ShuriZma
/
bsnes
mirror of https://github.com/bsnes-emu/bsnes.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity
bsnes/Core/apu.c

307 lines
12 KiB
C
Executable File
Raw Blame History

#include <stdint.h>
#include <math.h>
#include <string.h>
#include "gb.h"
#define likely(x) __builtin_expect((x), 1)
#define unlikely(x) __builtin_expect((x), 0)
static void refresh_channel(GB_gameboy_t *gb, unsigned index, unsigned cycles_offset)
{
unsigned multiplier = gb->apu_output.cycles_since_render + cycles_offset - gb->apu_output.last_update[index];
gb->apu_output.summed_samples[index].left += gb->apu_output.current_sample[index].left * multiplier;
gb->apu_output.summed_samples[index].right += gb->apu_output.current_sample[index].right * multiplier;
gb->apu_output.last_update[index] = gb->apu_output.cycles_since_render + cycles_offset;
}
static void update_sample(GB_gameboy_t *gb, unsigned index, uint8_t value, unsigned cycles_offset)
{
gb->apu.samples[index] = value;
if (gb->apu_output.sample_rate) {
unsigned left_volume = 0;
if (gb->io_registers[GB_IO_NR51] & (1 << index)) {
left_volume = gb->io_registers[GB_IO_NR50] & 7;
}
unsigned right_volume = 0;
if (gb->io_registers[GB_IO_NR51] & (0x10 << index)) {
right_volume = (gb->io_registers[GB_IO_NR50] >> 4) & 7;;
}
GB_sample_t output = {value * left_volume, value * right_volume};
if (*(uint32_t *)&(gb->apu_output.current_sample[index]) != *(uint32_t *)&output) {
refresh_channel(gb, index, cycles_offset);
gb->apu_output.current_sample[index] = output;
}
}
}
static void render(GB_gameboy_t *gb)
{
GB_sample_t output = {0,0};
for (unsigned i = GB_N_CHANNELS; i--;) {
if (likely(gb->apu_output.last_update[i] == 0)) {
output.left += gb->apu_output.current_sample[i].left * CH_STEP;
output.right += gb->apu_output.current_sample[i].right * CH_STEP;
}
else {
refresh_channel(gb, i, 0);
output.left += (unsigned) gb->apu_output.summed_samples[i].left * CH_STEP
/ gb->apu_output.cycles_since_render;
output.right += (unsigned) gb->apu_output.summed_samples[i].right * CH_STEP
/ gb->apu_output.cycles_since_render;
gb->apu_output.summed_samples[i] = (GB_sample_t){0, 0};
}
gb->apu_output.last_update[i] = 0;
}
gb->apu_output.cycles_since_render = 0;
while (gb->apu_output.copy_in_progress);
while (!__sync_bool_compare_and_swap(&gb->apu_output.lock, false, true));
if (gb->apu_output.buffer_position < gb->apu_output.buffer_size) {
gb->apu_output.buffer[gb->apu_output.buffer_position++] = output;
}
gb->apu_output.lock = false;
}
void GB_apu_div_event(GB_gameboy_t *gb)
{
if (gb->apu.is_active[GB_WAVE] && gb->apu.wave_channel.length_enabled) {
if (gb->apu.wave_channel.pulse_length) {
gb->apu.wave_channel.pulse_length--;
}
else {
gb->apu.is_active[GB_WAVE] = false;
gb->apu.wave_channel.current_sample = 0;
update_sample(gb, GB_WAVE, 0, 0);
}
}
}
void GB_apu_run(GB_gameboy_t *gb, uint8_t cycles)
{
/* Convert 4MHZ to 2MHz. cycles is always even. */
cycles >>= 1;
gb->apu.wave_channel.wave_form_just_read = false;
if (gb->apu.is_active[GB_WAVE]) {
uint8_t cycles_left = cycles;
while (unlikely(cycles_left > gb->apu.wave_channel.sample_countdown)) {
cycles_left -= gb->apu.wave_channel.sample_countdown + 1;
gb->apu.wave_channel.sample_countdown = gb->apu.wave_channel.sample_length;
gb->apu.wave_channel.current_sample_index++;
gb->apu.wave_channel.current_sample_index &= 0x1F;
gb->apu.wave_channel.current_sample =
gb->apu.wave_channel.wave_form[gb->apu.wave_channel.current_sample_index];
update_sample(gb, GB_WAVE,
gb->apu.wave_channel.current_sample >> gb->apu.wave_channel.shift,
cycles - cycles_left);
gb->apu.wave_channel.wave_form_just_read = true;
}
if (cycles_left) {
gb->apu.wave_channel.sample_countdown -= cycles_left;
gb->apu.wave_channel.wave_form_just_read = false;
}
}
if (gb->apu_output.sample_rate) {
gb->apu_output.cycles_since_render += cycles;
double cycles_per_sample = CPU_FREQUENCY / (double)gb->apu_output.sample_rate; // TODO: this should be cached!
