Measurement of activity of video images in the DCT domain

摘要

A method of measuring the activity of a macroblock of a picture in the direct cosine transform domain of values assumed by a selected component of the video signal comprises a) separately storing in a memory blocks of data into which is divided a macroblock in the discrete cosine transform domain before quantization; b) reading from said memory the data of each of the blocks constituting said macroblock representing said selected component in the discrete cosine transform domain obtaining the respective coefficients; c) multipliying the absolute value of said coefficients by a selected mask of words of a number not exceeding the number of words constituting the block; d) summing the results of said moltiplications producing an activity coefficient for each of the blocks constituting said macroblock; e) calculating a first activity coefficient of the macroblock (actj) as the sum of said activity coefficients produced for each block; f) calculating a normalized activity value of the macroblock as the ratio between the sum of the double of said activity coefficient (actj) with a mean activity (mean_actj) relative to the preceding coded frame and the sum of the double of the coefficient mean_actj with the activity coefficient actj. <IMAGE>