  We study an interactive live streaming scenario where multiple peers pull
streams of the same free viewpoint video that are synchronized in time but not
necessarily in view. In free viewpoint video, each user can periodically select
a virtual view between two anchor camera views for display. The virtual view is
synthesized using texture and depth videos of the anchor views via
depth-image-based rendering (DIBR). In general, the distortion of the virtual
view increases with the distance to the anchor views, and hence it is
beneficial for a peer to select the closest anchor views for synthesis. On the
other hand, if peers interested in different virtual views are willing to
tolerate larger distortion in using more distant anchor views, they can
collectively share the access cost of common anchor views.
  Given anchor view access cost and synthesized distortion of virtual views
between anchor views, we study the optimization of anchor view allocation for
collaborative peers. We first show that, if the network reconfiguration costs
due to view-switching are negligible, the problem can be optimally solved in
polynomial time using dynamic programming. We then consider the case of
non-negligible reconfiguration costs (e.g., large or frequent view-switching
leading to anchor-view changes). In this case, the view allocation problem
becomes NP-hard. We thus present a locally optimal and centralized allocation
algorithm inspired by Lloyd's algorithm in non-uniform scalar quantization. We
also propose a distributed algorithm with guaranteed convergence where each
peer group independently make merge-and-split decisions with a well-defined
fairness criteria. The results show that depending on the problem settings, our
proposed algorithms achieve respective optimal and close-to-optimal performance
in terms of total cost, and outperform a P2P scheme without collaborative
anchor selection.
