Signal processing used in DAC to shift the frequency of noise in a digital signal so that, on conversion, the noise will be outside (usually above) the audio range. This is done by reducing the number of parallel bits used to carry the data, increasing the number of serial bits and so the frequency of the digital signal. In oversampling digital systems, digital filtering is used to reduce quantization error. By changing the shape of the spectrum of the quantization noise, increasing its high-frequency content by lowering its low-frequency content, an anti-imaging filter can then be used to reduce the increased high-frequency noise.
See dither.