Calibrate pitch envelope

The rate was too slow, and not adaptive to sample rate. However, the
"TAKE OFF" sample still sounds too fast, so more investigation is
necessary.

cpp/src/dx7note.cc

@@ -170,7 +170,7 @@ void Dx7Note::init(const char patch[156], int midinote, int velocity) {
     rates[i] = patch[126 + i];
     levels[i] = patch[130 + i];
   }
-  pitchenv_.init(rates, levels);
+  pitchenv_.set(rates, levels);
   algorithm_ = patch[134];
   int feedback = patch[135];
   fb_shift_ = feedback != 0 ? 8 - feedback : 16;
@@ -190,7 +190,6 @@ void Dx7Note::compute(int32_t *buf, int32_t lfo_val, int32_t lfo_delay) {
     int32_t level = env_[op].getsample();
     int32_t gain = Exp2::lookup(level - (14 * (1 << 24)));
     //int32_t gain = pow(2, 10 + level * (1.0 / (1 << 24)));
-    // TODO: probably don't apply pitch env to fixed freq
     params_[op].freq = Freqlut::lookup(basepitch_[op] + pitchmod);
     params_[op].gain[1] = gain;
   }

cpp/src/pitchenv.cc

@@ -19,7 +19,13 @@
 
 using namespace std;
 
-void PitchEnv::init(const int r[4], const int l[4]) {
+int PitchEnv::unit_;
+
+void PitchEnv::init(double sample_rate) {
+  unit_ = N * (1 << 24) / (21.3 * sample_rate) + 0.5;
+}
+
+void PitchEnv::set(const int r[4], const int l[4]) {
   for (int i = 0; i < 4; i++) {
     rates_[i] = r[i];
     levels_[i] = l[i];
@@ -81,9 +87,7 @@ void PitchEnv::advance(int newix) {
     targetlevel_ = pitchtab[newlevel] << 19;
     rising_ = (targetlevel_ > level_);
 
-    // TODO: adapt to sample rate
-    // const is 1<<12 / 0.0104 * 44100
-    inc_ = ratetab[rates_[ix_]] * (8 * N);
+    inc_ = ratetab[rates_[ix_]] * unit_;
   }
 }
 

cpp/src/pitchenv.h

@@ -21,16 +21,18 @@
 
 class PitchEnv {
  public:
+  static void init(double sample_rate);
 
   // The rates and levels arrays are calibrated to match the Dx7 parameters
   // (ie, value 0..99).
-  void init(const int rates[4], const int levels[4]);
+  void set(const int rates[4], const int levels[4]);
 
   // Result is in Q24/octave
   int32_t getsample();
 
   void keydown(bool down);
  private:
+  static int unit_;
   int rates_[4];
   int levels_[4];
   int32_t level_;

cpp/src/synth_unit.cc

@@ -29,6 +29,7 @@
 #include "freqlut.h"
 #include "sin.h"
 #include "exp2.h"
+#include "pitchenv.h"
 #include "patch.h"
 #include "synth_unit.h"
 #include "aligned_buf.h"
@@ -50,6 +51,7 @@ void SynthUnit::Init(double sample_rate) {
   Exp2::init();
   Sin::init();
   Lfo::init(sample_rate);
+  PitchEnv::init(sample_rate);
 }
 
 SynthUnit::SynthUnit(RingBuffer *ring_buffer) {