[MPlayer-dev-eng] Soft volume clip methods
Zoltan Hidvegi
mplayer at hzoli.2y.net
Sat Feb 19 23:52:31 CET 2005
The current softclip method used my libaf is sin(x), which is slow,
and becomes hard at 4dB. What are the requirements for a good clip
functions? Obviously, it must clip to [-1,+1], it's first derivative
at zero must be 1, it must be strictly increasing and and it must
satisfy f(-x) = -f(x). The rest are fuzzy, like it should be
reasonable smooth etc. For example, what about this much faster
function:
sign(x) * (1 - (2-abs(x))^2/4) for -2 < x < 2 and sign(x) otherwise.
This hard clips above 6dB. And there are other possible clip
functions which have no hard limit, e.g. sign(x) * (1 - exp(-abs(x)))
or 2*atan(2x/pi)/pi or similar, like in
http://www.musicdsp.org/showone.php?id=104, but these are slow, what
would be a good unbounded clip funciton with parameterizable hardness?
Zoli
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