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Accuracy improvements to sweeping (Still not complete though, more research needed)

This commit is contained in:
Lior Halphon 2017-08-10 19:42:23 +03:00
parent ab5611119a
commit 1a8bcd314d
2 changed files with 45 additions and 32 deletions
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73
Core/apu.c
View File

@ -70,6 +70,28 @@ static void render(GB_gameboy_t *gb)
gb->apu_output.lock = false;
}
static uint16_t new_sweep_frequency(GB_gameboy_t *gb)
{
if ((gb->io_registers[GB_IO_NR10] & 0x70) == 0) {
return gb->apu.square_channels[GB_SQUARE_1].sample_length;
}
uint16_t delta = gb->apu.square_channels[GB_SQUARE_1].sample_length >> (gb->io_registers[GB_IO_NR10] & 7);
if (gb->io_registers[GB_IO_NR10] & 8) {
return gb->apu.square_channels[GB_SQUARE_1].sample_length - delta;
}
return gb->apu.square_channels[GB_SQUARE_1].sample_length + delta;
}
static void sweep_event(GB_gameboy_t *gb)
{
gb->apu.square_channels[GB_SQUARE_1].sample_length = new_sweep_frequency(gb);
/* Overflow checking only occurs after a delay */
gb->apu.square_sweep_stop_countdown = 0x13 - gb->apu.square_carry;
gb->apu.square_channels[GB_SQUARE_1].sample_length &= 0x7FF;
gb->apu.square_sweep_countdown = ((gb->io_registers[GB_IO_NR10] >> 4) & 7);
}
void GB_apu_div_event(GB_gameboy_t *gb)
{
if (!gb->apu.global_enable) return;
@ -123,22 +145,7 @@ void GB_apu_div_event(GB_gameboy_t *gb)
if ((gb->apu.div_divider & 3) == 3) {
if (gb->apu.square_sweep_countdown) {
if (!--gb->apu.square_sweep_countdown) {
gb->apu.square_channels[GB_SQUARE_1].sample_length ^= 0x7FF;
uint16_t delta = gb->apu.square_channels[GB_SQUARE_1].sample_length >> (gb->io_registers[GB_IO_NR10] & 7);
if (gb->io_registers[GB_IO_NR10] & 8) {
gb->apu.square_channels[GB_SQUARE_1].sample_length -= delta;
}
else {
gb->apu.square_channels[GB_SQUARE_1].sample_length += delta;
}
if (gb->apu.square_channels[GB_SQUARE_1].sample_length > 0x7f0) {
gb->apu.square_sweep_stop_countdown = 0x13 - gb->apu.square_carry;
}
gb->apu.square_channels[GB_SQUARE_1].sample_length ^= 0x7FF;
gb->apu.square_channels[GB_SQUARE_1].sample_length &= 0x7FF;
gb->apu.square_sweep_countdown = ((gb->io_registers[GB_IO_NR10] >> 4) & 7);
sweep_event(gb);
}
}
}
@ -159,9 +166,12 @@ void GB_apu_run(GB_gameboy_t *gb)
gb->apu.square_sweep_stop_countdown -= cycles;
}
else {
/* APU bug: sweep frequency is checked after adding the sweep delta twice */
if (new_sweep_frequency(gb) > 0x7ff) {
gb->apu.is_active[GB_SQUARE_1] = false;
update_sample(gb, GB_SQUARE_1, 0, gb->apu.square_sweep_stop_countdown - cycles);
}
gb->apu.square_sweep_stop_countdown = 0;
gb->apu.is_active[GB_SQUARE_1] = false;
update_sample(gb, GB_SQUARE_1, 0, 0);
}
}
@ -170,7 +180,7 @@ void GB_apu_run(GB_gameboy_t *gb)
uint8_t cycles_left = cycles;
while (unlikely(cycles_left > gb->apu.square_channels[i].sample_countdown)) {
cycles_left -= gb->apu.square_channels[i].sample_countdown + 1;
gb->apu.square_channels[i].sample_countdown = gb->apu.square_channels[i].sample_length * 2 + 1;
gb->apu.square_channels[i].sample_countdown = (gb->apu.square_channels[i].sample_length ^ 0x7FF) * 2 + 1;
gb->apu.square_channels[i].current_sample_index++;
gb->apu.square_channels[i].current_sample_index &= 0x7;
@ -193,7 +203,7 @@ void GB_apu_run(GB_gameboy_t *gb)
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.sample_countdown = gb->apu.wave_channel.sample_length ^ 0x7FF;
gb->apu.wave_channel.current_sample_index++;
gb->apu.wave_channel.current_sample_index &= 0x1F;
gb->apu.wave_channel.current_sample =
@ -257,9 +267,6 @@ void GB_apu_init(GB_gameboy_t *gb)
for (int i = 0; i < 4; i++) {
gb->apu.left_enabled[i] = gb->apu.right_enabled[i] = true;
}
gb->apu.square_channels[GB_SQUARE_1].sample_length = 0x7FF;
gb->apu.square_channels[GB_SQUARE_2].sample_length = 0x7FF;
