1,720,963 research outputs found
A Study of Digital Video Compression Technology
No full textIn this thesis, we studied the three methods of digital video encoder with either discrete cosine transform (DCT) or discrete wavelet transform (DWT), 2D method (DCT & DWT), 3D method (DCT & DWT) and hybrid method. The aim of the video compression is to achieve higher compression ratio with little elimination of visual quality and lower computational complexity. By exploiting the redundancies in the video sequence and the human visual response we could reduce storage of information in the video sequence and then apply the information theory (Huffman coding) which is a lossless coding method using by text compression tool such as Winzip or Winrar.
2D model with 2D-DCT is adopted by the JPEG for image compression. In application of video sequence, it is called motion JPEG. For preventing the block effects of the 2D-DCT method, DWT replaces DCT. The DWT is completed by two orthogonal or biorthogonal filter banks and then the DWT coefficients are transmitted by the SPIHT Algorithm.
For exploiting the temporal redundancies, the 3D model of digital video compression is the direct method. By applying the 3D transform either with the 3D-DCT or 3D-DWT, we can transform the temporal redundancies to the frequency domain and then quantize the coefficients according to the human visual response. In the previous study, the energy of 3D-DCT coefficients is highly compacted in the hyperbolic plane, thus our mission is to quantize the coefficients outside the plane to zero for achieving higher compression ratio without lower visual quality. The quantization value could be obtained form the proposed equation. The zig-zag scan order of the 2D-DCT is not suitable for the 3D-DCT, because it can’t achieve higher compression by using variable length coding. The optimal scan order should be implemented according to the probability of non-zero coefficients. Hybrid method is also a method of eliminating the temporal redundancies of video sequence by motion estimation. It reduces the temporal redundancies by subtracting the predicted frame from the current frame, thus it is more suitable for the high motion video sequence but 3D method isn’t.CHAPTER 1 MOTIVATION 6
CHAPTER 2 VIDEO BASICS 8
2.1 HUMAN PERCEPTION OF COLOR 8
2.2 FREQUENCY RESPONSE OF THE HVS 9
2.2.1 Spatial Frequency 9
2.2.2 Angular Frequency 9
2.2.3 Temporal Frequency 10
2.2.4 Temporal Frequency Response 11
2.2.5 Spatial Frequency Response 12
2.2.6 Spatiotemporal Frequency Response 12
2.3 DIGITAL VIDEO FORMAT AND CHROMINANCE SUBSAMPLING 13
2.4 VIDEO QUALITY MEASUREMENT 15
CHAPTER 3 2D METHOD OF DIGITAL VIDEO COMPRESSION –
2D-DCT & 2DDWT 17
3.1 INTRODUCTION TO 2D-DCT DIGITAL VIDEO COMPRESSION 17
3.2 DISCRETE COSINE TRANSFORM 18
3.3 QUANTIZATION 21
3.4 ZIG-ZAG SCAN 23
3.5 RUN LENGTH CODING & VARIABLE LENGTH CODING 24
3.6 INTRODUCTION TO 2D-DWT DIGITAL VIDEO COMPRESSION 27
3.7 2 DIMENSIONAL DISCRETE WAVELET TRANSFORM 27
3.8 SET PARTITIONING IN HIERARCHICAL TREES 31
3.9 EXPERIMENTAL RESULTS 35
CHAPTER 4 3D METHOD OF DIGITAL VIDEO COMPRESSION –
3D DCT & 3D DWT 41
4.1 INTRODUCTION TO 3D-DCT DIGITAL VIDEO COMPRESSION 41
4.2 3 DIMENSIONAL DISCRETE COSINE TRANSFORM 42
4.3 OPTIMAL QUANTIZATION TABLE 43
4.4 SCAN ORDER OF 3D-DCT QUANTIZED COEFFICIENTS 46
4.5 INTRODUCTION TO 3D-DWT DIGITAL VIDEO COMPRESSION 48
4.6 3 DIMENSIONAL DISCRETE WAVELET TRANSFORM 49
4.7 QUANTIZATION 50
4.8 HUFFMAN CODING 52
4.9 EXPERIMENTAL RESULTS 53
CHAPTER 5 HYBRID METHOD OF DIGITAL VIDEO COMPRESSION -
MPEG2 STANDARD 60
5.1 INTRODUCTION TO MPEG2 60
