static int resampler_basic_interpolate_double()

in subprojects/speex/resample.c [501:558]

• 50 lines of code
• 5 McCabe index (conditional complexity)

static int resampler_basic_interpolate_double(SpeexResamplerState *st, spx_uint32_t channel_index, const spx_word16_t *in, spx_uint32_t *in_len, spx_word16_t *out, spx_uint32_t *out_len)
{
   const int N = st->filt_len;
   int out_sample = 0;
   int last_sample = st->last_sample[channel_index];
   spx_uint32_t samp_frac_num = st->samp_frac_num[channel_index];
   const int out_stride = st->out_stride;
   const int int_advance = st->int_advance;
   const int frac_advance = st->frac_advance;
   const spx_uint32_t den_rate = st->den_rate;
   spx_word32_t sum;

   while (!(last_sample >= (spx_int32_t)*in_len || out_sample >= (spx_int32_t)*out_len))
   {
      const spx_word16_t *iptr = & in[last_sample];

      const int offset = samp_frac_num*st->oversample/st->den_rate;
#ifdef FIXED_POINT
      const spx_word16_t frac = PDIV32(SHL32((samp_frac_num*st->oversample) % st->den_rate,15),st->den_rate);
#else
      const spx_word16_t frac = ((float)((samp_frac_num*st->oversample) % st->den_rate))/st->den_rate;
#endif
      spx_word16_t interp[4];


#ifndef OVERRIDE_INTERPOLATE_PRODUCT_DOUBLE
      int j;
      double accum[4] = {0,0,0,0};

      for(j=0;j<N;j++) {
        const double curr_in=iptr[j];
        accum[0] += MULT16_16(curr_in,st->sinc_table[4+(j+1)*st->oversample-offset-2]);
        accum[1] += MULT16_16(curr_in,st->sinc_table[4+(j+1)*st->oversample-offset-1]);
        accum[2] += MULT16_16(curr_in,st->sinc_table[4+(j+1)*st->oversample-offset]);
        accum[3] += MULT16_16(curr_in,st->sinc_table[4+(j+1)*st->oversample-offset+1]);
      }

      cubic_coef(frac, interp);
      sum = MULT16_32_Q15(interp[0],accum[0]) + MULT16_32_Q15(interp[1],accum[1]) + MULT16_32_Q15(interp[2],accum[2]) + MULT16_32_Q15(interp[3],accum[3]);
#else
      cubic_coef(frac, interp);
      sum = interpolate_product_double(iptr, st->sinc_table + st->oversample + 4 - offset - 2, N, st->oversample, interp);
#endif

      out[out_stride * out_sample++] = PSHR32(sum,15);
      last_sample += int_advance;
      samp_frac_num += frac_advance;
      if (samp_frac_num >= den_rate)
      {
         samp_frac_num -= den_rate;
         last_sample++;
      }
   }

   st->last_sample[channel_index] = last_sample;
   st->samp_frac_num[channel_index] = samp_frac_num;
   return out_sample;
}