GNU Radio 3.6.5.1 C++ API
gr_decode_ccsds_27_fb.h
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1 /* -*- c++ -*- */
2 /*
3  * Copyright 2008 Free Software Foundation, Inc.
4  *
5  * GNU Radio is free software; you can redistribute it and/or modify
6  * it under the terms of the GNU General Public License as published by
7  * the Free Software Foundation; either version 3, or (at your option)
8  * any later version.
9  *
10  * GNU Radio is distributed in the hope that it will be useful,
11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13  * GNU General Public License for more details.
14  *
15  * You should have received a copy of the GNU General Public License
16  * along with GNU Radio; see the file COPYING. If not, write to
17  * the Free Software Foundation, Inc., 51 Franklin Street,
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19  */
20 #ifndef INCLUDED_GR_DECODE_CCSDS_27_FB_H
21 #define INCLUDED_GR_DECODE_CCSDS_27_FB_H
22 
23 #include <gr_core_api.h>
24 #include <gr_sync_decimator.h>
25 
26 extern "C" {
27 #include <viterbi.h>
28 }
29 
31 
33 
35 
36 /*! \brief A rate 1/2, k=7 convolutional decoder for the CCSDS standard
37  *
38  * This block performs soft-decision convolutional decoding using the Viterbi
39  * algorithm.
40  *
41  * The input is a stream of (possibly noise corrupted) floating point values
42  * nominally spanning [-1.0, 1.0], representing the encoded channel symbols
43  * 0 (-1.0) and 1 (1.0), with erased symbols at 0.0.
44  *
45  * The output is MSB first packed bytes of decoded values.
46  *
47  * As a rate 1/2 code, there will be one output byte for every 16 input symbols.
48  *
49  * This block is designed for continuous data streaming, not packetized data.
50  * The first 32 bits out will be zeroes, with the output delayed four bytes
51  * from the corresponding inputs.
52  */
53 
55 {
56 private:
58 
60 
61  // Viterbi state
62  int d_mettab[2][256];
63  struct viterbi_state d_state0[64];
64  struct viterbi_state d_state1[64];
65  unsigned char d_viterbi_in[16];
66 
67  int d_count;
68 
69 public:
71 
72  int work (int noutput_items,
73  gr_vector_const_void_star &input_items,
74  gr_vector_void_star &output_items);
75 };
76 
77 #endif /* INCLUDED_GR_DECODE_CCSDS_27_FB_H */