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// ---------------------------------------------------------------------------
// This file is part of reSID, a MOS6581 SID emulator engine.
// Copyright (C) 2002 Dag Lem <resid@nimrod.no>
//
// 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
// ---------------------------------------------------------------------------
#define __EXTFILT_CC__
#include "extfilt.h"
RESID_NAMESPACE_START
// ----------------------------------------------------------------------------
// Constructor.
// ----------------------------------------------------------------------------
ExternalFilter::ExternalFilter()
{
reset();
enable_filter(true);
set_sampling_parameter(15915.6);
set_chip_model(MOS6581);
}
// ----------------------------------------------------------------------------
// Enable filter.
// ----------------------------------------------------------------------------
void ExternalFilter::enable_filter(bool enable)
{
enabled = enable;
}
// ----------------------------------------------------------------------------
// Setup of the external filter sampling parameters.
// ----------------------------------------------------------------------------
void ExternalFilter::set_sampling_parameter(double pass_freq)
{
static const double pi = 3.1415926535897932385;
// Low-pass: R = 10kOhm, C = 1000pF; w0l = 1/RC = 1/(1e4*1e-9) = 100000
// High-pass: R = 1kOhm, C = 10uF; w0h = 1/RC = 1/(1e3*1e-5) = 100
// Multiply with 1.048576 to facilitate division by 1 000 000 by right-
// shifting 20 times (2 ^ 20 = 1048576).
//w0lp = 104858;
w0hp = 105;
w0lp = (sound_sample) (pass_freq * (2.0 * pi * 1.048576));
}
// ----------------------------------------------------------------------------
// Set chip model.
// ----------------------------------------------------------------------------
void ExternalFilter::set_chip_model(chip_model model)
{
if (model == MOS6581) {
// Maximum mixer DC output level; to be removed if the external
// filter is turned off: ((wave DC + voice DC)*voices + mixer DC)*volume
// See voice.cc and filter.cc for an explanation of the values.
mixer_DC = ((((0x800 - 0x380) + 0x800)*0xff*3 - 0xfff*0xff/18) >> 7)*0x0f;
}
else {
// No DC offsets in the MOS8580.
mixer_DC = 0;
}
}
// ----------------------------------------------------------------------------
// SID reset.
// ----------------------------------------------------------------------------
void ExternalFilter::reset()
{
// State of filter.
Vlp = 0;
Vhp = 0;
Vo = 0;
}
RESID_NAMESPACE_STOP
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