GNU Radio Manual and C++ API Reference 3.7.14.0
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equalizer_impl.h
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1/* -*- c++ -*- */
2/*
3 * Copyright 2002 Free Software Foundation, Inc.
4 *
5 * This file is part of GNU Radio
6 *
7 * GNU Radio is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 3, or (at your option)
10 * any later version.
11 *
12 * GNU Radio is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with GNU Radio; see the file COPYING. If not, write to
19 * the Free Software Foundation, Inc., 51 Franklin Street,
20 * Boston, MA 02110-1301, USA.
21 */
22
23#ifndef _ATSC_EQUALIZER_H_
24#define _ATSC_EQUALIZER_H_
25
26#include <gnuradio/atsc/api.h>
28#include <vector>
29
30/*!
31 * \brief abstract base class for ATSC equalizer
32 */
34{
35
36private:
37 /*
38 * have we seen a field sync since the last reset or problem?
39 */
40 bool d_locked_p;
41
42 /*
43 * sample offset from the beginning of the last field sync we saw
44 * to the beginning of our current input stream. When we're locked
45 * this will be in [0, 313*832] i.e., [0, 260416]
46 */
47 int d_offset_from_last_field_sync;
48
49 int d_current_field; // [0,1]
50
51
52public:
53 // CREATORS
56
57 virtual std::vector<double> taps() { return std::vector<double>(); }
58
59 // MANIPULATORS
60
61 /*!
62 * \brief reset state (e.g., on channel change)
63 *
64 * Note, subclasses must invoke the superclass's method too!
65 */
66 virtual void reset();
67
68 /*!
69 * \brief produce \p nsamples of output from given inputs and tags
70 *
71 * This is the main entry point. It examines the input_tags
72 * and local state and invokes the appropriate virtual function
73 * to handle each sub-segment of the input data.
74 *
75 * \p input_samples must have (nsamples + ntaps() - 1) valid entries.
76 * input_samples[0] .. input_samples[nsamples - 1 + ntaps() - 1] are
77 * referenced to compute the output values.
78 *
79 * \p input_tags must have nsamples valid entries.
80 * input_tags[0] .. input_tags[nsamples - 1] are referenced to
81 * compute the output values.
82 */
83 virtual void filter(const float* input_samples,
84 const atsc::syminfo* input_tags,
85 float* output_samples,
86 int nsamples);
87
88 // ACCESSORS
89
90 /*!
91 * \brief how much history the input data stream requires.
92 *
93 * This must return a value >= 1. Think of this as the number
94 * of samples you need to look at to compute a single output sample.
95 */
96 virtual int ntaps() const = 0;
97
98 /*!
99 * \brief how many taps are "in the future".
100 *
101 * This allows us to handle what the ATSC folks call "pre-ghosts".
102 * What it really does is allow the caller to jack with the offset
103 * between the tags and the data so that everything magically works out.
104 *
105 * npretaps () must return a value between 0 and ntaps() - 1.
106 *
107 * If npretaps () returns 0, this means that the equalizer will only handle
108 * multipath "in the past." I suspect that a good value would be something
109 * like 15% - 20% of ntaps ().
110 */
111 virtual int npretaps() const = 0;
112
113
114protected:
115 /*!
116 * Input range is known NOT TO CONTAIN data segment syncs
117 * or field syncs. This should be the fast path. In the
118 * non decicion directed case, this just runs the input
119 * through the filter without adapting it.
120 *
121 * \p input_samples has (nsamples + ntaps() - 1) valid entries.
122 * input_samples[0] .. input_samples[nsamples - 1 + ntaps() - 1] may be
123 * referenced to compute the output values.
124 */
125 virtual void
126 filter_normal(const float* input_samples, float* output_samples, int nsamples) = 0;
127
128 /*!
129 * Input range is known to consist of only a data segment sync or a
130 * portion of a data segment sync. \p nsamples will be in [1,4].
131 * \p offset will be in [0,3]. \p offset is the offset of the input
132 * from the beginning of the data segment sync pattern.
133 *
134 * \p input_samples has (nsamples + ntaps() - 1) valid entries.
135 * input_samples[0] .. input_samples[nsamples - 1 + ntaps() - 1] may be
136 * referenced to compute the output values.
137 */
138 virtual void filter_data_seg_sync(const float* input_samples,
139 float* output_samples,
140 int nsamples,
141 int offset) = 0;
142
143 /*!
144 * Input range is known to consist of only a field sync segment or a
145 * portion of a field sync segment. \p nsamples will be in [1,832].
146 * \p offset will be in [0,831]. \p offset is the offset of the input
147 * from the beginning of the data segment sync pattern. We consider the
148 * 4 symbols of the immediately preceding data segment sync to be the
149 * first symbols of the field sync segment. \p which_field is in [0,1]
150 * and specifies which field (duh).
151 *
152 * \p input_samples has (nsamples + ntaps() - 1) valid entries.
153 * input_samples[0] .. input_samples[nsamples - 1 + ntaps() - 1] may be
154 * referenced to compute the output values.
155 */
156 virtual void filter_field_sync(const float* input_samples,
157 float* output_samples,
158 int nsamples,
159 int offset,
160 int which_field) = 0;
161};
162
163
164#endif /* _ATSC_EQUALIZER_H_ */
abstract base class for ATSC equalizer
Definition: equalizer_impl.h:34
virtual void filter_data_seg_sync(const float *input_samples, float *output_samples, int nsamples, int offset)=0
virtual int npretaps() const =0
how many taps are "in the future".
virtual void filter_field_sync(const float *input_samples, float *output_samples, int nsamples, int offset, int which_field)=0
virtual void filter(const float *input_samples, const atsc::syminfo *input_tags, float *output_samples, int nsamples)
produce nsamples of output from given inputs and tags
virtual int ntaps() const =0
how much history the input data stream requires.
virtual ~atsci_equalizer()
virtual std::vector< double > taps()
Definition: equalizer_impl.h:57
virtual void reset()
reset state (e.g., on channel change)
virtual void filter_normal(const float *input_samples, float *output_samples, int nsamples)=0
#define ATSC_API
Definition: gr-atsc/include/gnuradio/atsc/api.h:30
Definition: syminfo_impl.h:31