// (C) 2008-2009, Lubomir I. Ivanov
//
// NO WARRANTY IS GRANTED. THIS PLUG-IN IS PROVIDED ON AN "AS IS" BASIS, WITHOUT
// WARRANTY OF ANY KIND. NO LIABILITY IS GRANTED, INCLUDING, BUT NOT LIMITED TO,
// ANY DIRECT OR INDIRECT,  SPECIAL,  INCIDENTAL OR CONSEQUENTIAL DAMAGE ARISING
// OUT OF  THE  USE  OR INABILITY  TO  USE  THIS PLUG-IN,  COMPUTER FAILTURE  OF
// MALFUNCTION INCLUDED.  THE USE OF THE SOURCE CODE,  EITHER  PARTIALLY  OR  IN
// TOTAL, IS ONLY GRANTED,  IF USED IN THE SENSE OF THE AUTHOR'S INTENTION,  AND
// USED WITH ACKNOWLEDGEMENT OF THE AUTHOR. FURTHERMORE IS THIS PLUG-IN A  THIRD
// PARTY CONTRIBUTION,  EVEN IF INCLUDED IN REAPER(TM),  COCKOS INCORPORATED  OR
// ITS AFFILIATES HAVE NOTHING TO DO WITH IT.  LAST BUT NOT LEAST, BY USING THIS
// PLUG-IN YOU RELINQUISH YOUR CLAIM TO SUE IT'S AUTHOR, AS WELL AS THE CLAIM TO
// ENTRUST SOMEBODY ELSE WITH DOING SO.
// 
// Released under GPL:
// <http://www.gnu.org/licenses/>.
//
//******************************************************************************
// butterworth filter implementation - 
// original port from apple.com au tutorial (c+)
// added HP version
// added 12 poles cascade
// * see note below about efficiency
//******************************************************************************

desc: AppleFilter v.2 (72dB LP/HP)

slider1:0<0,1,1{Stereo,Mono}>Processing
slider2:0<0,1,1{Off,12dB,24dB,36dB,48dB,60dB,72dB}>HP Slope (dB/oct)
slider3:0<0,100,0.01>HP Cut (Scale)
slider4:0<-16,16,0.01>HP Res (dB)
slider5:0<0,1,1{Off,12dB,24dB,36dB,48dB,60dB,72dB}>LP Slope (dB/oct)
slider6:100<0,100,0.01>LP Cut (Scale)
slider7:0<-16,16,0.01>LP Res (dB)
slider8:0<-24,24,0.01>Output (dB)

@slider
mono = slider1;
outgain = 10^(slider8/20);

//****************************
//hp

n_hp = slider2;
sx = 16+slider3*1.20103;
cx_hp = floor(exp(sx*log(1.059))*8.17742);
cutoff_hp = 2*cx_hp/srate;
res_hp = 10^(0.05*(-slider4/n_hp+1.5));

k = 0.5*res_hp*sin($pi*cutoff_hp);
c1 = 0.5*(1-k)/(1+k);
c2 = (0.5+c1)*cos($pi*cutoff_hp);
c3 = (0.5+c1+c2)*0.25;

a0_hp = 2*c3;
a1_hp = -4*c3;
a2_hp = 2*c3;
b1_hp = -2*c2;
b2_hp = 2*c1;

//****************************
//lp

n_lp = slider5;
sx = 16+slider6*1.20103;
cx_lp = floor(exp(sx*log(1.059))*8.17742);
cutoff_lp = 2*cx_lp/srate;
res_lp = 10^(0.05*(-slider7/n_lp+1.5));

k = 0.5*res_lp*sin($pi*cutoff_lp);
c1 = 0.5*(1-k)/(1+k);
c2 = (0.5+c1)*cos($pi*cutoff_lp);
c3 = (0.5+c1-c2)*0.25;

a0_lp = 2*c3;
a1_lp = 4*c3;
a2_lp = 2*c3;
b1_lp = -2*c2;
b2_lp = 2*c1;

