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Fixed Channel 3’s first sample behavior, update analog characteristic to more realistic values. Fixes #177

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This commit is contained in:
Lior Halphon 2019-05-25 19:12:09 +03:00
parent c29b5b5800
commit 85c43fa81f
2 changed files with 15 additions and 17 deletions
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24
Core/apu.c
View File

@ -107,6 +107,11 @@ static void update_sample(GB_gameboy_t *gb, unsigned index, int8_t value, unsign
}
}
static double smooth(double x)
{
return 3*x*x - 2*x*x*x;
}
static void render(GB_gameboy_t *gb, bool no_downsampling, GB_sample_t *dest)
{
GB_sample_t output = {0,0};
@ -123,7 +128,7 @@ static void render(GB_gameboy_t *gb, bool no_downsampling, GB_sample_t *dest)
gb->apu_output.dac_discharge[i] = 0;
}
else {
multiplier *= gb->apu_output.dac_discharge[i];
multiplier *= smooth(gb->apu_output.dac_discharge[i]);
}
}
else {
@ -132,7 +137,7 @@ static void render(GB_gameboy_t *gb, bool no_downsampling, GB_sample_t *dest)
gb->apu_output.dac_discharge[i] = 1;
}
else {
multiplier *= gb->apu_output.dac_discharge[i];
multiplier *= smooth(gb->apu_output.dac_discharge[i]);
}
}
}
@ -350,7 +355,6 @@ void GB_apu_div_event(GB_gameboy_t *gb)
if (gb->apu.wave_channel.pulse_length) {
if (!--gb->apu.wave_channel.pulse_length) {
gb->apu.is_active[GB_WAVE] = false;
gb->apu.wave_channel.current_sample = 0;
update_sample(gb, GB_WAVE, 0, 0);
}
}
@ -806,7 +810,6 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
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;
@ -815,7 +818,9 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
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);
if (gb->apu.is_active[GB_WAVE]) {
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;
@ -856,7 +861,9 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
}
if (!gb->apu.is_active[GB_WAVE]) {
gb->apu.is_active[GB_WAVE] = true;
update_sample(gb, GB_WAVE, 0, 0);
update_sample(gb, GB_WAVE,
gb->apu.wave_channel.current_sample >> gb->apu.wave_channel.shift,
0);
}
gb->apu.wave_channel.sample_countdown = (gb->apu.wave_channel.sample_length ^ 0x7FF) + 3;
gb->apu.wave_channel.current_sample_index = 0;
@ -865,11 +872,6 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
gb->apu.wave_channel.length_enabled = false;
}
/* Note that we don't change the sample just yet! This was verified on hardware. */
/* Todo: The first sample might *not* beskipped on the DMG, this could be a bug
introduced on the CGB. It appears that the bug was fixed on the AGB, but it's
not reflected by PCM34. This should be probably verified as this could just
mean differences in the DACs. */
/* Todo: Similar issues may apply to the other channels on the DMG/AGB, test, verify and fix if needed */
}
/* APU glitch - if length is enabled while the DIV-divider's LSB is 1, tick the length once. */

8
Core/apu.h
View File

@ -8,12 +8,8 @@
#ifdef GB_INTERNAL
/* Speed = 1 / Length (in seconds) */
/* Todo: Measure these and find the actual curve shapes.
They are known to be incorrect (Some analog test ROM sound different),
but are good enough approximations to fix Cannon Fodder's terrible audio.
It also varies by model. */
#define DAC_DECAY_SPEED 50000
#define DAC_ATTACK_SPEED 1000
#define DAC_DECAY_SPEED 20000
#define DAC_ATTACK_SPEED 20000
/* Divides nicely and never overflows with 4 channels and 8 (1-8) volume levels */