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Making the APU independent of sample rate

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This commit is contained in:
Lior Halphon 2016-09-13 01:21:47 +03:00
parent 43be91f032
commit b95860c034
5 changed files with 108 additions and 96 deletions
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181
Core/apu.c
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@ -16,26 +16,25 @@ _a > _b ? _a : _b; })
__typeof__ (b) _b = (b); \
_a < _b ? _a : _b; })
static __attribute__((unused)) int16_t generate_sin(double phase, int16_t amplitude)
{
return (int16_t)(sin(phase) * amplitude);
}
#define APU_FREQUENCY 0x80000
static int16_t generate_square(double phase, int16_t amplitude, double duty)
static int16_t generate_square(uint64_t phase, uint32_t wave_length, int16_t amplitude, double duty)
{
if (fmod(phase, 2 * M_PI) > duty * 2 * M_PI) {
if (!wave_length) return 0;
if (phase % wave_length > wave_length * duty) {
return amplitude;
}
return 0;
}
static int16_t generate_wave(double phase, int16_t amplitude, int8_t *wave, uint8_t shift)
static int16_t generate_wave(uint64_t phase, uint32_t wave_length, int16_t amplitude, int8_t *wave, uint8_t shift)
{
phase = fmod(phase, 2 * M_PI);
return ((wave[(int)(phase / (2 * M_PI) * 32)]) >> shift) * (int)amplitude / 0xF;
if (!wave_length) wave_length = 1;
phase = phase % wave_length;
return ((wave[(int)(phase * 32 / wave_length)]) >> shift) * (int)amplitude / 0xF;
}
static int16_t generate_noise(double phase, int16_t amplitude, uint16_t lfsr)
static int16_t generate_noise(int16_t amplitude, uint16_t lfsr)
{
if (lfsr & 1) {
return amplitude;
@ -62,71 +61,76 @@ static int16_t step_lfsr(uint16_t lfsr, bool uses_7_bit)
/* General Todo: The APU emulation seems to fail many accuracy tests. It might require a rewrite with
these tests in mind. */
void GB_apu_render(GB_gameboy_t *gb, unsigned int sample_rate, unsigned int n_samples, GB_sample_t *samples)
void GB_apu_run_internal(GB_gameboy_t *gb, unsigned int n_cycles, GB_sample_t *samples)
{
for (; n_samples--; samples++) {
samples->left = samples->right = 0;
if (!gb->apu.global_enable) {
continue;
while (n_cycles--) {
if (n_cycles == 0) {
samples->left = samples->right = 0;
if (!gb->apu.global_enable) {
continue;
}
gb->io_registers[GB_IO_PCM_12] = 0;
gb->io_registers[GB_IO_PCM_34] = 0;
{
int16_t sample = generate_square(gb->apu.wave_channels[0].phase,
gb->apu.wave_channels[0].wave_length,
gb->apu.wave_channels[0].amplitude,
gb->apu.wave_channels[0].duty);
if (gb->apu.wave_channels[0].left_on ) samples->left += sample;
if (gb->apu.wave_channels[0].right_on) samples->right += sample;
gb->io_registers[GB_IO_PCM_12] = ((int)sample) * 0xF / MAX_CH_AMP;
}
{
int16_t sample = generate_square(gb->apu.wave_channels[1].phase,
gb->apu.wave_channels[1].wave_length,
gb->apu.wave_channels[1].amplitude,
gb->apu.wave_channels[1].duty);
if (gb->apu.wave_channels[1].left_on ) samples->left += sample;
if (gb->apu.wave_channels[1].right_on) samples->right += sample;
gb->io_registers[GB_IO_PCM_12] |= (((int)sample) * 0xF / MAX_CH_AMP) << 4;
}
if (gb->apu.wave_enable)
{
int16_t sample = generate_wave(gb->apu.wave_channels[2].phase,
gb->apu.wave_channels[2].wave_length,
MAX_CH_AMP,
gb->apu.wave_form,
gb->apu.wave_shift);
if (gb->apu.wave_channels[2].left_on ) samples->left += sample;
if (gb->apu.wave_channels[2].right_on) samples->right += sample;
gb->io_registers[GB_IO_PCM_34] = ((int)sample) * 0xF / MAX_CH_AMP;
}
{
int16_t sample = generate_noise(gb->apu.wave_channels[3].amplitude,
gb->apu.lfsr);
