STATISTICAL COMPUTATION OF DISCRETE COSINE TRANSFORM IN VIDEO ENCODERS

Computation reduction is important for the implementation of software video codecs. This paper describes a scheme for reducing the required computations in video encoders by skipping some of the discrete cosine transformation (DCT) and quantization calculations. We study the rela tionship between the mean absolute error (MAE) of the motion compensat ed difference blocks and the distribution of DCT coefficients. The rel ationship between the quantized DCT coefficients and the quantization level is also investigated. Based on the MAE of the motion compensated difference block and the quantization level, three options for the DC T calculation can be chosen: calculating all 8 x 8 DCT coefficients, c alculating the DC coefficient only, or skipping the whole DCT computat ion. Simulation results show that the peak signal-to-noise ratio (PSNR ) degradation is negligible with significant computation reduction ach ieved. (C) 1998 Academic Press.