Multiple constraint bit allocation for foveated visual coding

This paper presents a new method in the multiple constraint bit allocation for foveated visual coding. First, the foveation effect is applied to the DCT transformed coefficients in macroblocks (MBs) of images and videos. The priorities of MBs are computed based on the retina eccentricity of human eyes, which is measured in terms of the distance from foveation points. Then, prioritized image slices are formed by comparing the priority of each MB with the preset threshold and grouping MBs having close priorities. With prioritized image slices, the proposed multiple constraint bit allocation based on the modified Lagrangian optimization is applied to all image slices. There are two constraints on the bit allocation. The first constraint is the target quality requirements of image slices. The second constraint is the bit rate constraint. The proposed multiple constraint bit allocation tries its best to achieve the best overall reconstructed image quality under these two constraints. The experimental results conducted with JPEG and H.263+ compression standards show that the proposed scheme can achieve better performance than the previous work with the traditional Lagrangian optimization and obtain the required quality of image slice in both subjective and objective quality.