;******************************************************************************* ; C H A M E L E O N DSP Assembler file * ;******************************************************************************* ; Copyright (C) 2001-2002 Soundart * ; www.soundart-hot.com * ; support@soundart-hot.com * ; ; Stereo Filter modified by Aleix Riera ; aleix@fjarre.com ; www.fjarre.com/~aleix ;******************************************************************************* ; ; MODULE: Filter2 (CUTOFF ISN'T A BUFFER) ; Implements a 24dB resonant lowpass filter (the code is based in the ; source code of the filter Moog VCF variation2 of the musicdsp.org ; filters source code page, thanks to Bram de Jong). ; ; Basicly, this filter implements this algorithm (four 1-pole ; stages with feedback) without optimization: ; ; fb = res * (1.0 - 0.15 * f * f); ; input -= out4 * fb; ; input *= 0.35013 * (f*f)*(f*f); ; out1 = input + 0.3 * in1 + (1 - f) * out1; // Pole 1 ; in1 = input; ; out2 = out1 + 0.3 * in2 + (1 - f) * out2; // Pole 2 ; in2 = out1; ; out3 = out2 + 0.3 * in3 + (1 - f) * out3; // Pole 3 ; in3 = out2; ; out4 = out3 + 0.3 * in4 + (1 - f) * out4; // Pole 4 ; in4 = out3; ; output = out4 ; ; NOTE: The filter cutoff range should be revised because values close to 0.0 ; makes the filter unstable. ; ; ARGUMENTS: ; (X) = InAddr - Input stereo buffer (L) ; (X+1) = OutAddr - Output stereo buffer (L) ; (X+2) = Control - Cutoff input (Y) ; LEFT: ; (X+3) = Resonance - Resonance constant ; (X+4) = In1 - Input1 state ; (X+5) = Out1 - Output1 state ; (X+6) = In2 - Input2 state ; (X+7) = Out2 - Output2 state ; (X+8) = In3 - Input3 state ; (X+9) = Out3 - Output3 state ; (X+10)= In4 - Input4 state ; (X+11)= Out4 - Output4 state ; RIGHT: ; (X+12) = Resonance - Resonance constant ; (X+13) = In1 - Input1 state ; (X+14) = Out1 - Output1 state ; (X+15) = In2 - Input2 state ; (X+16) = Out2 - Output2 state ; (X+17) = In3 - Input3 state ; (X+18) = Out3 - Output3 state ; (X+19)= In4 - Input4 state ; (X+20)= Out4 - Output4 state ; ;****************************************************************************** module_filter: define R_InL 'R1' define R_OutL 'R2' define R_InR 'R6' define R_OutR 'R7' define R_Control 'R5' ;===============================CODE===================================== MOVE X:(R_X)+,R_InL MOVE X:(R_X)+,R_OutL MOVE R_InL,R_InR MOVE X:(R_X)+,R_Control MOVE R_OutL,R_OutR MOVE #8,N_X .LOOP #BUFFER_SIZE ;---------------------------------------------------------------- ;MOVE Y:(R_Control)+,X0 ; X0=f MOVE Y:(R_Control),X0 ; X0=f MPY X0,X0,A ; A=K1=f*f MOVE X:(R_X)+,X1 ; X1=res MOVE A,Y0 ; Y0=K1 MPY X1,Y0,B ; B=K2=X1*Y0=res*K1 MOVE #0.15,Y1 ; Y1=0.15 TFR X1,B B,X1 ; X1=K2, B=res MAC -Y1,X1,B ; B=fb=B-Y1*X1=res-0.15*K2 MOVE X:(R_InL)+,A ; A=input MOVE X:(R_X+7),X1 ; X1=out4 MPY Y0,Y0,B B,Y0 ; Y0=fb, B=K3=Y0*Y0=K1*K1 ASR #2,A,A ; A=input=0.25*A=0.25*input MAC -X1,Y0,A ; A=input=A-X1*Y0=input-out4*fb MOVE #0.35013,Y0 ; Y0=0.35013 MOVE A,X1 ; X1=A=input MPY Y0,X1,A B,Y0 ; A=input=Y0*X1=0.35013*input, Y0=B=K3 ASL #2,A,A ; A=input=4*A=4*input