Image-independent optimal non-negative integer bit allocation technique for the DCT-based image transform coders

摘要

The optimum non-negative integer bit allocation (ONIBA) is an important technique, which provides optimal quantisation of transform coefficients for the image transform coders (ITCs). However, the existing ONIBA algorithms are still not popular for the discrete cosine transform (DCT)-based ITCs, due to their image-dependent nature and additional side information requirements. Therefore, this study presents a novel image-independent ONIBA (IIONIBA) technique to achieve efficient quantisation for the DCT-ITCs. For the development of the proposed IIONIBA technique, initially, an image-dependent ONIBA algorithm is proposed, which is then mapped into desired image-independent solution via utilisation of a prepared combined image and proposed modified step size mapping technique. Thereafter, a new lookup table for the elements of quantisation tables, obtained from the proposed IIONIBA technique, is established using non-linear regression analysis, to reduce the problem of additional side information requirements. Several experiments are performed to evaluate the performance of the proposed IIONIBA technique based on the visual quality assessment of reconstructed images and the image quality indexes peak signal to noise ratio (PSNR) and mean structural similarity index (MSSIM). The results show that the proposed IIONIBA technique delivers better quantisation and provides significant gains in the image quality indexes as compared to the recent quantisation techniques.