mirror of
https://github.com/ZDoom/raze-gles.git
synced 2024-11-14 16:40:40 +00:00
97 lines
2.8 KiB
C++
97 lines
2.8 KiB
C++
// Game_Music_Emu https://bitbucket.org/mpyne/game-music-emu/
|
|
|
|
#include "Kss_Scc_Apu.h"
|
|
|
|
/* Copyright (C) 2006 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"
|
|
|
|
// Tones above this frequency are treated as disabled tone at half volume.
|
|
// Power of two is more efficient (avoids division).
|
|
unsigned const inaudible_freq = 16384;
|
|
|
|
int const wave_size = 0x20;
|
|
|
|
void Scc_Apu::run_until( blip_time_t end_time )
|
|
{
|
|
for ( int index = 0; index < osc_count; index++ )
|
|
{
|
|
osc_t& osc = oscs [index];
|
|
|
|
Blip_Buffer* const output = osc.output;
|
|
if ( !output )
|
|
continue;
|
|
output->set_modified();
|
|
|
|
blip_time_t period = (regs [0x80 + index * 2 + 1] & 0x0F) * 0x100 +
|
|
regs [0x80 + index * 2] + 1;
|
|
int volume = 0;
|
|
if ( regs [0x8F] & (1 << index) )
|
|
{
|
|
blip_time_t inaudible_period = (blargg_ulong) (output->clock_rate() +
|
|
inaudible_freq * 32) / (inaudible_freq * 16);
|
|
if ( period > inaudible_period )
|
|
volume = (regs [0x8A + index] & 0x0F) * (amp_range / 256 / 15);
|
|
}
|
|
|
|
int8_t const* wave = (int8_t*) regs + index * wave_size;
|
|
if ( index == osc_count - 1 )
|
|
wave -= wave_size; // last two oscs share wave
|
|
{
|
|
int amp = wave [osc.phase] * volume;
|
|
int delta = amp - osc.last_amp;
|
|
if ( delta )
|
|
{
|
|
osc.last_amp = amp;
|
|
synth.offset( last_time, delta, output );
|
|
}
|
|
}
|
|
|
|
blip_time_t time = last_time + osc.delay;
|
|
if ( time < end_time )
|
|
{
|
|
if ( !volume )
|
|
{
|
|
// maintain phase
|
|
blargg_long count = (end_time - time + period - 1) / period;
|
|
osc.phase = (osc.phase + count) & (wave_size - 1);
|
|
time += count * period;
|
|
}
|
|
else
|
|
{
|
|
|
|
int phase = osc.phase;
|
|
int last_wave = wave [phase];
|
|
phase = (phase + 1) & (wave_size - 1); // pre-advance for optimal inner loop
|
|
|
|
do
|
|
{
|
|
int amp = wave [phase];
|
|
phase = (phase + 1) & (wave_size - 1);
|
|
int delta = amp - last_wave;
|
|
if ( delta )
|
|
{
|
|
last_wave = amp;
|
|
synth.offset( time, delta * volume, output );
|
|
}
|
|
time += period;
|
|
}
|
|
while ( time < end_time );
|
|
|
|
osc.phase = phase = (phase - 1) & (wave_size - 1); // undo pre-advance
|
|
osc.last_amp = wave [phase] * volume;
|
|
}
|
|
}
|
|
osc.delay = time - end_time;
|
|
}
|
|
last_time = end_time;
|
|
}
|