gb->apu.wave_channel.sample_length = 0x7FF;
gb->apu.square_carry = 1;
}
@ -371,7 +378,7 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
case GB_IO_NR23: {
unsigned index = reg == GB_IO_NR23? GB_SQUARE_2: GB_SQUARE_1;
gb->apu.square_channels[index].sample_length &= ~0xFF;
gb->apu.square_channels[index].sample_length |= (~value) & 0xFF;
gb->apu.square_channels[index].sample_length |= value & 0xFF;
break;
}
@ -380,19 +387,19 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
case GB_IO_NR24: {
unsigned index = reg == GB_IO_NR24? GB_SQUARE_2: GB_SQUARE_1;
gb->apu.square_channels[index].sample_length &= 0xFF;
gb->apu.square_channels[index].sample_length |= ((~value) & 7) << 8;
gb->apu.square_channels[index].sample_length |= (value & 7) << 8;
if (value & 0x80) {
gb->apu.square_channels[index].current_sample_index = 7;
if (!gb->apu.is_active[index]) {
gb->apu.square_channels[index].sample_countdown = gb->apu.square_channels[index].sample_length * 2 + 6 - gb->apu.square_carry;
gb->apu.square_channels[index].sample_countdown = (gb->apu.square_channels[index].sample_length ^ 0x7FF) * 2 + 6 - gb->apu.square_carry;
}
else {
/* Timing quirk: if already active, sound starts 2 (2MHz) ticks earlier.
if both active AND already emitted a sample, sound starts the next 1MHz tick,
and one sample is skipped */
if (!gb->apu.square_channels[index].sample_emitted) {
gb->apu.square_channels[index].sample_countdown = gb->apu.square_channels[index].sample_length * 2 + 4 - gb->apu.square_carry;
gb->apu.square_channels[index].sample_countdown = (gb->apu.square_channels[index].sample_length ^ 0x7FF) * 2 + 4 - gb->apu.square_carry;
}
else {
gb->apu.square_channels[index].sample_countdown = gb->apu.square_carry;
@ -409,6 +416,12 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
gb->apu.square_channels[index].pulse_length = 0x40;
gb->apu.square_channels[index].length_enabled = false;
}
if (index == GB_SQUARE_1 && gb->io_registers[GB_IO_NR10] & 7) {
/* APU bug: if shift is nonzero, overflow check also occurs on trigger */
gb->apu.square_sweep_stop_countdown = 0x13 - gb->apu.square_carry;
}
/* Note that we don't change the sample just yet! This was verified on hardware. */
}
@ -450,11 +463,11 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
break;
case GB_IO_NR33:
gb->apu.wave_channel.sample_length &= ~0xFF;
gb->apu.wave_channel.sample_length |= (~value) & 0xFF;
gb->apu.wave_channel.sample_length |= value & 0xFF;
break;
case GB_IO_NR34:
gb->apu.wave_channel.sample_length &= 0xFF;
gb->apu.wave_channel.sample_length |= ((~value) & 7) << 8;
gb->apu.wave_channel.sample_length |= (value & 7) << 8;
if ((value & 0x80)) {
/* DMG bug: wave RAM gets corrupted if the channel is retriggerred 1 cycle before the APU
reads from it. */
@ -481,7 +494,7 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
}
}
gb->apu.is_active[GB_WAVE] = true;
gb->apu.wave_channel.sample_countdown = gb->apu.wave_channel.sample_length + 3;
gb->apu.wave_channel.sample_countdown = (gb->apu.wave_channel.sample_length ^ 0x7FF) + 3;
gb->apu.wave_channel.current_sample_index = 0;
if (gb->apu.wave_channel.pulse_length == 0) {
gb->apu.wave_channel.pulse_length = 0x100;

4
Core/apu.h
View File

@ -53,7 +53,7 @@ typedef struct
uint8_t current_sample_index;
bool sample_emitted;
uint16_t sample_countdown; // in APU ticks
uint16_t sample_countdown; // in APU ticks (Reloaded from sample_length, xorred $7FF)
uint16_t sample_length; // From NRX3, NRX4, in APU ticks
bool length_enabled; // NRX4
@ -66,7 +66,7 @@ typedef struct
uint16_t sample_length; // NR33, NR34, in APU ticks
bool length_enabled; // NR34
uint16_t sample_countdown; // in APU ticks
uint16_t sample_countdown; // in APU ticks (Reloaded from sample_length, xorred $7FF)
uint8_t current_sample_index;
uint8_t current_sample; // Current sample before shifting.