Video scalability rate control method by dynamic controlling of hierarchical bit allocation ratio

This paper considers the hierarchical video coding system, and proposes a bit allocation rate control method by dynamic control of the hierarchical bit allocation ratio. As the first step, the MPEG-2 SNR scalability method is considered as the hierarchical video coding, and the relation between the hierarchical bit allocation and the basic/enhancement layer quality is analyzed. It is shown that the intermediate bit allocation ratio may degrade greatly the quality in the enhancement layer. The dependency of the image quality on the hierarchical bit allocation is noted, and video coding bit allocation control is proposed, where the hierarchical loss can be suppressed by dynamically controlling the bit allocation ratio for each picture. A control method is proposed particularly, where the optimal bit allocation ratio is calculated so that the characteristic function is maximized under the constraint that the bit allocation ratio for each GOP is kept constant. Lastly, a simulation experiment is presented. It is shown that the hierarchical loss, which is generated in the conventional bit allocation control, can be suppressed by the proposed control method, and the effectiveness of the proposed method is demonstrated.