[gstreamer-bugs] [Bug 360246] [audioconvert] Optionally apply dithering

[GStreamer (bugzilla.gnome.org)]

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  GStreamer | gst-plugins-base | Ver: HEAD CVS




------- Comment #12 from Sebastian Dröge  2007-04-15 10:00 UTC -------
My plan was to put the dithering and noise shaping in the pack functions which
would get an additional parameter (saved in the audioconvert structure)
containing the random number generator for dithering, the errors for noise
shaping, etc.

And then we would get many many different functions...
I wanted to implement for dithering:
a) RPDF
b) TPDF
c) high frequency TPDF
d) maybe gaussian

and for noise shaping 1st order, 3rd order and maybe 16 or 20th order.
Coefficients for the latter would be generated by dmaker[0].

Unfortunately this would give us either 5*3 unpack functions per target format
or a few function calls per sample in the unpack functions.

Your idea of refactoring audioconvert into unpack, mix, quantize and pack
sounds better, I'll care for it unless you want to do it :)

For the random numbers I planned to use GRandom anyway for now as it's fairly
fast...

As default settings the best would probably be:
- X to Y bits with Y >= X: nothing
- X to Y bits with Y >= 20: nothing
- X to Y bits with Y < 20: TPDF + 1st order noise shaping

Then either have just this implemented in audioconvert and create and
additional element which has all this configurable or have this as default in
audioconvert and add some parameters for every other possibility...


[0] http://shibatch.sourceforge.net/


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