The Rhombic Dodecahedron Map: An Efficient Scheme for Encoding Panoramic Video

 Chi-Wing Fu, Liang Wan, Tien-Tsin Wong and Chi-Sing Leung,
IEEE Transactions on Multimedia, Vol. 11, No. 4, pp. 634-644, 2009

Abstract

Omnidirectional videos are usually mapped to planar domain for encoding with off-the-shelf video compression standards. However, existing work typically neglects the effect of the sphere-to-plane mapping. In this paper, we show that by carefully designing the mapping, we can improve the visual quality, stability and compression efficiency of encoding omnidirectional videos. Here we propose a novel mapping scheme, known as the rhombic dodecahedron map (RD map) to represent data over the spherical domain. By using a family of skew great circles as the subdivision kernel, the RD map not only produces a sampling pattern with very low discrepancy, it can also support a highly efficient data indexing mechanism over the spherical domain. Since the proposed map is quad-based, geodesic-aligned, and of very low area and shape distortion, we can reliably apply 2D wavelet-based and DCT-based encoding methods that are originally designated to planar perspective videos. At the end, we perform a series of analysis and experiments to investigate and verify the effectiveness of the proposed method; with its ultra-fast data indexing capability, we show that we can playback omnidirectional videos with very high frame rates on conventional PCs with GPU support.

Download

Sampling Pattern

The table below shows the sampling pattern of the rhombic dodecahedron map.

 

　

Four-Strip Format for Video Compression

For compatibility with the existing MPEG framework, we proposed a four-strip encoding scheme to pack the image blocks. Given the twelve rhombi in the fish-like form, we rearrange them as four consecutive strips shown below. Using this scheme, four video streams are formed and each is encoded with the standard MPEG2.

 

 

　

copyright © Liang Wan / HOME