if (gb->apu.wave_channels[3].left_on ) samples->left += sample;
if (gb->apu.wave_channels[3].right_on) samples->right += sample;
gb->io_registers[GB_IO_PCM_34] |= (((int)sample) * 0xF / MAX_CH_AMP) << 4;
}
samples->left *= gb->apu.left_volume;
samples->right *= gb->apu.right_volume;
}
gb->io_registers[GB_IO_PCM_12] = 0;
gb->io_registers[GB_IO_PCM_34] = 0;
{
int16_t sample = generate_square(gb->apu.wave_channels[0].phase,
gb->apu.wave_channels[0].amplitude,
gb->apu.wave_channels[0].duty);
if (gb->apu.left_on [0]) samples->left += sample;
if (gb->apu.right_on[0]) samples->right += sample;
gb->io_registers[GB_IO_PCM_12] = ((int)sample) * 0xF / MAX_CH_AMP;
}
{
int16_t sample = generate_square(gb->apu.wave_channels[1].phase,
gb->apu.wave_channels[1].amplitude,
gb->apu.wave_channels[1].duty);
if (gb->apu.left_on [1]) samples->left += sample;
if (gb->apu.right_on[1]) samples->right += sample;
gb->io_registers[GB_IO_PCM_12] |= (((int)sample) * 0xF / MAX_CH_AMP) << 4;
}
if (gb->apu.wave_enable)
{
int16_t sample = generate_wave(gb->apu.wave_channels[2].phase,
MAX_CH_AMP,
gb->apu.wave_form,
gb->apu.wave_shift);
if (gb->apu.left_on [2]) samples->left += sample;
if (gb->apu.right_on[2]) samples->right += sample;
gb->io_registers[GB_IO_PCM_34] = ((int)sample) * 0xF / MAX_CH_AMP;
}
{
int16_t sample = generate_noise(gb->apu.wave_channels[3].phase,
gb->apu.wave_channels[3].amplitude,
gb->apu.lfsr);
if (gb->apu.left_on [3]) samples->left += sample;
if (gb->apu.right_on[3]) samples->right += sample;
gb->io_registers[GB_IO_PCM_34] |= (((int)sample) * 0xF / MAX_CH_AMP) << 4;
}
samples->left *= gb->apu.left_volume;
samples->right *= gb->apu.right_volume;
for (uint8_t i = 0; i < 4; i++) {
/* Phase */
gb->apu.wave_channels[i].phase += 2 * M_PI * gb->apu.wave_channels[i].frequency / sample_rate;
while (gb->apu.wave_channels[i].phase >= 2 * M_PI) {
gb->apu.wave_channels[i].phase++;
if (gb->apu.wave_channels[i].wave_length && gb->apu.wave_channels[i].phase >= gb->apu.wave_channels[i].wave_length) {
if (i == 3) {
gb->apu.lfsr = step_lfsr(gb->apu.lfsr, gb->apu.lfsr_7_bit);
}
gb->apu.wave_channels[i].phase -= 2 * M_PI;
gb->apu.wave_channels[i].phase %= gb->apu.wave_channels[i].wave_length;
}
/* Stop on Length */
if (gb->apu.wave_channels[i].stop_on_length) {
if (gb->apu.wave_channels[i].sound_length > 0) {
gb->apu.wave_channels[i].sound_length -= 1.0 / sample_rate;
gb->apu.wave_channels[i].sound_length -= 1.0 / APU_FREQUENCY;
}
if (gb->apu.wave_channels[i].sound_length <= 0) {
gb->apu.wave_channels[i].amplitude = 0;
@ -136,7 +140,7 @@ void GB_apu_render(GB_gameboy_t *gb, unsigned int sample_rate, unsigned int n_sa
}
}
gb->apu.envelope_step_timer += 1.0 / sample_rate;
gb->apu.envelope_step_timer += 1.0 / APU_FREQUENCY;
if (gb->apu.envelope_step_timer >= 1.0 / 64) {
gb->apu.envelope_step_timer -= 1.0 / 64;
for (uint8_t i = 0; i < 4; i++) {
@ -147,13 +151,13 @@ void GB_apu_render(GB_gameboy_t *gb, unsigned int sample_rate, unsigned int n_sa
}
}
gb->apu.sweep_step_timer += 1.0 / sample_rate;
gb->apu.sweep_step_timer += 1.0 / APU_FREQUENCY;
if (gb->apu.sweep_step_timer >= 1.0 / 128) {
gb->apu.sweep_step_timer -= 1.0 / 128;
if (gb->apu.wave_channels[0].sweep_steps && !--gb->apu.wave_channels[0].cur_sweep_steps) {
// Convert back to GB format
uint16_t temp = (uint16_t) (2048 - 131072 / gb->apu.wave_channels[0].frequency);
uint16_t temp = 2048 - gb->apu.wave_channels[0].wave_length / (APU_FREQUENCY / 131072);
// Apply sweep
temp = temp + gb->apu.wave_channels[0].sweep_direction *
@ -163,7 +167,8 @@ void GB_apu_render(GB_gameboy_t *gb, unsigned int sample_rate, unsigned int n_sa
}
// Back to frequency
