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plugout_altmidi.c
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plugout_altmidi.c
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/*
* gbsplay is a Gameboy sound player
*
* alternative MIDI output plugin
*
* 2006-2022 (C) by Christian Garbs <[email protected]>
* Vegard Nossum
*
* Licensed under GNU GPL v1 or, at your option, any later version.
*/
#include <math.h>
#include "common.h"
#include "midifile.h"
#include "plugout.h"
static int volume[4] = {0, 0, 0, 0};
static int playing[4] = {0, 0, 0, 0};
static int midi_step(cycles_t cycles, const struct gbs_channel_status status[])
{
int c;
int new_playing;
int new_note;
const struct gbs_channel_status *ch;
midi_update_mute(status);
for (c = 0; c < 3; c++) {
ch = &status[c];
new_playing = ch->playing;
if (playing[c]) {
if (new_playing) {
new_note = NOTE(ch->div_tc, c);
if (new_note != note[c]) {
midi_note_off(cycles, c);
if (new_note < 0 || new_note >= 0x80)
continue;
midi_note_on(cycles, c, new_note, volume[c]);
}
} else {
midi_note_off(cycles, c);
playing[c] = 0;
}
} else {
if (new_playing) {
new_note = NOTE(ch->div_tc, c);
if (new_note < 0 || new_note >= 0x80)
continue;
midi_note_on(cycles, c, new_note, volume[c]);
playing[c] = 1;
}
}
}
return midi_file_error();
}
static int midi_io(cycles_t cycles, uint32_t addr, uint8_t val)
{
long chan = (addr - 0xff10) / 5;
if (midi_file_is_closed())
return 1;
switch (addr) {
case 0xff12:
case 0xff17:
volume[chan] = 8 * (val >> 4);
break;
case 0xff14:
case 0xff19:
case 0xff1e:
/* Channel start trigger */
if ((val & 0x80) == 0x80) {
midi_note_off(cycles, chan);
playing[chan] = 0;
}
break;
case 0xff1c:
volume[2] = 32 * ((4 - (val >> 5)) & 3);
break;
case 0xff25:
for (chan = 0; chan < 4; chan++)
switch ((val >> chan) & 0x11) {
case 0x10:
midi_pan(cycles, chan, 0);
break;
case 0x01:
midi_pan(cycles, chan, 127);
break;
default:
midi_pan(cycles, chan, 64);
}
break;
}
return midi_file_error();
}
const struct output_plugin plugout_altmidi = {
.name = "altmidi",
.description = "alternative MIDI file writer",
.open = midi_open,
.skip = midi_skip,
.io = midi_io,
.step = midi_step,
.close = midi_close,
};