experimental RMS-meter and peak-signal (vs peak-power) query

1 files changed, 116 insertions, 0 deletions

diff --git a/libs/ardour/kmeterdsp.cc b/libs/ardour/kmeterdsp.cc
new file mode 100644
index 0000000000..77d1a87a81
--- /dev/null
+++ b/libs/ardour/kmeterdsp.cc
@@ -0,0 +1,116 @@
+/*
+    Copyright (C) 2008-2011 Fons Adriaensen <fons@linuxaudio.org>
+		Adopted for Ardour 2013 by Robin Gareus <robin@gareus.org>
+
+    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 <math.h>
+#include "kmeterdsp.h"
+
+float  Kmeterdsp::_omega;
+
+Kmeterdsp::Kmeterdsp (void) :
+    _z1 (0),
+    _z2 (0),
+    _rms (0),
+    _flag (false)
+{
+}
+
+
+Kmeterdsp::~Kmeterdsp (void)
+{
+}
+
+
+void Kmeterdsp::process (float *p, int n)
+{
+    // Called by JACK's process callback.
+    //
+    // p : pointer to sample buffer
+    // n : number of samples to process
+
+    float  s, t, z1, z2;
+
+    if (_flag) // Display thread has read the rms value.
+    {
+	_rms  = 0;
+	_flag = false;
+    }
+
+    // Get filter state.
+    z1 = _z1;
+    z2 = _z2;
+
+    // Process n samples. Find digital peak value for this
+    // period and perform filtering. The second filter is
+    // evaluated only every 4th sample - this is just an
+    // optimisation.
+    t = 0;
+    n /= 4;  // Loop is unrolled by 4.
+    while (n--)
+    {
+	s = *p++;
+	s *= s;
+	if (t < s) t = s;             // Update digital peak.
+	z1 += _omega * (s - z1);      // Update first filter.
+	s = *p++;
+	s *= s;
+	if (t < s) t = s;             // Update digital peak.
+	z1 += _omega * (s - z1);      // Update first filter.
+	s = *p++;
+	s *= s;
+	if (t < s) t = s;             // Update digital peak.
+	z1 += _omega * (s - z1);      // Update first filter.
+	s = *p++;
+	s *= s;
+	if (t < s) t = s;             // Update digital peak.
+	z1 += _omega * (s - z1);      // Update first filter.
+        z2 += 4 * _omega * (z1 - z2); // Update second filter.
+    }
+    t = sqrtf (t);
+
+    // Save filter state. The added constants avoid denormals.
+    _z1 = z1 + 1e-20f;
+    _z2 = z2 + 1e-20f;
+
+    // Adjust RMS value and update maximum since last read().
+    s = sqrtf (2 * z2);
+    if (s > _rms) _rms = s;
+}
+
+
+/* Returns highest _rms value since last call */
+float Kmeterdsp::read ()
+{
+    float rv= _rms;
+    _flag = true; // Resets _rms in next process().
+    return rv;
+}
+
+void Kmeterdsp::init (int fsamp)
+{
+    _omega = 9.72f / fsamp; // ballistic filter coefficient
+}
+
+void Kmeterdsp::reset ()
+{
+    _z1 = _z2 = _rms = 0.0;
+    _flag=false;
+}
+
+/* vi:set ts=8 sts=8 sw=8: */