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/*
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 "ardour/kmeterdsp.h"
float Kmeterdsp::_omega;
Kmeterdsp::Kmeterdsp (void) :
_z1 (0),
_z2 (0),
_rms (0),
_flag (false)
{
}
Kmeterdsp::~Kmeterdsp (void)
{
}
void Kmeterdsp::init (int fsamp)
{
_omega = 9.72f / fsamp; // ballistic filter coefficient
}
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::reset ()
{
_z1 = _z2 = _rms = .0f;
_flag = false;
}
/* vi:set ts=8 sts=8 sw=4: */
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