Maintaining Temporal Coherence in Video Retargeting Using Mosaic-Guided Scaling

Video retargeting from a full-resolution video to a lower resolution display will inevitably cause information loss. Content-aware video retargeting techniques have been studied to avoid critical visual information loss while resizing a video. Maintaining the spatio-temporal coherence of a retargeted video is very critical on visual quality. Camera motions and object motions, however, usually make it difficult to maintain temporal coherence using existing schemes. In this paper, we propose the use of a panoramic mosaic to guide the scaling of corresponding regions of video frames in a video shot to ensure good temporal coherence. In the proposed method, after aligning video frames in a shot to a panoramic mosaic constructed for the shot, a global scaling map for these frames is derived from the panoramic mosaic. Subsequently, the local scaling maps of individual frames are derived from the global map and is further refined according to spatial coherence constraints. Our experimental results show that the proposed method can effectively maintain temporal coherence so as to achieve good visual quality even a video contains camera motions and object motions.