soft/tune/eq/eq_define_parametric_eq.m

144 lines
4.6 KiB
Matlab

function [z, p, k] = eq_define_parametric_eq(peq, fs)
%%
% Copyright (c) 2016, Intel Corporation
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%
% Author: Seppo Ingalsuo <seppo.ingalsuo@linux.intel.com>
%
% Parametric types
PEQ_HP1 = 1; PEQ_HP2 = 2; PEQ_LP1 = 3; PEQ_LP2 = 4;
PEQ_LS1 = 5; PEQ_LS2 = 6; PEQ_HS1 = 7; PEQ_HS2 = 8;
PEQ_PN2 = 9; PEQ_LP4 = 10; PEQ_HP4 = 11;
sp = size(peq);
z = [];
p = [];
k = 1;
for i=1:sp(1)
type = peq(i,1);
f = peq(i,2);
g = peq(i,3);
Q = peq(i,4);
if f < fs/2
a0 = [];
b0 = [];
z0 = [];
p0 = [];
k0 = [];
switch peq(i,1)
case PEQ_HP1, [z0, p0, k0] = butter(1, 2*f/fs, 'high');
case PEQ_HP2, [z0, p0, k0] = butter(2, 2*f/fs, 'high');
case PEQ_HP4, [z0, p0, k0] = butter(4, 2*f/fs, 'high');
case PEQ_LP1, [z0, p0, k0] = butter(1, 2*f/fs);
case PEQ_LP2, [z0, p0, k0] = butter(2, 2*f/fs);
case PEQ_LP4, [z0, p0, k0] = butter(4, 2*f/fs);
case PEQ_LS1, [b0, a0] = low_shelf_1st(f, g, fs);
case PEQ_LS2, [b0, a0] = low_shelf_2nd(f, g, fs);
case PEQ_HS1, [b0, a0] = high_shelf_1st(f, g, fs);
case PEQ_HS2, [b0, a0] = high_shelf_2nd(f, g, fs);
case PEQ_PN2, [b0, a0] = peak_2nd(f, g, Q, fs);
otherwise
error('Unknown parametric EQ type');
end
if length(a0) > 0
[z0, p0, k0] = tf2zp(b0, a0);
end
if length(k0) > 0
z = [z ; z0(:)];
p = [p ; p0(:)];
k = k * k0;
end
end
end
end
function [b, a] = low_shelf_1st(fhz, gdb, fs)
zw = 2*pi*fhz;
w = wmap(zw, fs);
glin = 10^(gdb/20);
bs = [1 glin*w];
as = [1 w];
[b, a] = my_bilinear(bs, as, fs);
end
function [b, a] = low_shelf_2nd(fhz, gdb, fs)
zw = 2*pi*fhz;
w = wmap(zw, fs);
glin = 10^(gdb/20);
bs = [1 w*sqrt(2*glin) glin*w^2];
as = [1 w*sqrt(2) w^2];
[b, a] = my_bilinear(bs, as, fs);
end
function [b, a] = high_shelf_1st(fhz, gdb, fs)
zw = 2*pi*fhz;
w = wmap(zw, fs);
glin = 10^(gdb/20);
bs = [glin w];
as = [1 w];
[b, a] = my_bilinear(bs, as, fs);
end
function [b, a] = high_shelf_2nd(fhz, gdb, fs)
zw = 2*pi*fhz;
w = wmap(zw, fs);
glin = 10^(gdb/20);
bs = [glin w*sqrt(2*glin) w^2];
as = [1 w*sqrt(2) w^2];
[b, a] = my_bilinear(bs, as, fs);
end
function [b, a] = peak_2nd(fhz, gdb, Q, fs)
% Reference http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt
A = 10^(gdb/40); % Square root of linear gain
wc = 2*pi*fhz/fs;
alpha = sin(wc)/(2*Q);
b0 = 1 + alpha * A;
b1 = -2 * cos(wc);
b2 = 1 - alpha * A;
a0 = 1 + alpha / A;
a1 = -2 * cos(wc);
a2 = 1 - alpha / A;
b = [b0 / a0 b1 / a0 b2 / a0];
a = [1 a1 / a0 a2 / a0];
end
function [b, a] = my_bilinear(sb, sa, fs)
if exist('OCTAVE_VERSION', 'builtin')
[b, a] = bilinear(sb, sa, 1/fs);
else
[b, a] = bilinear(sb, sa, fs);
end
end
function sw = wmap(w, fs)
t = 1/fs;
sw = 2/t*tan(w*t/2);
end