Picturing Dither: Dithering Pictures
The desirable properties that follow from the use of (nonsubtractive) triangular probability density function (TPDF) random dither in digital audio quantization and noise shaping are now well known in the audio community. The principal purpose of this paper is to use a visual analogy to aid audio engineers in their understanding of how proper TPDF dithering and noise shaping can convert otherwise objectionable, correlated quantization errors into benign, uncorrelated and less visible ones. As they say, “a picture is worth a thousand words.” Our secondary purpose is to demonstrate, in the process, that the very same concepts, applied now in the spatial instead of the temporal domain, are just as useful and beneficial in the field of digital picture processing too. We present color (in the PDF version of this paper) and monochrome images of the results of coarse quantization, both with and without dither and/or noise shaping, to help us make our points. [In the “live” presentation of this paper, we shall play an audio example at the same time as we show each picture, so that one can simultaneously both see and hear each effect being discussed.]
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