Fabien Racape

A study of depth/texture bit-rate allocation in multi-view video plus depth compression

Multi-view video plus depth (MVD) data offer a reliable representation of three-dimensional (3D) scenes for 3D video applications. This is a huge amount of data whose compression is an important challenge for researchers at the current time. Consisting of texture and depth video sequences, the question of the relationship between these two types of data regarding bit-rate allocation often raises. This paper questions the required ratio between texture and depth when encoding MVD data. In particular, the paper investigates the elements impacting on the best bit-rate ratio between depth and color: total bit-rate budget, input data features, encoding strategy, and assessed view.

Spatiotemporal texture synthesis and region-based motion compensation for video compression

In this paper, a content-based approach for video compression is proposed. The main novelty relies on the complete texture analysis/synthesis framework, which enables the use of multiple algorithms, depending on texture characteristics. The idea comes from the efficient MPEG prediction based on a best mode selection. Existing synthesis algorithms cannot be efficient in synthesizing every kind of texture but a certain range of them. This approach is designed to be jointly used with current and future standard compression schemes. At encoder side, texture analysis includes segmentation and characterization tools, in order to localize candidate regions for synthesis: motion compensation or texture synthesis. The corresponding areas are not encoded. The decoder fills them using texture synthesis. The remaining regions in images are classically encoded. They can potentially serve as input for texture synthesis. The chosen tools are developed and adapted in order to ensure the coherency of the whole scheme. Thus, a texture characterization step provides required parameters to the texture synthesizer. Two texture synthesizers, including a pixel-based and a patch-based approach, are used on different types of texture, complementing each other. The scheme is coupled with a motion estimator in order to segment coherent regions and to interpolate rigid motions using an affine model. Inter frame adapted synthesis is therefore used for non-rigid texture regions. The framework has been validated within an H.264/MPEG4-AVC video codec. Experimental results show significant bit-rate saving at similar visual quality levels, assessed using subjective tests. The method can be coupled with the future HEVC in which blocks can be skipped by the encoder to be synthesized at decoder side.

Texture refinement framework for improved video coding

H.264/AVC standard offers an efficient way of reducing the noticeable artefacts of former video coding schemes, but it can be perfectible for the coding of detailed texture areas. This paper presents a conceptual coding framework, utilizing visual perception redundancy, which aims at improving both bit-rate and quality on textured areas. The approach is generic and can be integrated into usual coding scheme. The proposed scheme is divided into three steps: a first algorithm analyses texture regions, with an eye to build a dictionary of the most representative texture sub-regions (RTS). The encoder preserves then them at a higher quality than the rest of the picture, in order to enable a refinement algorithm to finally spread the preserved information over textured areas. In this paper, we present a first solution to validate the framework, detailing then the encoder side in order to define a simple method for dictionary building. The proposed H.264/AVC compliant scheme creates a dictionary of macroblocks