src/dither.h

   1 #ifdef IIR
   2 #define _ output += p->coefs[j] * p->previous_errors[p->pos + j] \
   3                   - p->coefs[N + j] * p->previous_outputs[p->pos + j], ++j;
   4 #else
   5 #define _ d -= p->coefs[j] * p->previous_errors[p->pos + j], ++j;
   6 #endif
   7 static int NAME(sox_effect_t * effp, const sox_sample_t * ibuf,
   8     sox_sample_t * obuf, size_t * isamp, size_t * osamp)
   9 {
  10   priv_t * p = (priv_t *)effp->priv;
  11   size_t len = *isamp = *osamp = min(*isamp, *osamp);
  12
  13   while (len--) {
  14     if (!p->auto_detect || (p->history = ((p->history << 1) + !!(*ibuf & (((unsigned)-1) >> p->prec))))) {
  15       int32_t r1 = RANQD1 >> p->prec, r2 = RANQD1 >> p->prec; /* Defer add! */
  16 #ifdef IIR
  17       double d1, d, output = 0;
  18 #else
  19       double d1, d = *ibuf++;
  20 #endif
  21       int i, j = 0;
  22       CONVOLVE
  23       assert(j == N);
  24       p->pos = p->pos? p->pos - 1 : p->pos - 1 + N;
  25 #ifdef IIR
  26       d = *ibuf++ - output;
  27       p->previous_outputs[p->pos + N] = p->previous_outputs[p->pos] = output;
  28 #endif
  29       d1 = (d + r1 + r2) / (1 << (32 - p->prec));
  30       i = d1 < 0? d1 - .5 : d1 + .5;
  31       p->previous_errors[p->pos + N] = p->previous_errors[p->pos] =
  32           (double)i * (1 << (32 - p->prec)) - d;
  33       if (i < (-1 << (p->prec-1)))
  34         ++effp->clips, *obuf = SOX_SAMPLE_MIN;
  35       else if (i > (int)SOX_INT_MAX(p->prec))
  36         ++effp->clips, *obuf = SOX_INT_MAX(p->prec) << (32 - p->prec);
  37       else *obuf = i << (32 - p->prec);
  38       ++obuf;
  39
  40       if (p->dither_off)
  41         lsx_debug("flow %u: on  @ %u", (unsigned)effp->flow, (unsigned)p->num_output);
  42       p->dither_off = sox_false;
  43     }
  44     else {
  45       *obuf++ = *ibuf++;
  46       if (!p->dither_off) {
  47         lsx_debug("flow %u: off @ %u", (unsigned)effp->flow, (unsigned)p->num_output);
  48         memset(p->previous_errors, 0, sizeof(p->previous_errors));
  49         memset(p->previous_outputs, 0, sizeof(p->previous_outputs));
  50       }
  51       p->dither_off = sox_true;
  52     }
  53     ++p->num_output;
  54   }
  55   return SOX_SUCCESS;
  56 }
  57 #undef CONVOLVE
  58 #undef _
  59 #undef NAME
  60 #undef N