@sample

// *NOTE: You can use 'loop' for the cascade (see example below)
// however its many times less efficient !
//
// comparison for - mono, lp, 72db:
// --------------------
// using loop - 13.8% cpu 
// long version - 3.3% cpu
/*
i = 0;
inl = (spl0+spl1)/2;
loop(n_lp,
outl = a0_lp*inl+a1_lp*mem[4*i+1]+a2_lp*mem[4*i+2]-b1_lp*mem[4*i+3]-b2_lp*mem[4*i+4];
mem[4*i+2] = mem[4*i+1];
mem[4*i+1] = inl;
mem[4*i+4] = mem[4*i+3];
mem[4*i+3] = outl;
inl = outl;
i += 1;
);
spl0=spl1=outl;
*/

//***************************************************************************
//mono
mono == 1 ? (
inl = (spl0+spl1)/2;
//*********************************************
//hp
n_hp > 0 ? (
out_hp_l_1 = a0_hp*inl+a1_hp*mem_hp_l_11+a2_hp*mem_hp_l_12-b1_hp*mem_hp_l_13-b2_hp*mem_hp_l_14;
mem_hp_l_12 = mem_hp_l_11;
mem_hp_l_11 = inl;
mem_hp_l_14 = mem_hp_l_13;
mem_hp_l_13 = out_hp_l_1;
out_hp_l = out_hp_l_1;
n_hp > 1 ? (
out_hp_l_2 = a0_hp*out_hp_l_1+a1_hp*mem_hp_l_21+a2_hp*mem_hp_l_22-b1_hp*mem_hp_l_23-b2_hp*mem_hp_l_24;
mem_hp_l_22 = mem_hp_l_21;
mem_hp_l_21 = out_hp_l_1;
mem_hp_l_24 = mem_hp_l_23;
mem_hp_l_23 = out_hp_l_2;
out_hp_l = out_hp_l_2;
);
n_hp > 2 ? (
out_hp_l_3 = a0_hp*out_hp_l_2+a1_hp*mem_hp_l_31+a2_hp*mem_hp_l_32-b1_hp*mem_hp_l_33-b2_hp*mem_hp_l_34;
mem_hp_l_32 = mem_hp_l_31;
mem_hp_l_31 = out_hp_l_2;
mem_hp_l_34 = mem_hp_l_33;
mem_hp_l_33 = out_hp_l_3;
out_hp_l = out_hp_l_3;
);
n_hp > 3 ? (
out_hp_l_4 = a0_hp*out_hp_l_3+a1_hp*mem_hp_l_41+a2_hp*mem_hp_l_42-b1_hp*mem_hp_l_43-b2_hp*mem_hp_l_44;
mem_hp_l_42 = mem_hp_l_41;
mem_hp_l_41 = out_hp_l_3;
mem_hp_l_44 = mem_hp_l_43;
mem_hp_l_43 = out_hp_l_4;
out_hp_l = out_hp_l_4;
);
n_hp > 4 ? (
out_hp_l_5 = a0_hp*out_hp_l_4+a1_hp*mem_hp_l_51+a2_hp*mem_hp_l_52-b1_hp*mem_hp_l_53-b2_hp*mem_hp_l_54;
mem_hp_l_52 = mem_hp_l_51;
mem_hp_l_51 = out_hp_l_4;
mem_hp_l_54 = mem_hp_l_53;
mem_hp_l_53 = out_hp_l_5;
