Dynamic bit allocation for multiple video object coding

In MPEG-4, a visual scene may be treated as a composition of video objects and coded at object level. Such a flexible video coding framework makes it possible to code different video objects with different priority according to human perceptual characteristics. In this paper, we introduce a novel dynamic bit allocation framework to improve the subjective quality in such an object-based video coding system. We incorporate the rate distortion models with the dynamic priorities of the video objects and jointly encode video objects to minimize the weighted distortion within the bit budget constraint. We guarantee the human-interested video objects a better reconstructed quality by using the weighted bit allocation strategy in favour of the video objects with higher priority. To obtain the priority automatically, we apply a visual attention model. Comparing with traditional bit allocation algorithms, the objective quality of the object with higher priority is significantly improved under this framework. These results demonstrate the usefulness of this dynamic bit allocation framework.