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Visibility of wavelet quantization noiseThe 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 we call DWT uniform quantization noise; it is the sum of a lattice of random amplitude basis functions of the corresponding DWT synthesis filter. 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-lambda, where r is display visual resolution in pixels/degree, and lambda is the wavelet level. Thresholds increase rapidly with wavelet spatial frequency. Thresholds also increase from Y to Cr to Cb, and with orientation from lowpass to horizontal/vertical to diagonal. We construct 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.
Document ID
Document Type
Reprint (Version printed in journal)
External Source(s)
Watson, A. B.
(NASA Ames Research Center Moffett Field CA United States)
Yang, G. Y.
Solomon, J. A.
Villasenor, J.
Date Acquired
August 21, 2013
Publication Date
August 1, 1997
Publication Information
Publication: IEEE transactions on image processing : a publication of the IEEE Signal Processing Society
Volume: 6
Issue: 8
ISSN: 1057-7149
Subject Category
Life Sciences (General)
Distribution Limits
NASA Discipline Space Human Factors
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