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Change Mulaw algorithm

This commit is contained in:
cam900 2023-08-09 20:33:42 +09:00
parent 14c5d94499
commit 1e2cd8282a
1 changed files with 13 additions and 9 deletions
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22
src/engine/platform/sound/c140.c
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@ -43,6 +43,7 @@ static int c140_max(int a, int b) { return (a > b) ? a : b; }
static int c140_min(int a, int b) { return (a < b) ? a : b; }
static int c140_clamp(int v, int min, int max) { return c140_min(c140_max(v,min),max); }
static int c140_bit(int val, int bit) { return (val >> bit) & 1; }
static int c140_bitfield(int val, int bit, int len) { return (val >> bit) & ((1 << len) - 1);}
void c140_tick(struct c140_t *c140, const int cycle)
{
@ -117,15 +118,18 @@ void c140_init(struct c140_t *c140)
// u-law table verified from Wii Virtual Console Arcade Starblade
for (int i = 0; i < 256; i++)
{
int j = (signed char)i;
signed char s1 = j & 7;
signed char s2 = abs(j >> 3) & 31;
c140->mulaw[i] = 0x80 << s1 & 0xff00;
c140->mulaw[i] += s2 << (s1 ? s1 + 3 : 4);
if (j < 0)
c140->mulaw[i] = -c140->mulaw[i];
const unsigned char exponent = c140_bitfield(i, 0, 3);
const unsigned char mantissa = c140_bitfield(i, 3, 4);
if (c140_bit(i, 7))
{
c140->mulaw[i] = (signed short)(((exponent ? 0xfe00 : 0xff00) | (mantissa << 4))
<< (exponent ? exponent - 1 : 0));
}
else
{
c140->mulaw[i] = (signed short)(((exponent ? 0x100 : 0) | (mantissa << 4))
<< (exponent ? exponent - 1 : 0));
}
}
}