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

[GStreamer (bugzilla.gnome.org)]

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




------- Comment #9 from David Schleef  2007-04-13 21:47 UTC -------
I have some test code for dithering, error feedback, and noise shaping that
works fairly well.  I think it would be a good idea to put these into
audioconvert and enable them by default.  I see audioconvert as being an
element that Just Works for the average user -- if we want to provide duplicate
functionality somewhere else that is more configurable, great.

The techniques tend to need to be used together, since they counteract each
other's bad features.  When all used together, the main badness is that it adds
a lot of noise at high frequencies.  This is ok if the output is going straight
to a sound card and then to speakers or headphones, but is very bad if you
intend to do any kind of post-processing.  Like, say, letting alsa's dmix touch
it.

Another problem that I'm trying to get around is that the literature designs
filters based on the standard F-weighted equi-loudness curves.  This assumes
that the average person cannot hear above about 16 kHz, so it pushes most of
the noise to that region.  Someone with better than average hearing (you know,
about *half* of people) will hear this clearly and find it stressful and/or
annoying.

Hopefully I'll find a pointer to research exploring the 90% percentile of
hearing, or similar.  I think that would be more useful.


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