dither [-S|-s|-f filter] [-a] [-p precision]
-s. With the -f option, it is
possible to select a particular noise-shaping filter from the
following list: lipshitz, f-weighted, modified-e-weighted,
improved-e-weighted, gesemann, shibata, low-shibata, high-shibata.
Note that most filter types are available only with
44100Hz sample rate. The filter types are distinguished by the
following properties: audibility of noise, level of (inaudible,
but in some circumstances, otherwise problematic) shaped high
frequency noise, and processing speed.
The -S option selects a slightly "sloped" TPDF, biased towards
higher frequencies. It can be used at any sampling rate but
below around 22k, plain TPDF is probably better, and above around 37k,
noise-shaping (if available) is probably better.
The -a option enables a mode where dithering (and noise-shaping
if applicable) are automatically enabled only when needed. The
most likely use for this is when applying fade in or out to an
already dithered sample, so that the redithering applies only to
the faded portions. However, auto dithering is not fool-proof,
so the fades should be carefully checked for any noise modulation;
if this occurs, then either re-dither the whole sample, or
use trim, fade, and concatencate.
The -p option allows overriding the target precision.
This effect should not be followed by any other effect that effects the audio.