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authorRobin Gareus <robin@gareus.org>2015-04-26 02:30:06 +0200
committerRobin Gareus <robin@gareus.org>2015-04-26 02:48:00 +0200
commit1b54b85da0f7fdda5940392318dc093b2ca32fde (patch)
tree0a8f30ec33c8beb0ea141faeea8ab6d4f41a60b6 /libs/ardour/amp.cc
parenta43901ead9eeae05b1c62f13d5c699bbaf3df22d (diff)
update amp for negative (polarity-invert) gain
fixes monitor-section “inv”
Diffstat (limited to 'libs/ardour/amp.cc')
-rw-r--r--libs/ardour/amp.cc35
1 files changed, 19 insertions, 16 deletions
diff --git a/libs/ardour/amp.cc b/libs/ardour/amp.cc
index efe776af24..caf00dc496 100644
--- a/libs/ardour/amp.cc
+++ b/libs/ardour/amp.cc
@@ -35,6 +35,9 @@
using namespace ARDOUR;
using namespace PBD;
+// used for low-pass filter denormal protection
+#define GAIN_COEFF_TINY (1e-10) // -200dB
+
Amp::Amp (Session& s, std::string type)
: Processor(s, "Amp")
, _apply_gain(true)
@@ -104,8 +107,8 @@ Amp::run (BufferSet& bufs, framepos_t /*start_frame*/, framepos_t /*end_frame*/,
}
- const float a = 62.78 / _session.nominal_frame_rate(); // 10 Hz LPF
- float lpf = _current_gain;
+ const double a = 62.78 / _session.nominal_frame_rate(); // 10 Hz LPF; see Amp::apply_gain for details
+ double lpf = _current_gain;
for (BufferSet::audio_iterator i = bufs.audio_begin(); i != bufs.audio_end(); ++i) {
Sample* const sp = i->data();
@@ -116,8 +119,8 @@ Amp::run (BufferSet& bufs, framepos_t /*start_frame*/, framepos_t /*end_frame*/,
}
}
- if (lpf < 1e-10) {
- _current_gain = 0;
+ if (fabs (lpf) < GAIN_COEFF_TINY) {
+ _current_gain = GAIN_COEFF_ZERO;
} else {
_current_gain = lpf;
}
@@ -207,11 +210,11 @@ 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 float a = 62.78 / sample_rate; // 10 Hz LPF
+ const double a = 62.78 / sample_rate; // 10 Hz LPF
for (BufferSet::audio_iterator i = bufs.audio_begin(); i != bufs.audio_end(); ++i) {
Sample* const buffer = i->data();
- float lpf = initial;
+ double lpf = initial;
for (pframes_t nx = 0; nx < nframes; ++nx) {
buffer[nx] *= lpf;
@@ -221,9 +224,8 @@ Amp::apply_gain (BufferSet& bufs, framecnt_t sample_rate, framecnt_t nframes, ga
rv = lpf;
}
}
- // 1e-10 ~ 200dB, prevent denormals.
- if (rv < 1e-10) return 0;
- if (fabsf(rv - 1.0) < 1e-10) return 1.0;
+ if (fabsf (rv - target) < GAIN_COEFF_TINY) return target;
+ if (fabsf (rv) < GAIN_COEFF_TINY) return GAIN_COEFF_ZERO;
return rv;
}
@@ -287,23 +289,23 @@ Amp::apply_gain (AudioBuffer& buf, framecnt_t sample_rate, framecnt_t nframes, g
}
Sample* const buffer = buf.data();
- const float a = 62.78 / sample_rate; // 10 Hz LPF, see [other] Amp::apply_gain() above,
+ const double a = 62.78 / sample_rate; // 10 Hz LPF, see [other] Amp::apply_gain() above,
- float lpf = initial;
+ double lpf = initial;
for (pframes_t nx = 0; nx < nframes; ++nx) {
buffer[nx] *= lpf;
lpf += a * (target - lpf);
}
- if (lpf < 1e-10) return 0; // TODO use GAIN_COEFF_TINY or _DENORMAL
- if (fabsf(lpf - GAIN_COEFF_UNITY) < 1e-10) return GAIN_COEFF_UNITY;
+ if (fabs (lpf - target) < GAIN_COEFF_TINY) return target;
+ if (fabs (lpf) < GAIN_COEFF_TINY) return GAIN_COEFF_ZERO;
return lpf;
}
void
Amp::apply_simple_gain (BufferSet& bufs, framecnt_t nframes, gain_t target, bool midi_amp)
{
- if (target < GAIN_COEFF_SMALL) {
+ if (fabsf (target) < GAIN_COEFF_SMALL) {
if (midi_amp) {
/* don't Trim midi velocity -- only relevant for Midi on Audio tracks */
@@ -348,7 +350,7 @@ Amp::apply_simple_gain (BufferSet& bufs, framecnt_t nframes, gain_t target, bool
void
Amp::apply_simple_gain (AudioBuffer& buf, framecnt_t nframes, gain_t target)
{
- if (target < GAIN_COEFF_SMALL) {
+ if (fabsf (target) < GAIN_COEFF_SMALL) {
memset (buf.data(), 0, sizeof (Sample) * nframes);
} else if (target != GAIN_COEFF_UNITY) {
apply_gain_to_buffer (buf.data(), nframes, target);
@@ -360,7 +362,8 @@ Amp::inc_gain (gain_t factor, void *src)
{
float desired_gain = _gain_control->user_double();
- if (desired_gain < GAIN_COEFF_SMALL) {
+ if (fabsf (desired_gain) < GAIN_COEFF_SMALL) {
+ // really?! what's the idea here?
set_gain (0.000001f + (0.000001f * factor), src);
} else {
set_gain (desired_gain + (desired_gain * factor), src);