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Diffstat (limited to 'gr-atsc/include/atsc/equalizer_impl.h')
| -rw-r--r-- | gr-atsc/include/atsc/equalizer_impl.h | 169 |
1 files changed, 169 insertions, 0 deletions
diff --git a/gr-atsc/include/atsc/equalizer_impl.h b/gr-atsc/include/atsc/equalizer_impl.h new file mode 100644 index 0000000000..e2baf537df --- /dev/null +++ b/gr-atsc/include/atsc/equalizer_impl.h @@ -0,0 +1,169 @@ +/* -*- c++ -*- */ +/* + * Copyright 2002 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. + */ + +#ifndef _ATSC_EQUALIZER_H_ +#define _ATSC_EQUALIZER_H_ + +#include <atsc/api.h> +#include <atsc/syminfo_impl.h> +#include <vector> + +/*! + * \brief abstract base class for ATSC equalizer + */ +class ATSC_API atsci_equalizer { + +private: + + /* + * have we seen a field sync since the last reset or problem? + */ + bool d_locked_p; + + /* + * sample offset from the beginning of the last field sync we saw + * to the beginning of our current input stream. When we're locked + * this will be in [0, 313*832] i.e., [0, 260416] + */ + int d_offset_from_last_field_sync; + + int d_current_field; // [0,1] + + +public: + + // CREATORS + atsci_equalizer (); + virtual ~atsci_equalizer (); + + virtual std::vector<double> taps () { + return std::vector<double>(); + } + + // MANIPULATORS + + /*! + * \brief reset state (e.g., on channel change) + * + * Note, subclasses must invoke the superclass's method too! + */ + virtual void reset (); + + /*! + * \brief produce \p nsamples of output from given inputs and tags + * + * This is the main entry point. It examines the input_tags + * and local state and invokes the appropriate virtual function + * to handle each sub-segment of the input data. + * + * \p input_samples must have (nsamples + ntaps() - 1) valid entries. + * input_samples[0] .. input_samples[nsamples - 1 + ntaps() - 1] are + * referenced to compute the output values. + * + * \p input_tags must have nsamples valid entries. + * input_tags[0] .. input_tags[nsamples - 1] are referenced to + * compute the output values. + */ + virtual void filter (const float *input_samples, + const atsc::syminfo *input_tags, + float *output_samples, + int nsamples); + + // ACCESSORS + + /*! + * \brief how much history the input data stream requires. + * + * This must return a value >= 1. Think of this as the number + * of samples you need to look at to compute a single output sample. + */ + virtual int ntaps () const = 0; + + /*! + * \brief how many taps are "in the future". + * + * This allows us to handle what the ATSC folks call "pre-ghosts". + * What it really does is allow the caller to jack with the offset + * between the tags and the data so that everything magically works out. + * + * npretaps () must return a value between 0 and ntaps() - 1. + * + * If npretaps () returns 0, this means that the equalizer will only handle + * multipath "in the past." I suspect that a good value would be something + * like 15% - 20% of ntaps (). + */ + virtual int npretaps () const = 0; + + +protected: + + /*! + * Input range is known NOT TO CONTAIN data segment syncs + * or field syncs. This should be the fast path. In the + * non decicion directed case, this just runs the input + * through the filter without adapting it. + * + * \p input_samples has (nsamples + ntaps() - 1) valid entries. + * input_samples[0] .. input_samples[nsamples - 1 + ntaps() - 1] may be + * referenced to compute the output values. + */ + virtual void filter_normal (const float *input_samples, + float *output_samples, + int nsamples) = 0; + + /*! + * Input range is known to consist of only a data segment sync or a + * portion of a data segment sync. \p nsamples will be in [1,4]. + * \p offset will be in [0,3]. \p offset is the offset of the input + * from the beginning of the data segment sync pattern. + * + * \p input_samples has (nsamples + ntaps() - 1) valid entries. + * input_samples[0] .. input_samples[nsamples - 1 + ntaps() - 1] may be + * referenced to compute the output values. + */ + virtual void filter_data_seg_sync (const float *input_samples, + float *output_samples, + int nsamples, + int offset) = 0; + + /*! + * Input range is known to consist of only a field sync segment or a + * portion of a field sync segment. \p nsamples will be in [1,832]. + * \p offset will be in [0,831]. \p offset is the offset of the input + * from the beginning of the data segment sync pattern. We consider the + * 4 symbols of the immediately preceding data segment sync to be the + * first symbols of the field sync segment. \p which_field is in [0,1] + * and specifies which field (duh). + * + * \p input_samples has (nsamples + ntaps() - 1) valid entries. + * input_samples[0] .. input_samples[nsamples - 1 + ntaps() - 1] may be + * referenced to compute the output values. + */ + virtual void filter_field_sync (const float *input_samples, + float *output_samples, + int nsamples, + int offset, + int which_field) = 0; +}; + + +#endif /* _ATSC_EQUALIZER_H_ */ |