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, 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

include/NotePlayHandle.h

@@ -49,6 +49,9 @@ class LMMS_EXPORT NotePlayHandle : public PlayHandle, public Note
  void * m_pluginData;
  std::unique_ptr<BasicFilters<>> m_filter;
 
+ // length of the declicking fade in
+ fpp_t m_fadeInLength;
+
  // specifies origin of NotePlayHandle
  enum Origins
  {

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,
@@ -78,8 +82,96 @@ bool Instrument::isFromTrack( const Track * _track ) const
  return( m_instrumentTrack == _track );
 }
 
+// helper function for Instrument::applyFadeIn
+int count_zero_crossings(sampleFrame *buf,fpp_t start, fpp_t frames)
+{
+ // 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 = start; f < frames; ++f)
+ {
+ for (ch_cnt_t ch=0; ch < DEFAULT_CHANNELS; ++ch)
+ {
+ // we don't want to count [-1, 0, 1] as two crossings
+ 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];
+ }
+ }
+ }
+ }
+
+ return max_zc;
+}
+
+// helper function for Instrument::applyFadeIn
+fpp_t getFadeInLength(float max_length, fpp_t frames, int zero_crossings)
+{
+ // calculate the length of the fade in
+ // Length is inversely proportional to the max of zero_crossings,
+ // because for low frequencies, we need a longer fade in to
+ // prevent clicking.
+ return (fpp_t) (max_length / ((float)zero_crossings / ((float)frames/128.0f) + 1.0f));
+}
+
 
+void Instrument::applyFadeIn(sampleFrame * buf, NotePlayHandle * n)
+{
+ const static float MAX_FADE_IN_LENGTH = 85.0;
+ f_cnt_t total = n->totalFramesPlayed();
+ if (total == 0)
+ {
+ const fpp_t frames = n->framesLeftForCurrentPeriod();
+ const f_cnt_t offset = n->offset();
 
+ // We need to skip the first sample because it almost always
+ // produces a zero crossing; it's not helpful while
+ // determining the fade in length. Hence 1
+ int max_zc = count_zero_crossings(buf, offset+1, offset+frames);
+
+ fpp_t length = getFadeInLength(MAX_FADE_IN_LENGTH,frames,max_zc);
+ n->m_fadeInLength = length;
+
+ // apply fade in
+ length = length < frames ? length : frames;
+ for (fpp_t f = 0; f < length; ++f)
+ {
+ for (ch_cnt_t ch = 0; ch < DEFAULT_CHANNELS; ++ch)
+ {
+ buf[offset+f][ch] *= 0.5 - 0.5 * cosf(F_PI * (float) f / (float)n->m_fadeInLength);
+ }
+ }
+ }
+ else if(total < n->m_fadeInLength)
+ {
+ const fpp_t frames = n->framesLeftForCurrentPeriod();
+
+ int new_zc = count_zero_crossings(buf, 1, frames);
+ fpp_t new_length = getFadeInLength(MAX_FADE_IN_LENGTH, frames, new_zc);
+
+ for (fpp_t f = 0; f < frames; ++f)
+ {
+ for (ch_cnt_t ch = 0; ch < DEFAULT_CHANNELS; ++ch)
+ {
+ float currentLength = n->m_fadeInLength*(1.0f-(float)f/frames) + new_length*((float)f/frames);
+ buf[f][ch] *= 0.5 - 0.5 * cosf(F_PI * (float) (total+f) / currentLength);
+ if(total+f >= currentLength)
+ {
+ n->m_fadeInLength = currentLength;
+ return;
+ }
+ }
+ }
+ n->m_fadeInLength = new_length;
+ }
+}
 
 void Instrument::applyRelease( sampleFrame * buf, const NotePlayHandle * _n )
 {
@@ -109,6 +201,3 @@ QString Instrument::fullDisplayName() const
 {
  return instrumentTrack()->displayName();
 }
-
-
-