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// Game_Music_Emu 0.6-pre. http://www.slack.net/~ant/
#include "Downsampler.h"
/* Copyright (C) 2004-2008 Shay Green. This module is free software; you
can redistribute it and/or modify it under the terms of the GNU Lesser
General Public License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version. This
module 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 Lesser General Public License for more
details. You should have received a copy of the GNU Lesser General Public
License along with this module; if not, write to the Free Software Foundation,
Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */
#include "blargg_source.h"
int const shift = 14;
int const unit = 1 << shift;
void Downsampler::clear_()
{
pos = 0;
Resampler::clear_();
}
Downsampler::Downsampler()
{
clear();
}
blargg_err_t Downsampler::set_rate_( double new_factor )
{
step = (int) (new_factor * unit + 0.5);
return Resampler::set_rate_( 1.0 / unit * step );
}
Resampler::sample_t const* Downsampler::resample_( sample_t** out_,
sample_t const* out_end, sample_t const in [], int in_size )
{
in_size -= write_offset;
if ( in_size > 0 )
{
sample_t* BLARGG_RESTRICT out = *out_;
sample_t const* const in_end = in + in_size;
int const step = this->step;
int pos = this->pos;
// TODO: IIR filter, then linear resample
// TODO: detect skipped sample, allowing merging of IIR and resample?
do
{
#define INTERP( i, out )\
out = (in [0 + i] * (unit - pos) + ((in [2 + i] + in [4 + i] + in [6 + i]) << shift) +\
in [8 + i] * pos) >> (shift + 2);
int out_0;
INTERP( 0, out_0 )
INTERP( 1, out [0] = out_0; out [1] )
out += stereo;
pos += step;
in += ((unsigned) pos >> shift) * stereo;
pos &= unit - 1;
}
while ( in < in_end && out < out_end );
this->pos = pos;
*out_ = out;
}
return in;
}
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