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Proceedings Paper

Visual thresholds for wavelet quantization error
Author(s): Andrew B. Watson; Gloria Y. Yang; Joshua A. Solomon; John D. Villasenor
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Paper Abstract

The discrete wavelet transform (DWT) decomposes an image into bands that vary in spatial frequency and orientation. It is widely used for image compression. Measures of the visibility of DWT quantization errors are required to achieve optimal compression. Uniform quantization of a single band of coefficients results in an artifact that is the sum of a lattice of random amplitude basis functions of the corresponding DWT synthesis filter, which we call DWT uniform quantization noise. We measured visual detection thresholds for samples of DWT uniform quantization noise in Y, Cb, and Cr color channels. The spatial frequency of a wavelet is r 2-L, where r is display visual resolution in pixels/degree, and L is the wavelet level. Amplitude thresholds increase rapidly with spatial frequency. Thresholds also increase from Y to Cr to Cb, and with orientation from low-pass to horizontal/vertical to diagonal. We propose a mathematical model for DWT noise detection thresholds that is a function of level, orientation, and display visual resolution. This allows calculation of a 'perceptually lossless' quantization matrix for which all errors are in theory below the visual threshold. The model may also be used as the basis for adaptive quantization schemes.

Paper Details

Date Published: 22 April 1996
PDF: 11 pages
Proc. SPIE 2657, Human Vision and Electronic Imaging, (22 April 1996); doi: 10.1117/12.238735
Show Author Affiliations
Andrew B. Watson, NASA Ames Research Ctr. (United States)
Gloria Y. Yang, Univ. of California/Los Angeles (United States)
Joshua A. Solomon, NASA Ames Research Ctr. (United States)
John D. Villasenor, Univ. of California/Los Angeles (United States)


Published in SPIE Proceedings Vol. 2657:
Human Vision and Electronic Imaging
Bernice E. Rogowitz; Jan P. Allebach, Editor(s)

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