DCT Image Coding Employing Emphasis

Emphasis filtering is very effective to improve reconstructed image quality in subband coding. In this paper, emphasis scheme is applied to DCT coding which is performed with subband filter banks. The characteristics of emphasis filter are dependent on the source image signal. A decoded image is subject to de-emphasis filter of the characteristics inverse to those of the emphasis filter. To avoid transmission of filter parameters for every image, the pair of filters of predetermined characteristics are used for emphasis and de-emphasis. A two-dimensional(2-d) model for approximating image spectrum is proposed for designing these filters. Coding simulations have shown that the proposed scheme achieves about 1dB improvement in the SN ratio compared to the pure DCT scheme. Also, it is shown that the proposed 2-d spectrum model derives more effect of emphasis than conventional models.

Published

1996-10

Content type

Original Research

DOI

10.5594/M001247

ISBN

978-1-61482-947-8