shithub: sox

ref: aac924f5cc55696f9771c3ed1a7a7f2d049e19dd
dir: /src/dither_fir.h/

#define _ d -= p->coefs[j] * p->previous_errors[p->pos + j], ++j;
static int NAME(sox_effect_t * effp, const sox_sample_t * ibuf,
    sox_sample_t * obuf, size_t * isamp, size_t * osamp)
{
  priv_t * p = (priv_t *)effp->priv;
  size_t len = *isamp = *osamp = min(*isamp, *osamp);
  int dummy = 0;

  while (len--) {
    double r = p->am0 * RANQD1 + p->am1 * RANQD1;
    double error, d = *ibuf++;
    int j = 0;
    CONVOLVE
    assert(j == N);
    *obuf = SOX_ROUND_CLIP_COUNT(d + r, dummy);
    error = ((*obuf++ + (1 << (31-PREC))) & (-1 << (32-PREC))) - d;
    p->pos = p->pos? p->pos - 1 : p->pos - 1 + N;
    p->previous_errors[p->pos + N] = p->previous_errors[p->pos] = error;
  }
  return SOX_SUCCESS;
}
#undef CONVOLVE
#undef _
#undef NAME
#undef N