With the popularity of diverse mobile devices, integrating existing systems or softwares of personal computers with different devices is an active research. Transcoding plays an important role in this issue. In the thesis, we develop a transcoding system that converts frames based on the device profile and user¡¦s preferences to present retrieved results of existing systems into image format. The proposed system allows a variety of mobile devices to efficiently display the retrieved results from existing systems. To overcome the weakness of the lack for interaction of existing transcoding systems, our proposed system supports interaction between clients and server.

The proposed transcoding system consists of the spatial-resolution reduction and the temporal-resolution reduction method via visual attention model analysis. In the spatial domain, the visual attention model can be used to obtain the visual attention region. Then, the bitrate can be reduced since we can extract attention region of the original frame. The attention region conveys the same concept as that of the original frame. In the temporal domain, a frame skipping algorithm is proposed for reducing the temporal resolution to fit the channel target bitrate. The visual attention model is employed to measure the frame complexity in order to determine whether the frames should be skipped or not. Then, we can preserve the significant frames to avoid jerky effect. After combining with the motion vector composition algorithm, we can speedup the transcoding process with slight quality degradation.

With the rapid growth of multimedia information, video coding standards have become crucial when transmitting large amount of video data. Motion estimation promises to be the key to high performance in video coding by removing the temporal redundancy of video data for storage and transmission. Video transcoding also becomes a significant scheme applied in different bandwidth transform. Due to their fundamentality, research works on motion estimation and video transcoding have been conducted extensively. In this thesis, an overview of video compression technique is presented with emphasis on motion estimation. Then, a survey of most representative motion estimation search algorithms and the proposed motion estimation algorithms are introduced. The evaluation and analysis of these algorithms based on a number of experiments on several famous test video sequences is presented. In addition, an efficient video transcoding via visual attention model with Lagrange optimization to minimum rate-distortion cost is proposed. Finally, an investigation of the future trend of video coding is discussed. Through the proposed algorithms of motion estimation, the computational complexity can be significantly reduced despite the fact that the objective quality of motion compensated images is slightly degraded. Moreover, through the proposed video transcoding method, the bit rate can be reduced to fit the requirement of bandwidth.

As wireless and wired network connectivity is rapidly expanding and the number of network users is steadily increasing, it has become more and more important to support universal access of multimedia content over the whole network. A big challenge, however, is the great diversity of network devices from full screen computers to small smart phones. This leads to research on transcoding, which involves in efficiently reformatting compressed data from its original high resolution to a desired spatial resolution supported by the displaying device. Particularly, there is a great momentum in the multimedia industry for H.264-based transcoding as H.264 has been widely employed as a mandatory player feature in applications ranging from television broadcast to video for mobile devices. While H.264 contains many new features for effective video coding with excellent rate distortion (RD) performance, a major issue for transcoding H.264 compressed video from one spatial resolution to another is the computational complexity. Specifically, it is the motion compensated prediction (MCP) part. MCP is the main contributor to the excellent RD performance of H.264 video compression, yet it is very time consuming. In general, a brute-force search is used to find the best motion vectors for MCP. In the scenario of transcoding, however, an immediate idea for improving the MCP efficiency for the re-encoding procedure is to utilize the motion vectors in the original compressed stream. Intuitively, motion in the high resolution scene is highly related to that in the down-scaled scene. In this thesis, we study homogeneous video transcoding from H.264 to H.264. Specifically, for the video transcoding with arbitrary spatial resolution conversion, we propose a motion vector estimation algorithm based on a multiple linear regression model, which systematically utilizes the motion information in the original scenes. We also propose a practical solution for efficiently determining a reference frame to take the advantage of the new feature of multiple references in H.264. The performance of the algorithm was assessed in an H.264 transcoder. Experimental results show that, as compared with a benchmark solution, the proposed method significantly reduces the transcoding complexity without degrading much the video quality.