NOP MOVE A,X1 ; X1=A=input MPY X1,Y0,A #0.3,Y0 ; A=input=X1*Y0=input*K3, Y0=0.3 MOVE X:(R_X)+,X1 ; X1=in1 MAC Y0,X1,A X:(R_X)-,X1 A,Y1 ; A=K4=A+Y0*X1=input+0.3*in1, X1=out1, Y1=input MAC -X0,X1,A Y1,X:(R_X)+ ; A=K5=A-X0*X1=K4-f*out1, in1=Y1=input ADD X1,A ; A=out1=A+X1=K5+out1 NOP MOVE A,X:(R_X)+ ; out1=A=out1 MOVE X:(R_X)+,X1 ; X1=in2 MAC Y0,X1,A X:(R_X)-,X1 A,Y1 ; A=K6=A+Y0*X1=out1+0.3*in2, X1=out2, Y1=out1 MAC -X0,X1,A Y1,X:(R_X)+ ; A=K7=A-X0*X1=K6-f*out2, in2=Y1=out1 ADD X1,A ; A=out2=A+X1=K7+out2 NOP MOVE A,X:(R_X)+ ; out2=A=out2 MOVE X:(R_X)+,X1 ; X1=in3 MAC Y0,X1,A X:(R_X)-,X1 A,Y1 ; A=K8=A+Y0*X1=out2+0.3*in3, X1=out3, Y1=out2 MAC -X0,X1,A Y1,X:(R_X)+ ; A=K9=A-X0*X1=K8-f*out3, in3=Y1=out2 ADD X1,A ; A=out3=A+X1=K9+out3 NOP MOVE A,X:(R_X)+ ; out3=A=out3 MOVE X:(R_X)+,X1 ; X1=in4 MAC Y0,X1,A X:(R_X)-,X1 A,Y1 ; A=K10=A+Y0*X1=out3+0.3*in4, X1=out4, Y1=out3 MAC -X0,X1,A Y1,X:(R_X)+ ; A=K11=A-X0*X1=K10-f*out4, in3=Y1=out3 ADD X1,A ; A=out4=A+X1=K11+out4 NOP MOVE A,X:(R_X)-N_X ; out4=A=out4 MOVE A,X:(R_OutL)+ ; output=A=out4 ;---------------------------------------------------------------- .ENDL LUA (R_X+9),R_X .LOOP #BUFFER_SIZE ;---------------------------------------------------------------- ;MOVE Y:(R_Control)+,X0 ; X0=f MOVE Y:(R_Control),X0 ; X0=f MPY X0,X0,A ; A=K1=f*f MOVE X:(R_X)+,X1 ; X1=res MOVE A,Y0 ; Y0=K1 MPY X1,Y0,B ; B=K2=X1*Y0=res*K1 MOVE #0.15,Y1 ; Y1=0.15 TFR X1,B B,X1 ; X1=K2, B=res MAC -Y1,X1,B ; B=fb=B-Y1*X1=res-0.15*K2 MOVE Y:(R_InR)+,A ; A=input MOVE X:(R_X+7),X1 ; X1=out4 MPY Y0,Y0,B B,Y0 ; Y0=fb, B=K3=Y0*Y0=K1*K1 ASR #2,A,A ; A=input=0.25*A=0.25*input MAC -X1,Y0,A ; A=input=A-X1*Y0=input-out4*fb MOVE #0.35013,Y0 ; Y0=0.35013 MOVE A,X1 ; X1=A=input MPY Y0,X1,A B,Y0 ; A=input=Y0*X1=0.35013*input, Y0=B=K3 ASL #2,A,A ; A=input=4*A=4*input NOP MOVE A,X1 ; X1=A=input MPY X1,Y0,A #0.3,Y0 ; A=input=X1*Y0=input*K3, Y0=0.3 MOVE X:(R_X)+,X1 ; X1=in1 MAC Y0,X1,A X:(R_X)-,X1 A,Y1 ; A=K4=A+Y0*X1=input+0.3*in1, X1=out1, Y1=input MAC -X0,X1,A Y1,X:(R_X)+ ; A=K5=A-X0*X1=K4-f*out1, in1=Y1=input ADD X1,A ; A=out1=A+X1=K5+out1 NOP MOVE A,X:(R_X)+ ; out1=A=out1 MOVE X:(R_X)+,X1 ; X1=in2 MAC Y0,X1,A X:(R_X)-,X1 A,Y1 ; A=K6=A+Y0*X1=out1+0.3*in2, X1=out2, Y1=out1 MAC -X0,X1,A Y1,X:(R_X)+ ; A=K7=A-X0*X1=K6-f*out2, in2=Y1=out1 ADD X1,A ; A=out2=A+X1=K7+out2 NOP MOVE A,X:(R_X)+ ; out2=A=out2 MOVE X:(R_X)+,X1 ; X1=in3 MAC Y0,X1,A X:(R_X)-,X1 A,Y1 ; A=K8=A+Y0*X1=out2+0.3*in3, X1=out3, Y1=out2 MAC -X0,X1,A Y1,X:(R_X)+ ; A=K9=A-X0*X1=K8-f*out3, in3=Y1=out2 ADD X1,A ; A=out3=A+X1=K9+out3 NOP MOVE A,X:(R_X)+ ; out3=A=out3 MOVE X:(R_X)+,X1 ; X1=in4 MAC Y0,X1,A X:(R_X)-,X1 A,Y1 ; A=K10=A+Y0*X1=out3+0.3*in4, X1=out4, Y1=out3 MAC -X0,X1,A Y1,X:(R_X)+ ; A=K11=A-X0*X1=K10-f*out4, in3=Y1=out3 ADD X1,A ; A=out4=A+X1=K11+out4 NOP MOVE A,X:(R_X)-N_X ; out4=A=out4 MOVE A,Y:(R_OutR)+ ; output=A=out4 ;---------------------------------------------------------------- .ENDL ;===============================CODE===================================== undef R_InL undef R_OutL undef R_InR undef R_OutR undef R_Control RTS