var:
...
  in_x_array: TReal1DArray; //input value of X from my signal
  in_y_array: TReal1DArray; //input value of Y from my signal
  out_x_array: TReal1DArray; //output value of X from interpolated signal
  out_y_array: TReal1DArray; //output value of Y from interpolated signal
  out_interp_array: TReal2DArray; //output value from unpack
  S: Spline1DInterpolant;
  N: AlglibInteger; //count of points for result of interpolation(?)
...
begin
  N:= 16384;
  Spline1DBuildLinear(in_x_array, in_y_array, N, S);
  SetLength(out_interp_arr,0,0);
  SetLength(out_interp_arr_x,0);
  SetLength(out_interp_arr_y,0);
  for m := 0 to N - 1 do
    begin
      SetLength(out_interp_array,m+1,2);
      SetLength(out_x_array,m+1);
      SetLength(out_y_array,m+1);
      Spline1DUnpack(S,N,out_interp_array);
      out_x_array[m]:=out_interp_array[m,1];
      out_y_array[m]:=out_interp_array[m,2];
      Form1.Series1.AddXY(out_x_array[m], out_y_array[m]);
    end;
...