allanger/ardour
1
0
Fork 0
Code Issues Pull Requests 1 Actions Packages Projects Releases Activity

low-pass filter gain-fader.

Browse Source 
fixes various fader zipper noise issues.
It voids sample accuate fader automation (the fader-gain
is low-pass filtered at 10Hz). Yet all musical purposes this
makes a lot more sense than sample accuracy anyway.
This commit is contained in:
Robin Gareus
2015-04-07 05:21:57 +02:00
parent 528f945ba3
commit 83519faffb
5 changed files with 72 additions and 84 deletions
Download Patch File Download Diff File Expand all files Collapse all files

142
libs/ardour/amp.cc
View File

@@ -41,6 +41,7 @@ Amp::Amp (Session& s)
, _apply_gain(true)
, _apply_gain_automation(false)
, _current_gain(1.0)
, _current_automation_frame (INT64_MAX)
, _gain_automation_buffer(0)
{
Evoral::Parameter p (GainAutomation);
@@ -88,14 +89,23 @@ Amp::run (BufferSet& bufs, framepos_t /*start_frame*/, framepos_t /*end_frame*/,
gain_t* gab = _gain_automation_buffer;
assert (gab);
const float a = 62.78 / _session.nominal_frame_rate(); // 10 Hz LPF
float lpf = _current_gain;
for (BufferSet::audio_iterator i = bufs.audio_begin(); i != bufs.audio_end(); ++i) {
Sample* const sp = i->data();
lpf = _current_gain;
for (pframes_t nx = 0; nx < nframes; ++nx) {
sp[nx] *= gab[nx];
sp[nx] *= lpf;
lpf += a * (gab[nx] - lpf);
}
}
_current_gain = gab[nframes-1];
if (lpf < 1e-10) {
_current_gain = 0;
} else {
_current_gain = lpf;
}
} else { /* manual (scalar) gain */
@@ -103,8 +113,7 @@ Amp::run (BufferSet& bufs, framepos_t /*start_frame*/, framepos_t /*end_frame*/,
if (_current_gain != dg) {
Amp::apply_gain (bufs, nframes, _current_gain, dg);
_current_gain = dg;
_current_gain = Amp::apply_gain (bufs, _session.nominal_frame_rate(), nframes, _current_gain, dg);
} else if (_current_gain != 1.0f) {
@@ -133,39 +142,34 @@ Amp::run (BufferSet& bufs, framepos_t /*start_frame*/, framepos_t /*end_frame*/,
_active = _pending_active;
}
void
Amp::apply_gain (BufferSet& bufs, framecnt_t nframes, gain_t initial, gain_t target)
gain_t
Amp::apply_gain (BufferSet& bufs, framecnt_t sample_rate, framecnt_t nframes, gain_t initial, gain_t target)
{
/** 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) {
return;
return initial;
}
// if we don't need to declick, defer to apply_simple_gain
if (initial == target) {
apply_simple_gain (bufs, nframes, target);
return;
}
const framecnt_t declick = std::min ((framecnt_t) 128, nframes);
gain_t delta;
double fractional_shift = -1.0/declick;
double fractional_pos;
if (target < initial) {
/* fade out: remove more and more of delta from initial */
delta = -(initial - target);
} else {
/* fade in: add more and more of delta from initial */
delta = target - initial;
return target;
}
/* MIDI Gain */
for (BufferSet::midi_iterator i = bufs.midi_begin(); i != bufs.midi_end(); ++i) {
gain_t delta;
if (target < initial) {
/* fade out: remove more and more of delta from initial */
delta = -(initial - target);
} else {
/* fade in: add more and more of delta from initial */
delta = target - initial;
}
MidiBuffer& mb (*i);
for (MidiBuffer::iterator m = mb.begin(); m != mb.end(); ++m) {
@@ -180,35 +184,35 @@ Amp::apply_gain (BufferSet& bufs, framecnt_t nframes, gain_t initial, gain_t tar
/* Audio Gain */
/* 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
for (BufferSet::audio_iterator i = bufs.audio_begin(); i != bufs.audio_end(); ++i) {
Sample* const buffer = i->data();
float lpf = initial;
fractional_pos = 1.0;
for (pframes_t nx = 0; nx < declick; ++nx) {
buffer[nx] *= (initial + (delta * (0.5 + 0.5 * cos (M_PI * fractional_pos))));
fractional_pos += fractional_shift;
for (pframes_t nx = 0; nx < nframes; ++nx) {
buffer[nx] *= lpf;
lpf += a * (target - lpf);
}
/* now ensure the rest of the buffer has the target value applied, if necessary. */
if (declick != nframes) {
if (target == 0.0) {
memset (&buffer[declick], 0, sizeof (Sample) * (nframes - declick));
} else if (target != 1.0) {
apply_gain_to_buffer (&buffer[declick], nframes - declick, target);
}
if (i == bufs.audio_begin()) {
rv = lpf;
}
}
// 1e-10 ~ 200dB, prevent denormals.
if (rv < 1e-10) return 0;
if (fabsf(rv - 1.0) < 1e-10) return 1.0;
return rv;
}
void
Amp::declick (BufferSet& bufs, framecnt_t nframes, int dir)
{
/* Almost exactly like ::apply_gain() but skips MIDI buffers and has fixed initial+target
values.
*/
/* Similar to ::apply_gain() but skips MIDI buffers
* and use cos() Sigmoid decay with fixed initial+target values.
*/
if (nframes == 0 || bufs.count().n_total() == 0) {
return;
@@ -256,55 +260,36 @@ Amp::declick (BufferSet& bufs, framecnt_t nframes, int dir)
}
}
void
Amp::apply_gain (AudioBuffer& buf, framecnt_t nframes, gain_t initial, gain_t target)
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()
*/
if (nframes == 0) {
return;
return initial;
}
// if we don't need to declick, defer to apply_simple_gain
if (initial == target) {
apply_simple_gain (buf, nframes, target);
return;
return target;
}
const framecnt_t declick = std::min ((framecnt_t) 128, nframes);
gain_t delta;
double fractional_shift = -1.0/declick;
double fractional_pos;
if (target < initial) {
/* fade out: remove more and more of delta from initial */
delta = -(initial - target);
} else {
/* fade in: add more and more of delta from initial */
delta = target - initial;
}
Sample* const buffer = buf.data();
const float a = 62.78 / sample_rate; // 10 Hz LPF, see [other] Amp::apply_gain() above,
fractional_pos = 1.0;
for (pframes_t nx = 0; nx < declick; ++nx) {
buffer[nx] *= (initial + (delta * (0.5 + 0.5 * cos (M_PI * fractional_pos))));
fractional_pos += fractional_shift;
float lpf = initial;
for (pframes_t nx = 0; nx < nframes; ++nx) {
buffer[nx] *= lpf;
lpf += a * (target - lpf);
}
/* now ensure the rest of the buffer has the target value applied, if necessary. */
if (declick != nframes) {
if (target == 0.0) {
memset (&buffer[declick], 0, sizeof (Sample) * (nframes - declick));
} else if (target != 1.0) {
apply_gain_to_buffer (&buffer[declick], nframes - declick, target);
}
}
if (lpf < 1e-10) return 0;
if (fabsf(lpf - 1.0) < 1e-10) return 1.0;
return lpf;
}
void
@@ -452,8 +437,13 @@ Amp::setup_gain_automation (framepos_t start_frame, framepos_t end_frame, framec
assert (_gain_automation_buffer);
_apply_gain_automation = _gain_control->list()->curve().rt_safe_get_vector (
start_frame, end_frame, _gain_automation_buffer, nframes);
if (start_frame != _current_automation_frame) {
_current_gain = _gain_automation_buffer[0];
}
_current_automation_frame = end_frame;
} else {
_apply_gain_automation = false;
_current_automation_frame = INT64_MAX;
}
}

