cvsd_decode_bs_impl.cc

/* -*- c++ -*- */
/*
 * Copyright 2007,2010,2011,2013 Free Software Foundation, Inc.
 *
 * This file is part of GNU Radio
 *
 * GNU Radio 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.
 *
 * GNU Radio 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 GNU Radio; 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 "cvsd_decode_bs_impl.h"
#include <gnuradio/io_signature.h>
#include <limits.h>

namespace gr {
  namespace vocoder {

    cvsd_decode_bs::sptr
    cvsd_decode_bs::make(short min_step, short max_step, double step_decay,
			 double accum_decay, int K, int J,
			 short pos_accum_max, short neg_accum_max)
    {
      return gnuradio::get_initial_sptr
	(new cvsd_decode_bs_impl(min_step, max_step,
				 step_decay, accum_decay, K, J,
				 pos_accum_max, neg_accum_max));
    }

    cvsd_decode_bs_impl::cvsd_decode_bs_impl(short min_step, short max_step, double step_decay,
					     double accum_decay, int K, int J,
					     short pos_accum_max, short neg_accum_max)
      : sync_interpolator("vocoder_cvsd_decode_bs",
			     io_signature::make(1, 1, sizeof(unsigned char)),
			     io_signature::make(1, 1, sizeof(short)),
			     8),
	d_min_step(min_step), d_max_step(max_step), d_step_decay(step_decay),
	d_accum_decay(accum_decay), d_K(K), d_J(J),
	d_pos_accum_max(pos_accum_max), d_neg_accum_max(neg_accum_max),
	d_accum(0),
	d_loop_counter(1),
	d_runner(0),
	d_runner_mask(0),
	d_stepsize(min_step)
    {
     if(d_K > 32)
       throw std::runtime_error("cvsd_decode_bs_impl: K must be <= 32\n");

     if(d_J > d_K)
       throw std::runtime_error("cvsd_decode_bs_impl: J must be <= K\n");
    }

    cvsd_decode_bs_impl::~cvsd_decode_bs_impl()
    {
      // nothing else required in this example
    }

    unsigned char
    cvsd_decode_bs_impl::cvsd_bitwise_sum(unsigned int input)
    {
      unsigned int temp = input;
      unsigned char bits = 0;

      while(temp) {
	temp=temp&(temp-1);
	bits++;
      }
      return bits;
    }

    int
    cvsd_decode_bs_impl::cvsd_round(double input)
    {
      double temp;
      temp=input+0.5;
      temp=floor(temp);

      return (int)temp;
    }

    unsigned int
    cvsd_decode_bs_impl::cvsd_pow(short radix, short power)
    {
      double d_radix = (double) radix;
      int i_power = (int) power;
      double output;

      output = pow(d_radix,i_power);
      return ( (unsigned int)cvsd_round(output));
    }

    int
    cvsd_decode_bs_impl::work(int noutput_items,
			      gr_vector_const_void_star &input_items,
			      gr_vector_void_star &output_items)
    {
      const unsigned char *in = (const unsigned char*)input_items[0];
      short *out = (short *) output_items[0];

      int i=0;
      short output_short=0;	         // 2 bytes 0 .. 65,535
      unsigned char bit_count=0;	 // 1 byte, 0 .. 255
      unsigned int mask=0;		 // 4 bytes, 0 .. 4,294,967,295
      unsigned char input_byte=0;	 //  1 bytes
      unsigned char input_bit=0;	 // 1 byte, 0 .. 255

      // Loop through each input data point
      for(i = 0; i < noutput_items/8.0; i++) {
	input_byte = in[i];
	// Initialize bit counter
	bit_count=0;

	while(bit_count<8) {
	  // Compute the Appropriate Mask
	  mask=cvsd_pow(2,7-bit_count);

	  // Pull off the corresponding bit
	  input_bit = input_byte & mask;

	  // Update the bit counter
	  bit_count++;

	  // Update runner with the next input bit
	  // Runner is a shift-register; shift left, add on newest output bit
	  d_runner = (d_runner<<1) | ((unsigned int) input_bit);

	  // Run this only if you have >= J bits in your shift register
	  if(d_loop_counter>=d_J) {
	    // Update Step Size
	    d_runner_mask=(cvsd_pow(2,d_J)-1);
	    if((cvsd_bitwise_sum(d_runner & d_runner_mask)>=d_J) ||
	       (cvsd_bitwise_sum((~d_runner) & d_runner_mask)>=d_J)) {
	      // Runs of 1s and 0s
	      d_stepsize = std::min( (short) (d_stepsize + d_min_step), d_max_step);
	    }
	    else {
	      // No runs of 1s and 0s
	      d_stepsize = std::max( (short) cvsd_round(d_stepsize*d_step_decay), d_min_step);
	    }
	  }

	  // Update Accum (i.e. the reference value)
	  if(input_bit) {
	    d_accum = d_accum+d_stepsize;
	  }
	  else {
	    d_accum = d_accum-d_stepsize;
	  }

	  // Multiply by Accum_Decay
	  d_accum = (cvsd_round(d_accum*d_accum_decay));

	  // Check for overflow
	  if(d_accum >=((int) d_pos_accum_max)) {
	    d_accum = (int)d_pos_accum_max;
	  }
	  else if(d_accum <=((int) d_neg_accum_max)) {
	    d_accum = (int)d_neg_accum_max;
	  }

	  // Find the output short to write to the file
	  output_short = ((short)d_accum);

	  if(d_loop_counter <= d_K) {
	    d_loop_counter++;
	  }

	  *(out++) = output_short;
	} // while ()

      } // for()

      return noutput_items;
    }

  } /* namespace vocoder */
} /* namespace gr */