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UBC Theses and Dissertations

Theoretical study of transform picture coding systems and an investigation of a new measure of distortion in processed images Baillie, Alexander John Main


The performance of systems which employ a linear transformation and block quantization to encode visual information sources has been investigated. The effect of several relevant design parameters upon the behavior of these systems was examined theoretically. The performance criterion used was the rate measured in bits-per-picture sample required to transmit an image through a noiseless digital channel such that the average distortion in the received picture is less than a specified value. As a measure of image distortion, the mean-squared-error, well-known for its analytical tractability, was used. A second measure of image distortion which incorporates knowledge of the human visual system was examined. The new distortion index proposed by Stockham is expected to correlate well with subjective assessments of picture distortion although no experiments have been performed, as yet, to show this. In order to determine what, if anything, could be learned about this second distortion measure from theoretical considerations alone, a procedure was developed to estimate its value for given bit rates. These values were compared to the mean-squared-error distortion values obtained for the same bit rates in an attempt to gain some insight into the usefulness of the second distortion measure.

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