Update amp.cc to use gain_t for maths (no more double)

Also tweak threshold for LPF, assume gain-differences < 10-e5 as
no-change

diff --git a/libs/ardour/amp.cc b/libs/ardour/amp.cc
index 29d43d60d95100722854288405bd2df96ae55ae8..0ce861ca4a659d97031ca46641a12b6375a0bfa9 100644 (file)
--- a/libs/ardour/amp.cc
+++ b/libs/ardour/amp.cc
@@ -35,8 +35,7 @@
 using namespace ARDOUR;
 using namespace PBD;
 
-// used for low-pass filter denormal protection
-#define GAIN_COEFF_TINY (1e-10) // -200dB
+#define GAIN_COEFF_DELTA (1e-5)
 
 Amp::Amp (Session& s, const std::string& name, boost::shared_ptr<GainControl> gc, bool control_midi_also)
        : Processor(s, "Amp")
@@ -103,9 +102,8 @@ Amp::run (BufferSet& bufs, framepos_t /*start_frame*/, framepos_t /*end_frame*/,
                        }
                }
 
-
-               const double a = 156.825 / _session.nominal_frame_rate(); // 25 Hz LPF; see Amp::apply_gain for details
-               double lpf = _current_gain;
+               const gain_t a = 156.825f / (gain_t)_session.nominal_frame_rate(); // 25 Hz LPF; see Amp::apply_gain for details
+               gain_t lpf = _current_gain;
 
                for (BufferSet::audio_iterator i = bufs.audio_begin(); i != bufs.audio_end(); ++i) {
                        Sample* const sp = i->data();
@@ -116,7 +114,7 @@ Amp::run (BufferSet& bufs, framepos_t /*start_frame*/, framepos_t /*end_frame*/,
                        }
                }
 
-               if (fabs (lpf) < GAIN_COEFF_TINY) {
+               if (fabsf (lpf) < GAIN_COEFF_SMALL) {
                        _current_gain = GAIN_COEFF_ZERO;
                } else {
                        _current_gain = lpf;
@@ -124,20 +122,20 @@ Amp::run (BufferSet& bufs, framepos_t /*start_frame*/, framepos_t /*end_frame*/,
 
        } else { /* manual (scalar) gain */
 
-               gain_t const dg = _gain_control->get_value();
+               gain_t const target_gain = _gain_control->get_value();
 
-               if (_current_gain != dg) {
+               if (fabsf (_current_gain - target_gain) >= GAIN_COEFF_DELTA) {
 
-                       _current_gain = Amp::apply_gain (bufs, _session.nominal_frame_rate(), nframes, _current_gain, dg, _midi_amp);
+                       _current_gain = Amp::apply_gain (bufs, _session.nominal_frame_rate(), nframes, _current_gain, target_gain, _midi_amp);
 
                        /* see note in PluginInsert::connect_and_run ()
                         * set_value_unchecked() won't emit a signal since the value is effectively unchanged
                         */
                        _gain_control->Changed (false, PBD::Controllable::NoGroup);
 
-               } else if (_current_gain != GAIN_COEFF_UNITY) {
+               } else if (target_gain != GAIN_COEFF_UNITY) {
 
-                       /* gain has not changed, but its non-unity */
+                       _current_gain = target_gain;
 
                        if (_midi_amp) {
                                /* don't Trim midi velocity -- only relevant for Midi on Audio tracks */
@@ -157,6 +155,9 @@ Amp::run (BufferSet& bufs, framepos_t /*start_frame*/, framepos_t /*end_frame*/,
                        for (BufferSet::audio_iterator i = bufs.audio_begin(); i != bufs.audio_end(); ++i) {
                                apply_gain_to_buffer (i->data(), nframes, _current_gain);
                        }
+               } else {
+                       /* unity target gain */
+                       _current_gain = target_gain;
                }
        }
 
@@ -166,7 +167,7 @@ Amp::run (BufferSet& bufs, framepos_t /*start_frame*/, framepos_t /*end_frame*/,
 gain_t
 Amp::apply_gain (BufferSet& bufs, framecnt_t sample_rate, framecnt_t nframes, gain_t initial, gain_t target, bool midi_amp)
 {
-        /** Apply a (potentially) declicked gain to the buffers of @a bufs */
+       /** Apply a (potentially) declicked gain to the buffers of @a bufs */
        gain_t rv = target;
 