out_hp_l = out_hp_l_5;
);
n_hp > 5 ? (
out_hp_l_6 = a0_hp*out_hp_l_5+a1_hp*mem_hp_l_61+a2_hp*mem_hp_l_62-b1_hp*mem_hp_l_63-b2_hp*mem_hp_l_64;
mem_hp_l_62 = mem_hp_l_61;
mem_hp_l_61 = out_hp_l_5;
mem_hp_l_64 = mem_hp_l_63;
mem_hp_l_63 = out_hp_l_6;
out_hp_l = out_hp_l_6;
);
) : (
out_hp_l = inl;
);
//*********************************************
//lp
n_lp > 0 ? (
out_lp_l_1 = a0_lp*out_hp_l+a1_lp*mem_lp_l_11+a2_lp*mem_lp_l_12-b1_lp*mem_lp_l_13-b2_lp*mem_lp_l_14;
mem_lp_l_12 = mem_lp_l_11;
mem_lp_l_11 = out_hp_l;
mem_lp_l_14 = mem_lp_l_13;
mem_lp_l_13 = out_lp_l_1;
out_lp_l = out_lp_l_1;
n_lp > 1 ? (
out_lp_l_2 = a0_lp*out_lp_l_1+a1_lp*mem_lp_l_21+a2_lp*mem_lp_l_22-b1_lp*mem_lp_l_23-b2_lp*mem_lp_l_24;
mem_lp_l_22 = mem_lp_l_21;
mem_lp_l_21 = out_lp_l_1;
mem_lp_l_24 = mem_lp_l_23;
mem_lp_l_23 = out_lp_l_2;
out_lp_l = out_lp_l_2;
);
n_lp > 2 ? (
out_lp_l_3 = a0_lp*out_lp_l_2+a1_lp*mem_lp_l_31+a2_lp*mem_lp_l_32-b1_lp*mem_lp_l_33-b2_lp*mem_lp_l_34;
mem_lp_l_32 = mem_lp_l_31;
mem_lp_l_31 = out_lp_l_2;
mem_lp_l_34 = mem_lp_l_33;
mem_lp_l_33 = out_lp_l_3;
out_lp_l = out_lp_l_3;
);
n_lp > 3 ? (
out_lp_l_4 = a0_lp*out_lp_l_3+a1_lp*mem_lp_l_41+a2_lp*mem_lp_l_42-b1_lp*mem_lp_l_43-b2_lp*mem_lp_l_44;
mem_lp_l_42 = mem_lp_l_41;
mem_lp_l_41 = out_lp_l_3;
mem_lp_l_44 = mem_lp_l_43;
mem_lp_l_43 = out_lp_l_4;
out_lp_l = out_lp_l_4;
);
n_lp > 4 ? (
out_lp_l_5 = a0_lp*out_lp_l_4+a1_lp*mem_lp_l_51+a2_lp*mem_lp_l_52-b1_lp*mem_lp_l_53-b2_lp*mem_lp_l_54;
mem_lp_l_52 = mem_lp_l_51;
mem_lp_l_51 = out_lp_l_4;
mem_lp_l_54 = mem_lp_l_53;
mem_lp_l_53 = out_lp_l_5;
out_lp_l = out_lp_l_5;
);
n_lp > 5 ? (
out_lp_l_6 = a0_lp*out_lp_l_5+a1_lp*mem_lp_l_61+a2_lp*mem_lp_l_62-b1_lp*mem_lp_l_63-b2_lp*mem_lp_l_64;
mem_lp_l_62 = mem_lp_l_61;
mem_lp_l_61 = out_lp_l_5;
mem_lp_l_64 = mem_lp_l_63;
mem_lp_l_63 = out_lp_l_6;
out_lp_l = out_lp_l_6;
);
) : (
out_lp_l = out_hp_l;
);

