Subband DCT: definition, analysis, and applications

The discrete cosine transform (DCT) is well known for its highly efficient coding performance and is widely used in many image compression applications. However, in low bit rate coding, it produces undesirable block artifacts that are visually not pleasing. In addition, in many practical applications, faster computation and easier VLSI implementation of DCT coefficients are also important issues. The removal of the block artifacts and faster DCT computation are therefore of practical interest. In this paper, we investigate a modified DCT computation scheme, to be called the subband DCT (SB-DCT), that provides a simple, efficient solution to the reduction of the block artifacts while achieving faster computation. We have applied the new approach for the low bit rate coding and decoding of images. Simulation results on real images have verified the improved performance obtained using the proposed method over the standard JPEG method.