5.2 MOTION ESTIMATION – BLOCK MATCHING METHODS 61
5.3 SEARCH ALGORITHM 62
5.3.1 Full Search Algorithm 62
5.3.2 One At a Time Search Algorithm 63
5.3.3 Two-Dimensional Logarithmic Search Algorithm 63
5.3.4 3-Steps Search Algorithm 64
5.3.5 Cross-Search Algorithm 65
5.3.6 Diamond Search 65
5.3.7 Half pixel Refinement 66
5.4 MOTION PREDICTION & COMPENSATION 67
5.5 GROUP OF PICTURE & TRANSMISSION ORDER OF THE VIDEO FRAMES 68
5.6 MPEG2 VIDEO STRUCTURE AND VIDEO STREAM SYNTAX 71
5.6.1 Video Sequence Header 72
5.6.2 Group of Picture Header 73
5.6.3 Picture Header 73
5.6.4 Slice Header 74
5.6.5 Macro Block Header 75
5.6.6 Block Header 76
5.8 EXPERIMENTAL RESULTS 77
CHAPTER 6 SUMMARY AND FUTURE WORKS 81
REFERENCES 8
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Comparative genomics approaches accurately predict deleterious variants in plants
No full textThe genes and mutations information in this table were downloaded from UniProt/Swiss-Prot database (http://www.uniprot.org/) and http://www.arabidopsis.org. Single nucleotide polymorphisms (SNPs) without any known phenotype were obtained from a set of 80 sequenced A. thaliana strains (Ensembl, version 81, “Cao_SNPs”, Cao, et al., 2011). We used six approaches: LRT, PolyPhen2, SIFT 4G, Provean, MAPP, Gerp++ to predict deleterious varaints. The details can be avaible in Kono, et al., 2017 (http://www.biorxiv.org/content/early/2017/02/27/112318)Recent advances in genome resequencing have led to increased interest in prediction of the functional consequences of genetic variants. Variants at phylogenetically conserved sites are of particular interest, because they are more likely than variants at phylogenetically variable sites to have deleterious effects on fitness and contribute to phenotypic variation. Numerous comparative genomic approaches have been developed to predict deleterious variants, but they are nearly always judged based on their ability to identify known disease-causing mutations in humans. Determining the accuracy of deleterious variant predictions in nonhuman species is important to understanding evolution, domestication, and potentially to improving crop quality and yield. To examine our ability to predict deleterious variants in plants we generated a curated database of 2,910 Arabidopsis thaliana mutants with known phenotypes. We evaluated seven approaches and found that while all performed well, the single best-performing approach was a likelihood ratio test applied to homologs identified in 42 plant genomes. Although the approaches did not always agree, we found only slight differences in performance when comparing mutations with gross versus biochemical phenotypes, duplicated versus single copy genes, and when using a single approach versus ensemble predictions. We conclude that deleterious mutations can be reliably predicted in A. thaliana and likely other plant species, but that the relative performance of various approaches can depend on the organism to which they are applied.US National Science Foundation Plant Genome Program grant (DBI-1339393 to JCF and PLM)US Department of Agriculture Biotechnology Risk Assessment Research Grants Program (BRAG) (USDA BRAG 2015-06504 to PLM)University of Minnesota Doctoral Dissertation Fellowship (to TJYK)Kono, Thomas John Y; Lei, Li; Shih, Ching-Hua; Hoffman, Paul J; Morrell, Peter L; Fay, Justin C. (2018). Comparative genomics approaches accurately predict deleterious variants in plants. Retrieved from the University Digital Conservancy, https://doi.org/10.13020/D6N69S
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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