blargg_err_t Fir_Resampler_::set_rate_( double new_factor )
{
double const rolloff = 0.999;
double const gain = 1.0;
// determine number of sub-phases that yield lowest error
double ratio_ = 0.0;
int res = -1;
{
double least_error = 2;
double pos = 0;
for ( int r = 1; r <= max_res; r++ )
{
pos += new_factor;
double nearest = floor( pos + 0.5 );
double error = fabs( pos - nearest );
if ( error < least_error )
{
res = r;
ratio_ = nearest / res;
least_error = error;
}
}
}
RETURN_ERR( Resampler::set_rate_( ratio_ ) );
// how much of input is used for each output sample
int const step = stereo * (int) floor( ratio_ );
double fraction = fmod( ratio_, 1.0 );
double const filter = (ratio_ < 1.0) ? 1.0 : 1.0 / ratio_;
double pos = 0.0;
//int input_per_cycle = 0;
sample_t* out = impulses;
for ( int n = res; --n >= 0; )
{
gen_sinc( rolloff, int (width_ * filter + 1) & ~1, pos, filter,
double (0x7FFF * gain * filter), (int) width_, out );
out += width_;
int cur_step = step;
pos += fraction;
if ( pos >= 0.9999999 )
{
pos -= 1.0;
cur_step += stereo;
}
*out++ = (cur_step - width_ * 2 + 4) * sizeof (sample_t);
*out++ = 4 * sizeof (sample_t);
//input_per_cycle += cur_step;
}
// last offset moves back to beginning of impulses
out [-1] -= (char*) out - (char*) impulses;
imp = impulses;
return blargg_ok;
}
double Fir_Resampler_::time_ratio( double new_factor, double rolloff, double gain )
{
ratio_ = new_factor;
double fstep = 0.0;
{
double least_error = 2;
double pos = 0;
res = -1;
for ( int r = 1; r <= max_res; r++ )
{
pos += ratio_;
double nearest = floor( pos + 0.5 );
double error = fabs( pos - nearest );
if ( error < least_error )
{
res = r;
fstep = nearest / res;
least_error = error;
}
}
}
skip_bits = 0;
step = stereo * (int) floor( fstep );
ratio_ = fstep;
fstep = fmod( fstep, 1.0 );
double filter = (ratio_ < 1.0) ? 1.0 : 1.0 / ratio_;
double pos = 0.0;
input_per_cycle = 0;
for ( int i = 0; i < res; i++ )
{
gen_sinc( rolloff, int (width_ * filter + 1) & ~1, pos, filter,
double (0x7FFF * gain * filter),
(int) width_, impulses + i * width_ );
pos += fstep;
input_per_cycle += step;
if ( pos >= 0.9999999 )
{
pos -= 1.0;
skip_bits |= 1 << i;
input_per_cycle++;
}
}
clear();
return ratio_;
}