if (gb->apu_output.sample_cycles > cycles_per_sample) {
gb->apu_output.sample_cycles -= cycles_per_sample;
render(gb);
}
}
}
void GB_apu_copy_buffer(GB_gameboy_t *gb, GB_sample_t *dest, size_t count)
{
gb->apu_output.copy_in_progress = true;
if (!gb->apu_output.stream_started) {
// Intentionally fail the first copy to sync the stream with the Gameboy.
gb->apu_output.stream_started = true;
gb->apu_output.buffer_position = 0;
}
if (count > gb->apu_output.buffer_position) {
// GB_log(gb, "Audio underflow: %d\n", count - gb->apu_output.buffer_position);
if (gb->apu_output.buffer_position != 0) {
for (unsigned i = 0; i < count - gb->apu_output.buffer_position; i++) {
dest[gb->apu_output.buffer_position + i] = gb->apu_output.buffer[gb->apu_output.buffer_position - 1];
}
}
else {
memset(dest + gb->apu_output.buffer_position, 0, (count - gb->apu_output.buffer_position) * sizeof(*gb->apu_output.buffer));
}
count = gb->apu_output.buffer_position;
}
memcpy(dest, gb->apu_output.buffer, count * sizeof(*gb->apu_output.buffer));
memmove(gb->apu_output.buffer, gb->apu_output.buffer + count, (gb->apu_output.buffer_position - count) * sizeof(*gb->apu_output.buffer));
gb->apu_output.buffer_position -= count;
gb->apu_output.copy_in_progress = false;
}
void GB_apu_init(GB_gameboy_t *gb)
{
memset(&gb->apu, 0, sizeof(gb->apu));
// gb->apu.wave_channels[0].duty = gb->apu.wave_channels[1].duty = 4;
// gb->apu.lfsr = 0x7FFF;
gb->io_registers[GB_IO_NR50] = 0x77;
for (int i = 0; i < 4; i++) {
gb->apu.left_enabled[i] = gb->apu.right_enabled[i] = true;
}
gb->apu.wave_channel.sample_length = 0x7FF;
}
uint8_t GB_apu_read(GB_gameboy_t *gb, uint8_t reg)
{
if (reg == GB_IO_NR52) {
uint8_t value = 0;
for (int i = 0; i < GB_N_CHANNELS; i++) {
value >>= 1;
if (gb->apu.is_active[i]) {
value |= 0x8;
}
}
if (gb->apu.global_enable) {
value |= 0x80;
}
value |= 0x70;
return value;
}
static const char read_mask[GB_IO_WAV_END - GB_IO_NR10 + 1] = {
/* NRX0 NRX1 NRX2 NRX3 NRX4 */
0x80, 0x3F, 0x00, 0xFF, 0xBF, // NR1X
0xFF, 0x3F, 0x00, 0xFF, 0xBF, // NR2X
0x7F, 0xFF, 0x9F, 0xFF, 0xBF, // NR3X
0xFF, 0xFF, 0x00, 0x00, 0xBF, // NR4X
0x00, 0x00, 0x70, 0xFF, 0xFF, // NR5X
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // Unused
// Wave RAM
0, /* ... */
};
if (reg >= GB_IO_WAV_START && reg <= GB_IO_WAV_END && gb->apu.is_active[GB_WAVE]) {
if (!gb->is_cgb && !gb->apu.wave_channel.wave_form_just_read) {
return 0xFF;
}
reg = GB_IO_WAV_START + gb->apu.wave_channel.current_sample_index / 2;
}
return gb->io_registers[reg] | read_mask[reg - GB_IO_NR10];
}
void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
{
if (!gb->apu.global_enable && reg != GB_IO_NR52) {
return;
}
if (reg >= GB_IO_WAV_START && reg <= GB_IO_WAV_END && gb->apu.is_active[GB_WAVE]) {
if (!gb->is_cgb && !gb->apu.wave_channel.wave_form_just_read) {
return;
}
reg = GB_IO_WAV_START + gb->apu.wave_channel.current_sample_index / 2;
}
gb->io_registers[reg] = value;
switch (reg) {
/* Globals */
case GB_IO_NR50:
case GB_IO_NR51:
