  Warping-based video stabilizers smooth camera trajectory by constraining each
pixel's displacement and warp stabilized frames from unstable ones accordingly.
However, since the view outside the boundary is not available during warping,
the resulting holes around the boundary of the stabilized frame must be
discarded (i.e., cropping) to maintain visual consistency, and thus does leads
to a tradeoff between stability and cropping ratio. In this paper, we make a
first attempt to address this issue by proposing a new Out-of-boundary View
Synthesis (OVS) method. By the nature of spatial coherence between adjacent
frames and within each frame, OVS extrapolates the out-of-boundary view by
aligning adjacent frames to each reference one. Technically, it first
calculates the optical flow and propagates it to the outer boundary region
according to the affinity, and then warps pixels accordingly. OVS can be
integrated into existing warping-based stabilizers as a plug-and-play module to
significantly improve the cropping ratio of the stabilized results. In
addition, stability is improved because the jitter amplification effect caused
by cropping and resizing is reduced. Experimental results on the NUS benchmark
show that OVS can improve the performance of five representative
state-of-the-art methods in terms of objective metrics and subjective visual
quality. The code is publicly available at
https://github.com/Annbless/OVS_Stabilization.
