/*
* NAME: fixed->div()
* DESCRIPTION: perform division using fixed-point math
*/
mad_fixed_t mad_f_div(mad_fixed_t x, mad_fixed_t y)
{
mad_fixed_t q, r;
unsigned int bits;
q = mad_f_abs(x / y);
if (x < 0) {
x = -x;
y = -y;
}
r = x % y;
if (y < 0) {
x = -x;
y = -y;
}
if (q > mad_f_intpart(MAD_F_MAX) &&
!(q == -mad_f_intpart(MAD_F_MIN) && r == 0 && (x < 0) != (y < 0)))
return 0;
for (bits = MAD_F_FRACBITS; bits && r; --bits) {
q <<= 1, r <<= 1;
if (r >= y)
r -= y, ++q;
}
/* round */
if (2 * r >= y)
++q;
/* fix sign */
if ((x < 0) != (y < 0))
q = -q;
return q << bits;
}
/*
* NAME: resample_block()
* DESCRIPTION: algorithmically change the sampling rate of a PCM sample block
*/
unsigned int
mad_resample_block(struct resample_state *state,
unsigned int nsamples, mad_fixed_t const *old,
mad_fixed_t *newdata)
{
mad_fixed_t const *end, *begin;
/*
* This resampling algorithm is based on a linear interpolation, which is
* not at all the best sounding but is relatively fast and efficient.
*
* A better algorithm would be one that implements a bandlimited
* interpolation.
*/
if (state->ratio == MAD_F_ONE) {
memcpy(newdata, old, nsamples * sizeof(mad_fixed_t));
return nsamples;
}
end = old + nsamples;
begin = newdata;
if (state->step < 0)
{
state->step = mad_f_fracpart(-state->step);
while (state->step < MAD_F_ONE) {
*newdata++ = state->step ?
state->last + mad_f_mul(*old - state->last, state->step) : state->last;
state->step += state->ratio;
if (((state->step + 0x00000080L) & 0x0fffff00L) == 0)
state->step = (state->step + 0x00000080L) & ~0x0fffffffL;
}
state->step -= MAD_F_ONE;
}
while (end - old > 1 + mad_f_intpart(state->step))
{
old += mad_f_intpart(state->step);
state->step = mad_f_fracpart(state->step);
*newdata++ = state->step ?
*old + mad_f_mul(old[1] - old[0], state->step) : *old;
state->step += state->ratio;
if (((state->step + 0x00000080L) & 0x0fffff00L) == 0)
state->step = (state->step + 0x00000080L) & ~0x0fffffffL;
}
if (end - old == 1 + mad_f_intpart(state->step)) {
state->last = end[-1];
state->step = -state->step;
}
else
state->step -= mad_f_fromint(end - old);
return newdata - begin;
}