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sound/k054539.cpp: Fixed DPCM table, and added cubic interpolation. (#9778)

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Using powers of 2 rather than squares for the DPCM table fixes DC offsets for 4-bit sample playback.
This commit is contained in:
Tony Konzel 2022-06-09 07:05:08 -05:00 committed by GitHub
parent a0f069a766
commit 21cf4d3cd4
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 56 additions and 7 deletions
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59
src/devices/sound/k054539.cpp
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@ -104,13 +104,34 @@ void k054539_device::keyoff(int channel)
regs[0x22c] &= ~(1 << channel);
}
void k054539_device::advance_filter(int channel, int val)
{
auto &hist = filter_hist[channel];
hist[0] = hist[1];
hist[1] = hist[2];
hist[2] = hist[3];
hist[3] = ((float) val) / 32768.0f;
}
float k054539_device::calculate_filter(int channel, float t)
{
// Cubic hermite interpolation
// t is domain [0,1]
auto &hist = filter_hist[channel];
const float a = (-hist[0] / 2.0f) + (3.0f * hist[1] / 2.0f) - (3.0f * hist[2] / 2.0f) + (hist[3] / 2.0f);
const float b = hist[0] - (5.0f * hist[1] / 2.0f) + (2.0f * hist[2]) - (hist[3] / 2.0f);
const float c = (-hist[0] / 2.0f) + (hist[2] / 2.0f);
return (t * t * t * a) + (t * t * b) + (t * c) + hist[1];
}
void k054539_device::sound_stream_update(sound_stream &stream, std::vector<read_stream_view> const &inputs, std::vector<write_stream_view> &outputs)
{
#define VOL_CAP 1.80
static const int16_t dpcm[16] = {
0 * 0x100, 1 * 0x100, 4 * 0x100, 9 * 0x100, 16 * 0x100, 25 * 0x100, 36 * 0x100, 49 * 0x100,
-64 * 0x100, -49 * 0x100, -36 * 0x100, -25 * 0x100, -16 * 0x100, -9 * 0x100, -4 * 0x100, -1 * 0x100
0 * 0x100, 1 * 0x100, 2 * 0x100, 4 * 0x100, 8 * 0x100, 16 * 0x100, 32 * 0x100, 64 * 0x100,
0 * 0x100, -64 * 0x100, -32 * 0x100, -16 * 0x100, -8 * 0x100, -4 * 0x100, -2 * 0x100, -1 * 0x100
};
@ -195,6 +216,8 @@ void k054539_device::sound_stream_update(sound_stream &stream, std::vector<read_
cur_pval = chan->pval;
}
float filter_frac = 0;
switch(base2[0] & 0xc) {
case 0x0: { // 8bit pcm
cur_pfrac += delta;
@ -208,12 +231,17 @@ void k054539_device::sound_stream_update(sound_stream &stream, std::vector<read_
cur_pos = (base1[0x08] | (base1[0x09] << 8) | (base1[0x0a] << 16));
cur_val = (int16_t)(read_byte(cur_pos) << 8);
}
if(cur_val == (int16_t)0x8000) {
keyoff(ch);
cur_val = 0;
break;
}
advance_filter(ch, cur_val);
}
filter_frac = (float)(cur_pfrac & 0xffff) / 65536.0f;
break;
}
@ -231,12 +259,17 @@ void k054539_device::sound_stream_update(sound_stream &stream, std::vector<read_
cur_pos = (base1[0x08] | (base1[0x09] << 8) | (base1[0x0a] << 16));
cur_val = (int16_t)(read_byte(cur_pos) | read_byte(cur_pos+1)<<8);
}
if(cur_val == (int16_t)0x8000) {
keyoff(ch);
cur_val = 0;
break;
}
advance_filter(ch, cur_val);
}
filter_frac = (float)(cur_pfrac & 0xffff) / 65536.0f;
break;
}
@ -273,8 +306,12 @@ void k054539_device::sound_stream_update(sound_stream &stream, std::vector<read_
cur_val = -32768;
else if(cur_val > 32767)
cur_val = 32767;
advance_filter(ch, cur_val);
}
filter_frac = (float)(cur_pfrac & 0xffff) / 65536.0f;
cur_pfrac >>= 1;
if(cur_pos & 1)
cur_pfrac |= 0x8000;
@ -285,9 +322,12 @@ void k054539_device::sound_stream_update(sound_stream &stream, std::vector<read_
LOG("Unknown sample type %x for channel %d\n", base2[0] & 0xc, ch);
break;
}
lval += cur_val * lvol;
rval += cur_val * rvol;
rbase[(rdelta + reverb_pos) & 0x1fff] += int16_t(cur_val*rbvol);
const float filter_val = calculate_filter(ch, filter_frac);
lval += filter_val * lvol;
rval += filter_val * rvol;
rbase[(rdelta + reverb_pos) & 0x1fff] += int16_t(filter_val*rbvol);
chan->pos = cur_pos;
chan->pfrac = cur_pfrac;
@ -299,10 +339,13 @@ void k054539_device::sound_stream_update(sound_stream &stream, std::vector<read_
base1[0x0d] = cur_pos>> 8 & 0xff;
base1[0x0e] = cur_pos>>16 & 0xff;
}
} else {
// Fill the interpolation vectors with silence when channel is disabled
advance_filter(ch, 0);
}
reverb_pos = (reverb_pos + 1) & 0x1fff;
outputs[0].put_int(sample, lval, 32768);
outputs[1].put_int(sample, rval, 32768);
outputs[0].put(sample, lval);
outputs[1].put(sample, rval);
}
}
@ -317,6 +360,7 @@ void k054539_device::init_chip()
{
memset(regs, 0, sizeof(regs));
memset(posreg_latch, 0, sizeof(posreg_latch)); //*
memset(filter_hist, 0, sizeof(filter_hist));
flags |= UPDATE_AT_KEYON; //* make it default until proven otherwise
ram = std::make_unique<uint8_t []>(0x4000);
@ -339,6 +383,7 @@ void k054539_device::init_chip()
save_item(NAME(cur_ptr));
save_item(NAME(cur_limit));
save_item(NAME(rom_addr));
save_item(NAME(filter_hist));
save_item(NAME(m_timer_state));
}

4
src/devices/sound/k054539.h
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@ -88,6 +88,8 @@ private:
uint8_t posreg_latch[8][3];
int flags;
float filter_hist[8][4];
unsigned char regs[0x230];
std::unique_ptr<uint8_t []> ram;
int reverb_pos;
@ -108,6 +110,8 @@ private:
void keyon(int channel);
void keyoff(int channel);
void init_chip();
void advance_filter(int channel, int val);
float calculate_filter(int channel, float t);
};
DECLARE_DEVICE_TYPE(K054539, k054539_device)