//out mono
spl0 = spl1 = out_lp_l*outgain;

//*****************************************************************************
//stereo
) : (
inl = spl0;
inr = spl1;
//********************************************* 
//hp
n_hp > 0 ? (
out_hp_l_1 = a0_hp*inl+a1_hp*mem_hp_l_11+a2_hp*mem_hp_l_12-b1_hp*mem_hp_l_13-b2_hp*mem_hp_l_14;
mem_hp_l_12 = mem_hp_l_11;
mem_hp_l_11 = inl;
mem_hp_l_14 = mem_hp_l_13;
mem_hp_l_13 = out_hp_l_1;
out_hp_l = out_hp_l_1;
out_hp_r_1 = a0_hp*inr+a1_hp*mem_hp_r_11+a2_hp*mem_hp_r_12-b1_hp*mem_hp_r_13-b2_hp*mem_hp_r_14;
mem_hp_r_12 = mem_hp_r_11;
mem_hp_r_11 = inr;
mem_hp_r_14 = mem_hp_r_13;
mem_hp_r_13 = out_hp_r_1;
out_hp_r = out_hp_r_1;
n_hp > 1 ? (
out_hp_l_2 = a0_hp*out_hp_l_1+a1_hp*mem_hp_l_21+a2_hp*mem_hp_l_22-b1_hp*mem_hp_l_23-b2_hp*mem_hp_l_24;
mem_hp_l_22 = mem_hp_l_21;
mem_hp_l_21 = out_hp_l_1;
mem_hp_l_24 = mem_hp_l_23;
mem_hp_l_23 = out_hp_l_2;
out_hp_l = out_hp_l_2;
out_hp_r_2 = a0_hp*out_hp_r_1+a1_hp*mem_hp_r_21+a2_hp*mem_hp_r_22-b1_hp*mem_hp_r_23-b2_hp*mem_hp_r_24;
mem_hp_r_22 = mem_hp_r_21;
mem_hp_r_21 = out_hp_r_1;
mem_hp_r_24 = mem_hp_r_23;
mem_hp_r_23 = out_hp_r_2;
out_hp_r = out_hp_r_2;
);
n_hp > 2 ? (
out_hp_l_3 = a0_hp*out_hp_l_2+a1_hp*mem_hp_l_31+a2_hp*mem_hp_l_32-b1_hp*mem_hp_l_33-b2_hp*mem_hp_l_34;
mem_hp_l_32 = mem_hp_l_31;
mem_hp_l_31 = out_hp_l_2;
mem_hp_l_34 = mem_hp_l_33;
mem_hp_l_33 = out_hp_l_3;
out_hp_l = out_hp_l_3;
out_hp_r_3 = a0_hp*out_hp_r_2+a1_hp*mem_hp_r_31+a2_hp*mem_hp_r_32-b1_hp*mem_hp_r_33-b2_hp*mem_hp_r_34;
mem_hp_r_32 = mem_hp_r_31;
mem_hp_r_31 = out_hp_r_2;
mem_hp_r_34 = mem_hp_r_33;
mem_hp_r_33 = out_hp_r_3;
out_hp_r = out_hp_r_3;
);
n_hp > 3 ? (
out_hp_l_4 = a0_hp*out_hp_l_3+a1_hp*mem_hp_l_41+a2_hp*mem_hp_l_42-b1_hp*mem_hp_l_43-b2_hp*mem_hp_l_44;
mem_hp_l_42 = mem_hp_l_41;
mem_hp_l_41 = out_hp_l_3;
mem_hp_l_44 = mem_hp_l_43;
mem_hp_l_43 = out_hp_l_4;
out_hp_l = out_hp_l_4;
out_hp_r_4 = a0_hp*out_hp_r_3+a1_hp*mem_hp_r_41+a2_hp*mem_hp_r_42-b1_hp*mem_hp_r_43-b2_hp*mem_hp_r_44;
mem_hp_r_42 = mem_hp_r_41;
mem_hp_r_41 = out_hp_r_3;
mem_hp_r_44 = mem_hp_r_43;
mem_hp_r_43 = out_hp_r_4;
out_hp_r = out_hp_r_4;
);
n_hp > 4 ? (
out_hp_l_5 = a0_hp*out_hp_l_4+a1_hp*mem_hp_l_51+a2_hp*mem_hp_l_52-b1_hp*mem_hp_l_53-b2_hp*mem_hp_l_54;
