Buffer data control circuit and method in image compression system using wavelet system using wavelet transform

摘要

An apparatus and method are provided for controlling the amount of image compression data which is to be encoded in an image compression system using a wavelet transform. The amount of data accumulated in a channel buffer is controlled by removing from the wavelet-transformed image data, data cells which contain a frequency band and having a spatial orientation to which human eyes are less sensitive. An estimation is made as to how much data will accumulate in the channel buffer, based on a cyclic integration of the rate at which data is input to the channel buffer. The estimation is compared to a set of predetermined thresholds to determine how much if any of the wavelet-transformed image data is to be removed. If the estimation indicates an overflow, data cells D₂³, D₄³, and D₈³ are removed from the wavelet-transformed image frame. After overflow has been avoided, only data cell D₂³ is removed. If the estimation indicates an underflow, no data cells are removed. This results in an improved data transmission rate, while at the same time good picture quality is still obtained when the image transmitted through the channel is reproduced.