gb->apu.wave_channels[0].frequency = 131072.0 / (2048 - temp);
gb->apu.wave_channels[0].wave_length = (2048 - temp) * (APU_FREQUENCY / 131072);
gb->apu.wave_channels[0].cur_sweep_steps = gb->apu.wave_channels[0].sweep_steps;
}
@ -176,20 +181,26 @@ void GB_apu_run(GB_gameboy_t *gb)
static bool should_log_overflow = true;
while (gb->audio_copy_in_progress);
double ticks_per_sample = (double) CPU_FREQUENCY / gb->sample_rate;
while (gb->apu_cycles > ticks_per_sample) {
GB_sample_t sample = {0, };
GB_apu_render(gb, gb->sample_rate, 1, &sample);
gb->apu_cycles -= ticks_per_sample;
GB_sample_t sample = {0, };
if (gb->apu.apu_cycles >= CPU_FREQUENCY / APU_FREQUENCY) {
GB_apu_run_internal(gb, gb->apu.apu_cycles / (CPU_FREQUENCY / APU_FREQUENCY), &sample);
gb->apu.apu_cycles %= (CPU_FREQUENCY / APU_FREQUENCY);
gb->audio_buffer[gb->audio_position] = sample;
}
if (gb->apu_sample_cycles > ticks_per_sample) {
gb->apu_sample_cycles -= ticks_per_sample;
if (gb->audio_position == gb->buffer_size) {
/*
if (should_log_overflow && !gb->turbo) {
GB_log(gb, "Audio overflow\n");
should_log_overflow = false;
}
GB_log(gb, "Audio overflow\n");
should_log_overflow = false;
}
*/
}
else {
gb->audio_buffer[gb->audio_position++] = sample;
gb->audio_position++;
should_log_overflow = true;
}
}
@ -225,7 +236,7 @@ void GB_apu_init(GB_gameboy_t *gb)
gb->apu.left_volume = 1.0;
gb->apu.right_volume = 1.0;
for (int i = 0; i < 4; i++) {
gb->apu.left_on[i] = gb->apu.right_on[i] = 1;
gb->apu.wave_channels[i].left_on = gb->apu.wave_channels[i].right_on = 1;
}
}
@ -335,10 +346,10 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
case GB_IO_NR13:
case GB_IO_NR23:
case GB_IO_NR33:
gb->apu.NRX3_X4_temp[channel] = (gb->apu.NRX3_X4_temp[channel] & 0xFF00) | value;
gb->apu.wave_channels[channel].frequency = 131072.0 / (2048 - gb->apu.NRX3_X4_temp[channel]);
gb->apu.wave_channels[channel].NRX3_X4_temp = (gb->apu.wave_channels[channel].NRX3_X4_temp & 0xFF00) | value;
gb->apu.wave_channels[channel].wave_length = (2048 - gb->apu.wave_channels[channel].NRX3_X4_temp) * (APU_FREQUENCY / 131072);
if (channel == 2) {
gb->apu.wave_channels[channel].frequency /= 2;
gb->apu.wave_channels[channel].wave_length *= 2;
}
break;
case GB_IO_NR14:
@ -352,10 +363,10 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
gb->apu.wave_channels[channel].cur_envelope_steps = gb->apu.wave_channels[channel].envelope_steps;
}
gb->apu.NRX3_X4_temp[channel] = (gb->apu.NRX3_X4_temp[channel] & 0xFF) | ((value & 0x7) << 8);
gb->apu.wave_channels[channel].frequency = 131072.0 / (2048 - gb->apu.NRX3_X4_temp[channel]);
gb->apu.wave_channels[channel].NRX3_X4_temp = (gb->apu.wave_channels[channel].NRX3_X4_temp & 0xFF) | ((value & 0x7) << 8);
gb->apu.wave_channels[channel].wave_length = (2048 - gb->apu.wave_channels[channel].NRX3_X4_temp) * (APU_FREQUENCY / 131072);
if (channel == 2) {
gb->apu.wave_channels[channel].frequency /= 2;
gb->apu.wave_channels[channel].wave_length *= 2;
}
break;
case GB_IO_NR30:
@ -379,7 +390,7 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
double r = value & 0x7;
if (r == 0) r = 0.5;
uint8_t s = value >> 4;
gb->apu.wave_channels[3].frequency = 524288.0 / r / (1 << (s + 1));
gb->apu.wave_channels[3].wave_length = r * (1 << s) * (APU_FREQUENCY / 262144) ;
gb->apu.lfsr_7_bit = value & 0x8;
break;
}
@ -400,8 +411,8 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
case GB_IO_NR51:
for (int i = 0; i < 4; i++) {
gb->apu.left_on[i] = value & 1;
gb->apu.right_on[i] = value & 0x10;
gb->apu.wave_channels[i].left_on = value & 1;
gb->apu.wave_channels[i].right_on = value & 0x10;
value >>= 1;
}
break;

