When approximating the shape of a region, a fixed bound on the tolerable distortion is set for approximating its contour points. An adaptive approximation bound for lossy coding of the contour points is proposed. A function representing the relative significance of the contour points is defined to adjust the distortion bound along the region contour allowing an adaptive approximation of the region shape. The effectiveness of the adaptive contour coding approach for a region-based coding system is verified through experiments.

We propose a two-stage variable block-size multiresolution motion estimation (MRME) algorithm. In this algorithm, a method to reduce the amount of motion information is developed, and a bit allocation method minimizing the sum of the motion information and the prediction error is obtained in the wavelet transform domain. In the first stage of the proposed scheme, we utilize a set of wavelet components of the four subbands in the lowest resolution. These motion vectors are directly used as motion vectors for the lowest subband, and are scaled into the initial biases for other subbands at every layer of the wavelet pyramid. In the second stage, the bottom-up construction of a quadtree based on the merge operation is performed. The proposed scheme reduces the uncompressed bit rate of 8 bits/pixel into 0.212 bits/pixel at 41.1 dB of PSNR for the "Claire" sequence, which can be regarded as nearly an 11% reduction compared with the conventional method.

A hierarchical wavelet transform coding structure which satisfies the requirements of a high definition video cassette recorder (HD-VCR) for studio application in wireless environments is proposed. All of the coefficients in the transformed image are adaptively quantized and hierarchically converted into a single stream or binary symbols using the monotone decreasing property. The resulting bit stream goes through an adaptive arithmetic coder, and two-level control of the bit rate is performed so as to maintain a constant target bit rate. The proposed algorithm can be efficiently implemented with much reduced computing time for the real world application. It is verified by simulation that for a test sequence of images at least 4 dB of PSNR improvement can be achieved compared with other DCT-based schemes at a constant target bit rate, avoiding the blocking effect which would be impossible otherwise.