Les travaux effectués durant cette thèse de doctorat ont pour but d’augmenter l’efficacité de codage dans 3D-HEVC. Nous proposons des approches conventionnelles orientées vers la normalisation vidéo, ainsi que des approches en rupture basées sur le flot optique. En approches conventionnelles, nous proposons une méthode qui prédit les modes Intra de profondeur avec ceux de texture. L’héritage est conditionné par un critère qui mesure le degré de similitude entre les deux modes. Ensuite, nous proposons deux méthodes pour améliorer la prédiction inter-vue du mouvement dans 3D-HEVC. La première ajoute un vecteur de disparité comme candidat inter-vue dans la liste des candidats du Merge, et la seconde modifie le processus de dérivation de ce vecteur. Finalement, un outil de codage intercomposantes est proposé, où le lien entre les arbres quaternaires de texture et de profondeur est exploité pour réduire le temps d’encodage et le débit, à travers un codage conjoint des deux arbres. Dans la catégorie des approches en rupture, nous proposons deux méthodes basées sur l’estimation de champs denses de vecteurs de mouvement en utilisant le flot optique. La première calcule un champ au niveau d’une vue de base reconstruite, puis l’extrapole au niveau d’une vue dépendante, où il est hérité par les unités de prédiction en tant que candidat dense du Merge. La deuxième méthode améliore la synthèse de vues : quatre champs sont calculés au niveau de deux vues de référence en utilisant deux références temporelles. Ils sont ensuite extrapolés au niveau d’une vue synthétisée et corrigés en utilisant une contrainte épipolaire. Les quatre prédictions correspondantes sont ensuite combinées. / This PhD. thesis deals with improving the coding efficiency in 3D-HEVC. We propose both constrained approaches aimed towards standardization, and also more innovative approaches based on optical flow. In the constrained approaches category, we first propose a method that predicts the depth Intra modes using the ones of the texture. The inheritance is driven by a criterion measuring how much the two are expected to match. Second, we propose two simple ways to improve inter-view motion prediction in 3D-HEVC. The first adds an inter-view disparity vector candidate in the Merge list and the second modifies the derivation process of this disparity vector. Third, an inter-component tool is proposed where the link between the texture and depth quadtree structures is exploited to save both runtime and bits through a joint coding of the quadtrees. In the more innovative approaches category, we propose two methods that are based on a dense motion vector field estimation using optical flow. The first computes such a field on a reconstructed base view. It is then warped at the level of a dependent view where it is inserted as a dense candidate in the Merge list of prediction units in that view. The second method improves the view synthesis process: four fields are computed at the level of the left and right reference views using a past and a future temporal reference. These are then warped at the level of the synthesized view and corrected using an epipolar constraint. The four corresponding predictions are then blended together. Both methods bring significant coding gains which confirm the potential of such innovative solutions.

Submitted by Aline Batista (alinehb.ufpel@gmail.com) on 2017-05-05T22:17:01Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) DissertacaoRuhan.pdf: 10210248 bytes, checksum: 75e231362cecb5676bd783b82978d99d (MD5) / Approved for entry into archive by Aline Batista (alinehb.ufpel@gmail.com) on 2017-05-05T22:17:49Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) DissertacaoRuhan.pdf: 10210248 bytes, checksum: 75e231362cecb5676bd783b82978d99d (MD5) / Made available in DSpace on 2017-05-05T22:18:00Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) DissertacaoRuhan.pdf: 10210248 bytes, checksum: 75e231362cecb5676bd783b82978d99d (MD5) Previous issue date: 2016-02-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Vídeos 3D provêem uma experiência visual elevada aos espectadores devido à percepção de profundidade das imagens. Apesar disto, o tamanho destes vídeos tende a crescer linearmente conforme o número de vistas codificadas, considerando formatos de vídeos convencionais. Neste cenário surge o formato Multiview plus Depth (MVD), o qual associa informações de distância entre os objetos da cena e a câmera (mapas de profundidade), permitindo um processo eficiente de síntese de vistas intermediárias, reduzindo o número de vistas a serem transmitidas. Ao contrário de padrões multivistas anteriores, o 3D-HEVC é capaz de processar mapas de profundidade, criando novas ferramentas para manipula-los e codifica-los. Embora este fato proporcione um aumento na eficiência de compressão, o acréscimo de novas ferramentas no codificador acarreta no aumento da complexidade do processo. Assim, cresce a relevância de soluções que reduzam o tempo de codificação do 3D-HEVC, sem impactar significativamente a eficiência de codificação. Este trabalho apresenta uma heurística de redução de complexidade para o codificador de mapas de profundidade do 3D-HEVC, chamada de Early Skip/DIS. Uma análise sobre mapas de profundidade do 3D-HEVC é apresentada nesta dissertação, demonstrando que o particionamento 2Nx2N é largamente utilizado pelo codificador, visto que diversas ferramentas eficientes de codificação, utilizam exclusivamente este modo. A análise demonstrou que, além do 2Nx2N ser o modo de particionamento mais usado, a exclusão dos demais modos gera um impacto desprezível em eficiência de codificação, com ganhos mínimos em termos de tempo de processamento. Este fato conduziu ao desenvolvimento da heurística Early Skip/DIS, a qual visa evitar o teste dos demais modos/ferramentas de predição com base no custo RD gerado por estes modos. Os thresholds utilizados nesta solução são definidos de forma adaptativa. Resultados de simulação demonstraram que a solução é capaz de reduzir o tempo de codificação dos mapas de profundidade em até 33,7%, com um impacto médio de apenas 0,047% na eficiência de compressão da textura. A heurística proposta apresenta os melhores resultados de redução de complexidade para o codificador de mapas de profundidade entre os trabalhos relacionados. / 3D videos provides a visual experience with depth perception through the usage of special displays that project a three-dimensional scene from slightly different directions for the left and right eyes. Despite this improved visual experience, the coded-video data volume tends to linearly increases with the number of processed views, mainly considering conventional 3D video formats. In this scenario emerges the Multiview plus Depth (MVD) format, which informs the distance between scene objects and the recording camera (depth maps), allowing an eficiently view-synthesis process while reducing the number of views to be transmitted. Unlike previous multiview video coding standards, 3D-HEVC is able to manipulate depth maps in an eficient way due the new defined tools which explores the depth maps characteristics. Although this fact leads to an improvement of 3D-HEVC compression eficiency, the addition of new coding tools also increases the coding process complexity. Thus, solutions, which reduces the 3D-HEVC coding time while does not affecting the compression eficiency at all, are important in this scenario. This work presents a complexity reduction heuristic for the 3D-HEVC depth maps coder, called Early Skip/DIS. Initially, an analysis about 3D-HEVC depth-maps coder is presented. This analysis showed that the 2Nx2N is the most used partitioning mode, since some eficient coding tools, like Skip and DIS, are applied exclusively over this partitioning mode. This analysis also showed that, beyond the 2Nx2N partitioning mode is the most used mode, the exclusion of the other partition modes causes an imperceptible impact in the encoding eficiency and a low impact in processing time. This fact leads to the development of an Early decision heuristic called Early Skip/DIS, which avoids the encoder checking unnecessary modes based on the RD cost generated by the Skip and DIS modes. The thresholds used in this solution are defined in an adaptively way, observing the occurrence rate of those modes as a function of its generated RD costs. Simulation results demonstrated that the proposed solution is able to reduce the depth-map coding time up to 33.7% while affecting the texture compression eficiency in 0.047% (in terms of BD-rate). The propose heuristic presented the best depth-map complexity reduction result among other related works.

