Dense light field coding: a survey

Light Field (LF) imaging is a promising solution for providing more immersive and closer to reality multimedia experiences to end-users with unprecedented creative freedom and flexibility for applications in different areas, such as virtual and augmented reality. Due to the recent technological advances in optics, sensor manufacturing and available transmission bandwidth, as well as the investment of many tech giants in this area, it is expected that soon many LF transmission systems will be available to both consumers and professionals. Recognizing this, novel standardization initiatives have recently emerged in both the Joint Photographic Experts Group (JPEG) and the Moving Picture Experts Group (MPEG), triggering the discussion on the deployment of LF coding solutions to efficiently handle the massive amount of data involved in such systems. Since then, the topic of LF content coding has become a booming research area, attracting the attention of many researchers worldwide. In this context, this paper provides a comprehensive survey of the most relevant LF coding solutions proposed in the literature, focusing on angularly dense LFs. Special attention is placed on a thorough description of the different LF coding methods and on the main concepts related to this relevant area. Moreover, comprehensive insights are presented into open research challenges and future research directions for LF coding.info:eu-repo/semantics/publishedVersio

Contributions in image and video coding

Orientador: Max Henrique Machado CostaTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: A comunidade de codificação de imagens e vídeo vem também trabalhando em inovações que vão além das tradicionais técnicas de codificação de imagens e vídeo. Este trabalho é um conjunto de contribuições a vários tópicos que têm recebido crescente interesse de pesquisadores na comunidade, nominalmente, codificação escalável, codificação de baixa complexidade para dispositivos móveis, codificação de vídeo de múltiplas vistas e codificação adaptativa em tempo real. A primeira contribuição estuda o desempenho de três transformadas 3-D rápidas por blocos em um codificador de vídeo de baixa complexidade. O codificador recebeu o nome de Fast Embedded Video Codec (FEVC). Novos métodos de implementação e ordens de varredura são propostos para as transformadas. Os coeficiente 3-D são codificados por planos de bits pelos codificadores de entropia, produzindo um fluxo de bits (bitstream) de saída totalmente embutida. Todas as implementações são feitas usando arquitetura com aritmética inteira de 16 bits. Somente adições e deslocamentos de bits são necessários, o que reduz a complexidade computacional. Mesmo com essas restrições, um bom desempenho em termos de taxa de bits versus distorção pôde ser obtido e os tempos de codificação são significativamente menores (em torno de 160 vezes) quando comparados ao padrão H.264/AVC. A segunda contribuição é a otimização de uma recente abordagem proposta para codificação de vídeo de múltiplas vistas em aplicações de video-conferência e outras aplicações do tipo "unicast" similares. O cenário alvo nessa abordagem é fornecer vídeo com percepção real em 3-D e ponto de vista livre a boas taxas de compressão. Para atingir tal objetivo, pesos são atribuídos a cada vista e mapeados em parâmetros de quantização. Neste trabalho, o mapeamento ad-hoc anteriormente proposto entre pesos e parâmetros de quantização é mostrado ser quase-ótimo para uma fonte Gaussiana e um mapeamento ótimo é derivado para fonte típicas de vídeo. A terceira contribuição explora várias estratégias para varredura adaptativa dos coeficientes da transformada no padrão JPEG XR. A ordem de varredura original, global e adaptativa do JPEG XR é comparada com os métodos de varredura localizados e híbridos propostos neste trabalho. Essas novas ordens não requerem mudanças nem nos outros estágios de codificação e decodificação, nem na definição da bitstream A quarta e última contribuição propõe uma transformada por blocos dependente do sinal. As transformadas hierárquicas usualmente exploram a informação residual entre os níveis no estágio da codificação de entropia, mas não no estágio da transformada. A transformada proposta neste trabalho é uma técnica de compactação de energia que também explora as similaridades estruturais entre os níveis de resolução. A idéia central da técnica é incluir na transformada hierárquica um número de funções de base adaptativas derivadas da resolução menor do sinal. Um codificador de imagens completo foi desenvolvido para medir o desempenho da nova transformada e os resultados obtidos são discutidos neste trabalhoAbstract: The image and video coding community has often been working on new advances that go beyond traditional image and video architectures. This work is a set of contributions to various topics that have received increasing attention from researchers in the community, namely, scalable coding, low-complexity coding for portable devices, multiview video coding and run-time adaptive coding. The first contribution studies the performance of three fast block-based 3-D transforms in a low complexity video codec. The codec has received the name Fast Embedded Video Codec (FEVC). New implementation methods and scanning orders are proposed for the transforms. The 3-D coefficients are encoded bit-plane by bit-plane by entropy coders, producing a fully embedded output bitstream. All implementation is performed using 16-bit integer arithmetic. Only additions and bit shifts are necessary, thus lowering computational complexity. Even with these constraints, reasonable rate versus distortion performance can be achieved and the encoding time is significantly smaller (around 160 times) when compared to the H.264/AVC standard. The second contribution is the optimization of a recent approach proposed for multiview video coding in videoconferencing applications or other similar unicast-like applications. The target scenario in this approach is providing realistic 3-D video with free viewpoint video at good compression rates. To achieve such an objective, weights are computed for each view and mapped into quantization parameters. In this work, the previously proposed ad-hoc mapping between weights and quantization parameters is shown to be quasi-optimum for a Gaussian source and an optimum mapping is derived for a typical video source. The third contribution exploits several strategies for adaptive scanning of transform coefficients in the JPEG XR standard. The original global adaptive scanning order applied in JPEG XR is compared with the localized and hybrid scanning methods proposed in this work. These new orders do not require changes in either the other coding and decoding stages or in the bitstream definition. The fourth and last contribution proposes an hierarchical signal dependent block-based transform. Hierarchical transforms usually exploit the residual cross-level information at the entropy coding step, but not at the transform step. The transform proposed in this work is an energy compaction technique that can also exploit these cross-resolution-level structural similarities. The core idea of the technique is to include in the hierarchical transform a number of adaptive basis functions derived from the lower resolution of the signal. A full image codec is developed in order to measure the performance of the new transform and the obtained results are discussed in this workDoutoradoTelecomunicações e TelemáticaDoutor em Engenharia Elétric