mem_hp_l_52 = mem_hp_l_51;
mem_hp_l_51 = out_hp_l_4;
mem_hp_l_54 = mem_hp_l_53;
mem_hp_l_53 = out_hp_l_5;
out_hp_l = out_hp_l_5;
out_hp_r_5 = a0_hp*out_hp_r_4+a1_hp*mem_hp_r_51+a2_hp*mem_hp_r_52-b1_hp*mem_hp_r_53-b2_hp*mem_hp_r_54;
mem_hp_r_52 = mem_hp_r_51;
mem_hp_r_51 = out_hp_r_4;
mem_hp_r_54 = mem_hp_r_53;
mem_hp_r_53 = out_hp_r_5;
out_hp_r = out_hp_r_5;
);
n_hp > 5 ? (
out_hp_l_6 = a0_hp*out_hp_l_5+a1_hp*mem_hp_l_61+a2_hp*mem_hp_l_62-b1_hp*mem_hp_l_63-b2_hp*mem_hp_l_64;
mem_hp_l_62 = mem_hp_l_61;
mem_hp_l_61 = out_hp_l_5;
mem_hp_l_64 = mem_hp_l_63;
mem_hp_l_63 = out_hp_l_6;
out_hp_l = out_hp_l_6;
out_hp_r_6 = a0_hp*out_hp_r_5+a1_hp*mem_hp_r_61+a2_hp*mem_hp_r_62-b1_hp*mem_hp_r_63-b2_hp*mem_hp_r_64;
mem_hp_r_62 = mem_hp_r_61;
mem_hp_r_61 = out_hp_r_5;
mem_hp_r_64 = mem_hp_r_63;
mem_hp_r_63 = out_hp_r_6;
out_hp_r = out_hp_r_6;
);
) : (
out_hp_l = inl;
out_hp_r = inr;
);
//*********************************************
//lp
n_lp > 0 ? (
out_lp_l_1 = a0_lp*out_hp_l+a1_lp*mem_lp_l_11+a2_lp*mem_lp_l_12-b1_lp*mem_lp_l_13-b2_lp*mem_lp_l_14;
mem_lp_l_12 = mem_lp_l_11;
mem_lp_l_11 = out_hp_l;
mem_lp_l_14 = mem_lp_l_13;
mem_lp_l_13 = out_lp_l_1;
out_lp_l = out_lp_l_1;
out_lp_r_1 = a0_lp*out_hp_r+a1_lp*mem_lp_r_11+a2_lp*mem_lp_r_12-b1_lp*mem_lp_r_13-b2_lp*mem_lp_r_14;
mem_lp_r_12 = mem_lp_r_11;
mem_lp_r_11 = out_hp_r;
mem_lp_r_14 = mem_lp_r_13;
mem_lp_r_13 = out_lp_r_1;
out_lp_r = out_lp_r_1;
n_lp > 1 ? (
out_lp_l_2 = a0_lp*out_lp_l_1+a1_lp*mem_lp_l_21+a2_lp*mem_lp_l_22-b1_lp*mem_lp_l_23-b2_lp*mem_lp_l_24;
mem_lp_l_22 = mem_lp_l_21;
mem_lp_l_21 = out_lp_l_1;
mem_lp_l_24 = mem_lp_l_23;
mem_lp_l_23 = out_lp_l_2;
out_lp_l = out_lp_l_2;
out_lp_r_2 = a0_lp*out_lp_r_1+a1_lp*mem_lp_r_21+a2_lp*mem_lp_r_22-b1_lp*mem_lp_r_23-b2_lp*mem_lp_r_24;
mem_lp_r_22 = mem_lp_r_21;
mem_lp_r_21 = out_lp_r_1;
mem_lp_r_24 = mem_lp_r_23;
mem_lp_r_23 = out_lp_r_2;
out_lp_r = out_lp_r_2;
);
n_lp > 2 ? (
out_lp_l_3 = a0_lp*out_lp_l_2+a1_lp*mem_lp_l_31+a2_lp*mem_lp_l_32-b1_lp*mem_lp_l_33-b2_lp*mem_lp_l_34;
mem_lp_l_32 = mem_lp_l_31;
mem_lp_l_31 = out_lp_l_2;
mem_lp_l_34 = mem_lp_l_33;
mem_lp_l_33 = out_lp_l_3;
out_lp_l = out_lp_l_3;
out_lp_r_3 = a0_lp*out_lp_r_2+a1_lp*mem_lp_r_31+a2_lp*mem_lp_r_32-b1_lp*mem_lp_r_33-b2_lp*mem_lp_r_34;
