Implement fade in to prevent Triple Osc from clicking

include/Instrument.h

@@ -132,6 +132,9 @@ class LMMS_EXPORT Instrument : public Plugin
 
 
 protected:
+ // fade in to prevent clicks
+ void applyFadeIn(sampleFrame * buf, const NotePlayHandle * _n);
+
  // instruments may use this to apply a soft fade out at the end of
  // notes - method does this only if really less or equal
  // desiredReleaseFrames() frames are left

plugins/triple_oscillator/TripleOscillator.cpp

@@ -364,6 +364,7 @@ void TripleOscillator::playNote( NotePlayHandle * _n,
  osc_l->update( _working_buffer + offset, frames, 0 );
  osc_r->update( _working_buffer + offset, frames, 1 );
 
+ applyFadeIn(_working_buffer, _n);
  applyRelease( _working_buffer, _n );
 
  instrumentTrack()->processAudioBuffer( _working_buffer, frames + offset, _n );

src/core/Instrument.cpp

@@ -23,8 +23,12 @@
  */
 
 #include "Instrument.h"
-#include "InstrumentTrack.h"
+
+#include <cmath>
+
 #include "DummyInstrument.h"
+#include "InstrumentTrack.h"
+#include "lmms_constants.h"
 
 
 Instrument::Instrument(InstrumentTrack * _instrument_track,
@@ -79,7 +83,50 @@ bool Instrument::isFromTrack( const Track * _track ) const
 }
 
 
+void Instrument::applyFadeIn(sampleFrame * buf, const NotePlayHandle * n)
+{
+ // apply only if it's the start of the note
+ if (n->totalFramesPlayed() == 0)
+ {
+ const fpp_t frames = n->framesLeftForCurrentPeriod();
+
+ // zero point crossing counts of all channels
+ int zero_crossings[DEFAULT_CHANNELS] = {0};
+ // maximum zero point crossing of all channels
+ int max_zc = 0;
 
+ // determine the zero point crossing counts
+ for (fpp_t f = 0; f < frames; ++f)
+ {
+ for (ch_cnt_t ch=0; ch < DEFAULT_CHANNELS; ++ch)
+ {
+ if ((buf[f-1][ch] < 0.0 && buf[f][ch] > 0.0) ||
+ (buf[f-1][ch] > 0.0 && buf[f][ch] < 0.0))
+ {
+ ++zero_crossings[ch];
+ if (zero_crossings[ch] > max_zc)
+ {
+ max_zc = zero_crossings[ch];
+ }
+ }
+ }
+ }
+
+ // calculate the length of the fade in
+ fpp_t length = (fpp_t) (
+ ((float)frames - 1) /
+ ((float)max_zc / 2.0f + 1.0f) / 3.0f);
+
+ // apply fade in
+ for (fpp_t f = 0; f < length; ++f)
+ {
+ for (ch_cnt_t ch = 0; ch < DEFAULT_CHANNELS; ++ch)
+ {
+ buf[f][ch] *= 0.5 - 0.5 * cosf(F_PI * (float) f / (float) length);
+ }
+ }
+ }
+}
 
 void Instrument::applyRelease( sampleFrame * buf, const NotePlayHandle * _n )
 {