As wireless and wired network connectivity is rapidly expanding and the number of network users is steadily increasing, it has become more and more important to support universal access of multimedia content over the whole network. A big challenge, however, is the great diversity of network devices from full screen computers to small smart phones. This leads to research on transcoding, which involves in efficiently reformatting compressed data from its original high resolution to a desired spatial resolution supported by the displaying device. Particularly, there is a great momentum in the multimedia industry for H.264-based transcoding as H.264 has been widely employed as a mandatory player feature in applications ranging from television broadcast to video for mobile devices. While H.264 contains many new features for effective video coding with excellent rate distortion (RD) performance, a major issue for transcoding H.264 compressed video from one spatial resolution to another is the computational complexity. Specifically, it is the motion compensated prediction (MCP) part. MCP is the main contributor to the excellent RD performance of H.264 video compression, yet it is very time consuming. In general, a brute-force search is used to find the best motion vectors for MCP. In the scenario of transcoding, however, an immediate idea for improving the MCP efficiency for the re-encoding procedure is to utilize the motion vectors in the original compressed stream. Intuitively, motion in the high resolution scene is highly related to that in the down-scaled scene. In this thesis, we study homogeneous video transcoding from H.264 to H.264. Specifically, for the video transcoding with arbitrary spatial resolution conversion, we propose a motion vector estimation algorithm based on a multiple linear regression model, which systematically utilizes the motion information in the original scenes. We also propose a practical solution for efficiently determining a reference frame to take the advantage of the new feature of multiple references in H.264. The performance of the algorithm was assessed in an H.264 transcoder. Experimental results show that, as compared with a benchmark solution, the proposed method significantly reduces the transcoding complexity without degrading much the video quality.

This report describes a master thesis performed at Degoo Backup AB in Stockholm, Sweden in the spring of 2012. The purpose was to design a compression suite in Java which aims to improve the compression ratio for file types assumed to be commonly used in a backup software. A tradeoff between compression ratio and compression speed has been made in order to meet the requirement that the compression suite has to be able to compress the data fast enough. A study of the best performing existing compression algorithms has been made in order to be able to choose the best suitable compression algorithm for every possible scenario and file type specific compression algorithms have been developed in order to further improve the compression ratio for files considered needing improved compression. The resulting compression performance is presented for file types assumed to be common in a backup software and the overall performance is good. The final conclusion is that the compression suite fulfills all requirements set of this thesis. / Denna rapport beskriver ett examensarbete genomfört på Degoo Backup AB i Stockholm under våren 2012. Syftet var att designa en kompressionssvit i Java vilket siktar på att förbättra kompressionsgraden för filtyper som anses vara vanliga att användas i en säkerhetskopieringsprogramvara. En avvägning mellan kompressionsgrad och kompressionshastighet har gjort för att uppfylla kravet att kompressionssviten ska kunna komprimera data tillräckligt snabbt. En studie över de bäst presterande existerande kompressionsalgoritmerna har gjorts för att möjliggöra ett val av den bäst anpassade kompressionsalgoritmen för varje tänkbar situation. Dessutom har filtypsspecifika komprimeringsalgoritmer utvecklats för att ytterligare förbättra kompressionsgraden för filer som anses var av behov av förbättrad komprimering. Den resulterande kompressionsprestandan finns presenterad för filtyper som antas vara vanliga i en säkerhetskopieringsprogramvara och på det hela taget är prestandan bra. Slutsatsen är att kompressionssviten uppfyller alla krav som var uppsatta för detta examensarbete.

As consumer demand for higher quality video at lower bit-rate increases, so does the need for more sophisticated methods of compressing videos into manageable file sizes. This research attempts to address these concerns while still maintaining reasonable encoding times. Modern segmentation and grouping analysis are used with code vectorization techniques and other optimization paradigms to improve quality and performance within the next generation coding standard, High Efficiency Video Coding. This research saw on average a 50% decrease in run-time by the encoder with marginal decreases in perceived quality.

