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added envelope attack rate

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This commit is contained in:
Michaël Banaan Ananas 2011-08-09 01:22:40 +00:00
parent b6ae4cc5d0
commit e818d68438
1 changed files with 39 additions and 10 deletions
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49
src/emu/sound/ymf278b.c
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@ -169,22 +169,32 @@ static int ymf278b_compute_rate(YMF278BSlot *slot, int val)
return res;
}
INLINE UINT32 ymf278_compute_attack_rate(int num)
{
// estimated (less accurate on high rates)
UINT32 samples;
if (num <= 3 || num == 63)
samples = 0;
else if (num >= 60)
samples = 17;
else
samples = (67 << (15 - num / 4)) / (4 + num % 4);
return samples;
}
static UINT32 ymf278_compute_decay_rate(int num)
{
int samples;
// estimated
UINT32 samples;
if (num <= 3)
samples = 0;
else if (num >= 60)
samples = 15 << 4;
else
{
samples = (15 << (21 - num / 4)) / (4 + num % 4);
if (num % 4 && num / 4 <= 11)
samples += 2;
else if (num == 51)
samples += 2;
}
return samples;
}
@ -194,10 +204,29 @@ static void ymf278b_envelope_next(YMF278BSlot *slot)
if(slot->env_step == 0)
{
// Attack
slot->env_vol = (256U << 23) - 1;
slot->env_vol_lim = 256U<<23;
LOG(("YMF278B: Skipping attack (rate = %d)\n", slot->AR));
int rate = ymf278b_compute_rate(slot, slot->AR);
slot->env_vol = 256U<<23;
slot->env_vol_lim = (256U<<23) - 1;
slot->env_step++;
if (rate==63)
{
// immediate
slot->env_vol = 0;
slot->env_vol_lim = 256U<<23;
}
else if (rate<4)
{
slot->env_vol_step = 0;
return;
}
else
{
// NOTE: attack rate is linear here, but datasheet shows a smooth curve
LOG(("YMF278B: Attack, val = %d, rate = %d, delay = %g\n", slot->AR, rate, ymf278_compute_attack_rate(rate)*1000.0));
slot->env_vol_step = ~((256U<<23) / ymf278_compute_attack_rate(rate));
return;
}
}
if(slot->env_step == 1)
{