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// ---------------------------------------------------------------------------
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// This file is part of reSID, a MOS6581 SID emulator engine.
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// Copyright (C) 2004 Dag Lem <resid@nimrod.no>
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//
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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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//
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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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//
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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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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// ---------------------------------------------------------------------------
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#define __EXTFILT_CC__
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#include "extfilt.h"
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RESID_NAMESPACE_START
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// ----------------------------------------------------------------------------
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// Constructor.
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// ----------------------------------------------------------------------------
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ExternalFilter::ExternalFilter()
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{
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reset();
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enable_filter(true);
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set_sampling_parameter(15915.6);
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set_chip_model(MOS6581);
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}
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// ----------------------------------------------------------------------------
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// Enable filter.
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// ----------------------------------------------------------------------------
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void ExternalFilter::enable_filter(bool enable)
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{
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enabled = enable;
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}
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// ----------------------------------------------------------------------------
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// Setup of the external filter sampling parameters.
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// ----------------------------------------------------------------------------
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void ExternalFilter::set_sampling_parameter(float pass_freq)
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{
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static const float pi = 3.1415926535897932385;
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// Low-pass: R = 10kOhm, C = 1000pF; w0l = 1/RC = 1/(1e4*1e-9) = 100000
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// High-pass: R = 1kOhm, C = 10uF; w0h = 1/RC = 1/(1e3*1e-5) = 100
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// Multiply with 1.048576 to facilitate division by 1 000 000 by right-
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// shifting 20 times (2 ^ 20 = 1048576).
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w0hp = 105;
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w0lp = (sound_sample) (pass_freq * (2.0 * pi * 1.048576));
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if (w0lp > 104858)
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w0lp = 104858;
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}
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// ----------------------------------------------------------------------------
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// Set chip model.
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// ----------------------------------------------------------------------------
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void ExternalFilter::set_chip_model(chip_model model)
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{
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if (model == MOS6581) {
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// Maximum mixer DC output level; to be removed if the external
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// filter is turned off: ((wave DC + voice DC)*voices + mixer DC)*volume
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// See voice.cc and filter.cc for an explanation of the values.
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mixer_DC = ((((0x800 - 0x380) + 0x800)*0xff*3 - 0xfff*0xff/18) >> 7)*0x0f;
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}
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else {
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// No DC offsets in the MOS8580.
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mixer_DC = 0;
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}
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}
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// ----------------------------------------------------------------------------
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// SID reset.
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// ----------------------------------------------------------------------------
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void ExternalFilter::reset()
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{
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// State of filter.
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Vlp = 0;
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Vhp = 0;
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Vo = 0;
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}
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RESID_NAMESPACE_STOP
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