Source coding for transmission of reconstructed dynamic geometry: a rate-distortion-complexity analysis of different approaches

Live 3D reconstruction of a human as a 3D mesh with commodity electronics is becoming a reality. Immersive applications (i.e. cloud gaming, tele-presence) benefit from effective transmission of such content over a bandwidth limited link. In this paper we outline different approaches for compressing live reconstructed mesh geometry based on distributing mesh reconstruction functions between sender and receiver. We evaluate rate-performance-complexity of different configurations. First, we investigate 3D mesh compression methods (i.e. dynamic/static) from MPEG-4. Second, we evaluate the option of using octree based point cloud compression and receiver side surface reconstruction

An Efficient Coding Method for Teleconferencing Video and Confocal Microscopic Image Sequences

In this paper we propose a three-dimensional vector quantization based video coding scheme. The algorithm uses a 3D vector quantization pyramidal code book based model with adaptive code book pyramidal codebook for compression. The pyramidal code book based model helps in getting high compression in case of modest motion. The adaptive vector quantization algorithm is used to train the code book for optimal performance with time. Some of the distinguished features of our algorithm are its excellent performance due to its adaptive behavior to the video composition and excellent compression due to codebook approach. We also propose an efficient codebook based post processing technique which enables the vector quantizer to possess higher correlation preservation property. Based on the special pattern of the codebook imposed by post-processing technique, a window based fast search (WBFS) algorithm is proposed. The WBFS algorithm not only accelerates the vector quantization processing, but also results in better rate-distortion performance. The proposed approach can be used for both teleconferencing videos and to compress images obtained from confocal laser scanning microscopy (CLSM). The results show that the proposed method gave higher subjective and objective image quality of reconstructed images at a better compression ratio and presented more acceptable results when applying image processing filters such as edge detection on reconstructed images. The experimental results demonstrate that the proposed method outperforms the teleconferencing compression standards H.261 and LBG based vector quantization technique

Coding of video with a single information plane

Mestrado em Engenharia Electrónica e TelecomunicaçõesAs actuais normas para codificação de vídeo, tais como os MPEG2/4 ou H.263/4, foram desenvolvidas para codificação de vídeo com cor. A informação de cor é representada usando um espaço apropriado, como, por exemplo, o YCbCr. Estes espaços de cor são constituídos por três planos: um para a dominância (no exemplo dado, o Y) e dois para a informação de crominância (neste caso, o Cb e o Cr). Contudo, há aplicações onde a informação a codificar é composta apenas por um plano de informação que pode, por exemplo, representar níveis de cinzento em imagem médica, ou índices para tabelas de cores. A motivação desta tese prende-se com dois factos: a produção de imagens médicas em formato digital estar a crescer, impondo técnicas eficazes para o tratamento e a compressão de dados e, embora os modelos de cor indexada sejam há muito utilizados para representar imagens, não têm sido convenientemente explorados em vídeo. Com esta dissertação pretende-se investigar novas estratégias de compressão sem perdas que explorem a redundância entre imagens consecutivas que caracterizam estas modalidades de imagem. Portanto, ao longo do trabalho implementou-se dois codificadores de vídeo para um só plano de informação, baseados num modelo híbrido. Um deles utiliza codificação de Golomb e o outro codificação aritmética, estudando-se assim a eficácia de cada um, quer para a escala de cinzentos, quer para vídeos com tabela de cores indexadas. Adicionalmente, para vídeos de cor indexada, implementou-se um algoritmo de reordenação da tabela de cores, o que torna a codificação mais eficaz. ABSTRACT: The current standards for video encoding, such as MPEG2/4 or H.263/4, have been developed for encoding video with color. The color information is represented using an appropriate space, such as YCbCr. These color spaces are made of three planes: one for luminance (in the given example, the Y) and two for the chrominance information (in this case, the Cb and Cr). However, there are applications where the information lies in a single information plane that may, for example, represent shades of gray (medical imaging) or indexes to color tables (color indexed video). The motivation of this thesis is related with two points: the production of medical images in digital format has been growing, imposing efficient techniques for the treatment and compression of data and, although color indexed models have been used for a long time to represent images, it has not been adequately explored in video. With this thesis, we intended to investigate new strategies for lossless compression which exploits the redundancy between consecutive images that characterize these types of images. Therefore, during this work, it has been implemented two video encoders with one information plane, based on a hybrid model. One of them uses Golomb codes and the other arithmetic coding. It has been studied the efficiency of each one, both using gray scale and color indexed videos. In addition, for color indexed videos, it has been implemented a palette reordering algorithm, making the encoding more efficient

