Multiple motion analysis: in spatial or in spectral domain?

In this paper, we compare the effects of multiple motions in spatial and spectral representations of an image sequence. We describe multiple motions in both domains and establish a comparison regarding their inherent properties when discretized. Though the spectral model provides us with an explicit description of both occlusion and transparency, it turns out that its resolution is very limited. We show that the spatial domain represented by the spatio-temporal derivatives has superior resolution properties and is thus more appropriate for the treatment of occlusion. We present an algorithm which based on an initial estimate of the number of motions uses the shift-and-subtract technique to localize occlusion boundaries and to track their movement in occlusion sequences. The same technique is used to distinguish occlusion from transparency and to decompose transparency scenes into multi-layers.