Video Compression Using Dpcm And Wt

Abstract

             Digital images are widely used in computer applications. Uncompressed digital images require considerable storage capacity and transmission bandwidth. Efficient image compression solutions are becoming more critical with the recent growth of data intensive, multimedia-based web applications.This paper develops hybrid technique which employs combines differential pulse code modulation (DPCM) with wavelet transform. The wavelet transform is applied to the difference signal instead of direct applying it to the original images, because difference signal is almost nearly stationary. The difference signal is determined using interframe and intraframe DPCM. Intraframe method has given smoother difference signal because the frames used in the interframe prediction were not successive. The difference signal is then wavelet transformed and encoded using predictive edge detection from the LL band of the lowest resolution level to predict the edge in LH, HL and HH bands in the higher resolution levels. If the coefficient is predicted as an edge it is preserved; otherwise, it is discarded. In the decoder, the location of the preserved coefficients can also be found as in the encoder. Therefore, no overhead is needed. Instead of complex vector quantization, which is commonly used in subband image coding for high compression ratio, simple scalar quantization is used to code the remaining coefficients. A remarkable compression ratio of about 30:1 has been achieved without noticeable degradation in the decompressed images.