text: void DSP_mat_mul_c
  (
      const short * x, int r1, int c1,
      const short * y,         int c2,
      short       * r,
      int                   qs
  )
  {
      int i, j, k;
      int sum;
      for (i = 0; i < r1; i++)
          for (j = 0; j < c2; j++)
          {
              sum = 0;
              for (k = 0; k < c1; k++)
                  sum += x[k + i*c1] * y[j + k*c2];
              r[j + i*c2] = sum >> qs;
          }
  }
  
  