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Video
Published in Jerry D. Gibson, The Communications Handbook, 2018
The goal of an efficient source coder is to maximize quality (or minimize distortion) subject to a number of constraints. In most applications of video compression, the quality or distortion are subjective measures determined by the visual properties of the viewer. However, if further signal processing or manipulation of the image sequence is to be performed, a more stringent objective criterion may be more appropriate, since impairments invisible to a viewer could have a negative effect on a signal processing operation such as chroma key. If subjective quality is the main concern, it would be very desirable to have a mathematical function that measures the subjective distortion. This distortion function could then be minimized during the optimization of the coding algorithm. Unfortunately, such a general purpose and widely accepted perceptual distortion measure is not available. Thus, properties of the human visual system are usually ex-ploited based on qualitative or empirical considerations that are obtained under restricted conditions. However, this approach may still be quite effective [Schreiber, 1993; Jayant et al., 1993]. The coding algorithm can then be evaluated using formal subjective testing under controlled conditions [Allnutt, 1983].
R
Published in Philip A. Laplante, Comprehensive Dictionary of Electrical Engineering, 2018
raster width (1) physical distance between raster lines on a display surface and between distinguishable points in the same raster line; the two distances are frequently different. (2) the physical distance between raster lines on a display surface and between distinguishable points in the same raster line. The two distances are frequently different. rate distortion function the minimum rate at which a source is represented by one of a set of discrete points. rate distortion theory a theory aimed at quantifying the optimum performance of source coding systems. Using information theory, for several source models and distortion measures, rate distortion theory provides the optimum distortion function and the optimum rate function. The distortion function is optimum in that the distortion for a given rate is the theoretical minimum value of distortion for encoding the source at the given or lower rate. The rate function is optimum in that the rate at a given distortion is the minimum
R
Published in Phillip A. Laplante, Dictionary of Computer Science, Engineering, and Technology, 2017
rate distortion theory a theory aimed at quantifying the optimum performance of source coding systems. Using information theory, for several source models and distortion measures, rate distortion theory provides the optimum distortion function and the optimum rate function. The distortion function is optimum in that the distortion for a given rate is the theoretical minimum value of distortion for encoding the source at the given or lower rate. The rate function is optimum in that the rate at a given distortion is the minimum possible rate for coding the source at the given or lower distortion.
Tutorial: Luminance Maps for Daylighting Studies from High Dynamic Range Photography
Published in LEUKOS, 2021
C. Pierson, C. Cauwerts, M. Bodart, J. Wienold
If the real projection function differs from the two most common theoretical projection functions (i.e. equidistant or orthographic) and if the application of the HDR image requires geometrical accuracy, a distortion function should be derived and applied to the HDR image to adjust its projection. The distortion function establishes the displacement that should be applied to a pixel according to its original position to get an equidistant projection in an HDR image.