Midi Volume plugin

I did a plugin that is meant to control the Volume of a track depending on a midi controller such as a Food Pedal.

Description:

The midi CC values 0 ... 127 are mapped to an "amplifier" curve that consists of a linear and an exponential part
in a way, that with CC = 0 the amplification is 0 (-inf dB) and with CC = 127 the amplification is 1 (0db)
A slider defines the amount (in dB), the amplification is reduced with each CC step.
According to that, the breakpoint between the exponential and the linear part is set so that
at this point the value and the slope of the curves match.
Below the breakpoint, a linear curve is used so that with CC = 0 the amplification is Zero (-infinity dB).
Another slider defines the maximum speed the amplification is modulated. This is set in dB per modulation step.
(Moreover the maximum speed used is reaching a new defined level in as many steps a samples in a block)
A graph shows as well the curve (Amplification vs CC steps), as the dynamic movement of the amplification level.

The @sample section only contains three instruction and so I believe the thingy does not eat up much performance.

Have fun,
-Michael

Code:

---

// Author: Michael Schnell, based on a work of Time Waster (M. Smith)
// License: LGPL - http://ift.tt/joBYRV
//
// The midi CC values 0 ... 127 are mapped to an "amplifier" curve that consists of a linear and an exponential part
// in a way, that with CC = 0 the amplification is 0 (-inf dB) and with CC = 127 the amplification is 1 (0db)
// A slider defines the amount (in dB), the amplification is reduced with each CC step.
// According to that, the breakpoint between the exponential and the linear part is set so that
// at this point the value and the slope of the curves match.
// Below the breakpoint, a linear curve is used so that with CC = 0 the amplification is Zero (-infinity dB).
// Another slider defines the maximum speed the amplification is modulated. This is set in dB per modulation step.
// (Moreover the maximum speed used is reaching a new defined level in as many steps a samples in a block)
// A graph shows as well the curve (Amplification vs CC steps), as the dynamic movement of the amplification level.



desc:Midi Volume Control

slider1:0<0,15,1{1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16}>MIDI Input Channel
slider2:1<0,127,1{0 Bank Sel M,1 Mod Wheel M,2 Breath M,3,4 Foot P M,5 Porta M,6 Data Entry M,7 Vol M,8 Balance M,9,10 Pan M,11 Expression M,12 Ctrl 1 M,13 Ctrl 2 M,14,15,16 GP Slider 1,17 GP Slider 2,18 GP Slider 3,19 GP Slider 4,20,21,22,23,24,25,26,27,28,29,30,31,32 Bank Sel L,33 Mod Wheel L,34 Breath L,35,36 Foot P L,37 Porta L,38 Data Entry L,39 Vol L,40 Balance L,41,42 Pan L,43 Expression L,44 Ctrl 1 L,45 Ctrl 2 L,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64 Hold P sw,65 Porta sw,66 Sustenuto sw,67 Soft P sw,68 Legato P sw,69 Hold 2 P sw,70 S.Variation,71 S.Timbre,72 S.Release,73 S.Attack,74 S.Brightness,75 S.Ctrl 6,76 S.Ctrl 7,77 S.Ctrl 8,78 S.Ctrl 9,79 S.Ctrl 10,80 GP B.1 sw,81 GP B.2 sw,82 GP B.3 sw,83 GP B.4 sw,84,85,86,87,88,89,90,91 Effects Lv,92 Trem Lv,93 Chorus Lv,94 Celeste Lv,95 Phaser Lv,96 Data B. Inc,97 Data B. Dec,98 NRP L,99 NRP M,100 RP L,101 RP M,102,103,104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119,120,121,122,123,124,125,126,127}>CC Input
slider3:-0.3<-1,-0.1,0.01>Attenuation per CC step
slider4:0.003<0.0005, 0.003, 0.0001>max step(dB)
//slider5:0<0,1,0.01>Factor (Test)

@init
  modval      = 0;
//  prelevel    = 0;
  maxCCvalue  = 127;
  r4          = log(10)/20;
 
  function f (x) (
    x < limit  ? (
      x*r3;
    ) : (
      exp((maxCCvalue-x) * r5);
    );
  )

@slider
  inChannel  = slider1;
  modcc      = slider2;
  dbperstep  = slider3;
  db20perstep = dbperstep/20;
  p1          = 1 / log(10) / db20perstep;
  p2          = 1 / maxCCvalue;
  p3          = p1 + p2;
  limit      = (-p3+0.5) |0;
  r1          = (maxCCvalue-limit) * dbperstep;
  r2          = exp(log(10)*r1/20);
  r3          = r2 / limit; 
  r5          = dbperstep*r4;
  s1          = exp(log(10)*slider4/20);
  s2          = 1 / s1;
  f1          = f(1);
 
@block
  while (midirecv(offset, msg1, msg2, msg3)) (
    status = msg1 & $xF0;      // Extract message type
    channel = msg1 & $x0F;
    channel == inChannel ? (  // Is it on our channel?
      status == $xB0 ? (      // Is it a controller event?
        msg2 == modcc ? (      // Is it the right CC?
          modval = msg3;
          modval ? (
            outlevel < f1 ? outlevel = f1;
          ); 
          modlevel = f(modval);
//        slider5 = modlevel;                        // test
        );
      );
    );
    midisend(offset, msg1, msg2, msg3); // pass through
  );   
 
  modval ? (
    modstep  = exp( log(modlevel / outlevel) / samplesblock);
    modstep == 1 ? (
      stepping = 0;
    ) : (
      modstep > s1 ? (
        modstep = s1;
      ) : modstep < s2 ? (
        modstep = s2;
      ); 
      stepping = 1;
    ); 
  ) : (
    modstep = s2;
 );   
 
 
@sample
  outlevel *= modstep;
  spl0*=outlevel;
  spl1*=outlevel; 
 
 
@gfx 640 400

gfx_r=gfx_g=gfx_b=0; gfx_a=1;
gfx_x=gfx_y=0;
gfx_rectto(gfx_w,gfx_h);

q1 = gfx_w / maxCCvalue;
q2 = gfx_h;


//gfx_line();
gfx_r=gfx_g=gfx_b=1;
gfx_y = 0;
gfx_x = 0;
x = 0;
while (x<=maxCCvalue) (
  a = x*q1;
  b = gfx_h - f(x)*q2;
  gfx_lineto(a, b, 1);
  x = x+1;
);
gfx_y = 0;
gfx_x = modval*q1;
gfx_lineto(gfx_x, gfx_h);
gfx_x = 0;
gfx_y = gfx_h-outlevel*q2; 
gfx_lineto(gfx_w, gfx_y);

---

Midi Volume plugin