SameBoy/Core/apu.h

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#ifndef apu_h
#define apu_h
#include <stdbool.h>
#include <stdint.h>
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#include <stddef.h>
#include "defs.h"
#ifdef GB_INTERNAL
/* Speed = 1 / Length (in seconds) */
#define DAC_DECAY_SPEED 20000
#define DAC_ATTACK_SPEED 20000
/* Divides nicely and never overflows with 4 channels and 8 (1-8) volume levels */
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#ifdef WIIU
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/* Todo: Remove this hack once https://github.com/libretro/RetroArch/issues/6252 is fixed*/
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#define MAX_CH_AMP (0xFF0 / 2)
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#else
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#define MAX_CH_AMP 0xFF0
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#endif
#define CH_STEP (MAX_CH_AMP/0xF/8)
#endif
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/* APU ticks are 2MHz, triggered by an internal APU clock. */
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typedef struct
{
int16_t left;
int16_t right;
} GB_sample_t;
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typedef struct
{
double left;
double right;
} GB_double_sample_t;
enum GB_CHANNELS {
GB_SQUARE_1,
GB_SQUARE_2,
GB_WAVE,
GB_NOISE,
GB_N_CHANNELS
};
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typedef struct
{
bool locked:1;
bool clock:1; // Represents FOSY on channel 4
unsigned padding:6;
} GB_envelope_clock_t;
typedef void (*GB_sample_callback_t)(GB_gameboy_t *gb, GB_sample_t *sample);
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typedef struct
{
bool global_enable;
uint8_t apu_cycles;
uint8_t samples[GB_N_CHANNELS];
bool is_active[GB_N_CHANNELS];
uint8_t div_divider; // The DIV register ticks the APU at 512Hz, but is then divided
// once more to generate 128Hz and 64Hz clocks
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uint8_t lf_div; // The APU runs in 2MHz, but channels 1, 2 and 4 run in 1MHZ so we divide
// need to divide the signal.
uint8_t square_sweep_countdown; // In 128Hz
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uint8_t square_sweep_calculate_countdown; // In 2 MHz
uint16_t sweep_length_addend;
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uint16_t shadow_sweep_sample_length;
bool unshifted_sweep;
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bool enable_zombie_calculate_stepping;
uint8_t channel_1_restart_hold;
uint16_t channel1_completed_addend;
struct {
uint16_t pulse_length; // Reloaded from NRX1 (xorred), in 256Hz DIV ticks
uint8_t current_volume; // Reloaded from NRX2
uint8_t volume_countdown; // Reloaded from NRX2
uint8_t current_sample_index;
bool sample_surpressed;
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
GB_envelope_clock_t envelope_clock;
} square_channels[2];
struct {
bool enable; // NR30
uint16_t pulse_length; // Reloaded from NR31 (xorred), in 256Hz DIV ticks
uint8_t shift; // NR32
uint16_t sample_length; // NR33, NR34, in APU ticks
bool length_enabled; // NR34
uint16_t sample_countdown; // in APU ticks (Reloaded from sample_length, xorred $7FF)
uint8_t current_sample_index;
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uint8_t current_sample_byte; // Current sample byte.
bool wave_form_just_read;
bool pulsed;
uint8_t bugged_read_countdown;
} wave_channel;
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struct {
uint16_t pulse_length; // Reloaded from NR41 (xorred), in 256Hz DIV ticks
uint8_t current_volume; // Reloaded from NR42
uint8_t volume_countdown; // Reloaded from NR42
uint16_t lfsr;
bool narrow;
uint8_t counter_countdown; // Counts from 0-7 to 0 to tick counter (Scaled from 512KHz to 2MHz)
uint16_t counter; // A bit from this 14-bit register ticks LFSR
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bool length_enabled; // NR44
uint8_t alignment; // If (NR43 & 7) != 0, samples are aligned to 512KHz clock instead of
// 1MHz. This variable keeps track of the alignment.
bool current_lfsr_sample;
int8_t delta;
bool countdown_reloaded;
uint8_t dmg_delayed_start;
GB_envelope_clock_t envelope_clock;
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} noise_channel;
enum {
GB_SKIP_DIV_EVENT_INACTIVE,
GB_SKIP_DIV_EVENT_SKIPPED,
GB_SKIP_DIV_EVENT_SKIP,
} skip_div_event:8;
uint8_t pcm_mask[2]; // For CGB-0 to CGB-C PCM read glitch
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} GB_apu_t;
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typedef enum {
GB_HIGHPASS_OFF, // Do not apply any filter, keep DC offset
GB_HIGHPASS_ACCURATE, // Apply a highpass filter similar to the one used on hardware
GB_HIGHPASS_REMOVE_DC_OFFSET, // Remove DC Offset without affecting the waveform
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GB_HIGHPASS_MAX
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} GB_highpass_mode_t;
typedef struct {
unsigned sample_rate;
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unsigned sample_cycles; // Counts by sample_rate until it reaches the clock frequency
// Samples are NOT normalized to MAX_CH_AMP * 4 at this stage!
unsigned cycles_since_render;
unsigned last_update[GB_N_CHANNELS];
GB_sample_t current_sample[GB_N_CHANNELS];
GB_sample_t summed_samples[GB_N_CHANNELS];
double dac_discharge[GB_N_CHANNELS];
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GB_highpass_mode_t highpass_mode;
double highpass_rate;
GB_double_sample_t highpass_diff;
GB_sample_callback_t sample_callback;
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double interference_volume;
double interference_highpass;
} GB_apu_output_t;
void GB_set_sample_rate(GB_gameboy_t *gb, unsigned sample_rate);
void GB_set_sample_rate_by_clocks(GB_gameboy_t *gb, double cycles_per_sample); /* Cycles are in 8MHz units */
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void GB_set_highpass_filter_mode(GB_gameboy_t *gb, GB_highpass_mode_t mode);
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void GB_set_interference_volume(GB_gameboy_t *gb, double volume);
void GB_apu_set_sample_callback(GB_gameboy_t *gb, GB_sample_callback_t callback);
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#ifdef GB_INTERNAL
internal bool GB_apu_is_DAC_enabled(GB_gameboy_t *gb, unsigned index);
internal void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value);
internal uint8_t GB_apu_read(GB_gameboy_t *gb, uint8_t reg);
internal void GB_apu_div_event(GB_gameboy_t *gb);
internal void GB_apu_div_secondary_event(GB_gameboy_t *gb);
internal void GB_apu_init(GB_gameboy_t *gb);
internal void GB_apu_run(GB_gameboy_t *gb);
#endif
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#endif /* apu_h */