Scalable video coding (SVC) supports full scalability by extracting a partial bitstream to adapt to transmission and display requirements in multimedia applications. Most conventional video content is stored in non-scalable format, e.g., H.264/AVC, necessitating the development of an efficient video transcoding from a conventional format to a scalable one. This work describes a fast video transcoding architecture that overcomes the complexity of different coding structures between H.264/AVC and SVC. The proposed algorithm simplifies the mode decision process in SVC owing to its heavy computations. The current mode in SVC is selected by the highest conditional probability of SVC¡¦s mode given the H.264/AVC¡¦s mode. Exactly when an error prediction occurs is then detected using Bayesian theorem, followed by its refinement using the Markov model. Experimental results indicate that the proposed algorithm saves on average 75.28% of coding time with 0.13 dB PSNR loss over that when using a cascaded pixel domain transcoder.

Mobile wireless communication technology is a fast developing field and every day new mobile communication techniques and means are becoming available. In this thesis multi-view video (MVV) is also refers to as 3D video. Thus, the 3D video signals through wireless communication are shaping telecommunication industry and academia. However, wireless channels are prone to high level of bit and burst errors that largely deteriorate the quality of service (QoS). Noise along the wireless transmission path can introduce distortion or make a compressed bitstream lose vital information. The error caused by noise progressively spread to subsequent frames and among multiple views due to prediction. This error may compel the receiver to pause momentarily and wait for the subsequent INTRA picture to continue decoding. The pausing of video stream affects the user's Quality of Experience (QoE). Thus, an error resilience strategy is needed to protect the compressed bitstream against transmission errors. This thesis focuses on error resilience Adaptive Intra Refresh (AIR) technique. The AIR method is developed to make the compressed 3D video more robust to channel errors. The process involves periodic injection of Intra-coded macroblocks in a cyclic pattern using H.264/AVC standard. The algorithm takes into account individual features in each macroblock and the feedback information sent by the decoder about the channel condition in order to generate an MVV-AIR map. MVV-AIR map generation regulates the order of packets arrival and identifies the motion activities in each macroblock. Based on the level of motion activity contained in each macroblock, the MVV-AIR map classifies frames as high or low motion macroblocks. A proxy MVV-AIR transcoder is used to validate the efficiency of the generated MVV-AIR map. The MVV-AIR transcoding algorithm uses spatial and views downscaling scheme to convert from MVV to single view. Various experimental results indicate that the proposed error resilient MVV-AIR transcoder technique effectively improves the quality of reconstructed 3D video in wireless networks. A comparison of MVV-AIR transcoder algorithm with some traditional error resilience techniques demonstrates that MVV-AIR algorithm performs better in an error prone channel. Results of simulation revealed significant improvements in both objective and subjective qualities. No additional computational complexity emanates from the scheme while the QoS and QoE requirements are still fully met.