16
Core/apu.h
View File

@ -21,8 +21,8 @@ typedef struct
/* Not all used on all channels */
typedef struct
{
GB_aligned_double phase;
GB_aligned_double frequency;
uint64_t phase;
uint32_t wave_length;
GB_aligned_double duty;
GB_aligned_double sound_length; /* In seconds */
int16_t amplitude;
@ -36,11 +36,15 @@ typedef struct
signed int sweep_direction;
uint8_t sweep_shift;
bool is_playing;
uint16_t NRX3_X4_temp;
bool left_on;
bool right_on;
} GB_apu_channel_t;
typedef struct
{
GB_apu_channel_t wave_channels[4];
uint8_t apu_cycles;
bool global_enable;
GB_aligned_double envelope_step_timer; /* In seconds */
GB_aligned_double sweep_step_timer; /* In seconds */
int8_t wave_form[32];
@ -50,13 +54,9 @@ typedef struct
bool lfsr_7_bit;
double left_volume;
double right_volume;
bool left_on[4];
bool right_on[4];
bool global_enable;
uint16_t NRX3_X4_temp[3];
GB_apu_channel_t wave_channels[4];
} GB_apu_t;
void GB_apu_render(GB_gameboy_t *gb, unsigned int sample_rate, unsigned int n_samples, GB_sample_t *samples);
void GB_apu_copy_buffer(GB_gameboy_t *gb, GB_sample_t *dest, unsigned int count);
void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value);
uint8_t GB_apu_read(GB_gameboy_t *gb, uint8_t reg);

2
Core/gb.c
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@ -491,7 +491,7 @@ void GB_set_sample_rate(GB_gameboy_t *gb, unsigned int sample_rate)
free(gb->audio_buffer);
}
gb->buffer_size = sample_rate / 25; // 40ms delay
gb->audio_buffer = malloc(gb->buffer_size * sizeof(*gb->audio_buffer));
gb->audio_buffer = malloc((gb->buffer_size + 1) * sizeof(*gb->audio_buffer));
gb->sample_rate = sample_rate;
gb->audio_position = 0;
}

2
Core/gb.h
View File

@ -293,7 +293,7 @@ typedef struct GB_gameboy_s {
uint32_t div_cycles;
GB_PADDING(uint32_t, tima_cycles);
GB_PADDING(uint32_t, dma_cycles);
GB_aligned_double apu_cycles;
GB_aligned_double apu_sample_cycles;
uint8_t tima_reload_state; /* After TIMA overflows, it becomes 0 for 4 cycles before actually reloading. */
uint16_t serial_cycles;
);

3
Core/timing.c
View File

@ -60,7 +60,8 @@ void GB_advance_cycles(GB_gameboy_t *gb, uint8_t cycles)
// Not affected by speed boost
gb->hdma_cycles += cycles;
gb->display_cycles += cycles;
gb->apu_cycles += cycles;
gb->apu_sample_cycles += cycles;
gb->apu.apu_cycles += cycles;
gb->cycles_since_ir_change += cycles;
gb->cycles_since_input_ir_change += cycles;
GB_dma_run(gb);