Improving Picture Quality for Regions of Interest

In order to improve the picture quality, the region of interest within video sequence should be handled differently to regions which are of less interest. Generally the region of interest is coded with smaller quantization step-size to give higher picture quality, compared with the remainder of the image. However the abrupt change picture quality variation on the boundary of regions of interest can cause the some degradation of the overall subjective picture quality. This paper presents a method where the local picture quality is varied smoothly between the region of interest and the remainder of the image. We first classify the type of subjectively region of interest which can be determined by using motion vectors estimated in the coding process. Then the region of interest is coded by decreasing the quantization step-size according to a gradual linear change from the other regions within a video sequence.