A Depth Map Post-Processing Framework for 3D-TV Systems based on Compression Artifact Analysis

Depth maps aid the generation of virtual viewpoints in multiview video applications. As the depth maps can be represented as a gray scale image sequence, they can be compressed using existing video codecs. However, when the depth maps are compressed using existing codecs, compression artifacts cause undesirable distortions in the rendered views. If the effects of compression artifacts can be minimized at the decoder, it would be possible to use the existing video codecs, which achieve significant compression ratios, to effectively compress depth maps. In this paper we theoretically analyze the effects of compression artifacts on the virtual view generation process. Based on this analysis, a set of guidelines are formulated for designing a post-processing filter, which could effectively minimize the effects of compression artifacts. Assuming that depth maps are piecewise smooth images with sharp discontinuities, an adaptive bilateral filtering technique is proposed as an out-of-the-loop filter at the decoder to post-process the compressed depth maps. Histograms of the compressed depth maps are analyzed on block basis to identify the dominant depth value bins in each block. Using the identified global depth value bins, the proposed technique successfully minimizes the artifacts by adjusting the histograms of the compressed depth maps. The experimental results suggest that the proposed depth map filtering technique can significantly improve the average perceptual quality of rendered views by up to 1.7dB over the state-of-the-art techniques. It is expected that the proposed post-processing technique will have important use cases in advanced 3-Dimensional Television systems.