noise shaping
<communications> Spectral noise transformation in a quantisation
processes. Noise is "colourised" in the time domain an/or frequency domain by
adding parts of the previous sample. The SNR bandwidth and SNR time integral
stay the same, so some noise decreases, some increases, but overall noise always
increases.
An example of noise shaping in the frequency domain is quantisation of samples
on a Compact Disc to reduce noise below -98 dB. The are different algorithms
with slightly different filters, e.g. Super Bitmapping, 4D Recording.
A time domain example is MPEG-4 AAC TNS, which is a method to enhance quality by
temporal forming of the noise in a transform block.
(2003-07-19)
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