Fractional delay

/* -*- c++ -*- */
/*
 * Copyright 2014 Carlos Alberto Ruiz Naranjo,
 * Center for Advanced Aerospace Technologies (CATEC).
 *
 * This is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3, or (at your option)
 * any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this software; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street,
 * Boston, MA 02110-1301, USA.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <gnuradio/io_signature.h>
#include "fractional_delay_impl.h"
#include <math.h>
#include <gnuradio/blocks/complex_to_float.h>

namespace gr {
  namespace howto {

    fractional_delay::sptr
    fractional_delay::make(float delay)
    {
      return gnuradio::get_initial_sptr
        (new fractional_delay_impl(delay));
    }

    /*
     * The private constructor
     */
    fractional_delay_impl::fractional_delay_impl(float delay)
      : gr::block("fractional_delay",
              gr::io_signature::make(2,2, sizeof(float)),
              gr::io_signature::make(2,2, sizeof(float)))
    {
        this->delay=delay;
        k=0;
    }

    /*
     * Our virtual destructor.
     */
    fractional_delay_impl::~fractional_delay_impl()
    {
    }

    void
    fractional_delay_impl::forecast (int noutput_items, gr_vector_int &ninput_items_required)
    {
        ninput_items_required[0] = noutput_items;
        ninput_items_required[1] = noutput_items;
    }



    int
    fractional_delay_impl::general_work (int noutput_items,
                       gr_vector_int &ninput_items,
                       gr_vector_const_void_star &input_items,
                       gr_vector_void_star &output_items)
    {
        int fft_length = 1024*10;

        const float *in_real = (const float *) input_items[0];
        const float *in_img = (const float *) input_items[1];

        float *out_real = (float *) output_items[0];
        float *out_img = (float *) output_items[1];

        for(int i=0;i<noutput_items;++i){
            //float argumento = ( (2*M_PI/fft_length)*delay*k );

            //out_real[i] = in_real[i]*cos(argumento) + in_img[i]*sin(argumento);
            //out_img[i] = -in_real[i]*sin(argumento) + in_img[i]*cos(argumento);

            if(k==0){
                out_real[i] = in_real[i];
                out_img[i] = in_img[i];
            }
            else if( (k>0) && (k<(fft_length/2)) ){
                float argumento = ( (2*M_PI/fft_length)*delay*k );

                out_real[i] = in_real[i]*cos(argumento) + in_img[i]*sin(argumento);
                out_img[i] = -in_real[i]*sin(argumento) + in_img[i]*cos(argumento);
            }
            else if(k==fft_length/2){
                out_real[i] = in_real[i]*cos(M_PI*delay);
                out_img[i] = in_img[i]*cos(M_PI*delay);
            }
            else if(k>(fft_length/2) ){
                float argumento = ( (2*M_PI/fft_length)*delay*(fft_length-k) );

                out_real[i] = in_real[i]*cos(argumento) - in_img[i]*sin(argumento);
                out_img[i] = in_real[i]*sin(argumento) + in_img[i]*cos(argumento);
            }


            ++k;
            if(k==fft_length){
                k=0;
            }
        }

        // Tell runtime system how many input items we consumed on
        // each input stream.
        consume_each (noutput_items);

        // Tell runtime system how many output items we produced.
        return noutput_items;
    }

        void fractional_delay_impl::set_delay(float delay)
    {
        this->delay=delay;
    }


  } /* namespace howto */
} /* namespace gr */