/* These registers affect the output of all 3 channels (but not the output of the PCM registers).*/
/* We call update_samples with the current value so the APU output is updated with the new outputs */
for (unsigned i = GB_N_CHANNELS; i--;) {
update_sample(gb, i, gb->apu.samples[i], 0);
}
break;
case GB_IO_NR52:
if ((value & 0x80) && !gb->apu.global_enable) {
GB_apu_init(gb);
gb->apu.global_enable = true;
}
else if (!(value & 0x80) && gb->apu.global_enable) {
for (unsigned i = GB_N_CHANNELS; i--;) {
update_sample(gb, i, 0, 0);
}
memset(&gb->apu, 0, sizeof(gb->apu));
memset(gb->io_registers + GB_IO_NR10, 0, GB_IO_WAV_START - GB_IO_NR10);
gb->apu.global_enable = false;
}
break;
/* Wave channel */
case GB_IO_NR30:
gb->apu.wave_channel.enable = value & 0x80;
if (!gb->apu.wave_channel.enable) {
gb->apu.is_active[GB_WAVE] = false;
gb->apu.wave_channel.current_sample = 0;
update_sample(gb, GB_WAVE, 0, 0);
}
break;
case GB_IO_NR31:
break;
case GB_IO_NR32:
gb->apu.wave_channel.shift = (uint8_t[]){4, 0, 1, 2}[(value >> 5) & 3];
update_sample(gb, GB_WAVE, gb->apu.wave_channel.current_sample >> gb->apu.wave_channel.shift, 0);
break;
case GB_IO_NR33:
gb->apu.wave_channel.sample_length &= ~0xFF;
gb->apu.wave_channel.sample_length |= (~value) & 0xFF;
break;
case GB_IO_NR34:
gb->apu.wave_channel.length_enabled = value & 0x40;
gb->apu.wave_channel.sample_length &= 0xFF;
gb->apu.wave_channel.sample_length |= ((~value) & 7) << 8;
if ((value & 0x80) && gb->apu.wave_channel.enable) {
/* DMG bug: wave RAM gets corrupted if the channel is retriggerred 1 cycle before the APU
reads from it. */
if (!gb->is_cgb && gb->apu.is_active[GB_WAVE] && gb->apu.wave_channel.sample_countdown == 0) {
unsigned offset = ((gb->apu.wave_channel.current_sample_index + 1) >> 1) & 0xF;
/* On SGB2 (and probably SGB1 and MGB as well) this behavior is not accurate,
however these systems are not currently emulated. */
if (offset < 4) {
gb->io_registers[GB_IO_WAV_START] = gb->io_registers[GB_IO_WAV_START + offset];
gb->apu.wave_channel.wave_form[0] = gb->apu.wave_channel.wave_form[offset / 2];
gb->apu.wave_channel.wave_form[1] = gb->apu.wave_channel.wave_form[offset / 2 + 1];
}
else {
memcpy(gb->io_registers + GB_IO_WAV_START,
gb->io_registers + GB_IO_WAV_START + (offset & ~3),
4);
memcpy(gb->apu.wave_channel.wave_form,
gb->apu.wave_channel.wave_form + (offset & ~3) * 2,
8);
}
}
gb->apu.is_active[GB_WAVE] = true;
gb->apu.wave_channel.pulse_length = (~gb->io_registers[GB_IO_NR31]) * 2;
gb->apu.wave_channel.sample_countdown = gb->apu.wave_channel.sample_length + 3;
gb->apu.wave_channel.current_sample_index = 0;
/* Note that we don't change the sample just yet! This was verified on hardware. */
}
break;
default:
if (reg >= GB_IO_WAV_START && reg <= GB_IO_WAV_END) {
gb->apu.wave_channel.wave_form[(reg - GB_IO_WAV_START) * 2] = value >> 4;
gb->apu.wave_channel.wave_form[(reg - GB_IO_WAV_START) * 2 + 1] = value & 0xF;
}
}
}
size_t GB_apu_get_current_buffer_length(GB_gameboy_t *gb)
{
return gb->apu_output.buffer_position;
}
Reference in New Issue View Git Blame Copy Permalink