Visual Media Coding and Transmission

6.1 Introduction

Existing video coding standards are suitable for coding 2D videos in a rate-distortion optimized sense, where rate-distortion optimization refers to the process of jointly optimizing both the resulting image quality and the required bit rate. The basic principle of block-based video coders is to remove temporal and spatial redundancies among successive frames of video sequences. However, as the viewing experience moves from 2D viewing to more realistic 3D viewing, it will become impossible to reconstruct a realistic 3D scene by using a simple 2D video scene, or to allow a user (or a group of users) to freely and interactively navigate in a visual scene [1]. More viewpoints of a given scene would be needed in such cases, which conventional video coders are not optimized to jointly code without modifying some of the existing compression tools.

As the number of representations of a certain scene from different viewpoints increases, the size of the total payload to be transmitted will increase by the same proportion where every single representation (or viewpoint) is encoded as a single 2D video. This method is highly impractical due to storage and bandwidth constraints. Therefore, other ways to jointly encode viewpoints have been developed, all of which take into account the exploitation of strong correlations that exist among different viewpoints of a certain scene. Exploitation of inter-view correlation reduces the number of bits required for coding. The correspondences ...