved by the proposed method and by existing methods is hardly distinguishable for target bit rates of 384 kb/s and 256 kb/s, as shown in our experimental results.

Perceptual quality evaluation of synthetic pictures distorted by compression and transmission

Abstract: Measuring visual quality, as perceived by human observers, is becoming increasingly important in a large number of applications where humans are the ultimate consumers of visual information. Many natural image databases have been developed that contain human subjective ratings of the images. Subjective quality evaluation data is less available for synthetic images, such as those commonly encountered in graphics novels, online games or internet ads. A wide variety of powerful full-reference, reduced-reference and no-reference Image Quality Assessment (IQA) algorithms have been proposed for natural images, but their performance has not been evaluated on synthetic images. In this paper we (1) conduct a series of subjective tests on a new publicly available Embedded Signal Processing Laboratory (ESPL) Synthetic Image Database, which contains 500 distorted images (20 distorted images for each of the 25 original images) in 1920 × 1080 resolution, and (2) evaluate the performance of more than 50 publicly available IQA algorithms on the new database. The synthetic images in the database were processed by post acquisition distortions, including those arising from compression and transmission. We collected 26,000 individual ratings from 64 human subjects which can be used to evaluate full-reference, reduced-reference, and no-reference IQA algorithm performance. We find that IQA models based on scene statistics models can successfully predict the perceptual quality of synthetic scenes. The database is available at: http://signal.ece.utexas.edu/%7Ebevans/synthetic/ .

Speeding Up VP9 Intra Encoder With Hierarchical Deep Learning-Based Partition Prediction

Abstract: In VP9 video codec, the sizes of blocks are decided during encoding by recursively partitioning $64\times 64$ superblocks using rate-distortion optimization (RDO). This process is computationally intensive because of the combinatorial search space of possible partitions of a superblock. Here, we propose a deep learning based alternative framework to predict the intra-mode superblock partitions in the form of a four-level partition tree, using a hierarchical fully convolutional network (H-FCN). We created a large database of VP9 superblocks and the corresponding partitions to train an H-FCN model, which was subsequently integrated with the VP9 encoder to reduce the intra-mode encoding time. The experimental results establish that our approach speeds up intra-mode encoding by 69.7% on average, at the expense of a 1.71% increase in the Bjontegaard-Delta bitrate (BD-rate). While VP9 provides several built-in speed levels which are designed to provide faster encoding at the expense of decreased rate-distortion performance, we find that our model is able to outperform the fastest recommended speed level of the reference VP9 encoder for the good quality intra encoding configuration, in terms of both speedup and BD-rate.

Image restoration using order-constrained least-squares methods

Abstract: In this paper we consider two new techniques for image restoration, using order-constrained least-squares methods. The first technique consists of a cross-shaped moving window, within which two operations are combined. The first operation consists of simple hypothesis tests for monotonicity in both the horizontal and vertical directions. The second step finds the best least-squares fit of the input variates in both directions, constrained by the results of the hypothesis tests. The second technique consists of a square moving window, again combining two operations. With the first operation, we introduce a new edge detector with specific edge height δ. Based on detection or non-detection of an edge, we either apply order-constrained least-squares methods to determine the output, or simply average. The techniques described are applied to an actual noise-corrupted image.

Three Dimensional Face Recognition using Wavelet Decomposition of Range Images

Abstract: Interest in face recognition systems has increased significantly due to the emergence of significant commercial opportunities in surveillance and security applications. In this paper we propose a novel technique to extract features from 3D face representations. In this technique, first the nose tip is automatically located on the range image, then the range data from a hexagonal region of interest around this landmark is decomposed using Barycentric wavelet kernels. The dimensionality of the extracted coefficients at each resolution level is reduced using principal component analysis (PCA). These new features are tested on 206 range images, and a high classification accuracy is achieved using a small number of features. The obtained accuracy is competitive to that of other techniques in literature.

Image quality assessment: from error visibility to structural similarity

Abstract: Objective methods for assessing perceptual image quality traditionally attempted to quantify the visibility of errors (differences) between a distorted image and a reference image using a variety of known properties of the human visual system. Under the assumption that human visual perception is highly adapted for extracting structural information from a scene, we introduce an alternative complementary framework for quality assessment based on the degradation of structural information. As a specific example of this concept, we develop a structural similarity index and demonstrate its promise through a set of intuitive examples, as well as comparison to both subjective ratings and state-of-the-art objective methods on a database of images compressed with JPEG and JPEG2000. A MATLAB implementation of the proposed algorithm is available online at http://www.cns.nyu.edu//spl sim/lcv/ssim/.

A wavelet tour of signal processing

Abstract: Introduction to a Transient World. Fourier Kingdom. Discrete Revolution. Time Meets Frequency. Frames. Wavelet Zoom. Wavelet Bases. Wavelet Packet and Local Cosine Bases. An Approximation Tour. Estimations are Approximations. Transform Coding. Appendix A: Mathematical Complements. Appendix B: Software Toolboxes.

Image-to-Image Translation with Conditional Adversarial Networks

Abstract: We investigate conditional adversarial networks as a general-purpose solution to image-to-image translation problems. These networks not only learn the mapping from input image to output image, but also learn a loss function to train this mapping. This makes it possible to apply the same generic approach to problems that traditionally would require very different loss formulations. We demonstrate that this approach is effective at synthesizing photos from label maps, reconstructing objects from edge maps, and colorizing images, among other tasks. Moreover, since the release of the pix2pix software associated with this paper, hundreds of twitter users have posted their own artistic experiments using our system. As a community, we no longer hand-engineer our mapping functions, and this work suggests we can achieve reasonable results without handengineering our loss functions either.

Image-to-Image Translation with Conditional Adversarial Networks

Abstract: We investigate conditional adversarial networks as a general-purpose solution to image-to-image translation problems. These networks not only learn the mapping from input image to output image, but also learn a loss function to train this mapping. This makes it possible to apply the same generic approach to problems that traditionally would require very different loss formulations. We demonstrate that this approach is effective at synthesizing photos from label maps, reconstructing objects from edge maps, and colorizing images, among other tasks. Indeed, since the release of the pix2pix software associated with this paper, a large number of internet users (many of them artists) have posted their own experiments with our system, further demonstrating its wide applicability and ease of adoption without the need for parameter tweaking. As a community, we no longer hand-engineer our mapping functions, and this work suggests we can achieve reasonable results without hand-engineering our loss functions either.

Phd by thesis

Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These