5
libs/ardour/ardour/amp.h
View File

@@ -59,10 +59,10 @@ public:
XMLNode& state (bool full);
int set_state (const XMLNode&, int version);
static void apply_gain (BufferSet& bufs, framecnt_t nframes, gain_t initial, gain_t target);
static gain_t apply_gain (BufferSet& bufs, framecnt_t sample_rate, framecnt_t nframes, gain_t initial, gain_t target);
static void apply_simple_gain(BufferSet& bufs, framecnt_t nframes, gain_t target);
static void apply_gain (AudioBuffer& buf, framecnt_t nframes, gain_t initial, gain_t target);
static gain_t apply_gain (AudioBuffer& buf, framecnt_t sample_rate, framecnt_t nframes, gain_t initial, gain_t target);
static void apply_simple_gain(AudioBuffer& buf, framecnt_t nframes, gain_t target);
static void declick (BufferSet& bufs, framecnt_t nframes, int dir);
@@ -111,6 +111,7 @@ private:
bool _apply_gain;
bool _apply_gain_automation;
float _current_gain;
framepos_t _current_automation_frame;
boost::shared_ptr<GainControl> _gain_control;

3
libs/ardour/delivery.cc
View File

@@ -262,8 +262,7 @@ Delivery::run (BufferSet& bufs, framepos_t start_frame, framepos_t end_frame, pf
if (tgain != _current_gain) {
/* target gain has changed */
Amp::apply_gain (bufs, nframes, _current_gain, tgain);
_current_gain = tgain;
_current_gain = Amp::apply_gain (bufs, _session.nominal_frame_rate(), nframes, _current_gain, tgain);
} else if (tgain == 0.0) {

3
libs/ardour/internal_send.cc
View File

@@ -194,8 +194,7 @@ InternalSend::run (BufferSet& bufs, framepos_t start_frame, framepos_t end_frame
/* target gain has changed */
Amp::apply_gain (mixbufs, nframes, _current_gain, tgain);
_current_gain = tgain;
_current_gain = Amp::apply_gain (mixbufs, _session.nominal_frame_rate(), nframes, _current_gain, tgain);
} else if (tgain == 0.0) {

3
libs/ardour/monitor_processor.cc
View File

@@ -301,8 +301,7 @@ MonitorProcessor::run (BufferSet& bufs, framepos_t /*start_frame*/, framepos_t /
if (target_gain != _channels[chn]->current_gain || target_gain != 1.0f) {
Amp::apply_gain (*b, nframes, _channels[chn]->current_gain, target_gain);
_channels[chn]->current_gain = target_gain;
_channels[chn]->current_gain = Amp::apply_gain (*b, _session.nominal_frame_rate(), nframes, _channels[chn]->current_gain, target_gain);
}
++chn;