Predictive transform image coding extensions.
Item
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Title
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Predictive transform image coding extensions.
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Identifier
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AAI9304724
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identifier
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9304724
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Creator
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Rivera, Jose A.
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Contributor
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Adviser: Erlan H. Feria
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Date
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1992
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Language
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English
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Publisher
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City University of New York.
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Subject
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Engineering, Electronics and Electrical | Engineering, General | Engineering, Aerospace
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Abstract
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Predictive Transform Coding (PTC) is a generalized coding approach that contains pulse code modulation, predictive coding and transform coding as special cases. This investigation: (a) initiated studies in adaptivity and transmission errors in PTC; and (b) reduced the blocking effect in the reconstructed image at low bit rate. A comparison of performance between the PTC system and the JPEG image compression is provided.;The statistics of signals, containing useful information, are usually unknown apriori; in addition, the signals are possibly characterized as nonstationary (time-varying statistics). For signals with this characterization, an adaptive implementation would be, in many cases, a suitable selection. When considering an adaptive implementation in digital coding, usually, there is a trade-off between the best adaptive approach to track the statistical variability in the input signals and the overhead in the bit rate incurring in such operation. The adaptive problem has been addressed by estimating the variance of the prediction coefficient error signal at the input of the quantizer corresponding to a block of data for an image partitioned and processed in blocks. The quantizer is changed in a discrete mode according to the value of the variance. The estimated variance is used as a measure of the image activity at the block level where it can be considered locally stationary.;The transmission error problem has been addressed by introducing a leak factor constraint when designing the transform and predictor matrices of the coder. The leak factor, by making the channel errors decay faster, results in the substantial improvement in the signal-to-noise ratio and in the image quality.;The blocking effect has been reduced by partitioning the original image in vertical strips (picture element blocks of M rows and only one column) and by overlapping one line during each horizontal scanning. At the completion of the communication process, each pair of overlapped lines are averaged when the image is being reconstructed. The prediction elements considered are the ones contained in the vertical strip right behind the one being encoded. The high correlation provided by the proximity of the prediction elements and the averaging of the overlapped lines are major contributors in the reduction of the blocking effect.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