Optimum Implementation of Compound Compression of a Computer Screen for Real-Time Transmission in Low Network Bandwidth Environments

Remote working is becoming increasingly more prevalent in recent times. A large part of remote working involves sharing computer screens between servers and clients. The image content that is presented when sharing computer screens consists of both natural camera captured image data as well as computer generated graphics and text. The attributes of natural camera captured image data differ greatly to the attributes of computer generated image data. An image containing a mixture of both natural camera captured image and computer generated image data is known as a compound image. The research presented in this thesis focuses on the challenge of constructing a compound compression strategy to apply the ‘best fit’ compression algorithm for the mixed content found in a compound image. The research also involves analysis and classification of the types of data a given compound image may contain. While researching optimal types of compression, consideration is given to the computational overhead of a given algorithm because the research is being developed for real time systems such as cloud computing services, where latency has a detrimental impact on end user experience. The previous and current state of the art videos codec’s have been researched along many of the most current publishing’s from academia, to design and implement a novel approach to a low complexity compound compression algorithm that will be suitable for real time transmission. The compound compression algorithm will utilise a mixture of lossless and lossy compression algorithms with parameters that can be used to control the performance of the algorithm. An objective image quality assessment is needed to determine whether the proposed algorithm can produce an acceptable quality image after processing. Both traditional metrics such as Peak Signal to Noise Ratio will be used along with a new more modern approach specifically designed for compound images which is known as Structural Similarity Index will be used to define the quality of the decompressed Image. In finishing, the compression strategy will be tested on a set of generated compound images. Using open source software, the same images will be compressed with the previous and current state of the art video codec’s to compare the three main metrics, compression ratio, computational complexity and objective image quality

Compression of dynamic polygonal meshes with constant and variable connectivity

This work was supported by the projects 20-02154S and 17-07690S of the Czech Science Foundation and SGS-2019-016 of the Czech Ministry of Education.Polygonal mesh sequences with variable connectivity are incredibly versatile dynamic surface representations as they allow a surface to change topology or details to suddenly appear or disappear. This, however, comes at the cost of large storage size. Current compression methods inefficiently exploit the temporal coherence of general data because the correspondences between two subsequent frames might not be bijective. We study the current state of the art including the special class of mesh sequences for which connectivity is static. We also focus on the state of the art of a related field of dynamic point cloud sequences. Further, we point out parts of the compression pipeline with the possibility of improvement. We present the progress we have already made in designing a temporal model capturing the temporal coherence of the sequence, and point out to directions for a future research

Técnicas de compresión de imágenes hiperespectrales sobre hardware reconfigurable

Tesis de la Universidad Complutense de Madrid, Facultad de Informática, leída el 18-12-2020Sensors are nowadays in all aspects of human life. When possible, sensors are used remotely. This is less intrusive, avoids interferces in the measuring process, and more convenient for the scientist. One of the most recurrent concerns in the last decades has been sustainability of the planet, and how the changes it is facing can be monitored. Remote sensing of the earth has seen an explosion in activity, with satellites now being launched on a weekly basis to perform remote analysis of the earth, and planes surveying vast areas for closer analysis...Los sensores aparecen hoy en día en todos los aspectos de nuestra vida. Cuando es posible, de manera remota. Esto es menos intrusivo, evita interferencias en el proceso de medida, y además facilita el trabajo científico. Una de las preocupaciones recurrentes en las últimas décadas ha sido la sotenibilidad del planeta, y cómo menitoirzar los cambios a los que se enfrenta. Los estudios remotos de la tierra han visto un gran crecimiento, con satélites lanzados semanalmente para analizar la superficie, y aviones sobrevolando grades áreas para análisis más precisos...Fac. de InformáticaTRUEunpu