B-spline-based shape coding with accurate distortion measurement using analytical model.

In this paper, we present a new model to measure the contour point distortion for the vertex-based shape coding with B-splines, called accurate distortion measurement using analytical model (ADMAM). Different from existing distortion measurements containing approximation, quantization or parameterization process, our distortion is defined on the original B-spline. It is modeled as the shortest distance of associated contour point from the original B-spline, which is in line with the subjective-based objective quality metric. The geometric relationships are introduced to simplify the model computation, followed by a hybrid admissible distortion checking algorithm to reduce the execution time. Our theoretical analysis and experimental results demonstrate that the ADMAM can lead to the smallest bit-rate among all the distortion measurements that guarantee the admissible distortion, when the operational rate-distortion optimal shape coding framework is applied. Moreover, if the original contour has NC points, it takes only O(NC) time for both peak and mean-squared segment distortion measuring paradigms, which is the lowest computational complexity among all the existing distortion measurements.