The discrete cosine transform (DCT) has a variety of applications in image and speech coding [1, 2]. The idea of the approximate subband DFT (SB-DFT) [3, 4] is applied in [5] and [6] to the DCT. In this paper the basic idea of the subband DCT (SB-DCT) is reviewed. The calculation of the approximate SB-DCT is done with the aid of a fast cosine-transform method [7]. The subband DCT is generalized such that any band out of M subbands can be calculated. For this purpose the fast DCT method [7] is modified to calculate the fast DST. A general analysis of the errors due to the approximation is presented. The adaptive capability of the SB-DFT given in [8] is added to the SB-DCT to calculate adaptively the band of the dominant energy. The two-dimensional (2-D) SB-DCT is also investigated in this work. Applications of the general adaptive SB-DCT in speech cepstrum analysis and in echo detection are included.
展开▼