mem_lp_r_32 = mem_lp_r_31;
mem_lp_r_31 = out_lp_r_2;
mem_lp_r_34 = mem_lp_r_33;
mem_lp_r_33 = out_lp_r_3;
out_lp_r = out_lp_r_3;
);
n_lp > 3 ? (
out_lp_l_4 = a0_lp*out_lp_l_3+a1_lp*mem_lp_l_41+a2_lp*mem_lp_l_42-b1_lp*mem_lp_l_43-b2_lp*mem_lp_l_44;
mem_lp_l_42 = mem_lp_l_41;
mem_lp_l_41 = out_lp_l_3;
mem_lp_l_44 = mem_lp_l_43;
mem_lp_l_43 = out_lp_l_4;
out_lp_l = out_lp_l_4;
out_lp_r_4 = a0_lp*out_lp_r_3+a1_lp*mem_lp_r_41+a2_lp*mem_lp_r_42-b1_lp*mem_lp_r_43-b2_lp*mem_lp_r_44;
mem_lp_r_42 = mem_lp_r_41;
mem_lp_r_41 = out_lp_r_3;
mem_lp_r_44 = mem_lp_r_43;
mem_lp_r_43 = out_lp_r_4;
out_lp_r = out_lp_r_4;
);
n_lp > 4 ? (
out_lp_l_5 = a0_lp*out_lp_l_4+a1_lp*mem_lp_l_51+a2_lp*mem_lp_l_52-b1_lp*mem_lp_l_53-b2_lp*mem_lp_l_54;
mem_lp_l_52 = mem_lp_l_51;
mem_lp_l_51 = out_lp_l_4;
mem_lp_l_54 = mem_lp_l_53;
mem_lp_l_53 = out_lp_l_5;
out_lp_l = out_lp_l_5;
out_lp_r_5 = a0_lp*out_lp_r_4+a1_lp*mem_lp_r_51+a2_lp*mem_lp_r_52-b1_lp*mem_lp_r_53-b2_lp*mem_lp_r_54;
mem_lp_r_52 = mem_lp_r_51;
mem_lp_r_51 = out_lp_r_4;
mem_lp_r_54 = mem_lp_r_53;
mem_lp_r_53 = out_lp_r_5;
out_lp_r = out_lp_r_5;
);
n_lp > 5 ? (
out_lp_l_6 = a0_lp*out_lp_l_5+a1_lp*mem_lp_l_61+a2_lp*mem_lp_l_62-b1_lp*mem_lp_l_63-b2_lp*mem_lp_l_64;
mem_lp_l_62 = mem_lp_l_61;
mem_lp_l_61 = out_lp_l_5;
mem_lp_l_64 = mem_lp_l_63;
mem_lp_l_63 = out_lp_l_6;
out_lp_l = out_lp_l_6;
out_lp_r_6 = a0_lp*out_lp_r_5+a1_lp*mem_lp_r_61+a2_lp*mem_lp_r_62-b1_lp*mem_lp_r_63-b2_lp*mem_lp_r_64;
mem_lp_r_62 = mem_lp_r_61;
mem_lp_r_61 = out_lp_r_5;
mem_lp_r_64 = mem_lp_r_63;
mem_lp_r_63 = out_lp_r_6;
out_lp_r = out_lp_r_6;
);
) : (
out_lp_l = out_hp_l;
out_lp_r = out_hp_r;
);

//out stereo
spl0 = out_lp_l*outgain;
spl1 = out_lp_r*outgain;

);

@gfx 100 10
gfx_x=gfx_y=5;
gfx_lineto(gfx_x, gfx_y,0);
gfx_r=0.7;
gfx_b=0.1;
gfx_g=1;
gfx_a=1;
gfx_drawchar($'H');
gfx_drawchar($'P');
gfx_drawchar($' ');
gfx_drawchar($'=');
gfx_drawchar($' ');
gfx_drawnumber(cx_hp,0);
gfx_drawchar($' ');
gfx_drawchar($'H');
gfx_drawchar($'z');
gfx_y += 15;
gfx_x = 5;
gfx_drawchar($'L');
gfx_drawchar($'P');
gfx_drawchar($' ');
gfx_drawchar($'=');
gfx_drawchar($' ');
gfx_drawnumber(cx_lp,0);
gfx_drawchar($' ');
gfx_drawchar($'H');
gfx_drawchar($'z');


