Picture data compressor

TL;DR: In this paper, the authors proposed to improve the quality of restored pictures while keeping the same extent of compressibility of picture data by setting the lower limit level of the frequencies to be cut so as to prevent the cut of frequencies lower than the lower-limit level when the high frequencies are adaptively cut for improving the compressibility.

Abstract: PURPOSE: To improve the quality of restored pictures while keeping the same extent of compressibility of picture data by setting the lower limit level of the frequencies to be cut so as to prevent the cut of frequencies lower than the lower limit level when the high frequencies are adaptively cut for improvement of the compressibility. CONSTITUTION: The transformation coefficients F(u, v) are successively stored in a buffer memory, e.g. a FIFO 30 which can store (N×N) pieces of coefficient value from the DC component side. At the same time, the coefficients F are also supplied to a distribution estimating device 40 and a frequency deciding means 80 respectively. The quantized transformation coefficients F'(u, v) are coded by a coding device 60, and this code data is outputted via a terminal 70. The device 80 calculates adaptively the highest frequency (cut-off frequency) C to be treated in a block of the device 80. In this case, the device 80 calculates the statistic feature value showing the block characteristics for each block and then obtains the number of transformation coefficients to be cut, i.e., a cut-off frequency. This cut-off frequency also shows the lower limit level of the cut-off frequency. COPYRIGHT: (C)1990,JPO&Japio