A low-complexity computation scheme of discrete cosine transform and quantization with adaptation to block contents

In this paper, we propose a low-complexity computation scheme of Discrete Cosine Transform (DCT) and quantization, which is adaptive to block contents of image frames. With consideration of maintaining the quality of the decoded image and reducing the computational complexity, we take a closer look at the relationship between block contents and the quantization table. Based on this relationship to predict the number of DCT coefficients required for calculation, we develop an adaptive scheme to update the DCT calculation structure. Comparing our scheme in deriving DCT coefficients with that of DCT calculation for a fixed number of coefficients. Our scheme can compromise image qualities with computational complexities. In other words, the proposed scheme could adjust the DCT calculation complexity depending on the image contents. The image quality from our scheme is comparable to that of a complete 64-coefficient DCT calculation process. Therefore, our proposed scheme to calculate DCT and quantization, with abilities to reduce the computational complexity and preserve the picture quality, is suitable and applicable in video and image compression used nowadays