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Irem GA20: rewrite sound update

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In all currently supported GA20 sample ROMs, samples are followed by
1 to 16 bytes with value 00. (depends on alignment) Thus I assume that
this is a sample end marker.
The "sample end" register might be used for something else. (looping?)
This commit is contained in:
Valley Bell 2018-09-25 22:40:21 +02:00 committed by hap
parent f5504bba24
commit 22a963fade
1 changed files with 23 additions and 59 deletions
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82
src/devices/sound/iremga20.cpp
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@ -1,5 +1,5 @@
// license:BSD-3-Clause
// copyright-holders:Acho A. Tang,R. Belmont
// copyright-holders:Acho A. Tang,R. Belmont, Valley Bell
/*********************************************************
Irem GA20 PCM Sound Chip
@ -26,6 +26,9 @@ Revisions:
02-03-2007 R. Belmont
- Cleaned up faux x86 assembly.
09-25-2018 Valley Bell
- rewrote channel update to make data 0 act as sample terminator
*********************************************************/
#include "emu.h"
@ -122,75 +125,36 @@ void iremga20_device::rom_bank_updated()
void iremga20_device::sound_stream_update(sound_stream &stream, stream_sample_t **inputs, stream_sample_t **outputs, int samples)
{
uint32_t rate[4], pos[4], frac[4], end[4], vol[4], play[4];
stream_sample_t *outL, *outR;
int i, sampleout;
/* precache some values */
for (i=0; i < 4; i++)
{
rate[i] = m_channel[i].rate;
pos[i] = m_channel[i].pos;
frac[i] = m_channel[i].frac;
end[i] = m_channel[i].end - 0x20;
vol[i] = m_channel[i].volume;
play[i] = m_channel[i].play;
}
i = samples;
outL = outputs[0];
outR = outputs[1];
for (i = 0; i < samples; i++)
for (int i = 0; i < samples; i++)
{
sampleout = 0;
stream_sample_t sampleout = 0;
// update the 4 channels inline
if (play[0])
for (auto & ch : m_channel)
{
sampleout += (read_byte(pos[0]) - 0x80) * vol[0];
frac[0] += rate[0];
pos[0] += frac[0] >> 24;
frac[0] &= 0xffffff;
play[0] = (pos[0] < end[0]);
}
if (play[1])
{
sampleout += (read_byte(pos[1]) - 0x80) * vol[1];
frac[1] += rate[1];
pos[1] += frac[1] >> 24;
frac[1] &= 0xffffff;
play[1] = (pos[1] < end[1]);
}
if (play[2])
{
sampleout += (read_byte(pos[2]) - 0x80) * vol[2];
frac[2] += rate[2];
pos[2] += frac[2] >> 24;
frac[2] &= 0xffffff;
play[2] = (pos[2] < end[2]);
}
if (play[3])
{
sampleout += (read_byte(pos[3]) - 0x80) * vol[3];
frac[3] += rate[3];
pos[3] += frac[3] >> 24;
frac[3] &= 0xffffff;
play[3] = (pos[3] < end[3]);
if (ch.play)
{
int sample = read_byte(ch.pos);
if (sample == 0x00) // check for sample end marker
ch.play = 0;
else
sampleout += (sample - 0x80) * (int32_t)ch.volume;
ch.frac += ch.rate;
ch.pos += (ch.frac >> 24);
ch.frac &= ((1 << 24) - 1);
if (ch.pos >= ch.end) // for safety (the actual chip probably doesn't check this)
ch.play = 0;
}
}
sampleout >>= 2;
outL[i] = sampleout;
outR[i] = sampleout;
}
/* update the regs now */
for (i=0; i < 4; i++)
{
m_channel[i].pos = pos[i];
m_channel[i].frac = frac[i];
m_channel[i].play = play[i];
}
}
WRITE8_MEMBER( iremga20_device::irem_ga20_w )
@ -215,16 +179,16 @@ WRITE8_MEMBER( iremga20_device::irem_ga20_w )
m_channel[channel].start = ((m_channel[channel].start)&0x00ff0) | (data<<12);
break;
case 2: /* end address low */
case 2: /* end? address low */
m_channel[channel].end = ((m_channel[channel].end)&0xff000) | (data<<4);
break;
case 3: /* end address high */
case 3: /* end? address high */
m_channel[channel].end = ((m_channel[channel].end)&0x00ff0) | (data<<12);
break;
case 4:
m_channel[channel].rate = 0x1000000 / (256 - data);
m_channel[channel].rate = (1 << 24) / (256 - data);
break;
case 5: //AT: gain control