Indiana University-Purdue University Indianapolis (IUPUI) / In this thesis, we describe a different implementation for in loop filtering method for 3D-HEVC. First we propose the use of adaptive loop filtering (ALF) technique for 3D-HEVC standard in-loop filtering. This filter uses Wiener–based method to minimize the Mean Squared Error between filtered pixel and original pixels. The performance of adaptive loop filter in picture based level is evaluated. Results show up to of 0.2 dB PSNR improvement in Luminance component for the texture and 2.1 dB for the depth. In addition, we obtain up to 0.1 dB improvement in Chrominance component for the texture view after applying this filter in picture based filtering. Moreover, a design of an in-loop filtering with Fast Bilateral Filter for 3D-HEVC standard is proposed. Bilateral filter is a filter that smoothes an image while preserving strong edges and it can remove the artifacts in an image. Performance of the bilateral filter in picture based level for 3D-HEVC is evaluated. Test model HTM- 6.2 is used to demonstrate the results. Results show up to of 20 percent of reduction in processing time of 3D-HEVC with less than affecting PSNR of the encoded 3D video using Fast Bilateral Filter.

Les travaux effectués durant cette thèse de doctorat ont pour but d'augmenter l'efficacité de codage dans 3D-HEVC. Nous proposons des approches conventionnelles orientées vers la normalisation vidéo, ainsi que des approches en rupture basées sur le flot optique. En approches conventionnelles, nous proposons une méthode qui prédit les modes Intra de profondeur avec ceux de texture. L'héritage est conditionné par un critère qui mesure le degré de similitude entre les deux modes. Ensuite, nous proposons deux méthodes pour améliorer la prédiction inter-vue du mouvement dans 3D-HEVC. La première ajoute un vecteur de disparité comme candidat inter-vue dans la liste des candidats du Merge, et la seconde modifie le processus de dérivation de ce vecteur. Finalement, un outil de codage intercomposantes est proposé, où le lien entre les arbres quaternaires de texture et de profondeur est exploité pour réduire le temps d'encodage et le débit, à travers un codage conjoint des deux arbres. Dans la catégorie des approches en rupture, nous proposons deux méthodes basées sur l'estimation de champs denses de vecteurs de mouvement en utilisant le flot optique. La première calcule un champ au niveau d'une vue de base reconstruite, puis l'extrapole au niveau d'une vue dépendante, où il est hérité par les unités de prédiction en tant que candidat dense du Merge. La deuxième méthode améliore la synthèse de vues : quatre champs sont calculés au niveau de deux vues de référence en utilisant deux références temporelles. Ils sont ensuite extrapolés au niveau d'une vue synthétisée et corrigés en utilisant une contrainte épipolaire. Les quatre prédictions correspondantes sont ensuite combinées. Les deux méthodes apportent des gains de codage significatifs, qui confirment le potentiel de ces solutions innovantes.