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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 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(exp)-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 describe a mathematical model to predict DWT noise detection thresholds as 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
20020034889
Acquisition Source
Ames Research Center
Document Type
Preprint (Draft being sent to journal)
Authors
Watson, Andrew B.
(NASA Ames Research Center Moffett Field, CA United States)
Yang, Gloria Y.
(California Univ. Los Angeles, CA United States)
Solomon, Joshua A.
(NASA Ames Research Center Moffett Field, CA United States)
Villasenor, John
(California Univ. Los Angeles, CA United States)
Null, Cynthia H.
Date Acquired
August 20, 2013
Publication Date
January 1, 1995
Subject Category
Physics Of Elementary Particles And Fields
Funding Number(s)
PROJECT: RTOP 199-06-12
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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