Light field image compression

Light field imaging based on a single-tier camera equipped with a micro-lens array has currently risen up as a practical and prospective approach for future visual applications and services. However, successfully deploying actual light field imaging applications and services will require identifying adequate coding solutions to efficiently handle the massive amount of data involved in these systems. In this context, this chapter presents some of the most recent light field image coding solutions that have been investigated. After a brief review of the current state of the art in image coding formats for light field photography, an experimental study of the rate-distortion performance for different coding formats and architectures is presented. Then, aiming at enabling faster deployment of light field applications and services in the consumer market, a scalable light field coding solution that provides backward compatibility with legacy display devices (e.g., 2D, 3D stereo, and 3D multiview) is also presented. Furthermore, a light field coding scheme based on a sparse set of microimages and the associated blockwise disparity is also presented. This coding scheme is scalable with three layers such that the rendering can be performed with the sparse micro-image set, the reconstructed light field image, and the decoded light field image.info:eu-repo/semantics/acceptedVersio

Multiview Video Coding for Virtual Reality

Virtual reality (VR) is one of the emerging technologies in recent years. It brings a sense of real world experience in simulated environments, hence, it is being used in many applications for example in live sporting events, music recordings and in many other interactive multimedia applications. VR makes use of multimedia content, and videos are a major part of it. VR videos are captured from multiple directions to cover the entire 360 field-of-view. It usually employs, multiple cameras of wide field-of-view such as fisheye lenses and the camera arrangement can also vary from linear to spherical set-ups. Videos in VR system are also subjected to constraints such as, variations in network bandwidth, heterogeneous mobile devices with limited decoding capacity, adaptivity for view switching in the display. The uncompressed videos from multiview cameras are redundant and impractical for storage and transmission. The existing video coding standards compresses the multiview videos effi ciently. However, VR systems place certain limitations on the video and camera arrangements, such as, it assumes rectilinear properties for video, translational motion model for prediction and the camera set-up to be linearly arranged. The aim of the thesis is to propose coding schemes which are compliant to the current video coding standards of H.264/AVC and its successor H.265/HEVC, the current state-of-the-art and multiview/scalable extensions. This thesis presents methods that compress the multiview videos which are captured from eight cameras that are arranged spherically, pointing radially outwards. The cameras produce circular fi sheye videos of 195 degree field-of-view. The final goal is to present methods, which optimize the bitrate in both storage and transmission of videos for the VR system. The presented methods can be categorized into two groups: optimizing storage bitrate and optimizing streaming bitrate of multiview videos. In the storage bitrate category, six methods were experimented. The presented methods competed against simulcast coding of individual views. The coding schemes were experimented with two data sets of 8 views each. The method of scalable coding with inter-layer prediction in all frames outperformed simulcast coding with approximately 7.9%. In the case of optimizing streaming birates, five methods were experimented. The method of scalable plus multiview skip-coding outperformed the simulcast method of coding by 36% on average. Future work will focus on pre-processing the fi sheye videos to rectilinear videos, in-order to fit them to the current translational model of the video coding standards. Moreover, the methods will be tested in comprehensive applications and system requirements

Livrable D3.4 of the PERSEE project : 2D coding tools final report

Livrable D3.4 du projet ANR PERSEECe rapport a été réalisé dans le cadre du projet ANR PERSEE (n° ANR-09-BLAN-0170). Exactement il correspond au livrable D3.4 du projet. Son titre : 2D coding tools final repor

Dünaamiline kiiruse jaotamine interaktiivses mitmevaatelises video vaatevahetuse ennustamineses

In Interactive Multi-View Video (IMVV), the video has been captured by numbers of cameras positioned in array and transmitted those camera views to users. The user can interact with the transmitted video content by choosing viewpoints (views from different cameras in the array) with the expectation of minimum transmission delay while changing among various views. View switching delay is one of the primary concern that is dealt in this thesis work, where the contribution is to minimize the transmission delay of new view switch frame through a novel process of selection of the predicted view and compression considering the transmission efficiency. Mainly considered a realtime IMVV streaming, and the view switch is mapped as discrete Markov chain, where the transition probability is derived using Zipf distribution, which provides information regarding view switch prediction. To eliminate Round-Trip Time (RTT) transmission delay, Quantization Parameters (QP) are adaptively allocated to the remaining redundant transmitted frames to maintain view switching time minimum, trading off with the quality of the video till RTT time-span. The experimental results of the proposed method show superior performance on PSNR and view switching delay for better viewing quality over the existing methods