Numa perspectiva transdisciplinar, entre os estudos de Terminologia Aplicada, Semiótica e Etnoliteratura, desenvolvemos a presente Tese, cujo principal objetivo é demonstrar a importância do processo de transcodificação de textos técnicos e científicos (A) em textos etnoliterários (B), especificamente, seus efeitos no desenvolvimento da habilidade de compreensão de A, conduzindo à cognição por meio da reflexão crítica. O corpus da pesquisa compreende excertos do livro Curso de Linguística Geral, de Ferdinand de Saussure, e seu correspondente etnoliterário A vida e as idéias geniais e dicotômicas do pai da ciência linguística, de José Lira. Compreende, ainda, a Nova Gramática do Português Contemporâneo de Celso Cunha e Lindley Cintra, e seu correspondente etnoliterário Lições de Gramática em versos de Cordel, de Junduhi Dantas. Os modelos teóricos, nos quais se calcaram as análises e sistematizações, são os que privilegiam o percurso de transmissão da metalinguagem técnica e científica; os que enfatizam os processos de cientificidade e popularização do conhecimento; a natureza dos texto A e B como linguagem conotativa e metassemiótica; as delimitações conceituais do texto transcodificado e do texto transcodificante; as relações de intertextualidade e de equivalência que se estabelecem entre ambos. O trabalho destacou os processos de banalização de linguagens de especialidade como importante mecanismo de circulação e de difusão do conhecimento. Caracterizou ainda, o texto transcodificado como meta-metassemiótico e, por isso, pluriconceptual, plurivalorativo, plurissignificativo e metareferencial, já que não cria, mas retoma conceitos, sem tirar a especificidade de tratamento: uma coisa é o fato científico tratado no Discurso Científico; outra coisa é esse mesmo fato tratado no Discurso Poético. Outra constatação importante é que o grau de equivalência entre A e B são inversamente proporcionais: quanto menor a densidade de equivalência, tanto maior será a densidade de reflexão que se exige do estudante. O texto A e o texto B são mono e homotemáticos, na medida em que abordam o mesmo tema, porém, são plurifigurativos, pois actantes e relações actanciais são diferentes de um para outro. Concluímos, ainda, que o texto A determina a isotopia do texto B, que mesmo sendo um texto poético, preserva a sua função primária que é a de ser um texto interpretante. Pelos motivos expostos, apresentamos como conclusão geral, que o processo de transcodificação, no enfoque que demos, é um dos principais meios de desenvolvimento de mecanismo muito importante na assimilação de teorias científicas, na medida em que conduz o estudante à cognição por meio da reflexão crítica. Desenvolver o refletir, tornou-se mais importante que o conhecer pois a reflexão conduz ao questionamento, à indagação, fatores fundamentais na formação do conceptus de cognição. Essas questões constituíram o ponto de partida e o ponto de chegada desta pesquisa. / In a transdisciplinary perspective, among the studies of Applied Terminology Semiotics and Etnoliterature, we developed the present work, whose main objective is to demonstrate the importance of the transcoding process of scientific and technical papers (A) into etnoliterary texts (B), specifically, its effects in the development of comprehension skills of A, leading to cognition by means of a critical reflection. The corpus includes excerpts from the book Course in General Linguistics written by Ferdinand de Saussure, and its related ethnoliterary The life and the brilliantl and dichotomous ideas of the father of language science by José Lira. The corpus also comprises the New Grammar of Contemporary Portuguese by Celso Cunha and Lindley Cintra, and its related etnoliterary \"Grammar Lessons in Cordel verses by Junduhi Dantas. The theoretical models, in which the analysis and systematization are based are those that favor the route of transmission of scientific and technical metalanguage; the ones that emphasize the processes of scientificity and popularization of knowledge the nature of the texts A and B as connotative language metasemiotics, the conceptual boundaries of the text and the transcoded and transcoding text; relations of intertextuality and equivalence established between both types of texts. The work has highlighted the processes of trivialization of specialized languages as an important mechanism of movement and diffusion of knowledge. The transcoded text was characterized as metametasemiotic and therefore multiconceptual, multivalued, multi-significant and metareferencial, once it doesnt create, but recovers concepts without taking the specificity of treatment: one thing is the scientific fact discussed in Scientific Discourse; another thing is that same fact treated in Poetic Discourse. Another important finding is that the degree of equivalence between A and B is inversely proportional: the smaller the density of equivalence, the greater the density of reflection that is required of the student. Text A and text B are mono and homothematic while they discuss the same topic, but are multifigurative because actants, and actant relationships are different from one to another. Its also concluded that text A determines the isotopy of text B, that even being a poetic text, preserves its primary function which is to be a text interpreter. For these reasons, it is presented as a general conclusion, that the transcoding process, which has been our focus is one of the chief means to develop this very important mechanism in the scientific theory construction, as it leads the student to cognition by critical reflection. The reflection development has become more important than the knowledge because reflection leads to questioning at the inquiry, which is crucial in the cognitive concept building. These issues are the starting point and the final point for this research.