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Copyright (C) 2008-2011 Fons Adriaensen <fons@linuxaudio.org>
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Adopted for Ardour 2013 by Robin Gareus <robin@gareus.org>
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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#include "ardour/kmeterdsp.h"
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float Kmeterdsp::_omega;
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Kmeterdsp::Kmeterdsp (void) :
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Kmeterdsp::~Kmeterdsp (void)
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void Kmeterdsp::init (int fsamp)
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_omega = 9.72f / fsamp; // ballistic filter coefficient
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void Kmeterdsp::process (float *p, int n)
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// Called by JACK's process callback.
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// p : pointer to sample buffer
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// n : number of samples to process
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z1 = _z1 > 50 ? 50 : (_z1 < 0 ? 0 : _z1);
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z2 = _z2 > 50 ? 50 : (_z2 < 0 ? 0 : _z2);
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// Perform filtering. The second filter is evaluated
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// only every 4th sample - this is just an optimisation.
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n /= 4; // Loop is unrolled by 4.
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z1 += _omega * (s - z1); // Update first filter.
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z1 += _omega * (s - z1); // Update first filter.
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z1 += _omega * (s - z1); // Update first filter.
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z1 += _omega * (s - z1); // Update first filter.
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z2 += 4 * _omega * (z1 - z2); // Update second filter.
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if (isnan(z1)) z1 = 0;
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if (isnan(z2)) z2 = 0;
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// Save filter state. The added constants avoid denormals.
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s = sqrtf (2.0f * z2);
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if (_flag) // Display thread has read the rms value.
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// Adjust RMS value and update maximum since last read().
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if (s > _rms) _rms = s;
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/* Returns highest _rms value since last call */
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float Kmeterdsp::read ()
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_flag = true; // Resets _rms in next process().
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void Kmeterdsp::reset ()
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_z1 = _z2 = _rms = .0f;
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/* vi:set ts=8 sts=8 sw=4: */