        if (nframes == 0 || bufs.count().n_total() == 0) {
@@ -211,7 +212,7 @@ Amp::apply_gain (BufferSet& bufs, framecnt_t sample_rate, framecnt_t nframes, ga
        /* Low pass filter coefficient: 1.0 - e^(-2.0 * π * f / 48000) f in Hz.
         * for f << SR,  approx a ~= 6.2 * f / SR;
         */
-       const double a = 156.825 / sample_rate; // 25 Hz LPF
+       const gain_t a = 156.825f / (gain_t)sample_rate; // 25 Hz LPF
 
        for (BufferSet::audio_iterator i = bufs.audio_begin(); i != bufs.audio_end(); ++i) {
                Sample* const buffer = i->data();
@@ -225,8 +226,7 @@ Amp::apply_gain (BufferSet& bufs, framecnt_t sample_rate, framecnt_t nframes, ga
                        rv = lpf;
                }
        }
-       if (fabsf (rv - target) < GAIN_COEFF_TINY) return target;
-       if (fabsf (rv) < GAIN_COEFF_TINY) return GAIN_COEFF_ZERO;
+       if (fabsf (rv - target) < GAIN_COEFF_DELTA) return target;
        return rv;
 }
 
@@ -244,11 +244,11 @@ Amp::declick (BufferSet& bufs, framecnt_t nframes, int dir)
        if (dir < 0) {
                /* fade out: remove more and more of delta from initial */
                delta = -1.0;
-                initial = GAIN_COEFF_UNITY;
+               initial = GAIN_COEFF_UNITY;
        } else {
                /* fade in: add more and more of delta from initial */
                delta = 1.0;
-                initial = GAIN_COEFF_ZERO;
+               initial = GAIN_COEFF_ZERO;
        }
 
        /* Audio Gain */
@@ -265,7 +265,7 @@ Amp::declick (BufferSet& bufs, framecnt_t nframes, int dir)
                /* now ensure the rest of the buffer has the target value applied, if necessary. */
                if (declick != nframes) {
                        if (dir < 0) {
-                                memset (&buffer[declick], 0, sizeof (Sample) * (nframes - declick));
+                               memset (&buffer[declick], 0, sizeof (Sample) * (nframes - declick));
                        }
                }
        }
@@ -275,7 +275,7 @@ Amp::declick (BufferSet& bufs, framecnt_t nframes, int dir)
 gain_t
 Amp::apply_gain (AudioBuffer& buf, framecnt_t sample_rate, framecnt_t nframes, gain_t initial, gain_t target)
 {
-        /* Apply a (potentially) declicked gain to the contents of @a buf
+       /* Apply a (potentially) declicked gain to the contents of @a buf
         * -- used by MonitorProcessor::run()
         */
 
@@ -289,17 +289,16 @@ Amp::apply_gain (AudioBuffer& buf, framecnt_t sample_rate, framecnt_t nframes, g
                return target;
        }
 
-        Sample* const buffer = buf.data();
-       const double a = 156.825 / sample_rate; // 25 Hz LPF, see [other] Amp::apply_gain() above for details
+       Sample* const buffer = buf.data();
+       const gain_t a = 156.825f / (gain_t)sample_rate; // 25 Hz LPF, see [other] Amp::apply_gain() above for details
 
-       double lpf = initial;
-        for (pframes_t nx = 0; nx < nframes; ++nx) {
-                buffer[nx] *= lpf;
+       gain_t lpf = initial;
+       for (pframes_t nx = 0; nx < nframes; ++nx) {
+               buffer[nx] *= lpf;
                lpf += a * (target - lpf);
-        }
+       }
 
-       if (fabs (lpf - target) < GAIN_COEFF_TINY) return target;
-       if (fabs (lpf) < GAIN_COEFF_TINY) return GAIN_COEFF_ZERO;
+       if (fabsf (lpf - target) < GAIN_COEFF_DELTA) return target;
        return lpf;
 }
 
@@ -352,9 +351,9 @@ void
 Amp::apply_simple_gain (AudioBuffer& buf, framecnt_t nframes, gain_t target)
 {
        if (fabsf (target) < GAIN_COEFF_SMALL) {
-                memset (buf.data(), 0, sizeof (Sample) * nframes);
+               memset (buf.data(), 0, sizeof (Sample) * nframes);
        } else if (target != GAIN_COEFF_UNITY) {
-                apply_gain_to_buffer (buf.data(), nframes, target);
+               apply_gain_to_buffer (buf.data(), nframes, target);
        }
 }
 
@@ -419,7 +418,6 @@ Amp::visible() const
  *  gain automationc curves.  Must be called before setup_gain_automation,
  *  and must be called with process lock held.
  */
-
 void
 Amp::set_gain_automation_buffer (gain_t* g)
 {