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(simplify slot->bits)

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This commit is contained in:
Michaël Banaan Ananas 2011-08-10 15:09:33 +00:00
parent 3b23aa9e97
commit 869fe20d5e
1 changed files with 15 additions and 21 deletions
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36
src/emu/sound/ymf278b.c
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@ -244,7 +244,8 @@ static UINT32 ymf278_compute_decay_env_vol_step(YMF278BSlot *slot, int val)
if (rate < 4)
res = 0;
else res = (256U<<23) / ymf278_compute_decay_rate(rate);
else
res = (256U<<23) / ymf278_compute_decay_rate(rate);
return res;
}
@ -370,16 +371,18 @@ static STREAM_UPDATE( ymf278b_pcm_update )
{
slot->stepptr = slot->stepptr - slot->endaddr + slot->loopaddr;
if (slot->stepptr >= slot->endaddr)
slot->stepptr = slot->loopaddr;
slot->stepptr = slot->loopaddr; // loop overflow
}
switch (slot->bits)
{
case 8:
// 8 bit
case 0:
sample = ymf278b_read_memory(chip, slot->startaddr + (slot->stepptr>>16))<<8;
break;
case 12:
// 12 bit
case 1:
if (slot->stepptr & 1)
sample = ymf278b_read_memory(chip, slot->startaddr + (slot->stepptr>>17)*3+2)<<8 |
(ymf278b_read_memory(chip, slot->startaddr + (slot->stepptr>>17)*3+1) << 4 & 0xf0);
@ -388,10 +391,16 @@ static STREAM_UPDATE( ymf278b_pcm_update )
(ymf278b_read_memory(chip, slot->startaddr + (slot->stepptr>>17)*3+1) & 0xf0);
break;
case 16:
// 16 bit
case 2:
sample = ymf278b_read_memory(chip, slot->startaddr + ((slot->stepptr>>16)*2))<<8 |
ymf278b_read_memory(chip, slot->startaddr + ((slot->stepptr>>16)*2)+1);
break;
// ?? bit, effect is unknown, datasheet says it's prohibited
case 3:
sample = 0;
break;
}
*mixp++ += (sample * chip->volume[slot->TL+chip->pan_left [slot->pan]+(slot->env_vol>>23)])>>17;
@ -595,22 +604,7 @@ static void ymf278b_C_w(YMF278BChip *chip, UINT8 reg, UINT8 data, int init)
for (i = 0; i < 12; i++)
p[i] = ymf278b_read_memory(chip, offset+i);
switch (p[0]&0xc0)
{
case 0:
slot->bits = 8;
break;
case 0x40:
slot->bits = 12;
break;
case 0x80:
slot->bits = 16;
break;
case 0xc0:
// prohibited, effect unknown
break;
}
slot->bits = (p[0]&0xc0)>>6;
slot->startaddr = (p[2] | (p[1]<<8) | ((p[0]&0x3f)<<16));
slot->loopaddr = (p[4]<<16) | (p[3]<<24);
slot->endaddr = (p[6]<<16) | (p[5]<<24);