Rounding - Dithering and Error Diffusion

Dithering and Error Diffusion

When digitising continuous signals, for example images or sound, the overall effect of a number of measurements is more important than the accuracy of each individual measurement. In these circumstances dithering, and a related technique, error diffusion, are normally used. A related technique called pulse-width modulation is used to achieve analogue type output from an inertial device by rapidly pulsing the power with a variable duty cycle.

Error diffusion tries to ensure the error on average is minimized. When dealing with a gentle slope from one to zero the output would be zero for the first few terms until the sum of the error and the current value becomes greater than 0.5, in which case a 1 is output and the difference subtracted from the error so far. Floyd–Steinberg dithering is a popular error diffusion procedure when digitising images.

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