GNU Radio C++ API
atsci_equalizer.h
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/* -*- c++ -*- */
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/*
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* Copyright 2002 Free Software Foundation, Inc.
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*
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* This file is part of GNU Radio
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*
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* GNU Radio is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3, or (at your option)
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* any later version.
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*
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* GNU Radio is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with GNU Radio; see the file COPYING. If not, write to
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* the Free Software Foundation, Inc., 51 Franklin Street,
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* Boston, MA 02110-1301, USA.
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*/
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#ifndef _ATSC_EQUALIZER_H_
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#define _ATSC_EQUALIZER_H_
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#include <
atsc_api.h
>
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#include <
atsci_syminfo.h
>
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/*!
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* \brief abstract base class for ATSC equalizer
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*/
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class
ATSC_API
atsci_equalizer
{
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private
:
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/*
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* have we seen a field sync since the last reset or problem?
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*/
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bool
d_locked_p;
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/*
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* sample offset from the beginning of the last field sync we saw
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* to the beginning of our current input stream. When we're locked
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* this will be in [0, 313*832] i.e., [0, 260416]
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*/
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int
d_offset_from_last_field_sync;
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int
d_current_field;
// [0,1]
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public
:
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// CREATORS
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atsci_equalizer
();
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virtual
~
atsci_equalizer
();
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// MANIPULATORS
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/*!
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* \brief reset state (e.g., on channel change)
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*
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* Note, subclasses must invoke the superclass's method too!
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*/
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virtual
void
reset ();
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/*!
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* \brief produce \p nsamples of output from given inputs and tags
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*
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* This is the main entry point. It examines the input_tags
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* and local state and invokes the appropriate virtual function
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* to handle each sub-segment of the input data.
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*
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* \p input_samples must have (nsamples + ntaps() - 1) valid entries.
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* input_samples[0] .. input_samples[nsamples - 1 + ntaps() - 1] are
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* referenced to compute the output values.
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*
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* \p input_tags must have nsamples valid entries.
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* input_tags[0] .. input_tags[nsamples - 1] are referenced to
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* compute the output values.
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*/
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virtual
void
filter (
const
float
*input_samples,
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const
atsc::syminfo
*input_tags,
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float
*output_samples,
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int
nsamples);
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// ACCESSORS
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/*!
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* \brief how much history the input data stream requires.
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*
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* This must return a value >= 1. Think of this as the number
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* of samples you need to look at to compute a single output sample.
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*/
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virtual
int
ntaps ()
const
= 0;
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/*!
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* \brief how many taps are "in the future".
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*
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* This allows us to handle what the ATSC folks call "pre-ghosts".
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* What it really does is allow the caller to jack with the offset
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* between the tags and the data so that everything magically works out.
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*
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* npretaps () must return a value between 0 and ntaps() - 1.
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*
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* If npretaps () returns 0, this means that the equalizer will only handle
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* multipath "in the past." I suspect that a good value would be something
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* like 15% - 20% of ntaps ().
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*/
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virtual
int
npretaps ()
const
= 0;
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protected
:
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/*!
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* Input range is known NOT TO CONTAIN data segment syncs
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* or field syncs. This should be the fast path. In the
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* non decicion directed case, this just runs the input
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* through the filter without adapting it.
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*
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* \p input_samples has (nsamples + ntaps() - 1) valid entries.
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* input_samples[0] .. input_samples[nsamples - 1 + ntaps() - 1] may be
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* referenced to compute the output values.
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*/
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virtual
void
filter_normal (
const
float
*input_samples,
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float
*output_samples,
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int
nsamples) = 0;
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/*!
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* Input range is known to consist of only a data segment sync or a
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* portion of a data segment sync. \p nsamples will be in [1,4].
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* \p offset will be in [0,3]. \p offset is the offset of the input
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* from the beginning of the data segment sync pattern.
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*
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* \p input_samples has (nsamples + ntaps() - 1) valid entries.
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* input_samples[0] .. input_samples[nsamples - 1 + ntaps() - 1] may be
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* referenced to compute the output values.
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*/
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virtual
void
filter_data_seg_sync (
const
float
*input_samples,
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float
*output_samples,
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int
nsamples,
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int
offset) = 0;
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/*!
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* Input range is known to consist of only a field sync segment or a
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* portion of a field sync segment. \p nsamples will be in [1,832].
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* \p offset will be in [0,831]. \p offset is the offset of the input
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* from the beginning of the data segment sync pattern. We consider the
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* 4 symbols of the immediately preceding data segment sync to be the
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* first symbols of the field sync segment. \p which_field is in [0,1]
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* and specifies which field (duh).
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*
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* \p input_samples has (nsamples + ntaps() - 1) valid entries.
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* input_samples[0] .. input_samples[nsamples - 1 + ntaps() - 1] may be
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* referenced to compute the output values.
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*/
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virtual
void
filter_field_sync (
const
float
*input_samples,
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float
*output_samples,
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int
nsamples,
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int
offset,
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int
which_field) = 0;
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};
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#endif
/* _ATSC_EQUALIZER_H_ */
gr-atsc
src
lib
atsci_equalizer.h
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