Computation reduction for discrete cosine transform

This paper presents a method to accelerate software video encoders by reducing the number of operations for discrete cosine transform (DCT) and quantization. We present a model of DCT coefficients based on the information of motion compensated difference blocks. The relationship between the quantization level and DCT coefficients is also studied. Based on the model, we can adaptively make the decision of DCT calculations. A fast algorithm is also proposed for approximating the 4×4 low-frequency coefficients. The results show that significant computation reductions can be achieved with negligible peak signal-to-noise ratio (PSNR) degradations