Measurement of activity of video image by DCT and filtering of the prediction error coefficients

摘要

A method for measuring the activity of a macroblock of a video picture in the direct cosine transform domain of values assumed by a selected component of the video signal includes dividing the macroblock into blocks of data in the discrete cosine transform domain before quantization, and separately storing each block of data in a memory. The method further includes reading each block of data stored in the memory for obtaining respective coefficients, and multiplying an absolute value of each coefficient by a selected mask of words comprising a number of words not exceeding a number of words forming each block. The results of the multiplications are summed for producing an activity coefficient for each block. A first activity coefficient of the macroblock is calculated corresponding to a sum of the activity coefficients produced for each block. A normalized activity value of the macroblock is calculated as the ratio between a sum of double the first activity coefficient with a mean activity coefficient relative to a preceding coded frame, and a sum of double the mean activity coefficient with the first activity coefficient.