1 files changed, 85 insertions, 0 deletions
diff --git a/libs/ardour/declicker.cc b/libs/ardour/declicker.cc
new file mode 100644
index 0000000000..dd40fe83b2
--- /dev/null
+++ b/libs/ardour/declicker.cc
@@ -0,0 +1,85 @@
+/*
+    Copyright (C) 2006 Paul Davis 
+    
+    This program is free software; you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by the Free
+    Software Foundation; either version 2 of the License, or (at your option)
+    any later version.
+    
+    This program is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+    for more details.
+    
+    You should have received a copy of the GNU General Public License along
+    with this program; if not, write to the Free Software Foundation, Inc.,
+    675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+#include <ardour/declicker.h>
+
+#include <algorithm>
+#include <cmath>
+#include <ardour/buffer_set.h>
+#include <ardour/buffer.h>
+
+namespace ARDOUR {
+
+
+/** Apply a declick operation to the audio buffers of @a bufs */
+void
+Declicker::run (BufferSet& bufs, jack_nframes_t nframes, gain_t initial, gain_t target, bool invert_polarity)
+{
+	if (bufs.count().get(DataType::AUDIO) == 0)
+		return;
+
+	assert(bufs.buffer_capacity(DataType::AUDIO) >= nframes);
+
+	const jack_nframes_t declick = std::min ((jack_nframes_t)4096, nframes);
+	gain_t         delta;
+	double         fractional_shift = -1.0/declick;
+	double         fractional_pos;
+	gain_t         polscale = invert_polarity ? -1.0f : 1.0f;
+
+	if (nframes == 0)
+		return;
+
+	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;
+	}
+
+	for (BufferSet::audio_iterator i = bufs.audio_begin(); i != bufs.audio_end(); ++i) {
+		Sample* const buffer = i->data(nframes);
+
+		fractional_pos = 1.0;
+
+		for (jack_nframes_t nx = 0; nx < declick; ++nx) {
+			buffer[nx] *= polscale * (initial + (delta * (0.5 + 0.5 * cos (M_PI * fractional_pos))));
+			fractional_pos += fractional_shift;
+		}
+		
+		/* now ensure the rest of the buffer has the target value applied, if necessary. */
+		
+		if (declick != nframes) {
+
+			if (invert_polarity) {
+				target = -target;
+			}
+
+			if (target == 0.0) {
+				memset (&buffer[declick], 0, sizeof (Sample) * (nframes - declick));
+			} else if (target != 1.0) {
+				for (jack_nframes_t nx = declick; nx < nframes; ++nx) {
+					buffer[nx] *= target;
+				}
+			}
+		}
+	}
+}
+
+
+} // namespace ARDOUR